Article

Intraoperative Ventilatory Strategies for Prevention of Pulmonary Atelectasis in Obese Patients Undergoing Laparoscopic Bariatric Surgery

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Abstract

Atelectasis occurs regularly after induction of general anesthesia, persists postoperatively, and may contribute to significant postoperative morbidity and additional health care costs. Laparoscopic surgery has been reported to be associated with an increased incidence of postoperative atelectasis. It has been shown that during general anesthesia, obese patients have a greater risk of atelectasis than nonobese patients. Preventing atelectasis is important for all patients but is especially important when caring for obese patients. We randomly allocated 66 adult obese patients with a body mass index between 30 and 50 kg/m(2) scheduled to undergo laparoscopic bariatric surgery into 3 groups. According to the recruitment maneuver used, the zero end-expiratory pressure (ZEEP) group (n = 22) received the vital capacity maneuver (VCM) maintained for 7-8 s applied immediately after intubation plus ZEEP; the positive end-expiratory pressure (PEEP) 5 group (n = 22) received the VCM maintained for 7-8 s applied immediately after intubation plus 5 cm H(2)O of PEEP; and the PEEP 10 group (n = 22) received the VCM maintained for 7-8 s applied immediately after intubation plus 10 cm H(2)O of PEEP. All other variables (e.g., anesthetic and surgical techniques) were the same for all patients. Heart rate, noninvasive mean arterial blood pressure, arterial oxygen saturation, and alveolar-arterial Pao(2) gradient (A-a Pao(2)) were measured intraoperatively and postoperatively in the postanesthesia care unit (PACU). Length of stay in the PACU and the use of a nonrebreathing O(2) mask (100% Fio(2)) or reintubation were also recorded. A computed tomographic scan of the chest was performed preoperatively and postoperatively after discharge from the PACU to evaluate lung atelectasis. Patients in the PEEP 10 group had better oxygenation both intraoperatively and postoperatively in the PACU, lower atelectasis score on chest computed tomographic scan, and less postoperative pulmonary complications than the ZEEP and PEEP 5 groups. There was no evidence of barotrauma in any patient in the 3 study groups. Intraoperative alveolar recruitment with a VCM followed by PEEP 10 cm H(2)O is effective at preventing lung atelectasis and is associated with better oxygenation, shorter PACU stay, and fewer pulmonary complications in the postoperative period in obese patients undergoing laparoscopic bariatric surgery.

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... This incidence is increased in thoracoabdominal surgery. In the study of Talab et al. (21) illustrated that during the first 48 h postoperatively, no significant desaturation, chest infection, or bronchospasm were noted in the positive end expiratory pressure "PEEP" (10 cmH 2 O) group, compared to PEEP (5cmH 2 O) and ZEEP (zero-end-expiratory pressure) groups respectively. Talab et al. (21) found that postoperative pulmonary complications occurred only in the ZEEP and "PEEP" (5 cm H 2 O). ...
... In the study of Talab et al. (21) illustrated that during the first 48 h postoperatively, no significant desaturation, chest infection, or bronchospasm were noted in the positive end expiratory pressure "PEEP" (10 cmH 2 O) group, compared to PEEP (5cmH 2 O) and ZEEP (zero-end-expiratory pressure) groups respectively. Talab et al. (21) found that postoperative pulmonary complications occurred only in the ZEEP and "PEEP" (5 cm H 2 O). Our results are in agreement with the results obtained by Talab et al. (21) and Duggan and Kavanagh (22) as postoperative pulmonary complications were present in VC, PC, VC+PEEP groups while not present in VC + PEEP + recruitment maneuver. ...
... Talab et al. (21) found that postoperative pulmonary complications occurred only in the ZEEP and "PEEP" (5 cm H 2 O). Our results are in agreement with the results obtained by Talab et al. (21) and Duggan and Kavanagh (22) as postoperative pulmonary complications were present in VC, PC, VC+PEEP groups while not present in VC + PEEP + recruitment maneuver. The same finding was reached with Duggan and Kavanagh (22) who reported that development of atelectasis is associated with decreased lung compliance, impairment of oxygenation, increased pulmonary vascular resistance, and development of lung injury. ...
