Article

Death by hyperventilation: A common and life-threatening problem during cardiopulmonary resuscitation

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Abstract

This translational research initiative focused on the physiology of cardiopulmonary resuscitation (CPR) initiated by a clinical observation of consistent hyperventilation by professional rescuers in out-of-hospital cardiac arrest. This observation generated scientific hypotheses that could only ethically be tested in the animal laboratory. To examine the hypothesis that excessive ventilation rates during performance of CPR by overzealous but well-trained rescue personnel causes a significant decrease in coronary perfusion pressure and an increased likelihood of death. In the in vivo human aspect of the study, we set out to objectively and electronically record rate and duration of ventilation during performance of CPR by trained professional rescue personnel in a prospective clinical trial in intubated, adult patients with out-of-hospital cardiac arrest. In the in vivo animal aspect of the study, to simulate the clinically observed hyperventilation, nine pigs in cardiac arrest were ventilated in a random order with 12, 20, or 30 breaths/min, and physiologic variables were assessed. Next, three groups of seven pigs in cardiac arrest were ventilated at 12 breaths/min with 100% oxygen, 30 breaths/min with 100% oxygen, or 30 breaths/min with 5% CO2/95% oxygen, and survival was assessed. Ventilation rate and duration in humans; mean intratracheal pressure, coronary perfusion pressure, and survival rates in animals. In 13 consecutive adults (average age, 63 +/- 5.8 yrs) receiving CPR (seven men) the average ventilation rate was 30 +/- 3.2 breaths/min (range, 15 to 49 breaths/min) and the average duration of each breath was 1.0 +/- 0.07 sec. The average percentage of time in which a positive pressure was recorded in the lungs was 47.3 +/- 4.3%. No patient survived. In animals treated with 12, 20, and 30 breaths/min, the mean intratracheal pressures and coronary perfusion pressures were 7.1 +/- 0.7, 11.6 +/- 0.7, 17.5 +/- 1.0 mm Hg/min (p < .0001) and 23.4 +/- 1.0, 19.5 +/- 1.8, 16.9 +/- 1.8 mm Hg (p = .03) with each of the different ventilation rates, respectively (p = comparison of 12 breaths/min vs. 30 breaths/min for mean intratracheal pressure and coronary perfusion pressure). Survival rates were six of seven, one of seven, and one of seven with 12, 30, and 30 + CO2 breaths/min, respectively (p = .006). Despite seemingly adequate training, professional rescuers consistently hyperventilated patients during out-of-hospital CPR. Subsequent hemodynamic and survival studies in pigs demonstrated that excessive ventilation rates significantly decreased coronary perfusion pressures and survival rates, despite supplemental CO2 to prevent hypocapnia. This translational research initiative demonstrates an inversely proportional relationship between mean intratracheal pressure and coronary perfusion pressure during CPR. Additional education of CPR providers is urgently needed to reduce these newly identified and deadly consequences of hyperventilation during CPR. These findings also have significant implications for interpretation and design of resuscitation research, CPR guidelines, education, the development of biomedical devices, emergency medical services quality assurance, and clinical practice.

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... Likewise, assisted breathing components not only require attention to the frequency, force, and speed of delivery of each breath but also the actual volume and the rapid release of each positive pressure breath once delivered. These ventilatory variables significantly impact circulation and thus the effectiveness of other interventions, including medications, and CPR itself (5,9,10). In addition, all of these factors need to be well-controlled and adjusted under certain conditions, particularly when flow-enhancing devices are used or when spontaneous circulation or respirations resume (9). ...
... These ventilatory variables significantly impact circulation and thus the effectiveness of other interventions, including medications, and CPR itself (5,9,10). In addition, all of these factors need to be well-controlled and adjusted under certain conditions, particularly when flow-enhancing devices are used or when spontaneous circulation or respirations resume (9). ...
... Most of those trials were typically perplexed by the pivotal interactive nature of various interdependent variables. In addition, underrecognized confounding factors such as suboptimal quality of CPR, overzealous positive pressure ventilation, time delays to interventions, and many other systematic factors played large roles (9,10,14,17,19,21,23,31,(35)(36)(37)(38). Low survival rates create further statistical quandaries, especially in essential subgroup analyses. ...
Article
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Objectives: To construct a highly detailed yet practical, attainable roadmap for enhancing the likelihood of neurologically intact survival following sudden cardiac arrest. Design, Setting, and Patients: Population-based outcomes following out-of-hospital cardiac arrest were collated for 10 U.S. counties in Alaska, California, Florida, Ohio, Minnesota, Utah, and Washington. The 10 identified emergency medical services systems were those that had recently reported significant improvements in neurologically intact survival after introducing a more comprehensive approach involving citizens, hospitals, and evolving strategies for incorporating technology-based, highly choreographed care and training. Detailed inventories of in-common elements were collated from the ten 9-1-1 agencies and assimilated. For reference, combined averaged outcomes for out-of-hospital cardiac arrest occurring January 1, 2017, to February 28, 2018, were compared with concurrent U.S. outcomes reported by the well-established Cardiac Arrest Registry to Enhance Survival. Interventions: Most commonly, interventions and components from the ten 9-1-1 systems consistently included extensive public cardiopulmonary resuscitation training, 9-1-1 system-connected smart phone applications, expedited dispatcher procedures, cardiopulmonary resuscitation quality monitoring, mechanical cardiopulmonary resuscitation, devices for enhancing negative intrathoracic pressure regulation, extracorporeal membrane oxygenation protocols, body temperature management procedures, rapid cardiac angiography, and intensive involvement of medical directors, operational and quality assurance officers, and training staff. Measurements and Main Results: Compared with Cardiac Arrest Registry to Enhance Survival (n = 78,704), the cohorts from the 10 emergency medical services agencies examined (n = 2,911) demonstrated significantly increased likelihoods of return of spontaneous circulation (mean 37.4% vs 31.5%; p < 0.001) and neurologically favorable hospital discharge, particularly after witnessed collapses involving bystander cardiopulmonary resuscitation and shockable cardiac rhythms (mean 10.7% vs 8.4%; p < 0.001; and 41.6% vs 29.2%; p < 0.001, respectively). Conclusions: The likelihood of neurologically favorable survival following out-of-hospital cardiac arrest can improve substantially in communities that conscientiously and meticulously introduce a well-sequenced, highly choreographed, system-wide portfolio of both traditional and nonconventional approaches to training, technologies, and physiologic management. The commonalities found in the analyzed systems create a compelling case that other communities can also improve out-of-hospital cardiac arrest outcomes significantly by conscientiously exploring and adopting similar bundles of system organization and care.
... Likewise, assisted breathing components not only require attention to the frequency, force, and speed of delivery of each breath but also the actual volume and the rapid release of each positive pressure breath once delivered. These ventilatory variables significantly impact circulation and thus the effectiveness of other interventions, including medications, and CPR itself (5,9,10). In addition, all of these factors need to be well-controlled and adjusted under certain conditions, particularly when flow-enhancing devices are used or when spontaneous circulation or respirations resume (9). ...
... These ventilatory variables significantly impact circulation and thus the effectiveness of other interventions, including medications, and CPR itself (5,9,10). In addition, all of these factors need to be well-controlled and adjusted under certain conditions, particularly when flow-enhancing devices are used or when spontaneous circulation or respirations resume (9). ...
... Most of those trials were typically perplexed by the pivotal interactive nature of various interdependent variables. In addition, underrecognized confounding factors such as suboptimal quality of CPR, overzealous positive pressure ventilation, time delays to interventions, and many other systematic factors played large roles (9,10,14,17,19,21,23,31,(35)(36)(37)(38). Low survival rates create further statistical quandaries, especially in essential subgroup analyses. ...
... Several studies have reported significant rates of misplacement of the tube, insertion failure, iatrogenic hyperventilation, and chest compression interruptions during ETI [7,8]. SGA insertion can be performed rapidly and requires brief training compared to that required for ETI; however, SGA might lead to misplacement of the tube, airway trauma, and aspiration of gastric content compared with ETI [9,10]. Some studies reported decreased carotid artery blood flow after the insertion of SGA in a porcine model [11]. ...
... Several studies, including one meta-analysis, have reported that a longer TTI is not associated with decreased survival [9,10,16]. However, Park et al. [21] reported a longer TTI had a negative effect on the neurological outcome in OHCA patients without prehospital ROSC, by analyzing the national OHCA registry of Korea. ...
Article
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Introduction Despite numerous studies on airway management in out-of-hospital cardiac arrest (OHCA) patients, the choice of prehospital airway management technique remains controversial. Our study aimed to investigate the association between prehospital advanced airway management and survival outcomes according to a transport time interval (TTI) using nationwide OHCA registry database in Korea. Methods The inclusion criteria were patients with OHCA aged over 18 years old with a presumed cardiac etiology between January 2015 and December 2018. The primary outcome was survival to hospital discharge. The main exposure was the prehospital airway management technique performed by the emergency medical technicians (EMTs), classified as bag-valve mask (BVM), supraglottic airway (SGA), or endotracheal intubation (ETI).We performed multivariable logistic regression analysis and interaction analysis between the type of airway management and TTI for adjusted odds ratios (aORs) and 95% confidence intervals (CIs). Results Of a total of 70,530 eligible OHCA patients, 26,547 (37.6%), 38,391 (54.4%), and 5,592 (7.9%) were managed with BVM, SGA, ETI, respectively. Patients in the SGA and ETI groups had a higher odds of survival to discharge than BVM groups (aOR, 1.11 (1.05–1.16) and 1.13 (1.05–1.23)). And the rates of survival to discharge with SGA and ETI were significantly higher in groups with TTI more than 8 minutes (1.17 (1.08–1.27) and 1.38 (1.20–1.59)). Conclusion The survival to discharge was significantly higher among patients who received ETI and SGA than in those who received BVM. The transport time interval influenced the effect of prehospital airway management on the clinical outcomes after OHCA.
... The current recommendation to ventilate at a rate of one breath every 6 s when an advanced airway is in place is based on observational studies demonstrating that hyperventilation is common during CPR [6]. Cardiopulmonary resuscitation studies using a pig model further demonstrate that hyperventilation during CPR is associated with an increase in intrathoracic pressure, decrease in coronary and cerebral perfusion, and decreased rates of return of spontaneous circulation [7,8]. ...
... Excessive ventilation and associated hypocapnia results in respiratory alkalosis, inducing cerebral vasoconstriction further limiting oxygen delivery to the brain, which has already likely experienced significant hypoxia from the cardiac arrest no-flow state. Alkalosis also shifts the oxyhemoglobin curve to the left, possibly reducing oxygen off-loading to tissues [7,[22][23][24]. These findings, suggesting that the optimal PEEP during CPR should be less than 10 cmH 2 O when lung compliance is high, are in line with results from another study by our laboratory, which demonstrate that in terms of oxygen delivery during CPR, the optimal PEEP level was a PEEP of 5 cmH 2 O, which optimized both oxygenation and cardiac output to achieve the best oxygen delivery [18]. ...
Article
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Background Compressions given during cardiopulmonary resuscitation generate small, ineffective passive ventilations through oscillating waves. Positive end-expiratory pressure increases the volume of these passive ventilations; however, its effect on passive ventilation is unknown. Our objective was to determine if increasing positive end-expiratory pressure during cardiopulmonary resuscitation increases passive ventilation generated by compressions to a clinically significant point. This study was conducted on 13 Landrace-Yorkshire pigs. After inducing cardiac arrest with bupivacaine, cardiopulmonary resuscitation was performed with a LUCAS 3.1. During cardiopulmonary resuscitation, pigs were ventilated at a positive end-expiratory pressure of 0, 5, 10, 15, 20 cmH 2 O (randomly determined) for 9 min. Using the NM3 respiratory monitoring device, expired minute ventilation and volumetric capnography were measured. Arterial blood gas was obtained for each positive end-expiratory pressure level to compare the effects of positive end-expiratory pressure on carbon dioxide. Results Increasing positive end-expiratory pressure from 0 to 20 cmH 2 O increased the mean (SEM) expired minute ventilation from 6.33 (0.04) to 7.33 (0.04) mL/min. With the 5-cmH 2 O incremental increases in positive end-expiratory pressure from 0 to 20 cmH 2 O, volumetric capnography increased from a mean (SEM) of 94.19 (0.78) to 115.18 (0.8) mL/min, except for 15 cmH 2 O, which showed greater carbon dioxide exhalation with volumetric capnography compared with 20 cmH 2 O. PCO 2 declined significantly as positive end-expiratory pressure was increased from 0 to 20 cmH 2 O. Conclusions When increasing positive end-expiratory pressure from 0 to 20, the contribution to overall ventilation from gas oscillations generated by the compressions became more significant, and may even lead to hypocapnia, especially when using positive end-expiratory pressures between 15 and 20.
... 51 However, increased intrathoracic pressure also reduces venous return to the right side of the heart and high intrathoracic pressures during CPR have been found to correlate inversely to CPP and cerebral blood flow. 52 In summary, hypoventilation during CPR can cause hypoxia and hypercarbia, 53 while hyperventilation may adversely affect circulation. 52 There is arguably a balance between too much and too little ventilation during CPR. ...
... 52 In summary, hypoventilation during CPR can cause hypoxia and hypercarbia, 53 while hyperventilation may adversely affect circulation. 52 There is arguably a balance between too much and too little ventilation during CPR. ...
Article
Full-text available
Out of Hospital Cardiac Arrest (OHCA) is a major cause of death in the western world with an estimated number of 275 000 treated with resuscitation attempts by the Emergency Medical Services (EMS) in Europe each year. Overall survival rates remain low, and most studies indicate that around 1 out 10 will survive to 30 days. Among the strongest factors associated with survival in OHCA is first recorded rhythm amendable to defibrillation, early defibrillation and prompt initiation of Cardiopulmonary resuscitation (CPR). Overall, CPR started prior to EMS arrival has repeatedly been shown to be associated with survival rates 2‐3 times higher compared with no such initiation. The primary goal of CPR is to generate sufficient blood flow to vital organs, mainly the brain and heart, until restoration of spontaneous circulation can be achieved. Barriers to the initiation of CPR by bystanders in OHCA include fear of being incapable, causing harm, and transmission of infectious diseases. Partly due to these barriers, and low rates of CPR, the concept of CPR with compression only was proposed as a simpler form of resuscitation with the aim to be more widely accepted by the public in the 1990s. But how reliable is the evidence supporting this simpler form of CPR, and are the outcomes after CO‐CPR comparable to standard CPR? Abstract
... 6,7,9 Furthermore, despite good training and experience, health care professionals tend to excessively ventilate during CA, 10,11 resulting in increased intrathoracic pressure blocking venous return. 12,13 In practice, many ventilation strategies are used, sometimes in contradiction with published guidelines. 14 Constant flow insufflation of oxygen (CFIO) is a new technology that could potentially improve ventilation and facilitate CA management. ...
... 16,17 Negative intrathoracic pressure obtained with CFIO during decompression could be beneficial, as excessive ventilation often performed by rescuers is known to significantly alter venous return and reduce chances of ROSC. 12,13,18,19 Despite recent studies published on this technology, its impact on patient-centered outcomes are uncertain. 20, 21 We performed a systematic review to synthetize and assess the evidence, for both human and animal studies, regarding the effect of CFIO as the ventilation mode during CA on the rate of ROSC. ...
Article
Objective: To synthetize the evidence regarding the effect of constant flow insufflation of oxygen (CFIO) on the rate of return of spontaneous circulation (ROSC) and other clinical outcomes during cardiac arrest (CA). Methods: A systematic review was performed using four databases (PROSPERO: CRD42020071960). Studies reporting on adult CA patients or on animal models simulating CA and assessing the effect of CFIO on ROSC or other clinical outcomes were considered. Results: A total of 3540 citations were identified, of which 16 studies were included. Four studies (two randomized controlled trials (RCT), two cohort studies), reported on humans while 12 studies used animal models. No meta-analysis was performed due to clinical heterogeneity. There were no differences in the ROSC (18.9% vs 20.8%, p = 0.99; 27.1% vs 21.3%, p = 0.51) and sustained ROSC rates (16.1% vs 17.3%, p = 0.81; 12.5% vs 14.9%, p = 0.73) with CFIO compared to intermitant positive pressure ventilation (IPPV) in the two human RCTs. Survival to ICU discharge was similar between CFIO (2.3%) and IPPV (2.3%) in the largest RCT (p = 0.96). Human studies were at serious or high risk of bias. In animal models' studies, ROSC rates were presented in seven RCTs. CFIO was superior to IPPV in one trial, but was associated with similar ROSC rates using different ventilation strategies in the remaining six studies. Conclusions: No definitive association between CFIO and ROSC, sustained ROSC or survival compared to other ventilation strategies could be demonstrated. Future studies should assess CFIO effect on post-survival neurological functions and patient-important CA outcomes.
... During CPR, the purpose of ventilation is to ensure that sufficient oxygen is supplied and carbon dioxide (CO 2 ) is removed, thereby maintaining proper blood oxygen and CO 2 levels. Simultaneously, another important principle of ventilation is to avoid adverse effects on hemodynamics (11)(12)(13). Thus, it is not reasonable to evaluate ventilation status using RR, VT, or minute volume (MV) alone. ...
... Although the guidelines recommend that the provider should deliver 10 breaths per min when ventilating via an advanced airway, hyperventilation during advanced life support remains common among uncertified or inexperienced CPR providers (22). An inappropriately high RR (>25 breaths/min) is commonly observed during CPR (11,23). For this reason, capnography is important as a continuous monitoring method to avoid hyperventilation. ...
Article
Background: Volumetric capnography is increasingly being applied in cardiopulmonary resuscitation. However, during cardiopulmonary resuscitation, the abnormal ventilation state affects the monitoring effect of the most commonly used capnography-derived parameter, the partial carbon dioxide end-tidal pressure (PetCO2). In this study, we evaluated the ability of a new volumetric capnography-derived parameter, the ratio between the PetCO2 and the volume of carbon dioxide (CO2) eliminated per min and per kilogram of body weight, for detecting hyperventilation during cardiopulmonary resuscitation. Methods: We used 12 porcine models of primary ventricular fibrillation-induced cardiac arrest. Ventricular fibrillation was induced and left untreated for 4 min. Standardized chest compressions were performed throughout the experiment using mechanical cardiopulmonary resuscitation. Following 5 min of normal ventilation as a washout period, each animal underwent 4 types of ventilation. The main outcome measures were the PetCO2, the ratio between the PetCO2 and the volume of CO2 eliminated per min and per kilogram of body weight with each ventilation type. Results: Different ventilation types had a significant effect on the volumetric capnography-derived parameters. The PetCO2 and ratio between the PetCO2 and the volume of CO2 eliminated per min and per kilogram of body weight values during cardiopulmonary resuscitation was significantly higher in non-hyperventilating than in hyperventilating animals. The ratio reflected hyperventilation accurately and immediately, with an area under the curve (AUC) of 0.98. The optimal cut-off point of the ratio for discriminating hyperventilation from non-hyperventilation was 6.36, with a sensitivity and specificity of 0.99 and 0.89, respectively. Conclusions: The ratio between the PetCO2 and the volume of CO2 eliminated per min and per kilogram of body weight showed good performance in discriminating hyperventilation from non-hyperventilation and was sensitive to changes in ventilation status. This ratio may be a valuable clinical indicator for monitoring the ventilation status during cardiopulmonary resuscitation.
... 16 Gould et al. (2020) found similar results when they used a VFD to improve poor rescuer performance when delivering ventilations. Ventilation rates improved from 41À71% and tidal volume from 31% to 78%. 17 The effect of delivering ventilations during OHCA outside of recommendations are well documented and are known to reduce coronary perfusion pressure, 18,19 increase pulmonary vascular resistance and decrease cardiac output. 20 Aufderheide et al. (2004) conducted a porcine study to determine the association between hyperventilation increased mortality. ...
... 20 Aufderheide et al. (2004) conducted a porcine study to determine the association between hyperventilation increased mortality. 19 In their cardiac arrest model, they demonstrated a reduction in ventilation rate from 30 breaths per minute to 12, with 100% oxygen, increased survival rate from 17% to 86%. Given that participants in this study were experienced clinicians undertaking a variety of clinical roles, who regularly ventilate patients in clinical practice, many were naive to the unintended consequences of delivering ventilations outside of recommendations. ...
Article
Full-text available
Background Research suggests rescuers deliver ventilations outside of recommendations during out of hospital cardiac arrest (OHCA), which can be deleterious to survival. We aimed to determine if ambulance clinician compliance with ventilation recommendations could be improved using the Zoll Accuvent real time ventilation feedback device (VFD). Methods Participants simulated a two-minute cardiac arrest scenario using a mannequin and defibrillator without ventilation feedback. Eligible for inclusion were all clinicians aged ≥18 years who perform cardiopulmonary resuscitation (CPR) as part of their role, who had completed an internal advanced life support (ALS) refresher. Following familiarisation of a few minutes with the VFD, participants repeated the two-minute scenario with ventilation feedback. Ventilation rate and volume and CPR quality were recorded. Primary outcome was % difference in ventilation compliance with and without feedback. Secondary outcomes were differences between paramedic and non-paramedic clinicians and compliance with chest compression guidelines. Results One hundred and six participants completed the study. Median ventilation rate without feedback was 10 (IQR 8–14, range 4–30) compared to 9 (IQR 9–9, range 6–17) with feedback; median tidal volume without feedback was 630 mls (IQR 518–725, range 201–1114) compared to 546 mls (IQR 531–560, range 490–750) with feedback. Proportion of clinicians ≥50% compliant with European Resuscitation Council ventilation recommendations were significantly greater with ventilation feedback compared to without, 91% vs. 9%, (McNemars test p = <0.0001). Paramedics out performed non-paramedic clinicians with and without feedback and compression quality was not compromised by using the VFD. Conclusions Ambulance clinician baseline ventilation quality was frequently outside of recommendations, but a VFD can ensure treatment is within evidence-based recommendations. Further research is required to validate the use of the VFD in true clinical practice and to evaluate the relationship between improved ventilation quality during OHCA and patient outcomes.
... However, PetCO 2 is dependent on multiple variables including minute ventilation, ventilation perfusion mismatch, and mechanical complications. Clinical and animal experimental data show that hyperventilation during resuscitation significantly reduces the value of PetCO 2 [14][15][16][17]. Despite these limitations, capnography is an appealing monitoring tool during CPR because of its simplicity, availability, real-time monitoring, and noninvasive technique [18]. ...
Article
Full-text available
We aimed to evaluate a volumetric capnography (Vcap)-derived parameter, the volume of CO2 eliminated per minute and per kg body weight (VCO2/kg), as an indicator of the quality of chest compression (CC) and to predict the return to spontaneous circulation (ROSC) under stable ventilation status. Twelve male domestic pigs were utilized for the randomized crossover study. After 4 min of untreated ventricular fibrillation (VF), mechanical cardiopulmonary resuscitation and ventilation were administered. Following 5-min washout periods, each animal underwent two sessions of experiments: three types of CC quality for 5 min stages in the first session, followed by advanced life support, consecutively in two sessions. Different CC quality had a significant effect on the partial pressure of end-tidal carbon dioxide (PetCO2), VCO2/kg, aortic pressure (mean), aortic systolic pressure, aortic diastolic pressure, right atrial pressure (mean), and carotid blood flow (P < 0.05). With the improvement in CC quality, the values of PetCO2 and VCO2/kg also increased, and the difference between the groups was statistically significant (P < 0.05). The Spearman rank test revealed a significant correlation between the Vcap-derived parameters and hemodynamics. PetCO2 and VCO2/kg have similar capabilities for discriminating survivors from non-survivors, and the area under the curve for both was 0.97. VCO2/kg had similar performance as PetCO2 in reflecting the quality of CC and prediction of achieving ROSC under stable ventilation status in a porcine model of VF-related cardiac arrest. However, VCO2/kg requires a longer time to achieve a stable state after adjusting for quality of CC than PetCO2.
... These findings sparked a broad academic discourse 5 and triggered a reprint of the same results under the title "Death by hyperventilation: A common and life-threatening problem during cardiopulmonary resuscitation". 6 In the following year ILCOR included those publications into the Consensus of Science with Treatment Recommendations. 7 Much less attention was spent on the work of Gazmuri et al., published in 2011, which could not reproduce the deleterious hemodynamic effects of hyperventilation, also in a pig model during cardiac arrest, with ventilatory rates of 33 min À1 and tidal volumes of 18 mL/kg body weight. ...
... This is deeply associated with the survival rate as well as oxygenation of patients with cardiac or respiratory arrest (2). Excessive ventilation, however, results in signi cantly increased intrathoracic pressure and decreased coronary perfusion pressures and survival rates (3,4). Rescuers seal the mask against the face using either one-or two-handed techniques, with the thumb and index nger wrapped in a " C "shape around the mask apex, and the remaining ngers in an "E" shape, lifting the jaw (5); this is called the "EC grip". ...
Preprint
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Background For adequate ventilation during bag-valve-mask ventilation, rescuers should ensure a proper mask seal using the one-handed or two-handed technique. Little is known how much sealing forces of bag-valve-mask are needed for adequate ventilation. This study aimed to explored the effect of the 4-point sealing forces of a bag-valve-mask on tidal volume while using the one-handed technique, focusing on the moderating effect of C length ( C length is the distance from the thumb to index finger in the C shape of in the one-hand EC grip). Methods This was a prospective, descriptive simulation study design. Convenience sample of 125 undergraduate paramedic students from two universities was participated. A self-reported questionnaire was used to collect subject data. Tidal volumes, 4-point sealing forces of the mask, peak pressure, and C length of the C shape in the one-hand EC grip, were measured using the mechanical lung model under a simulated adult respiratory arrest. Hierarchical regression analysis was used to determine the moderating effect of C length on tidal volume in bag-valve-mask ventilation. Results The average C length, peak pressure and tidal volume were 7.54 (± 1.85) cm, 11.62 (± 5.40) cmH2O, and 321.66 (± 135.18) mL, respectively. The average range of the 4-point sealing forces were 0.03–0.69 newton. The apex sealing force was the weakest point among the 4-point sealing forces. Hierarchical regression analysis demonstrated that tidal volume accounted for 62.7% of the variance by C length, peak pressure, and apex sealing force during bag-valve-mask ventilation (F = 9.676, p < .001). C length moderated the effect of apex sealing force and peak pressure on tidal volume. That is, the more peak pressure and apex sealing force, the more the tidal volume, and the longer the C length, the more the tidal volume. Conclusion We developed effective advice that can be adopted in clinical practice without side effects as the first simulation study measuring the 4-point sealing forces during bag-valve-mask ventilation, as well as underpin continuous retraining and assessment that focus on individual physical characteristics, such as C length and bag-valve-mask sealing force.
... Mechanical ventilation assisted with typical bag valve mask is predominantly used procedures to deliver manually some positive pressure in the ventilation process to the human subjects suffering critically from respiratory ailments [11][12][13][14][15][16][17][18]. From the time period of mid-sixteenth century till the early twentieth century, specially fabricated ventilation techniques described in the contemporary literature refer only typical mouth to mouth modes of operation and the practice of using bellows [1,[19][20][21][22][23][24][25][26][27][28][29][30][31][32][33]. In fact, in the fifteenth century, Paulus Bagellardus, a professor of medicine at the University of Padua, reported the first known documents on neonatal ailments and discussed general mouth-to-mouth resuscitation aided by advising midwives to deliver oxygenated air pressure into the mouths of the newly born subjects if there is the possibility of the absence of respiratory activities [3,5]. is occurrence manifested that mouth-tomouth mode-based ventilation strategies were already in vogue at that period of time. ...
Article
Full-text available
The outbreak of novel COVID-19 has severely and unprecedentedly affected millions of people across the globe. The painful respiratory distress caused during this disease calls for external assistance to the victims in the form of ventilation. The most common types of artificial ventilating units available at the healthcare facilities and hospitals are exorbitantly expensive to manufacture, and their number is fairly inadequate even in the so-called developed countries to cater to the burning needs of an ever-increasing number of ailing human subjects. According to available reports, without the provision of ventilation, the novel COVID-19 patients are succumbing to their ailments in a huge number of cases. This colossal problem of the availability of ventilator units can be addressed to a great extent by readily producible and cost-effective ventilating units that can be used on those suffering patients during an acute emergency and in the absence of conventional expensive ventilators at hospitals and medical care units. This paper has made an attempt to design and simulate a simple, yet effective, mechanized ventilator unit, which can be conveniently assembled without a profuse skillset and operated to resuscitate an ailing human patient. The stepper motor-controlled kinematic linkage is designed to deliver the patient with a necessitated discharge of air at optimum oxygen saturation through the AMBU bag connected in a ventilation circuit. With the associated code on MATLAB, the motor control parameters such as angular displacement and speed are deduced according to the input patient conditions (age group, tidal volume, breathing rate, etc.) and thereafter fed to the controller that drives the stepper motor. With a proposed feedback loop, the real-time static and dynamic compliance, airway resistance values can be approximately determined from the pressure variation cycle and fed to the controller unit to adjust the tidal volume as and when necessary. The simplistic yet robust design not only renders easy manufacturability by conventional and rapid prototyping techniques like 3D printing at different scales but also makes the product easily portable with minimal handling difficulty. Keeping the motto of Health for All as envisioned by the WHO, this low-cost indigenously engineered ventilator will definitely help the poor and afflicted towards their right to health and will help the medical professionals buy some time to manage the patient with acute respiratory distress syndrome (ARDS) towards recovery. Moreover, this instrument mostly includes readily available functional units having standard specifications and can be considered as standard bought-out items.
... For asynchronous ventilation during ongoing compressions, ventilation frequency can be adjusted. An optimal ventilation frequency, sufficient for adequate oxygenation, but as few as possible to prevent a high intrathoracic pressure with a decrease in venous return, is assumed [72]. The current recommended ventilation frequency of 10 ventilations per minute is based on animal studies [73]. ...
Article
Full-text available
Airway management and ventilation are essential components of cardiopulmonary resuscitation to achieve oxygen delivery in order to prevent hypoxic injury and increase the chance of survival. Weighing the relative benefits and downsides, the best approach is a staged strategy; start with a focus on high-quality chest compressions and defibrillation, then optimize mask ventilation while preparing for advanced airway management with a supraglottic airway device. Endotracheal intubation can still be indicated, but has the largest downsides of all advanced airway techniques. Whichever stage of airway management, ventilation and chest compression quality should be closely monitored. Capnography has many advantages and should be used routinely. Optimizing ventilation strategies, harmonizing ventilation with mechanical chest compression devices, and implementation in complex and stressful environments are challenges we need to face through collaborative innovation, research, and implementation.