... This incidence is increased in thoracoabdominal surgery. In the study of Talab et al. (21) illustrated that during the first 48 h postoperatively, no significant desaturation, chest infection, or bronchospasm were noted in the positive end expiratory pressure "PEEP" (10 cmH 2 O) group, compared to PEEP (5cmH 2 O) and ZEEP (zero-end-expiratory pressure) groups respectively. Talab et al. (21) found that postoperative pulmonary complications occurred only in the ZEEP and "PEEP" (5 cm H 2 O). ...
... In the study of Talab et al. (21) illustrated that during the first 48 h postoperatively, no significant desaturation, chest infection, or bronchospasm were noted in the positive end expiratory pressure "PEEP" (10 cmH 2 O) group, compared to PEEP (5cmH 2 O) and ZEEP (zero-end-expiratory pressure) groups respectively. Talab et al. (21) found that postoperative pulmonary complications occurred only in the ZEEP and "PEEP" (5 cm H 2 O). Our results are in agreement with the results obtained by Talab et al. (21) and Duggan and Kavanagh (22) as postoperative pulmonary complications were present in VC, PC, VC+PEEP groups while not present in VC + PEEP + recruitment maneuver. ...
... Talab et al. (21) found that postoperative pulmonary complications occurred only in the ZEEP and "PEEP" (5 cm H 2 O). Our results are in agreement with the results obtained by Talab et al. (21) and Duggan and Kavanagh (22) as postoperative pulmonary complications were present in VC, PC, VC+PEEP groups while not present in VC + PEEP + recruitment maneuver. The same finding was reached with Duggan and Kavanagh (22) who reported that development of atelectasis is associated with decreased lung compliance, impairment of oxygenation, increased pulmonary vascular resistance, and development of lung injury. ...
Article
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Background: Upper abdominal surgeries have been reported to be associated with an increased incidence of postoperative atelectasis. Preventing atelectasis is important for all patients but is more important when caring for obese patients. Objectives: To determine which of the following ventilatory strategies is better in prevention of pulmonary atelectasis in obese patients undergoing non-bariatric surgery: Volume control ventilation "VC", Pressure control Ventilation "PC", Volume control ventilation + Positive End Expiratory Pressure "PEEP", Volume control ventilation + Positive End Expiratory Pressure "PEEP" + lung recruitment maneuver. Patients and methods: A randomized-controlled trial study was carried out in the operating room (OR) in Zagazig University Hospital including 92 patients. Patients were randomly allocated into four groups. G1: Volume control ventilation "VC", G2: Pressure control Ventilation "PC", G3: Volume control ventilation + Positive End Expiratory Pressure "PEEP", G4: as in G3 + lung recruitment maneuver. Results: There was significant difference between the studied groups as regards PaO 2 /FiO 2 ratio as the 4 th group was highly significant. There was also significant difference between the studied groups as regards atelectasis score with the least atelectasis score in group 4. There was a significant difference in group 4 than the other groups as regards length of stay in PACU, and need for 100% Fio2 in PACU. Finally, there was a significant difference between the studied groups as regards postoperative pulmonary complications with the 4 th group has the least postoperative complication. Conclusion: Our results suggest that volume control ventilation + Positive End Expiratory Pressure "PEEP" + lung recruitment maneuver had beneficial effects on oxygenation continued into the early recovery period and decrease pulmonary complications in the early post-operative period in obese patients undergoing non-bariatric upper abdominal surgeries.
... Atelectasis can lead to further complications in post-operative patients including pneumonia, respiratory failure, and the exacerbation of underlying chronic lung disease (Qaseem et al., 2006). Regardless of weight, atelectasis occurs regularly after the induction of anesthesia and continues through the postoperative period (Talab et al., 2009). With a wide array of potential postoperative complications, anesthesia professionals must be vigilant in their practice to identify measures that could potentiate these complications after surgery. ...