... Advanced airway procedures should be attempted by experienced and skilled providers to avoid prolonged interruptions of chest compressions and to delay defibrillation [3,5]. Advanced airway techniques in the out-of-hospital setting have been associated with increased hands-off time and hyperventilation, causing decreased coronary perfusion pressures (in animal studies) and increased mortality [8][9][10][11][12][13]. Although the use of BVM and laryngeal mask airway (LMA) is simple and quick in emergencies and requires minimal training, these devices are used less frequently. ...
Article
Background There is a lack of studies addressing the short and long-term outcomes of using different airway interventions in patients with cardiopulmonary arrest in the emergency department (ED). This retrospective chart review aimed to investigate the effect of endotracheal intubation (ETI) versus no ETI during cardiopulmonary arrest in the ED on return of spontaneous circulation (ROSC) and survival to discharge. Methodology A total of 168 charts were reviewed from August 2017 to April 2019. Resuscitation characteristics were obtained from Utstein-style-based cardiopulmonary arrest flow sheets. Results Unadjusted analysis showed no difference in ROSC (45.5% in ETI vs. 54.5% in no-ETI) (p = 0.08) and survival to hospital discharge at 28 days (26.7% in ETI vs. 73.3% in non-ETI) (p = 0.07) when comparing ETI versus non-ETI airway management methods during cardiopulmonary resuscitation (CPR). After adjusting for confounding factors, our regression analysis revealed that the use of ETI is associated with lower odds of ROSC (odds ratio [OR] = 3.40, 95% confidence interval [CI] = [0.14-0.84]) and survival to hospital discharge at 28 days (OR = 0.20, 95% CI = [0.04-0.84]). Conclusions ETI during CPR in the ED is associated with worse ROSC and survival to hospital discharge at 28 days.
... To the Editor, current guidelines on cardiopulmonary resuscitation (CPR) urge avoidance of hyperventilation based on a small number of studies that have reported hyperventilation to be common in CPR and associated high ventilation rates with adverse outcomes [1][2][3]. Contrarily, studies analysing arterial blood gases during CPR at our institution suggest that hypercapnia and acidaemia, mostly caused by hypoventilation, are commonly encountered [4,5]. We hypothesise low ventilation rates to be the cause for these findings: at a rate of 10 breaths per minute, inspiration-to-expiration ratio of 1:2, and J o u r n a l P r e -p r o o f ongoing chest compressions at a rate of 100 min -1 , 3 compressions coincide with every breath and obstruct ventilation. ...
... This is deeply associated with the survival rate as well as oxygenation of patients with cardiac or respiratory arrest [2]. However, excessive ventilation results in significantly increased intrathoracic pressure and decreased coronary perfusion pressures and survival rates [3,4]. Rescuers seal the mask against the face using either one-or two-handed techniques, with the thumb and the index finger wrapped in a "C" shape around the mask apex, and the remaining fingers in an "E" shape, lifting the jaw [5]; this is called the "EC grip". ...
Article
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Background For adequate ventilation during bag-valve-mask ventilation, rescuers should ensure a proper mask seal using the one-handed or two-handed technique. Little is known about the magnitude of sealing forces of a bag-valve-mask needed for adequate ventilation. This study aimed to explore the effect of the 4-point sealing forces of a bag-valve-mask on tidal volume while using the one-handed technique, focusing on the moderating effect of C length (the distance from the thumb to the index finger in the C shape of the one-hand EC grip). Methods A prospective, descriptive simulation study was conducted. A convenience sample of 125 undergraduate paramedic students from two universities was recruited. A self-reported questionnaire was used to collect subjective variables. Tidal volumes, 4-point sealing forces of the mask, peak pressure, and C length of the C shape in the one-hand EC grip were measured using the mechanical lung model under a simulated adult respiratory arrest. Hierarchical regression analysis was used to determine the moderating effect of C length on tidal volume in bag-valve-mask ventilation. Results The average C length, peak pressure, and tidal volume were 7.54 (± 1.85) cm, 11.62 (± 5.40) cmH 2 O, and 321.66 (± 135.18) mL, respectively. The average range of the 4-point sealing forces was 0.03–0.69 N. The apex sealing force was the weakest among the 4-point sealing forces. Hierarchical regression analysis demonstrated that tidal volume accounted for 62.7% of the variance by C length, peak pressure, and apex sealing force during bag-valve-mask ventilation (F = 9.676, p < 0.001). C length moderated the effect of the apex sealing force and peak pressure on the tidal volume, meaning the higher the peak pressure and apex sealing force, the more the tidal volume and the longer the C length. Conclusion This first simulation study measuring the 4-point sealing forces during bag-valve-mask ventilation provides effective advice that can be adopted in clinical practice without side effects and underpins the importance of continuous retraining and assessment focused on individual physical characteristics, such as C length and bag-valve-mask sealing forces.
... PLR mimics rapid volume expansion and is often used in intensive care units during the hemodynamic assessment of patients [7]. During CPR, cardiac output is limited, leading to a low flow state [8,9]. Increasing the venous and arterial bed resistances can improve myocardial and cerebral blood flow [10]. ...
Article
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Background There are data suggesting that passive leg raising (PLR) improves hemodynamics during cardiopulmonary resuscitation (CPR). This trial aimed to determine the effectiveness and safety of PLR during CPR in out-of-hospital cardiac arrest (OHCA). Methods We conducted a randomized controlled trial with blinded assessment of the outcomes that assigned adults OHCA to be treated with PLR or in the flat position. The trial was conducted in the Camp de Tarragona region. The main end point was survival to hospital discharge with good neurological outcome defined as cerebral performance category (CPC 1–2). To study possible adverse effects, we assessed the presence of pulmonary complications on the first chest X-rays, brain edema on the computerized tomography (CT) in survivors and brain and lungs weights from autopsies in non-survivors. Results In total, 588 randomized cases were included, 301 were treated with PLR and 287 were controls. Overall, 67.8% were men and the median age was 72 (IQR 60–82) years. At hospital discharge, 3.3% in the PLR group and 3.5% in the control group were alive with CPC 1–2 (OR 0.9; 95% CI 0.4–2.3, p = 0.91). No significant differences in survival at hospital admission were found in all patients (OR 1.0; 95% CI 0.7–1.6, p = 0.95) and among patients with an initial shockable rhythm (OR 1.7; 95% CI 0.8–3.4, p = 0.15). There were no differences in pulmonary complication rates in chest X-rays [7 (25.9%) vs 5 (17.9%), p = 0.47] and brain edema on CT [5 (29.4%) vs 10 (32.6%), p = 0.84]. There were no differences in lung weight [1223 mg (IQR 909–1500) vs 1239 mg (IQR 900–1507), p = 0.82] or brain weight [1352 mg (IQR 1227–1457) vs 1380 mg (IQR 1255–1470), p = 0.43] among the 106 autopsies performed. Conclusion In this trial, PLR during CPR did not improve survival to hospital discharge with CPC 1–2. No evidence of adverse effects has been found. Clinical trial registration ClinicalTrials.gov: NCT01952197, registration date: September 27, 2013, https://clinicaltrials.gov/ct2/show/NCT01952197 .
... Another contributing factor is hyperventilation, which may occur more frequently with advanced airways (SGA or A c c e p t e d M a n u s c r i p t ETI) than with BVM. Hyperventilation has been shown to adversely impact patient outcomes in part by increasing intrathoracic pressure and decreasing venous return, ultimately leading to decreased cerebral and coronary perfusion pressures (69)(70)(71)(72)(73). ...
Article
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Objective. To assess comparative benefits and harms across three airway management approaches (bag valve mask [BVM], supraglottic airway [SGA], and endotracheal intubation [ETI]) used by prehospital emergency medical services (EMS) to treat patients with trauma, cardiac arrest, or medical emergencies, and how they differ based on techniques and devices, EMS personnel and patient characteristics. Data sources. We searched electronic citation databases (Ovid® MEDLINE®, CINAHL®, the Cochrane Central Register of Controlled Trials, the Cochrane Database of Systematic Reviews, and Scopus®) from 1990 to September 2020. Review methods. We followed Agency for Healthcare Research and Quality Effective Health Care Program Methods guidance. Outcomes included mortality, neurological function, return of spontaneous circulation (ROSC), and successful advanced airway insertion. Meta-analyses using profile-likelihood random effects models were conducted, with analyses stratified by study design, emergency type, and age. Results. We included 99 studies involving 630,397 patients. We found few differences in primary outcomes across airway management approaches. For survival, there was no difference for BVM versus ETI or SGA in adult and pediatric patients with cardiac arrest or trauma. For neurological function, there was no difference for BVM versus ETI and SGA versus ETI in pediatric patients with cardiac arrest. There was no difference in BVM versus ETI in adults with cardiac arrest, but improved neurological function with BVM or ETI versus SGA. There was no difference in ROSC for patients with cardiac arrest for BVM versus ETI or SGA in adults and pediatrics, or SGA versus ETI in pediatrics. There was higher frequency of ROSC in adults with SGA versus ETI. For successful advanced airway insertion, there was higher first-pass success with SGA versus ETI for all patients except adult medical patients (no difference), and no difference in overall success using SGA versus ETI in adults. Conclusions. The currently available evidence does not indicate benefits of more invasive airway approaches based on survival, neurological function, ROSC, or successful airway insertion. Strength of evidence was low or moderate; most included studies were observational. This supports the need for high-quality randomized controlled trials to advance clinical practice and EMS education and policy, and improve patient-centered outcomes.
... Excessive ventilation rates lead to untoward increases in intrathoracic pressure, decreased venous return, increased intracranial pressure, as well as high no flow times and prolonged pauses in CPR (24). Providers frequently overventilate while delivering BVM (5,25,26). However, compression-only CPR has not been shown to result in better outcomes in adult studies and is not recommended either in the adult or in the pediatric population (27). ...
Article
Objectives: To determine the impact of a cardiopulmonary resuscitation coach on the frequency and duration of pauses during simulated pediatric cardiac arrest. Design: This is a secondary analysis of video data collected from a prospective multicenter trial. Forty simulated pediatric cardiac arrest scenarios (20 noncoach and 20 coach teams), each lasting 18 minutes in duration, were reviewed by three clinical experts to document events surrounding each pause in chest compressions. Setting: Four pediatric academic medical centers from Canada and the United States. Subjects: Two-hundred healthcare providers in five-member interprofessional resuscitation teams that included either a cardiopulmonary resuscitation coach or a noncoach clinical provider. Interventions: Teams were randomized to include either a trained cardiopulmonary resuscitation coach or an additional noncoach clinical provider. Measurements and main results: The frequency, duration, and associated factors with each interruption in chest compressions were recorded and compared between the groups with and without a cardiopulmonary resuscitation coach, using t tests, Wilcoxon rank-sum tests, or chi-squared tests, depending on the distribution and types of outcome variables. Mixed-effect linear models were used to explore the effect of cardiopulmonary resuscitation coaching on pause durations, accounting for multiple measures of pause duration within teams. A total of 655 pauses were identified (noncoach n = 304 and coach n = 351). Cardiopulmonary resuscitation-coached teams had decreased total mean pause duration (98.6 vs 120.85 s, p = 0.04), decreased intubation pause duration (median 4.0 vs 15.5 s, p = 0.002), and similar mean frequency of pauses (17.6 vs 15.2, p = 0.33) when compared with noncoach teams. Teams with cardiopulmonary resuscitation coaches are more likely to verbalize the need for pause (86.5% vs 73.7%, p < 0.001) and coordinate change of the compressors, rhythm check, and pulse check (31.7% vs 23.2%, p = 0.05). Teams with cardiopulmonary resuscitation coach have a shorter pause duration than non-coach teams, adjusting for number and types of tasks performed during the pause. Conclusions: When compared with teams without a cardiopulmonary resuscitation coach, the inclusion of a trained cardiopulmonary resuscitation coach leads to improved verbalization before pauses, decreased pause duration, shorter pauses during intubation, and better coordination of key tasks during chest compression pauses.
... The least sensible trigger pressure on the ventilator settings (−20 cmH 2 O) was effective in avoiding those undesired cycles, maintaining the respiratory rate similar to precompression conditions [10]. This is of considerable importance since it has been shown that hyperventilation during CPR [11] may lead to higher intrathoracic pressures, decreased coronary perfusion pressures, induce hypotension and consequently death [12,13]. ...
Article
Background: Cardiac arrest is a critical event requiring adequate and timely response in order to increase a patient's chance of survival. In patients mechanically ventilated with advanced airways, cardiopulmonary resuscitation (CPR) maneuver may be simplified by keeping the ventilator on. This work assessed the response of an intensive care mechanical ventilator to CPR using a patient manikin ventilated in three conventional modes. Methods: Volume-controlled (VCV), pressure-controlled (PCV) and pressure regulated volume-controlled (PRVC) ventilation were applied in a thorax physical model, with or without chest compressions. The mechanical ventilator was set with inspiratory time of 1.0 s, ventilation rate of 10 breaths/minute, positive end-expiratory pressure of 0 cmH 2 O, FiO2 of 1.0, target tidal volume of 600 ml and trigger level of-20 cmH 2 O. Airway opening pressure and ventilatory flow signals were continuously recorded. Results: Chest compression resulted in increased airway peak pressure in all ventilation modes (p<0.001), especially with VCV (137% in VCV, 83% in PCV, 80% in PRVC). However, these pressures were limited to levels similar to release valves in manual resuscitators (~60 cmH 2 O). In pressure-controlled modes tidal/minute volumes decreased (PRVC=11%, p=0.027 and PCV=12%, p<0.001), while still within the variability observed during bag-valve-mask ventilation. During VCV, variation in tidal/minute volumes were not significant (p=0.140). Respiratory rate did not change with chest compression. Conclusions: Volume and pressure ventilation modes responded differently to chest compressions. Yet, variation in delivered volume and the measured peak pressures were within the reported for the standard bag-valve-mask system.
... PaCO 2 is ideally maintained at 40-45 mm Hg and ETCO 2 at 35-40 mm Hg by adjusting the respiratory rate. This permissible hypercapnia can prevent hypocapnia-induced cerebral vasoconstriction [29]. ...
Article
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Urgent surgery should not be performed preferably for at least 72 hours after a cardiac arrest to minimize the risk for additional perfusion-related organ injury. However, in peculiar circumstances, especially in a military setting, emergency surgery may be necessary in selected patients to save health and life. A previously healthy 34-year-old soldier developed multiple splinter injuries and mangled injury to his right arm after a missile attack. Due to heavy shelling and enemy fire, he bled profusely and could not be immediately evacuated to the medical aid post. After reaching the first-aid post, he was navigated through various medical echelons before reaching our center (Level III) where he was resuscitated and limb-salvage surgery was done. En route to the hospital, he suffered a cardiac arrest, was resuscitated, and had the second arrest on arrival. He was revived within 3 minutes and rushed to the operation theatre, where damage control surgery was done, including a brachial artery anastomosis. After the initial surgery, he was air-evacuated to the nearest tertiary centre, where he was further managed by the vascular surgeon and cardiologist and made a full recovery. Immediate hemostasis of culprit injury is mandatory to make fluid resuscitation effective. Administering effective CPR, volume replenishment using crystalloids and whole blood, balanced anaesthesia, damage control surgery, and teamwork can save patients' limbs and lives.
... Moreover, in intubated animals with SV or with VTF of 10 ml/kg, hyperventilation values were found after 3 min of resuscitation. These data are consistent with previous studies showing that hyperventilation is more common in intubated patients 28 . However, most of the studies considered hyperventilation as high ventilatory parameters but not as a low arterial pCO2. ...
Article
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To compare the effect on the recovery of spontaneous circulation (ROSC) of early endotracheal intubation (ETI) versus bag-mask ventilation (BMV), and expiratory real-time tidal volume (VTe) feedback (TVF) ventilation versus without feedback or standard ventilation (SV) in a pediatric animal model of asphyxial cardiac arrest. Piglets were randomized into five groups: 1: ETI and TVF ventilation (10 ml/kg); 2: ETI and TVF (7 ml/kg); 3: ETI and SV; 4: BMV and TVF (10 ml/kg) and 5: BMV and SV. Thirty breaths-per-minute guided by metronome were given. ROSC, pCO2, pO2, EtCO2 and VTe were compared among groups. Seventy-nine piglets (11.3 ± 1.2 kg) were included. Twenty-six (32.9%) achieved ROSC. Survival was non-significantly higher in ETI (40.4%) than BMV groups (21.9%), p = 0.08. No differences in ROSC were found between TVF and SV groups (30.0% versus 34.7%, p = 0.67). ETI groups presented lower pCO2, and higher pO2, EtCO2 and VTe than BMV groups ( p < 0.05). VTe was lower in TVF than in SV groups and in BMV than in ETI groups ( p < 0.05). Groups 1 and 3 showed higher pO2 and lower pCO2 over time, although with hyperventilation values (pCO2 < 35 mmHg). ETI groups had non significantly higher survival rate than BMV groups. Compared to BMV groups, ETI groups achieved better oxygenation and ventilation parameters. VTe was lower in both TVF and BMV groups. Hyperventilation was observed in intubated animals with SV and with 10 ml/kg VTF.
... Another hypothesis raised is associated with poorly controlled ventilation techniques such as the process of dynamic hyperinflation of the lungs for excess tidal volumes or rapid increase in positive pressure without adequate time for exhalation in artificial ventilation, generating hemodynamic involvement [15]. In other words, the increase in intrathoracic pressure may have led to air trapping with increased pressure at the end of expiration, known as auto-PEEP (auto-positive end-expiratory pressure), which led to a significant impedance to venous return, affecting cardiac output, leading to cardiac arrest [16]. ...
Article
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The pandemic caused by the SARS-CoV-2 or COVID-19 infection has had an unimaginable impact on health systems worldwide. Cardiorespiratory arrest remains a potentially reversible medical emergency that requires the performance of a set of maneuvers designed to replace and restore spontaneous breathing and circulation. Suspending cardiopulmonary resuscitation (CPR) usually corresponds to an ethical-clinical dilemma that the health professional in charge must assume. The "Lazarus phenomenon" is an unusual syndrome with a difficult pathophysiological explanation, defined as the spontaneous return of circulation in the absence of any life support technique or after the cessation of failed CPR maneuvers. We present the case of a 79-year-old patient hospitalized in the intensive care unit for septic shock of pulmonary origin associated with COVID-19 infection who presented cardiorespiratory arrest that required unsuccessful resuscitation maneuvers for 40 minutes, declared deceased. After 20 minutes of death, he presented a return to spontaneous circulation. The pathophysiological changes of the Lazarus phenomenon remind us of the limitations we have in determining when to end cardiopulmonary resuscitation and that its interruption must be approached with more caution, especially in the context of the COVID-19 pandemic.
... Hyperventilation is commonly revealed as a higher incidence among prehospital intubated patients. Hemodynamically, hyperventilation rises the intrathoracic pressure, leading to a decrease in cardiac output [76][77][78]. Regarding the cerebral perfusion, hypocapnia decrease the cerebral blood volume (CBV), which directly decrease the cerebral blood flow (CBF), and lower ICP [79][80][81][82]. Studies had shown regional and local ischemia with tissue lactic acidosis immediately after hyperventilation, suggesting harmful effects in cerebral tissue due to cerebral vasoconstriction [7, 81,82]. ...
Chapter
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Severe traumatic brain injury (TBI) patients are constantly submitted to interventions to cope secondary injury and insults. Oxygen therapy is mostly initiated by endotracheal intubation at the scene of the accident. Due to the severity of the trauma, prolonged mechanical ventilation is expected and tracheostomy (TQT) is often indicated. TQT became one of the most common bedside surgical procedure performed in an Intensive Care Unit (ICU). However, discussion regarding the optimal time for TQT placement to improve outcomes of severe TBI patients remains under discussion. This chapter aims to review TBI’s physiopathology and enlighten early tracheostomy’s role in severe TBI management
Article
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Objectives To investigate whether real-time ventilation feedback would improve provider adherence to ventilation guidelines. Design Non-blinded randomised controlled simulation trial. Setting One Emergency Medical Service trust in Copenhagen. Participants 32 ambulance crews consisting of 64 on-duty basic or advanced life support paramedics from Copenhagen Emergency Medical Service. Intervention Participant exposure to real-time ventilation feedback during simulated out-of-hospital cardiac arrest. Main outcome measures The primary outcome was ventilation quality, defined as ventilation guideline-adherence to ventilation rate (8–10 bpm) and tidal volume (500−600 ml) delivered simultaneously. Results The intervention group performed ventilations in adherence with ventilation guideline recommendations for (Interquartile range (IQR) 66.2%–82.9%) of delivered ventilations, compared to 22.1% (IQR 0%–44.0%) provided by the control group. When controlling for participant covariates, adherence to ventilation guidelines was 44.7% higher in participants receiving ventilation feedback. Analysed separately, the intervention group performed a ventilation guideline-compliant rate in 97.4% (IQR 97.1%–100%) of delivered ventilations, versus 66.7% (IQR 40.9%–77.9%) for the control group. For tidal volume compliance, the intervention group reached 77.5% (IQR 64.9%–83.8%) of ventilations within target compared to 53.4% (IQR 8.4%–66.7%) delivered by the control group. Conclusions Real-time ventilation feedback increased guideline compliance for both ventilation rate and tidal volume (combined and as individual parameters) in a simulated OHCA setting. Real-time feedback has the potential to improve manual ventilation quality and may allow providers to avoid harmful hyperventilation.
Article
Introduction: Excessive minute ventilation during cardiac arrest may cause lung injury and decrease the effectiveness of cardiopulmonary resuscitation (CPR). However, little is known about how clinicians deliver tidal volumes and respiratory rates during CPR. Methods: In this cross-sectional study, licensed practitioners attending an American Heart Association (AHA) Advanced Cardiac Life Support (ACLS) course performed CPR and manual ventilation on a high-fidelity simulator during the megacode portion of the course. Delivered tidal volumes and respiratory rates were measured on a monitor. During the first scenario, results were not displayed to participants, but were displayed during the second scenario. Results: Fifty-two clinicians participated in this study. Average height was 169 (157,178) cm. Pre-monitor display tidal volumes delivered were larger in male participants compared to female participants (684.6 ± 134.4 vs 586.7 ± 167.6 ml, P = 0.05). Those using medium-sized gloves delivered smaller tidal volumes than those using small or large gloves. Twenty-two (42.3%) delivered tidal volume in the range of 5-8 ml/kg of predicted body weight for the simulation manikin, and 35 (67.3%) delivered tidal volumes with >20% variability among breaths. All participants met the target respiratory rate around 10 breaths/min. Conclusion: Tidal volume delivery varied greatly during manual ventilation and fewer than half participants delivered tidal volume at 5-8 ml/kg to the manikin. Sex and glove size appeared to impact tidal volume delivery when the participants were unaware of what they were delivering. Participants were able to meet the target respiratory rate around 10 without audio or visual feedback.
Chapter
Cardiac arrest is rare in pregnancy. Therefore, most intensivists will have limited experience with post-cardiac arrest care in pregnancy. Intensive care should be tailored to the state of pregnancy while adhering to general guidelines on post cardiac arrest care whenever possible. Accurate details regarding cardiac arrest and resuscitation (in particular information regarding delays and initial rhythm) are important for identifying the cause of the arrest and assessing the risk of hypoxic-ischaemic brain injury. Fever is common after return of spontaneous circulation and has been shown to be detrimental. Thus, targeting a temperature of 33–36 °C is paramount. Haemodynamic, oxygenation, ventilation and sedation goals follow general recommendations. Prolonged unconsciousness requires a multimodal prognostication strategy. Both patient and family commonly require support and counselling given the traumatic nature of such events.
Article
Introduction: Cardiopulmonary arrest (CPA) is the acute cessation of systemic perfusion and ventilation. It leads to a lack of tissue oxygen delivery and, if not addressed quickly, will inevitably cause death. Cardiopulmonary resuscitation (CPR) is the only available treatment for CPA and several opportunities exist to improve the veterinary team's resuscitation approach and optimize small animal CPR patient outcomes. In 2012, the Reassessment Campaign on Veterinary Resuscitation (RECOVER) initiative generated evidence-based clinical guidelines to form the basis for training and practice of CPR in dogs and cats. When employing an evidence-based, standardized approach to small animal CPR, return of spontaneous circulation can be achieved in up to 58% of patients and up to 7% of dogs and 19% of cats can be discharged from the veterinary hospital alive. Survival for dogs and cats that suffer CPA is best in patients that suffer a peri-anesthetic arrest, so high quality CPR in the anesthesia patient population is of utmost importance and expected to be the most rewarding. To ensure the best possible outcomes for any patient suffering from CPA and undergoing CPR, a comprehensive resuscitation strategy is necessary, that includes preventive and preparedness measures, basic life support (chest compressions and ventilation), advanced life support (optimization of the patient status by targeted drug therapy, cardiac rhythm monitoring, and defibrillation), and post-cardiac arrest critical care. This article summarizes the most important RECOVER CPR guidelines for the small animal practitioner.
Article
Purpose of review: To discuss recent studies relevant to the utility of measuring end-tidal carbon dioxide (ETCO2) during cardiopulmonary resuscitation (CPR) and its correlation with outcome in adults experiencing cardiac arrest. Recent findings: Over the past couple of years, at least five studies have included measurement of ETCO2 in their methods. Two of these studies were prospective and two retrospective. All considered ETCO2 measurements after out-of-hospital cardiac arrest, either in the prehospital setting, or after arrival in the emergency department. All assessed for an association between ETCO2 measurement and return of spontaneous circulation (ROSC). However, the timing of measurement, whether a one-off value or a trend and the cut-off values used to determine whether or not there was an association were different in all cases. Summary: Higher values of ETCO2 during resuscitation from cardiac arrest are generally associated with a greater likelihood of ROSC. However, timing of measurements and cut-off values used show significant variability across different studies, making it hard to draw any conclusions about the utility of any particular reading for prognostication. Future studies might aim to develop an accepted standard for the timing and cut-off value of ETCO2 used, to enable comparison of the parameter across different studies.
Article
Objective: The American Heart Association Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care recommend ventilation rates of eight to ten breaths per minute or two ventilations every 30 compressions, and tidal volumes between 500-600 ml. However, compliance with these guidelines is mainly unknown. The objective of this study is to estimate the proportion of simulated adult OHCA cases that meet guideline-based ventilation targets. Methods: We conducted a blinded prospective observational study of standardized simulated cases of EMS-witnessed adult OHCA. During scheduled training sessions, resuscitations were performed by high-quality CPR trained EMS teams composed of four on-duty, full-time EMT/Paramedics from a large urban fire-based EMS agency. A high-fidelity simulation center allowed complete audio and video monitoring from a control room. Rescuers were unaware of the study, or that ventilation practices were being observed. All interventions, including airway and ventilation strategies, were at the discretion of the clinical team. A calibrated Laerdal SimMan 3 G manikin and associated Laerdal Debrief Viewer software recorded ventilation rate, tidal volume, and minute ventilation. Simulations achieving median ventilation rate 7-10 breaths/min, tidal volume 500-600 ml, and minute ventilation 3.5-6 liters/min were considered meeting guideline-based targets. Results: A total of 106 EMS teams were included in the study. Only 3/106 [2.8% (95% CI: 0.6-8.0)] of the EMS teams demonstrated ventilation characteristics meeting all guideline-based targets. The median ventilation rate was 5.8 breaths/min (IQR 4.4-7.7 breaths/min) with 26/106 [24.5% (95% CI: 17.2-33.7)] between 7-10 breaths/min. The median tidal volume was 413.5 ml (IQR 280.5-555.4 ml), with 18/106 [17.0% (95% CI: 10.9-25.5)] between 500-600 ml. The median minute ventilation was 2.4 L/min (IQR 1.2-3.6 L/min) with 16/106 [15.1% (95% CI: 9.4-23.3)] between 3.5-6.0 L/min. Conclusion: During simulated adult OHCA resuscitation attempts, ventilation practices rarely met guideline-based targets, despite being performed by well-trained EMS providers. Methods should be developed to monitor and ensure high-quality ventilation during actual OHCA resuscitation attempts.
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Pediatric cardiac arrest is a relatively rare but devastating presentation in infants and children. In contrast to adult patients, in whom a primary cardiac dysrhythmia is the most likely cause of cardiac arrest, pediatric patients experience cardiovascular collapse most frequently after an initial respiratory arrest. Aggressive treatment in the precardiac arrest state should be initiated to prevent deterioration and should focus on support of oxygenation, ventilation, and hemodynamics, regardless of the presumed cause. Unfortunately, outcomes for pediatric cardiac arrest, whether in hospital or out of hospital, continue to be poor.
Article
Emergency Medical Services personnel are often the first to intervene in the care of critically ill children. Airway management is a fundamental step in prehospital resuscitation, yet there is significant variation in current prehospital airway management practices. Our objective is to present a methodologic approach to determine the optimal strategy for prehospital pediatric airway management. We describe the conceptual premise for the Pediatric Prehospital Airway Resuscitation Trial, a novel Bayesian adaptive sequential platform trial. We developed an innovative design to enable comparison of the three predominant prehospital pediatric airway techniques (bag-mask-ventilation, supraglottic airway insertion, and endotracheal intubation) in three distinct disease groups (cardiac arrest, major trauma, and other respiratory failure). We used a Bayesian statistical approach to provide flexible modeling that can adapt based on prespecified rules according to accumulating trial data with patient enrollment continuing until stopping rules are met. The approach also allows the comparison of multiple interventions in sequence across the different disease states. This Bayesian hierarchical model will be the primary analysis method for the Pediatric Prehospital Airway Resuscitation Trial. The model integrates information across subgroups, a technique known as “borrowing” to generate accurate global and subgroup-specific estimates of treatment effects and enables comparisons of airway intervention arms within the overarching trial. We will use this Bayesian hierarchical linear model that adjusts for subgroup to estimate treatment effects within each subgroup. The model will predict a patient-centered score of 30-day intensive care unit-free survival using arm, subgroup, and emergency medical services agency as predictors. The novel approach of Pediatric Prehospital Airway Resuscitation Trial will provide a feasible method to determine the optimal strategy for prehospital pediatric airway management and may transform the design of future prehospital resuscitation trials.
Article
Airway management is a critical component of out-of-hospital cardiac arrest (OHCA) resuscitation. Multiple cardiac arrest airway management techniques are available to EMS clinicians including bag-valve-mask (BVM) ventilation, supraglottic airways (SGAs), and endotracheal intubation (ETI). Important goals include achieving optimal oxygenation and ventilation while minimizing negative effects on physiology and interference with other resuscitation interventions. NAEMSP recommends: • Based on the skill of the clinician and available resources, BVM, SGA, or ETI may be considered as airway management strategies in OHCA. • Airway management should not interfere with other key resuscitation interventions such as high-quality chest compressions, rapid defibrillation, and treatment of reversible causes of the cardiac arrest. • EMS clinicians should take measures to avoid hyperventilation during cardiac arrest resuscitation. • Where available for clinician use, capnography should be used to guide ventilation and chest compressions, confirm and monitor advanced airway placement, identify return of spontaneous circulation (ROSC), and assist in the decision to terminate resuscitation.