... Obese patients are at a higher risk than non-obese patients to develop postoperative atelectasis after having laparoscopic surgery (Talab et al., 2009 were assessed pre-and post-operatively to evaluate for atelectasis. CT scan can measure lung volumes in all or part of the lung and is a more sensitive study in detecting 9 atelectasis than X-ray (Miller, 2015). ...
... The five studies are presented in chronological order with the oldest study first (Whalen et al., 2006, Chalhoub et al., 2007, Reinius et al., 2009, Talab et al., 2009, Futier et al., 2011. Each study is summarized in data collection tables (Appendix A) and appraised using the Critical Appraisal Skills Programme (CASP) Randomised Controlled Trials Checklist (Appendix C). ...
Preprint
General anesthesia has a profound effect on respiratory dynamics in the obese population. Obesity can contribute to a decreased functional residual capacity, reduced lung volumes, and an increased closing capacity. Positioning and procedural requirements can further complicate the respiratory status of the obese patient. Surgical procedures in the obese population have an increased risk for the formation of atelectasis. Ventilation can be compromised due to atelectatic lung tissue and may result in post operative complications such as pneumonia, acute respiratory distress, hypoxia, a prolonged hospital stay, and the need for prolonged mechanical ventilation. Positive end-expiratory pressure (PEEP) is utilized in the operating room to increase arterial oxygenation, prevent airway collapse and expand alveoli during each breath. Alveolar recruitment maneuvers can be supplementary throughout surgical procedures to recruit and restore atelectatic lung tissue and prevent further formation of atelectasis. The purpose of this systematic review was to evaluate the effect of PEEP with recruitment maneuvers in obese patients undergoing abdominal surgery with general anesthesia. The theoretical framework that guided this systematic review was the Preferred Reporting Items for Systematic Review and Meta- Analysis (PRISMA) Statement. Randomized control trials included in this systematic review were appraised using the Critical Appraisal Skills Programme (CASP) to evaluate reliability. Alveolar recruitment maneuvers increase lung compliance, arterial oxygenation, and decrease complications associated with atelectasis formation. The use of PEEP with alveolar recruitment maneuvers should be employed for obese patients that undergo abdominal surgery with general anesthesia.
... Finally, poxemia than initially expected, 24 likely because it was estimated very early in the immediate postoperative period, we did not observe an increase in postoperative morbidity and mortality, as reported in previous studies, [1][2][3][4] This can be explained by the development of mild complications only, which is in agreement to previous trials comparing different intraoperative ventilator strategies in bariatric surgery. [25][26][27] Previous physiological studies have shown that the maximum airway pressure achieved with HFNC under "optimal" conditions is around five cmH 2 o. 28,29 While it is unlikely that that pressure favors the recruitment of collapsed lung areas, especially in patients with diaphragmatic dysfunction, it seems reasonable that this constant airway pressure might prevent lung derecruitment. Indeed, we believe that some of the methodological approaches applied in our study strengthened the performance of HFNC therapy and could justify the positive results we found in terms of a reduction in the prevalence of hypoxemia and atelectasis. ...
... First, we performed an intraoperative OLA, while avoiding or minimizing alveolar collapse. 19,25,30 The effectiveness of recruitment maneuvers and the PEEP setting in morbidly obese patients undergoing bariatric surgery it seems limited to the intubation period (Supplementary Text File 1). 19 Our findings are ...