Conference Paper
Poor airway management in severely injured patients is a source of significant morbidity and mortality and frequently identified as a cause of preventable death in this group of patients. Traditionally the majority of patients have not received definitive airway management until arrival at hospital and those patients who were sufficiently obtunded on scene to tolerate tracheal intubation without the use of drugs had a universally poor outcome. Pre-hospital Emergency Medicine (PHEM) is now a recognised medical subspecialty and is usually delivered by doctors and paramedics with specific training in this field. The development of this subspecialty has increased the practice of Pre-Hospital Emergency Anaesthesia (PHEA). Despite improvements in the delivery of PHEM and consequently of PHEA, controversy surrounding this intervention exists and it has failed to demonstrate an obvious survival benefit. This thesis sets out to further examine the practice of PHEA and attempt to establish why this intervention does not appear to be reducing mortality in patients who have sustained major trauma. I designed and developed studies to address a number of key questions including whether there is a requirement for PHEA, the potential benefit of it, and to identify areas of practice that can be improved. Through studies conducted at a local and national level I have been able to provide evidence that not only is PHEA an essential and beneficial intervention for a subset of major trauma patients, but also that there is a demand for this intervention which is not met by the current prehospital practice and infrastructure in the UK.
Article
BACKGROUND Chest compression (CC) quality is associated with improved out-of-hospital cardiopulmonary arrest (OHCA) outcomes. Airway management efforts may adversely influence CC quality. We sought to compare the effects of initial laryngeal tube (LT) and initial endotracheal intubation (ETI) airway management strategies upon chest compression fraction (CCF), rate and interruptions in the Pragmatic Airway Resuscitation Trial (PART). METHODS We analyzed CPR process files collected from adult OHCA enrolled in PART. We used automated signal processing techniques and a graphical user interface to calculate CC quality measures and defined interruptions as pauses in chest compressions longer than 3 seconds. We determined CC fraction, rate and interruptions (number and total duration) for the entire resuscitation and compared differences between LT and ETI using t-tests. We repeated the analysis stratified by time before, during and after airway insertion as well as by successive 3-minute time segments. We also compared CC quality between single vs. multiple airway insertion attempts, as well as between bag-valve-mask (BVM-only) vs. ETI or LT. RESULTS Of 3,004 patients enrolled in PART, CPR process data were available for 1,996 (1,001 LT, 995 ETI). Mean CPR analysis duration were: LT 22.6 ± 10.8 min vs. ETI 25.3 ± 11.3 min (p < 0.001). Mean CC fraction (LT 88% vs. ETI 87%, p = 0.05) and rate (LT 114 vs. ETI 114 compressions per minute (cpm), p = 0.59) were similar between LT and ETI. Median number of CC interruptions were: LT 11 vs. ETI 12 (p = 0.001). Total CC interruption duration was lower for LT than ETI (LT 160 vs. ETI 181 sec, p = 0.002); this difference was larger before airway insertion (LT 56 vs. ETI 78 sec, p < 0.001). There were no differences in CC quality when stratified by 3-min time epochs. CONCLUSION In the PART trial, compared with ETI, LT was associated with shorter total CC interruption duration but not other CC quality measures. CC quality may be associated with OHCA airway management.
Article
Current guidelines emphasize the use of 100% oxygen during CPR after cardiac arrest. When patients are ventilated for variable periods after return of spontaneous circulation (ROSC), hyperoxia causes increased morbidity and mortality by overproduction of Reactive Oxygen Species (ROS). Various patient, volunteer, and animal studies have shown the harmful effects of hyperoxia. This mini-review article aims to expand the potential clinical spectrum of hyperoxia on individual organ systems leading to organ dysfunction. A framework to achieve and maintain normoxia after ROSC is proposed. Despite the harmful considerations of hyperoxia in critically ill patients, further safety studies including dose-effect, level-and-onset of ROS effect, and safe hyperoxia applicability period after ROSC need to be performed in various animal and human models to further elucidate the role of oxygen therapy following cardiac arrest.
Article
Airway management is important in trauma and critically ill patients. Prolonged mechanical ventilation results in over-ventilation induced lung barotrauma, but few studies have examined the consequence of acute (1 h or less) over-ventilation. We hypothesized that acute hyperventilation, as might inadvertently be performed in pre-hospital settings, would elevate systemic inflammation and cause lung damage. Female Yorkshire pigs (40-50 kg, n=10/group) were anesthetized, instrumented for hemodynamic measurements and blood sampling, and. underwent a 25% controlled hemorrhage followed by 1 h of: 1) spontaneous breathing; 2) "normal" bag ventilation (4.8 L minute volume, ~400 mL tidal volume, 12 breaths/minute); 3) bag hyperventilation (9 L minute volume, ~750 mL tidal volume, 12 breaths/minute); 4) maximum hyperventilation (15 L minute volume, ~~750 mL tidal volume, 20 breaths/minute); or, 5) mechanical ventilation. Pigs then regained consciousness and recovered for 24 hrs, followed by euthanasia and collection of blood and tissue samples. No level of manual ventilation had any significant impact on hemodynamic variables. Blood markers of tissue damage and plasma cytokines were not statistically different between groups with the exception of a transient increase in IL-1β; all values returned to baseline by 24 hrs. On pathological review, severity and distribution of lung edema or other gross pathologies were not significantly different between groups. These data indicate hyperventilation causes no adverse effects, to include inflammation and tissue damage; and that acute over-ventilation, as could be seen in the pre-hospital phase of trauma care, does not produce evidence of adverse effects on the lungs following moderate hemorrhage.
Article
Background We sought to describe ventilation rates during out-of-hospital cardiac arrest (OHCA) resuscitation and their associations with airway management strategy and outcomes. Methods We analyzed continuous end-tidal carbon dioxide capnography data from adult OHCA enrolled in the Pragmatic Airway Resuscitation Trial (PART). Using automated signal processing techniques, we determined continuous ventilation rate for consecutive 10-second epochs after airway insertion. We defined hypoventilation as a ventilation rate <6 breaths/min. We defined hyperventilation as a ventilation rate >12 breaths/min. We compared differences in total and percentage post-airway hyper- and hypoventilation between airway interventions (laryngeal tube (LT) vs. endotracheal intubation (ETI). We also determined associations between hypo-/hyperventilation and OHCA outcomes (ROSC, 72-hour survival, hospital survival, hospital survival with favorable neurologic status). Results Adequate post-airway capnography were available for 1,010 (LT n=714, ETI n=296) of 3,004 patients. Median ventilation rates were: LT 8.0 (IQR 6.5-9.6) breaths/min, ETI 7.9 (6.5-9.7) breaths/min. Total duration and percentage of post-airway time with hypoventilation were similar between LT and ETI: median 1.8 vs. 1.7 minutes, p=0.94; median 10.5% vs. 11.5%, p=0.60. Total duration and percentage of post-airway time with hyperventilation were similar between LT and ETI: median 0.4 vs. 0.4 minutes, p=0.91; median 2.1% vs. 1.9%, p=0.99. Hypo- and hyperventilation exhibited limited associations with OHCA outcomes. Conclusion In the PART Trial, EMS personnel delivered post-airway ventilations at rates satisfying international guidelines, with only limited hypo- or hyperventilation. Hypo- and hyperventilation durations did not differ between airway management strategy and exhibited uncertain associations with OCHA outcomes.
Article
Manual ventilation using a self-inflating bag device paired with a facemask (bag-valve-mask, or BVM ventilation) or invasive airway (bag-valve-device, or BVD ventilation) is a fundamental airway management skill for all Emergency Medical Services (EMS) clinicians. Delivery of manual ventilations is challenging. Several strategies and adjunct technologies can increase the effectiveness of manual ventilation. NAEMSP recommends: • All EMS clinicians must be proficient in bag-valve-mask ventilation. • BVM ventilation should be performed using a two-person technique whenever feasible. • EMS clinicians should use available techniques and adjuncts to achieve optimal mask seal, improve airway patency, optimize delivery of the correct rate, tidal volume, and pressure during manual ventilation, and allow continual assessment of manual ventilation effectiveness.
Chapter
Airway management is a critical process that requires a blend of competent decision making, psychomotor skill, and vigilance in monitoring. EMS medical directors must choose the appropriate tools and training for their systems and field personnel. Airway skills must be obtained and competency must be maintained through comprehensive training and rigorous continuing education informed by a process of total quality management. Airway management algorithms may help to facilitate sound decision-making and application. The EMS medical director should also frequently review system airway procedures and outcomes to ensure maximum quality and minumum occurrence of adverse events.
Article
The IoT-based Ambu bag mechanical ventilator is a ventilator that automates the process of hand press mechanism using the rack and pinion mechanism. The circulatory motion of the rack is converted into linear motion which helps to press the Ambu bag. The proposed project works on three modes of operation that is child-adult and elder which is set wrt to the breaths per minute. There are two states of operation one normal state where the normal working is evidenced whereas the other operation mode is emergency where the buzzer is themed on in case of emergency. All the parameters are displayed on LCD and connected to the IoT cloud to communicate remotely in the end device Keywords: Ambulatory Bag, IoT network, Rack and Pinion mechanism, Manual resuscitator, mechanical ventilators
Article
Background and aim Measuring tidal volumes (TV) during bag-valve ventilation is challenging in the clinical setting. The ventilation waveform amplitude of the transthoracic impedance (TTI-amplitude) correlates well with TV for an individual, but poorer between patients. We hypothesized that TV to TTI-amplitude relations could be improved when adjusted for morphometric variables like body mass index (BMI), gender or age, and that TTI-amplitude cut-offs for ventilations with adequate TV (>400ml) could be established. Materials and methods Twenty-one consenting adults (9 female, and 9 overall overweight) during positive pressure ventilation in anaesthesia before scheduled surgery were included. Seventeen ventilator modes were used (⩾five breaths per mode) to adjust different TVs (150–800ml), ventilation frequencies (10–30min⁻¹) and insufflation times (0.5–3.5s). TTI from the defibrillation pads was filtered to obtain ventilation TTI-amplitudes. Linear regression models were fitted between target and explanatory variables, and compared (coefficient of determination, R2). Results The TV to TTI-amplitude slope was 1.39Ω/l (R2=0.52), with significant differences (p<0.05) between male/female (1.04Ω/l vs 1.84Ω/l) and normal/overweight subjects (1.65Ω/l vs 1.04Ω/l). The median (interquartile range) TTI-amplitude cut-off for adequate TV was 0.51Ω(0.14-1.20) with significant differences between males and females (0.58Ω/0.39Ω), and normal and overweight subjects (0.52Ω/0.46Ω). The TV to TTI-amplitude model improved (R2=0.66) when BMI, age and gender were included. Conclusions TTI-amplitude to TV relations were established and cut-offs for ventilations with adequate TV determined. Patient morphometric variables related to gender, age and BMI explain part of the variability in the measurements.
Article
Background Significant challenges exist in measuring ventilation quality during out-of-hospital cardiopulmonary arrest (OHCA) outcomes. Since ventilation is associated with outcomes in cardiac arrest, tools that objectively describe ventilation dynamics are needed. We sought to characterize thoracic impedance (TI) oscillations associated with ventilation waveforms in the Pragmatic Airway Resuscitation Trial (PART). Methods We analyzed CPR process files collected from adult OHCA enrolled in PART. We limited the analysis to cases with simultaneous capnography ventilation recordings at the Dallas-Fort Worth site. We identified ventilation waveforms in the thoracic impedance signal by applying automated signal processing with adaptive filtering techniques to remove overlying artifacts from chest compressions. We correlated detected ventilations with the end-tidal capnography signals. We determined the amplitudes (Ai, Ae) and durations (Di, De) of both insufflation and exhalation phases. We compared differences between laryngeal tube (LT) and endotracheal intubation (ETI) airway management during mechanical or manual chest compressions using Mann-Whitney U-test. Results We included 303 CPR process cases in the analysis; 209 manual (77 ETI, 132 LT), 94 mechanical (41 ETI, 53 LT). Ventilation Ai and Ae were higher for ETI than LT in both manual (ETI: Ai 0.71Ω, Ae 0.70Ω vs LT: Ai 0.46Ω, Ae 0.45Ω; p<0.01 respectively) and mechanical chest compressions (ETI: Ai 1.22Ω, Ae 1.14Ω VS LT: Ai 0.74Ω, Ae 0.68Ω; p<0.01 respectively). Ventilations per minute, duration of TI amplitude insufflation and exhalation did not differ among groups. Conclusion Compared with LT, ETI thoracic impedance ventilation insufflation and exhalation amplitude were higher while duration did not differ. TI may provide a novel approach to characterizing ventilation during OHCA.
Article
Study objective: While often prioritized in the resuscitation of patients with out-of-hospital cardiac arrest, the optimal timing of advanced airway insertion is unknown. We evaluated the association between the timing of advanced airway (laryngeal tube and endotracheal intubation) insertion attempt and survival to hospital discharge in adult out-of-hospital cardiac arrest. Methods: We performed a secondary analysis of the Pragmatic Airway Resuscitation Trial (PART), a clinical trial comparing the effects of laryngeal tube and endotracheal intubation on outcomes after adult out-of-hospital cardiac arrest. We stratified the cohort by randomized airway strategy (laryngeal tube or endotracheal intubation). Within each subset, we defined a time-dependent propensity score using patients, arrest, and emergency medical services systems characteristics. Using the propensity score, we matched each patient receiving an initial attempt of laryngeal tube or endotracheal intubation with a patient at risk of receiving laryngeal tube or endotracheal intubation attempt within the same minute. Results: Of 2,146 eligible patients, 1,091 (50.8%) and 1,055 (49.2%) were assigned to initial laryngeal tube and endotracheal intubation strategies, respectively. In the propensity score-matched cohort, timing of laryngeal tube insertion attempt was not associated with survival to hospital discharge: 0 to lesser than 5 minutes (risk ratio [RR]=1.35, 95% confidence interval [CI] 0.53 to 3.44); 5 to lesser than10 minutes (RR=1.07, 95% CI 0.66 to 1.73); 10 to lesser than 15 minutes (RR=1.17, 95% CI 0.60 to 2.31); or 15 to lesser than 20 minutes (RR=2.09, 95% CI 0.35 to 12.47) after advanced life support arrival. Timing of endotracheal intubation attempt was also not associated with survival: 0 to lesser than 5 minutes (RR=0.50, 95% CI 0.05 to 4.87); 5 to lesser than10 minutes (RR=1.20, 95% CI 0.51 to 2.81); 10 to lesser than15 minutes (RR=1.03, 95% CI 0.49 to 2.14); 15 to lesser than 20 minutes (RR=0.85, 95% CI 0.30 to 2.42); or more than/equal to 20 minutes (RR=0.71, 95% CI 0.07 to 7.14). Conclusion: In the PART, timing of advanced airway insertion attempt was not associated with survival to hospital discharge.
Article
Introducción: la pandemia por la infección del SARS-CoV-2 o COVID-19 ha impactado de manera inimaginable los sistemas de salud a nivel mundial. La parada cardiorrespiratoria sigue siendo una emergencia médica potencialmente reversible que requiere la realización de un conjunto de maniobras destinadas a sustituir y restaurar la respiración y la circulación espontánea. Suspender una reanimación cardiopulmonar corresponde usualmente a un dilema ético-clínico que debe asumir el profesional de salud a cargo. El “fenómeno de Lázaro” es un síndrome inusual y de difícil explicación fisiopatológica definido como el retorno espontáneo de la circulación en ausencia de cualquier técnica de soporte vital o tras el cese de las maniobras de reanimación cardiopulmonar fallidas. Caso clínico: se presenta el caso de una paciente de 79 años hospitalizada en unidad de cuidados intensivos por choque séptico de origen pulmonar asociado a infección por COVID-19 quien presenta parada cardiorrespiratoria que requirió maniobras de reanimación durante 40 minutos no exitosas, declarada fallecida. Tras 20 minutos del fallecimiento presenta retorno a la circulación espontánea. Conclusión: los cambios fisiopatológicos del fenómeno de Lázaro nos recuerdan las limitaciones que tenemos para determinar cuándo finalizar la reanimación cardiopulmonar y su interrupción debe abordarse con más cuidado, especialmente en el marco de la pandemia de COVID-19.
Article
Full-text available
This study was designed to assess whether intermittent impedance of inspiratory gas exchange improves the efficiency of standard cardiopulmonary resuscitation (CPR). Standard CPR relies on the natural elastic recoil of the chest to transiently decrease intrathoracic pressures and thereby promote venous blood return to the heart. To further enhance the negative intrathoracic pressures during the "relaxation" phase of CPR, we tested the hypothesis that intermittent impedance to inspiratory gases during standard CPR increases coronary perfusion pressures and vital organ perfusion. CPR was performed with a pneumatically driven automated device in a porcine model of ventricular fibrillation. Eight pigs were randomized to initially receive standard CPR alone, while seven pigs initially received standard CPR plus intermittent impedance to inspiratory gas exchange with a threshold valve set to -40 cm H2O. The compression:ventilation ratio was 5:1 and the compression rate was 80/min. At 7-min intervals the impedance threshold valve (ITV) was either added or removed from the ventilation circuit such that during the 28 min of CPR, each animal received two 7-min periods of CPR with the ITV and two 7-min periods without the valve. Vital organ blood flow was significantly higher during CPR performed with the ITV than during CPR performed without the valve. Total left ventricular blood flow (mean+/-SEM) (mL/min/g) was 0.32+/-0.04 vs 0.23+/-0.03 without the ITV (p<0.05). Cerebral blood flow (mL/min/g) was 20% higher with the ITV (+ITV, 0.23+/-0.02; -ITV, 0.19+/-0.02; p<0.05). Each time the ITV was removed, there was a statistically significant decrease in the vital organ blood flow and coronary perfusion pressure. Intermittent impedance to inspiratory flow of respiratory gases during standard CPR significantly improves CPR efficiency during ventricular fibrillation. These studies underscore the importance of lowering intrathoracic pressures during the relaxation phase of CPR.
Article
Full-text available
This study evaluated the potential for an inspiratory impedance threshold valve (ITV) to improve 24-hour survival and neurological function in a pig model of cardiac arrest. Using a randomized, prospective, and blinded design, we compared the effects of a sham versus active ITV on 24-hour survival and neurological function. After 6 minutes of ventricular fibrillation (VF), followed by 6 minutes of cardiopulmonary resuscitation (CPR) with either a sham or an active valve, anesthetized pigs received 3 sequential 200-J shocks. If VF persisted, they received epinephrine (0.045 mg/kg), 90 seconds of CPR, and 3 more 200-J shocks. A total of 11 of 20 pigs (55%) in the sham versus 17 of 20 (85%) in the active valve group survived for 24 hours (P<0.05). Neurological scores were significantly higher with the active valve; the cerebral performance score (1=normal, 5=brain death) was 2.2+/-0.2 with the sham ITV versus 1.4+/-0.2 with the active valve (P<0.05). A total of 1 of 11 in the sham versus 12 of 17 in the active valve group had completely normal neurological function (P<0.05). Peak end-tidal CO2 (PETCO2) values were significantly higher with the active valve (20.4+/-1.0) than the sham (16.8+/-1.5) (P<0.05). PETCO2 >18 mm Hg correlated with increased survival (P<0.05). Use of a functional ITV during standard CPR significantly improved 24-hour survival rates and neurological recovery. PETCO2 and systolic blood pressure were also significantly higher in the active valve group. These data support further evaluation of ITV during standard CPR.
Article
Objectives This study was designed to assess whether a new method of cardiopulmonary resuscitation (CPR), termed active compression-decompression CPR, or ACD-CPR, improves organ perfusion when compared with standard (S) CPR in a dog model of ventricular fibrillation. Background ACD-CPR has recently been shown to improve hemodynamic and respiratory parameters during cardiac arrest when compared with standard CPR. However, to our knowledge, the effects of ACD-CPR on tissue perfusion have not been investigated. Methods Ventricular fibrillation was induced in eight anesthetized, intubated animals. ACD-CPR and standard CPR were each performed twice in alternating order. All interventions were preceded by 1 min of ventricular fibrillation, in which no CPR was performed, and consisted of 6 min of CPR with either technique during which tissue perfusion was measured. Compressions were performed at 80/min with a 50 percent duty cycle and 175 to 200 N downward force applied to the chest wall for both techniques. Epinephrine was administered at the beginning of each 6-min CPR interval. Hemodynamic monitoring of aortic and right atrial pressure was performed continuously and myocardial, cerebral, and renal blood flows were measured using the radiolabeled microsphere technique at baseline and during all interventions. Results Baseline organ perfusion and hemodynamics were similar for all dogs. Baseline left ventricular, brain, and renal blood flows were 62.0±5.5, 14.1±2.1, and 476.3±55.5 ml/min/100 g, respectively (mean±SEM). Compared with standard CPR, ACD-CPR resulted in higher global left ventricular (22.5±6.2 vs 14.1±4.0 ml/min/100 g, p<0.01), cerebral (12.0±2.4 vs 8.5±2.3 ml/min/100 g, p<0.01), and renal cortical (27.8±5.0 vs 17.5±5.0 ml/min/100 g, p<0.05) blood flows. Regional flows to the epicardium, endocardium, and midmyocardium as well as to the frontal, parietal, and occipital lobes of the brain were all significantly improved by ACD-CPR. Aortic systolic (61.7±4.1 vs 49.5±3.1 mm Hg, p<0.01), aortic mean (31.6±2.8 vs 27.2±2.2 mm Hg, p=0.001), and myocardial perfusion pressure (12.9±3.4 vs 10.4±3.4 mm Hg, ACD-CPR vs standard CPR, p<0.01) were all higher during ACD-CPR than during standard CPR. Conclusions We conclude that ACD-CPR improves tissue perfusion and systemic hemodynamics compared with standard CPR.
Article
Background — This study evaluated the potential for an inspiratory impedance threshold valve (ITV) to improve 24-hour survival and neurological function in a pig model of cardiac arrest. Methods and Results — Using a randomized, prospective, and blinded design, we compared the effects of a sham versus active ITV on 24-hour survival and neurological function. After 6 minutes of ventricular fibrillation (VF), followed by 6 minutes of cardiopulmonary resuscitation (CPR) with either a sham or an active valve, anesthetized pigs received 3 sequential 200-J shocks. If VF persisted, they received epinephrine (0.045 mg/kg), 90 seconds of CPR, and 3 more 200-J shocks. A total of 11 of 20 pigs (55%) in the sham versus 17 of 20 (85%) in the active valve group survived for 24 hours ( P 18 mm Hg correlated with increased survival ( P <0.05). Conclusions — Use of a functional ITV during standard CPR significantly improved 24-hour survival rates and neurological recovery. Petco2 and systolic blood pressure were also significantly higher in the active valve group. These data support further evaluation of ITV during standard CPR. Received August 7, 2001; revision received October 12, 2001; accepted October 15, 2001.
Article
Objective. —To determine survival from out-of-hospital cardiac arrest in New York City and to compare this with other urban, suburban, and rural areas.Design. —Observational cohort study.Setting. —New York City.Participants. —Consecutive out-of-hospital cardiac arrests occurring between October 1, 1990, and April 1, 1991.Intervention. —Trained paramedics performed immediate postarrest interviews with care providers, using a standardized questionnaire.Main Outcome Measures. —Entry criteria, elapsed time intervals, and nodal events conformed to Utstein recommendations. The single target end point was death or discharge home.Results. —Of 3243 consecutive cardiac arrests on which resuscitation was attempted, 2329 (72%) met entry criteria as primary cardiac events. Overall survival was 1.4% (99% confidence interval [CI], 0.9% to 2.3%). No patients were lost to follow-up. Survival from witnessed ventricular fibrillation was 5.3% (99% CI, 2.9% to 8.8%). Using survival from witnessed ventricular fibrillation for intersystem comparison, our survival rate was similar to that of Chicago, III (4.0%; 99% CI, 1.9% to 7.5%; P=.41), the only other large city on which data were available. However, it was significantly lower than that reported from midsized urban/suburban areas (33.0%; 99% CI, 30.4% to 35.6%; P<.0001) and suburban/rural areas (12.6%; 99% CI, 8.9% to 16.3%; P<.0001). Survival rate among arrests occurring after arrival of emergency medical services personnel (8.5%; 99% CI, 4.7% to 14.0%) was comparable with Chicago (6.6%; 99% CI, 3.3% to 11.5%; P=.41) but markedly lower than King County, Washington (36%; 99% CI, 28.6% to 43.8%; P<.0001).Conclusions. —Survival from out-of-hospital cardiac arrest in New York City was poor. This was partly attributable to lengthy elapsed time intervals at every step in the chain of survival. However, examination of survival among arrests occurring after emergency medical services arrival suggests that other features may predispose residents of large cities to higher cardiac arrest mortality than individuals living in more suburban or rural settings. Since half the US population resides in large metropolitan areas, this represents a public health problem of considerable magnitude.(JAMA. 1994;271:678-683)
Article
Objectives: To determine: 1) whether chest compressions during CPR are being performed according to American Heart Association (AHA) guidelines during cardiac arrest; and 2) the effect of an audio prompt to guide chest compressions on compliance with AHA guidelines and hemodynamic parameters associated with successful resuscitation. Methods: An observational clinical report and laboratory study was conducted. A research observer responded to a convenience sample of cardiac arrests within a 300-bed hospital and counted the rate of chest compressions and ventilations during CPR. To evaluate the effect of an audio prompt on CPR, health care providers performed chest compression without guidance using a porcine cardiac arrest model for 1 minute, followed by a second minute in which audio guidance was added. Chest compression rates, arterial and venous blood pressures, end-tidal CO2 (ETCO2) levels, and coronary perfusion pressures were measured and compared for the two periods. Results: Twelve in-hospital cardiac arrests were observed in the clinical part of the study. Only two of 12 patients had chest compressions performed within AHA guidelines. No patient had respirations performed within AHA guidelines. In the laboratory, 41 volunteers were tested, with 66% performing chest compressions outside the AHA standards for compression rate without audible tone guidance. With guided chest compressions, the mean (± SD) chest compression rate increased from 74 ± 22 to 100 ± 3/min (p < 0.01). End-tidal CO2 levels increased from 15 ± 7 to 17 ± 7 torr (p < 0.01). Coronary perfusion pressure increased minimally with audible tone-guided chest compressions. Conclusions: The majority of Basic Cardiac Life Support-certified health care professionals did not perform CPR according to AHA-recommended guidelines. The use of audible tones to guide chest compression resulted in significantly higher chest compression rates and ETCO2 levels.
Article
Mechanical hyperventilation not only reduces brain oedema after neurotrauma but also affects the central and systemic circulation. We have, in pigs, measured blood flow in the pulmonary artery, the portal vein and in the femoral artery, as well as estimated the splanchnic blood flow and studied the relative perfusion using the microsphere technique in normo– and hypocarbia during intermittent positive pressure ventilation. A normoventilated control group did not change in cardiac output, portal vein blood flow, splanchnic blood flow and femoral arterial blood flow. Hyperventilation was performed to a Pco2 of 3.0± 0.1 kPa. We found that in pigs ventilated with high tidal volume skeletal muscle blood flow did not change during the first 60 min of hyperventilation but gradually decreased thereafter. Blood flow to the cerebellum decreased soon after the induction of hyperventilation, whereas the cerebral blood flow did not decrease until the second hour of hyperventilation. Cardiac output, splanchnic perfusion and portal vein blood flow all decreased. Myocardial perfusion and arterial blood flow to spleen and kidney decreased while pancreatic and liver arterial blood flows were unaffected. It is concluded that mechanical hyperventilation with low frequency and large tidal volumes reduces the flow to most tissues, where the relative decrease according to microsphere measurements is most pronounced in skeletal muscles, heart muscle and cerebellum. However, the changes in cardiac output and splanchnic blood flow were not observed when hyperventilation was induced by increased frequency, keeping the tidal volume constant.
Article
SUMMARY The effects of altering end-expiratory inflation pressure were studied in mechanically ventilated dogs in the normo-, hypo- and hypervolaemic state. The mean fall in cardiac output resulting from an increase in end-expiratory pressure was smaller in the hypervolaemic group than in the other two groups. A positive end-expiratory pressure increased the mean deadspace/tidal volume ratio in all groups. A negative end-expiratory pressure increased venous admixture, particularly in the over-transfused animals, but the increase was not significant in the hypovolaemic group. A negative end-expiratory pressure did not affect deadspace/tidal volume ratio.
Article
Survival from out-of-hospital cardiac arrest in cities with populations of more than 1 million has not been studied adequately. This study was undertaken to determine the overall survival rate for Chicago and the effect of previously reported variables on survival, and to compare the observed survival rates with those previously reported. Consecutive prehospital arrest patients were studied prospectively during 1987. The study area was the city of Chicago, which has more than 3 million inhabitants in 228 square miles. The emergency medical services system, with 55 around-the-clock ambulances and 550 paramedics, is single-tiered and responds to more than 200,000 emergencies per year. We studied 3,221 victims of out-of-hospital cardiac arrest on whom paramedics attempted resuscitation. Ninety-one percent of patients were pronounced dead in emergency departments, 7% died in hospitals, and 2% survived to hospital discharge. Survival was significantly greater with bystander-witnessed arrest, bystander-initiated CPR, paramedic-witnessed arrest, initial rhythm of ventricular fibrillation, and shorter treatment intervals. The overall survival rates were significantly lower than those reported in most previous studies, all based on smaller communities; they were consistent with the rates reported in the one comparable study of a large city. The single factor that most likely contributed to the poor overall survival was the relatively long interval between collapse and defibrillation. Logistical, demographic, and other special characteristics of large cities may have affected the rates. To improve treatment of cardiac arrest in large cities and maximize the use of community resources, we recommend further study of comparable metropolitan areas using standardized terms and methodology. Detailed analysis of each component of the emergency medical services systems will aid in making improvements to maximize survival of out-of-hospital cardiac arrest.
Article
Published reports of out-of-hospital cardiac arrest give widely varying results. The variation in survival rates within each type of system is due, in part, to variation in definitions. To determine other reasons for differences in survival rates, we reviewed published studies conducted from 1967 to 1988 on 39 emergency medical services programs from 29 different locations. These programs could be grouped into five types of prehospital systems based on the personnel who deliver CPR, defibrillation, medications, and endotracheal intubation; the five systems were three types of single-response systems (basic emergency medical technician [EMT], EMT-defibrillation [EMT-D], and paramedic) and two double-response systems (EMT/paramedic and EMT-D/paramedic). Reported discharge rates ranged from 2% to 25% for all cardiac rhythms and from 3% to 33% for ventricular fibrillation. The lowest survival rates occurred in single-response systems and the highest rates in double-response systems, although there was considerable variation within each type of system. Hypothetical survival curves suggest that the ability to resuscitate is a function of time, type, and sequence of therapy. Survival appears to be highest in double-response systems because CPR is started early. We speculate that early CPR permits definitive procedures, including defibrillation, medications, and intubation, to be more effective.
Article
Survival from cardiac arrest is higher when the collapse occurs outside the home. Of 781 patients collapsing at home, 101 (13%) survived to hospital discharge. This compared with 66 survivors among 248 (27%) patients arresting outside the home (P less than .001). Patients collapsing outside the home were younger and more frequently were men. Cardiac arrests outside the home were more often witnessed, more likely to have bystander CPR, less often preceded by symptoms, and the collapsing rhythm was more frequently ventricular fibrillation. Mean time to CPR was shorter. Multivariate logistic regression showed that the effect of location on survival was still statistically significant, although diminished, after adjusting for the above variables (P less than .01). We speculate that comorbidity, underlying etiology, and activity level may explain the remaining difference. Because 76% of arrests occur in the home, efforts to increase the frequency of bystander-CPR through targeted and dispatcher-assisted CPR programs are warranted.
Article
The effectiveness of bystander CPR recently has been challenged. We undertook a ten-year retrospective review of our prehospital experience with witnessed cardiorespiratory arrest to ascertain save rates in patients receiving and not receiving CPR before paramedic advanced life support (ALS). Traumatic and poisoning arrests and children less than 18 years old were excluded. A total of 1,905 patients presenting to a paramedic system from November 1, 1973, to October 31, 1983, were bystander-witnessed arrests and attempted paramedic resuscitations. Four hundred five paramedic-witnessed arrests were excluded. One hundred eighty-two of 1,248 (14.6%) who had CPR initiated before paramedic ALS arrival were saves, compared to 38 of 252 (15%) who had no CPR initiated until paramedic arrival (P = NS). A save was defined as a patient discharged from the hospital. The respective save rates for coarse ventricular fibrillation were 148 of 628 (23.6%) (CPR before paramedic arrival) vs 35 of 151 (CPR delayed until paramedic arrival) (23.2%); electromechanical dissociation (EMD), 11 of 209 (5.3%) vs 0 of 38; asystole, 19 of 401 (4.7%) vs 3 of 61 (4.9%); and ventricular tachycardia, four of ten (40%) vs 0 of two. In this prehospital system, bystander/first responder CPR was found not to improve hospital discharge rates except in patients with initially documented rhythm of EMD.
Article
We investigated the mechanism(s) responsible for the decreased cardiac output during continuous positive-pressure ventilation (CPPV). Seven dogs were anesthetized with chloralose-urethane, intubated, and ventilated using a volume ventilator. We measured heart rate, stroke volume, and the determinants of stroke volume: left and right ventricular end-diastolic volumes, isovolumic and ejection phase indices of myocardial contractility, and pulmonary and systemic arterial pressures. Myocardial blood flow was estimated using radioactive microspheres. Variables were measured during a control period of intermittent positive-pressure ventilation (IPPV), 8-20 minutes after the initiation of CPPV using 12 cm H2O positive end-expiratory pressure (PEEP), and 8-20 minutes after the removal of PEEP. CPPV decreased cardiac output but did not affect total or regional myocardial blood flow or the ratio of subendocardial to subepicardial blood flow. Isovolumic and ejection phase indices of myocardial cointractility, heart rate, and systemic arterial pressure did not change during CPPV. Right and left ventricular end-diastolic and end-systolic volumes decreased markedly during CPPV. We conclude that CPPV decreases cardiac output in accordance with Starling's law by decreasing preload.
Article
Within the last several years a new method of CPR, termed active compression-decompression (ACD) CPR was developed. Based upon the theory that active rather than passive chest wall decompression would augment venous return and ventilation by causing an increase in negative intrathoracic pressure during the decompression phase of CPR, a hand-held device was designed and is now being used clinically. Studies in dogs and pigs in ventricular fibrillation have demonstrated a significant improvement in systolic blood pressure, coronary perfusion pressure and total brain and myocardial blood flow with ACD CPR compared with standard CPR. Animal and human studies suggest that the mechanism of ACD CPR is complex, with coronary perfusion occurring during both the compression and decompression phases. Clinical studies comparing ACD to standard CPR in patients in cardiac arrest demonstrate that immediate resuscitation rates are nearly doubled when ACD CPR is started within 10 min after cardiac arrest. The potential long term benefits of ACD CPR remain under investigation.
Article
Active compression-decompression (ACD) cardiopulmonary resuscitation (CPR) has recently been demonstrated to provide significantly more blood flow to vital organs during cardiac arrest. To further enhance the effectiveness of this technique, we tested the hypothesis that intermittent impedance to inspiratory gas exchange during the decompression phase of ACD CPR enhances vital organ blood flow. ACD CPR was performed with a pneumatically driven automated compression-decompression device in a porcine model of ventricular fibrillation (VF). Nine pigs were randomized to receive ACD CPR alone, while 8 pigs received ACD CPR plus intermittent impedance to inspiratory gas exchange with a threshold valve set to 40 cm H2O. Results comparing 2 minutes of ACD CPR alone versus ACD CPR with the inspiratory impedance threshold valve (ITV) revealed significantly higher mean (+/- SEM) coronary perfusion pressures (diastolic aortic minus diastolic right atrial pressures) in the ITV (31.0 +/- 2.3 mm Hg) group versus with ACD CPR alone (21 +/- 3.6 mm Hg) (P < .05). Total left ventricular and cerebral blood flows, determined by radiolabeled microspheres, were 0.77 +/- 0.095 and 0.47 +/- 0.06 mL/min per gram, respectively, with ACD CPR plus the ITV versus 0.45 +/- 0.1 and 0.32 +/- 0.016 mL/min per gram, respectively, with ACD CPR alone (P < .05). Similar improvements in the ITV group were observed after 7 minutes of ACD CPR. After 16 minutes of VF and 13 minutes of ACD CPR, 6 of 8 pigs in the ITV group were successfully resuscitated with less than three successive 150-J shocks, whereas only 2 of 9 pigs with ACD CPR alone were resuscitated with equivalent energy levels (P < .02). With up to three additional and successive 200-J shocks, all pigs in the ITV group and 7 of 9 pigs with ACD CPR alone were resuscitated (P = .18). Intermittent impedance to inspiratory flow of respiratory gases during ACD CPR significantly improves coronary perfusion pressures and vital organ blood flow and lowers defibrillation energy requirements in a porcine model of VF.
Article
This study was designed to assess whether a new method of cardiopulmonary resuscitation (CPR), termed active compression-decompression CPR, or ACD-CPR, improves organ perfusion when compared with standard (S) CPR in a dog model of ventricular fibrillation. ACD-CPR has recently been shown to improve hemodynamic and respiratory parameters during cardiac arrest when compared with standard CPR. However, to our knowledge, the effects of ACD-CPR on tissue perfusion have not been investigated. Ventricular fibrillation was induced in eight anesthetized, intubated animals. ACD-CPR and standard CPR were each performed twice in alternating order. All interventions were preceded by 1 min of ventricular fibrillation, in which no CPR was performed, and consisted of 6 min of CPR with either technique during which tissue perfusion was measured. Compressions were performed at 80/min with a 50 percent duty cycle and 175 to 200 N downward force applied to the chest wall for both techniques. Epinephrine was administered at the beginning of each 6-min CPR interval. Hemodynamic monitoring of aortic and right atrial pressure was performed continuously and myocardial, cerebral, and renal blood flows were measured using the radiolabeled microsphere technique at baseline and during all interventions. Baseline organ perfusion and hemodynamics were similar for all dogs. Baseline left ventricular, brain, and renal blood flows were 62.0 +/- 5.5, 14.1 +/- 2.1, and 476.3 +/- 55.5 ml/min/100 g, respectively (mean +/- SEM). Compared with standard CPR, ACD-CPR resulted in higher global left ventricular (22.5 +/- 6.2 vs 14.1 +/- 4.0 ml/min/100 g, p < 0.01), cerebral (12.0 +/- 2.4 vs 8.5 +/- 2.3 ml/min/100 g, p < 0.01), and renal cortical (27.8 +/- 5.0 vs 17.5 +/- 5.0 ml/min/100 g, p < 0.05) blood flows. Regional flows to the epicardium, endocardium, and midmyocardium as well as to the frontal, parietal, and occipital lobes of the brain were all significantly improved by ACD-CPR. Aortic systolic (61.7 +/- 4.1 vs 49.5 +/- 3.1 mm Hg, p < 0.01), aortic mean (31.6 +/- 2.8 vs 27.2 +/- 2.2 mm Hg, p = 0.001), and myocardial perfusion pressure (12.9 +/- 3.4 vs 10.4 +/- 3.4 mm Hg, ACD-CPR vs standard CPR, p < 0.01) were all higher during ACD-CPR than during standard CPR. We conclude that ACD-CPR improves tissue perfusion and systemic hemodynamics compared with standard CPR.
Article
Mechanical hyperventilation not only reduces brain oedema after neurotrauma but also affects the central and systemic circulation. We have, in pigs, measured blood flow in the pulmonary artery, the portal vein and in the femoral artery, as well as estimated the splanchnic blood flow and studied the relative perfusion using the microsphere technique in normo- and hypocarbia during intermittent positive pressure ventilation. A normoventilated control group did not change in cardiac output, portal vein blood flow, splanchnic blood flow and femoral arterial blood flow. Hyperventilation was performed to a PCO2 of 3.0 +/- 0.1 kPa. We found that in pigs ventilated with high tidal volume skeletal muscle blood flow did not change during the first 60 min of hyperventilation but gradually decreased thereafter. Blood flow to the cerebellum decreased soon after the induction of hyperventilation, whereas the cerebral blood flow did not decrease until the second hour of hyperventilation. Cardiac output, splanchnic perfusion and portal vein blood flow all decreased. Myocardial perfusion and arterial blood flow to spleen and kidney decreased while pancreatic and liver arterial blood flows were unaffected. It is concluded that mechanical hyperventilation with low frequency and large tidal volumes reduces the flow to most tissues, where the relative decrease according to microsphere measurements is most pronounced in skeletal muscles, heart muscle and cerebellum. However, the changes in cardiac output and splanchnic blood flow were not observed when hyperventilation was induced by increased frequency, keeping the tidal volume constant.
Article
To determine survival from out-of-hospital cardiac arrest in New York City and to compare this with other urban, suburban, and rural areas. Observational cohort study. New York City. Consecutive out-of-hospital cardiac arrests occurring between October 1, 1990, and April 1, 1991. Trained paramedics performed immediate postarrest interviews with care providers, using a standardized questionnaire. Entry criteria, elapsed time intervals, and nodal events conformed to Utstein recommendations. The single target end point was death or discharge home. Of 3243 consecutive cardiac arrests on which resuscitation was attempted, 2329 (72%) met entry criteria as primary cardiac events. Overall survival was 1.4% (99% confidence interval [CI], 0.9% to 2.3%). No patients were lost to follow-up. Survival from witnessed ventricular fibrillation was 5.3% (99% CI, 2.9% to 8.8%). Using survival from witnessed ventricular fibrillation for intersystem comparison, our survival rate was similar to that of Chicago, Ill (4.0%; 99% CI, 1.9% to 7.5%; P = .41), the only other large city on which data were available. However, it was significantly lower than that reported from midsized urban/suburban areas (33.0%; 99% CI, 30.4% to 35.6%; P < .0001) and suburban/rural areas (12.6%; 99% CI, 8.9% to 16.3%; P < .0001). Survival rate among arrests occurring after arrival of emergency medical services personnel (8.5%; 99% CI, 4.7% to 14.0%) was comparable with Chicago (6.6%; 99% CI, 3.3% to 11.5%; P = .41) but markedly lower than King County, Washington (36%; 99% CI, 28.6% to 43.8%; P < .0001). Survival from out-of-hospital cardiac arrest in New York City was poor. This was partly attributable to lengthy elapsed time intervals at every step in the chain of survival. However, examination of survival among arrests occurring after emergency medical services arrival suggests that other features may predispose residents of large cities to higher cardiac arrest mortality than individuals living in more suburban or rural settings. Since half the US population resides in large metropolitan areas, this represents a public health problem of considerable magnitude.
Article
In a pediatric swine model, the effects of increasing tidal volumes and the subsequent development of pulmonary overdistention on cardiopulmonary interactions were studied. The objective was to test the hypothesis that increasing tidal volumes adversely affect pulmonary vascular mechanics and cardiac output. An additional goal was to determine whether the effects of pulmonary overdistention are dependent on delivered tidal volume and/or positive end-expiratory pressure (PEEP, end-expiratory lung volume). Prospective, randomized, controlled laboratory trial. University research laboratory. Eleven 4- to 6-wk-old swine, weighing 8 to 12 kg. Piglets with normal lungs were anesthetized, intubated, and paralyzed. After median sternotomy, pressure transducers were placed in the right ventricle, pulmonary artery, and left atrium. An ultrasonic flow probe was placed around the pulmonary artery. The swine were ventilated and data were collected with delivered tidal volumes of 10, 15, 20, and 25 mL/kg and PEEP settings of 5 and 10 cm H2O in a random order. Pulmonary overdistention was defined as a decrease in dynamic compliance of > or =20% when compared with a compliance measured at a baseline tidal volume of 10 mL/kg. At this baseline tidal volume, airway pressure-volume curves did not demonstrate pulmonary overdistention. Tidal volumes and airway pressures were measured by a pneumotachometer and the Pediatric Pulmonary Function Workstation. Inspiratory time (0.75 sec), FIO2 (0.3), and minute ventilation were held constant. We evaluated the pulmonary vascular and cardiac effects of the various tidal volume and PEEP settings by measuring pulmonary vascular resistance, pulmonary characteristic impedance, and cardiac output. When compared with a tidal volume of 10 mL/kg, a tidal volume of 20 mL/kg resulted in a significant decrease in dynamic compliance from 10.5 +/- 0.9 to 8.4 +/- 0.6 mL/cm H2O (p = .02) at a constant PEEP of 5 cm H2O. The decrease in dynamic compliance of 20% indicated the presence of pulmonary overdistention by definition. As the tidal volume was increased from 10 to 20 mL/kg, pulmonary vascular resistance (1351 +/- 94 vs. 2266 +/- 233 dyne x sec/cm5; p = .004) and characteristic impedance (167 +/- 12 vs. 219 +/- 22 dyne x sec/cm5; p = .02) significantly increased, while cardiac output significantly decreased (951 +/- 61 vs. 708 +/- 48 mL/min; p = .001). Each of these effects of pulmonary overdistention were further magnified when the tidal volume was increased to 25 mL/kg. The tidal volume-induced alterations in pulmonary vascular mechanics, characteristic impedance, and cardiac output occurred to a greater degree when the PEEP was increased to 10 cm H2O. Pulmonary vascular resistance and characteristic impedance were significantly increased and cardiac output significantly decreased for all tidal volumes studied at a PEEP of 10 cm H2O as compared with 5 cm H2O. Increasing tidal volumes, increasing PEEP levels, and the development of pulmonary overdistention had detrimental effects on the cardiovascular system by increasing pulmonary vascular resistance and characteristic impedance while significantly decreasing cardiac output. Delivered tidal volumes of >15 mL/kg should be utilized cautiously. Careful monitoring of respiratory mechanics and cardiac function, especially in neonatal and pediatric patients, is warranted.
Article
There are at least 300,000 cardiac arrests annually in the United States. Cardiopulmonary resuscitation (CPR) effectively restores hemodynamic stability, return of spontaneous circulation (ROSC), in 40% to 60% of arrests. Prolonged survival is significantly lower because of underlying illness and the postresuscitation syndrome, specifically central nervous system injury and left ventricular stunning after resuscitation. Prognostic variables have been shown to predict survival in multivariate analyses, but no models are sufficiently accurate to predict futility. End-tidal carbon dioxide has prognostic value and can measure the efficacy of CPR. Cardiac arrest outcomes will be most improved with public education and earlier initiation of resuscitative efforts, both Basic Life Support and Advanced Cardiac Life Support, notably defibrillation. Active compression-decompression and interposed abdominal compressions improved ROSC in prospective randomized trials; abdominal compressions have also been shown to increase survival to hospital discharge. Despite 30 years of research, CPR is now performed much as it was initially. Further research into the mechanisms of cardiac arrest, development of predictive models, and improved means to improve cardiac output and survival are needed.
Article
[Becker LB, Berg RA, Pepe PE, et al: A reappraisal of mouth-to-mouth ventilation during bystander-initiated cardiopulmonary resuscitation: A statement for Healthcare Professionals From the Ventilation Working Group of the Basic Life Support and Pediatric Life Support Subcommittees, American Heart Association. Ann Emerg Med November 1997;30:654-666.]
Article
To examine determinants of right ventricular function throughout the ventilatory cycle under volume-controlled mechanical ventilation with various positive end-expiratory pressure (PEEP) stages. Prospective observational animal pilot study. Animal research laboratory at a university hospital. Eight healthy swine under volume- controlled mechanical ventilation. Flow probes were implanted in eight swine in order to continuously measure blood flow in the pulmonary artery and inferior vena cava. After a recovery phase of 14 days, the swine were subjected to various PEEP stages (0, 5, 10 cm H2O) during volume-controlled positive pressure ventilation. Continuous flow measurement took place in the pulmonary artery and inferior vena cava. Data on standard hemodynamic parameters were additionally acquired. Respiration-phase-specific analysis of right ventricular cardiac output and of additional hemodynamic function parameters followed, after calculation of mean values throughout five respiration cycles. PEEP at 5 cm H2O led to significant decreases in inferior vena cava flow (4.1%), and in right ventricular cardiac output (5.2%); the respective decreases at PEEP 10 cm H2O were 13.9% and 18.3%. In the inspiration phase at PEEP 10 cm H2O, results revealed an overproportionally pronounced decrease in comparison with the expiration phase in inferior vena cava flow (-24.6% vs. -10%) and right ventricular cardiac output (-35% vs. -13.5%). This phenomenon is presumably caused by a PEEP-related increase in mean airway pressure by the amount of 10.7 cm H2O in inspiration. Increases in PEEP during volume-controlled mechanical ventilation leads to respiration-phase-specific reduction of right ventricular cardiac output, with a significantly pronounced decrease during the inspiration phase. This decrease in cardiac output should be taken into particular consideration for patients with already critically reduced cardiac output.
Article
Despite extensive training of citizens of Seattle in cardiopulmonary resuscitation (CPR), bystanders do not perform CPR in almost half of witnessed cardiac arrests. Instructions in chest compression plus mouth-to-mouth ventilation given by dispatchers over the telephone can require 2.4 minutes. In experimental studies, chest compression alone is associated with survival rates similar to those with chest compression plus mouth-to-mouth ventilation. We conducted a randomized study to compare CPR by chest compression alone with CPR by chest compression plus mouth-to-mouth ventilation. The setting of the trial was an urban, fire-department-based, emergency-medical-care system with central dispatching. In a randomized manner, telephone dispatchers gave bystanders at the scene of apparent cardiac arrest instructions in either chest compression alone or chest compression plus mouth-to-mouth ventilation. The primary end point was survival to hospital discharge. Data were analyzed for 241 patients randomly assigned to receive chest compression alone and 279 assigned to chest compression plus mouth-to-mouth ventilation. Complete instructions were delivered in 62 percent of episodes for the group receiving chest compression plus mouth-to-mouth ventilation and 81 percent of episodes for the group receiving chest compression alone (P=0.005). Instructions for compression required 1.4 minutes less to complete than instructions for compression plus mouth-to-mouth ventilation. Survival to hospital discharge was better among patients assigned to chest compression alone than among those assigned to chest compression plus mouth-to-mouth ventilation (14.6 percent vs. 10.4 percent), but the difference was not statistically significant (P=0.18). The outcome after CPR with chest compression alone is similar to that after chest compression with mouth-to-mouth ventilation, and chest compression alone may be the preferred approach for bystanders inexperienced in CPR.
Article
Current resuscitation methods, although occasionally effective, rarely perform as well as initially anticipated. Some of the disappointment can be attributed to the difficulty of the task for many, including both professional and lay first responders. Significant attention has been paid recently to the need to simplify both the technique and the teaching of resuscitation. In considering simplification of the current resuscitation scheme, a logical start is an honest reappraisal of the importance and priorities of each of the once sacrosanct ABCs, specifically, establishment of an Airway, artificial Breathing (mouth-to-mouth breathing), and chest compressions for temporary Circulation. Experimental data continue to accumulate indicating that most important within this triad is circulation. Adequate oxygen exists within the blood during at least the first 10 mins of cardiac arrest. If circulation is provided to distribute such oxygen, no survival disadvantage results with chest compression-only basic life support (BLS) efforts. Even a totally occluded airway during the first 6 mins of cardiac arrest does not compromise survival if reasonable circulation is provided with chest compressions. Clinical studies support the same conclusion that what most influences survival in any BLS effort is circulation, not ventilation. Belgium investigators have shown equal survival rates among those treated with chest compressions plus ventilation and those who received chest compressions alone. Telephone dispatcher-guided BLS cardiopulmonary resuscitation (CPR) has likewise shown no survival disadvantage to chest compression-only CPR when compared with telephone-guided standard BLS CPR. Based on this reasoning, a new simplified BLS method has been proposed. "Staged" CPR consists of a strategy to initially teach laypersons a simplified approach to BLS, which requires only chest compressions and not mouth-to-mouth breathing. "Bronze" CPR, in which chest compression-only BLS is taught, was compared with the standard European Resuscitation Council BLS course for laypersons. Manikin "exit testing" at course completion has revealed significant advantages of the simplified approach compared with standard CPR courses for the lay public.
Article
Despite improving arterial oxygen saturation and pH, bystander cardiopulmonary resuscitation (CPR) with chest compressions plus rescue breathing (CC+RB) has not improved survival from ventricular fibrillation (VF) compared with chest compressions alone (CC) in numerous animal models and 2 clinical investigations. After 3 minutes of untreated VF, 14 swine (32+/-1 kg) were randomly assigned to receive CC+RB or CC for 12 minutes, followed by advanced cardiac life support. All 14 animals survived 24 hours, 13 with good neurological outcome. For the CC+RB group, the aortic relaxation pressures routinely decreased during the 2 rescue breaths. Therefore, the mean coronary perfusion pressure of the first 2 compressions in each compression cycle was lower than those of the final 2 compressions (14+/-1 versus 21+/-2 mm Hg, P<0.001). During each minute of CPR, the number of chest compressions was also lower in the CC+RB group (62+/-1 versus 92+/-1 compressions, P<0.001). Consequently, the integrated coronary perfusion pressure was lower with CC+RB during each minute of CPR (P<0.05 for the first 8 minutes). Moreover, at 2 to 5 minutes of CPR, the median left ventricular blood flow by fluorescent microsphere technique was 60 mL. 100 g(-1). min(-1) with CC+RB versus 96 mL. 100 g(-1). min(-1) with CC, P<0.05. Because the arterial oxygen saturation was higher with CC+RB, the left ventricular myocardial oxygen delivery did not differ. Interrupting chest compressions for rescue breathing can adversely affect hemodynamics during CPR for VF.
Article
Interruptions to chest compression-generated blood flow during cardiopulmonary resuscitation (CPR) are detrimental. Data show that such interruptions for mouth-to-mouth ventilation require a period of "rebuilding" of coronary perfusion pressure to obtain the level achieved before the interruption. Whether such hemodynamic compromise from pausing to ventilate is enough to affect outcome is unknown. Thirty swine (weight 35 +/- 2 kg) underwent 3 minutes of untreated ventricular fibrillation before 12 minutes of basic life support CPR. Animals were randomized to receive either standard airway (A), breathing (B), and compression (C) CPR with expired-gas ventilation in a 15:2 compression-to-ventilation ratio or continuous chest compression CPR. Those randomized to the standard 15:2 group had no chest compressions for a period of 16 seconds each time the 2 ventilations were delivered. Defibrillation was attempted at 15 minutes of cardiac arrest. All resuscitated animals were supported in an intensive care environment for 1 hour, then in a maintenance facility for 24 hours. The primary end point of neurologically normal 24-hour survival was significantly better in the experimental group receiving continuous chest compression CPR (12 of 15 versus 2 of 15; P<0.0001). Mouth-to-mouth ventilation performed by single layperson rescuers produces substantial interruptions in chest compression-supported circulation. Continuous chest compression CPR produces greater neurologically normal 24-hour survival than standard ABC CPR when performed in a clinically realistic fashion. Any technique that minimizes lengthy interruptions of chest compressions during the first 10 to 15 minutes of basic life support should be given serious consideration in future efforts to improve outcome results from cardiac arrest.
Article
To develop and evaluate a practical formula for the optimum ratio of compressions to ventilations in cardiopulmonary resuscitation (CPR). The optimum value of a variable is that for which a desired result is maximized. Here the desired result is assumed to be either oxygen delivery to peripheral tissues or a combination of oxygen delivery and waste product removal. Equations describing oxygen delivery and blood flow during CPR as functions of the number of compressions and the number of ventilations delivered over time were developed from principles of classical physiology. These equations were solved explicitly in terms of the compression/ventilation ratio and evaluated for a wide range of conditions using Monte Carlo simulations. As the compression to ventilation ratio was increased from 0 to 50 or more, both oxygen delivery and the combination of oxygen delivery with blood flow increased to maximum values and then gradually declined. For variables typical of standard CPR as taught and specified in international guidelines, maximum values occurred at compression/ventilation ratios near 30:2. For variables typical of actual lay rescuer performance in the field, maximal values occurred at compression/ventilation ratios near 60:2. Current guidelines overestimate the need for ventilation during standard CPR by two to four-fold. Blood flow and oxygen delivery to the periphery can be improved by eliminating interruptions of chest compression for these unnecessary ventilations.
Article
Transthoracic impedance and current flow are determinants of defibrillation success with monophasic shocks. Whether transthoracic impedance, either independently or via its association with body weight, is a determinant of biphasic waveform shock success has not been determined. We studied 22 swine, weighing 18-41 kg. After 15 s of ventricular fibrillation, each pig received transthoracic truncated exponential biphasic shocks (5/5 ms), 70-360 J. Shock success was strongly associated individually with body weight, leading-edge transthoracic impedance and current at low energy levels (70 and 100 J, all P<0.001). Multiple logistic regression analysis showed a significant association of body weight with shock success after adjusting for the effect of leading-edge impedance (odds ratio of success for 1 kg decrease in weight at 70 J was 1.29, 95% CI: 1.05-1.59, P=0.02; and at 100 J was 1.30, 95% CI: 1.14-1.49, P<0.0001). The same result was observed after adjusting for the effect of leading-edge current. At 150 J or higher energy levels, no significant association was observed. Body weight is a determinant of shock success with biphasic waveforms at low energy levels in this swine model.
Article
We developed an integrated model of telemedicine services in emergency medical care. The architecture was designed to support pre-hospital management. The experimental work was carried out with the collaboration of the emergency medical services (EMS) in Madrid. Two different study populations were defined: a control population using conventional EMS protocols and a population using the telemedicine system. The telemedicine system was based on a telepresence service; electrocardiograms and images were transmitted from the ambulance to the health emergency coordination centre. The cost of dealing with 100 patients using telemedicine was C6030 less than the cost of conventional care. The response times using telemedicine were significantly lower.
Article
The optimal ratio of chest compressions to ventilations during cardiopulmonary resuscitation (CPR) is unknown. We determine 24-hour survival and neurologic outcome, comparing 4 different chest compression-ventilation CPR ratios in a porcine model of prolonged cardiac arrest and bystander CPR. Forty swine were instrumented and subjected to 3 minutes of ventricular fibrillation followed by 12 minutes of CPR by using 1 of 4 models of chest compression-ventilation ratios as follows: (1) standard CPR with a ratio of 15:2; (2) CC-CPR, chest compressions only with no ventilations for 12 minutes; (3) 50:5-CPR, CPR with a ratio of 50:5 compressions to ventilations, as advocated by authorities in Great Britain; and (4) 100:2-CPR, 4 minutes of chest compressions only followed by CPR with a ratio of 100:2 compressions to ventilations. CPR was followed by standard advanced cardiac life support, 1 hour of critical care, and 24 hours of observation, followed by a neurologic evaluation. There were no statistically significant differences in 24-hour survival among the 4 groups (standard CPR, 7/10; CC-CPR, 7/10; 50:5-CPR, 8/10; 100:2-CPR, 9/10). There were significant differences in 24-hour neurologic function, as evaluated by using the swine cerebral performance category scale. The animals receiving 100:2-CPR had significantly better neurologic function at 24 hours than the standard CPR group with a 15:2 ratio (1.5 versus 2.5; P =.007). The 100:2-CPR group also had better neurologic function than the CC-CPR group, which received chest compressions with no ventilations (1.5 versus 2.3; P =.027). Coronary perfusion pressures, aortic pressures, and myocardial and kidney blood flows were not significantly different among the groups. Coronary perfusion pressure as an integrated area under the curve was significantly better in the CC-CPR group than in the standard CPR group (P =.04). Minute ventilation and PaO (2) were significantly lower in the CC-CPR group. In this experimental model of bystander CPR, the group receiving compressions only for 4 minutes followed by a compression-ventilation ratio of 100:2 achieved better neurologic outcome than the group receiving standard CPR and CC-CPR. Consideration of alternative chest compression-ventilation ratios might be appropriate.
Article
A study was performed to demonstrate that slower respiratory rates (RRs) of positive-pressure ventilation can preserve adequate oxygenation and acid-base status in hemorrhagic states, whereas "normal" or higher RRs worsen hemodynamics. Eight swine (ventilated with 12 mL/kg tidal volume, 0.28 Fio(2); RR of 12 breaths/min) were hemorrhaged to < 65 mm Hg systolic arterial blood pressure (SABP). RRs were then sequentially changed every 10 minutes to 6, 20, 30, and 6 breaths/min. With RRs at 6 breaths/min, the animals maintained pH > 7.25/Sao(2) > 99%, but increased mean SABP (from 65 to 84 mm Hg; p < 0.05), time-averaged coronary perfusion pressure (CPP) (from 50 +/- 2 to 60 +/- 4 mm Hg; p < 0.05), and cardiac output (Qt) (from 2.4 to 2.8 L/min; p < 0.05). With RRs of 20 and 30 breaths/min, SABP (73 and 66 mm Hg), CPP (47 +/- 3 and 42 +/- 4 mm Hg), and Qt (2.5 and 2.4 L/min) decreased, as did Pao(2) and Paco(2) (< 30 mm Hg), with p < 0.05 for each comparison, respectively. When RR returned to 6 breaths/min, SABP (95 mm Hg), CPP (71 +/- 6 mm Hg), and Qt (3.0 L/min) improved significantly (p < 0.05). After even moderate levels of hemorrhage in animals, positive-pressure ventilation with "normal" or higher RRs can impair hemodynamics. Hemodynamics can be improved with lower RRs while still maintaining adequate oxygenation and ventilation.