Article
Background: Postoperative pulmonary complications (PPCs) are common in high-risk surgical patients. Postoperative ventilatory management may improve their outcome. Supplemental oxygen through a high-flow nasal cannula (HFNC) has become an alternative to classical oxygenation techniques, although the results published for postoperative patients are contradictory. We examined the efficacy of HFNC in postoperative morbidly obese patients who were ventilated intraoperatively with an open-lung approach (OLA). Methods: We performed an open, two-arm, randomized controlled trial in 64 patients undergoing bariatric surgery (N.=32 in each arm) from May to November 2017 at the Hospital Clínico of Valencia. Patients were randomly assigned to receive HFNC oxygen therapy at the time of extubation or to receive conventional oxygen therapy, both applied during the first three postoperative hours. Intraoperatively, a recruitment maneuver and individualized positive end-expiratory pressure was applied in all patients. The primary outcome was postoperative hypoxemia. Results: All patients were included in the final analysis. There were no significant differences between the baseline characteristics. Postoperative hypoxemia was less frequent in the HFNC group compared to those who received standard care (28.6% vs. 80.0%, relative risk [RR]: 0.35; 95%CI: 0.150-0.849, P=0.009). Prevalence of atelectasis was lower in the HFNC group (31% vs. 77%, RR: 0.39; 95%CI: 0.166-0.925, P=0.013). No severe PPCs were reported in any patient. Conclusions: Early application of HFNC in the operating room before extubation and during the immediate postoperative period decreases postoperative hypoxemia in obese patients after bariatric surgery who were intraoperatively ventilated using an OLA approach.
... • вероятность гиперкапнии во время анестезии. Комментарии: применение конечно-экспираторного давления позволяет улучшить биомеханику дыхания, препятствовать развитию ателектазов [85][86][87]. Маневр открытия альвеол обеспечивает мобилизацию альвеол, коллапс которых уже произошел в течение индукции анестезии, механическом воздействии на легкие, после дисконнеции дыхательного контура [82][83][84][85][86][87][88]. Сочетание PEEP и маневра открытия альвеол снижает частоту гипоксемии, однако рекомендуемая стратегия должна выполняться с осторожностью, поскольку сопряжена с увеличением риска гипотензии и брадикардии [89]. ...
... Комментарии: применение конечно-экспираторного давления позволяет улучшить биомеханику дыхания, препятствовать развитию ателектазов [85][86][87]. Маневр открытия альвеол обеспечивает мобилизацию альвеол, коллапс которых уже произошел в течение индукции анестезии, механическом воздействии на легкие, после дисконнеции дыхательного контура [82][83][84][85][86][87][88]. Сочетание PEEP и маневра открытия альвеол снижает частоту гипоксемии, однако рекомендуемая стратегия должна выполняться с осторожностью, поскольку сопряжена с увеличением риска гипотензии и брадикардии [89]. ...
... Anesthetic induction in obese patients can result in a significant reduction in respiratory compliance and increase resistance and pressure in the airway [5]. A correlation has also been found between a high BMI and an increase in breathing effort and a reduction in oxygenation levels, which may lead to atelectasis and slower weaning from mechanical ventilation [6,7]. ...
... In the blinding of participants and personnel domain all the studies were classified as high risk as the personnel could not be blinded. Four studies [7,13,17,25] adequately described the blinding of outcome assessment. Eleven studies [7, 14-21, 24, 25] did not describe losses or exclusions which could cause imbalance between the groups. ...
Article
Full-text available
Background: Obesity is a global epidemic, and it is widely known that increased Body mass index (BMI) is associated with alterations in respiratory mechanics. Bariatric surgery is established as an effective treatment for this condition. Objective: To assess the safety and effectiveness of different ventilation strategies in obese patients undergoing bariatric surgery. Methods: A systematic review of randomized clinical trials aimed at evaluating ventilation strategies for obese patients was carried out. Primary outcomes: in-hospital mortality, adequacy of gas exchange, and respiration mechanics alterations. Results: Fourteen clinical trials with 574 participants were included. When recruitment maneuvers (RM) vs Positive end-expiratory pressure (PEEP) were compared, RM resulted in better oxygenation p = 0.03 (MD 79.93), higher plateau pressure p < 0.00001 (MD 7.30), higher mean airway pressure p < 0.00001 (MD 6.61), and higher compliance p < 0.00001 (MD 21.00); when comparing RM + Zero end-expiratory pressure (ZEEP) vs RM + PEEP 5 or 10 cmH2O, RM associated with PEEP led to better oxygenation p = 0.001 (MD 167.00); when comparing Continuous Positive Airway Pressure (CPAP) 40 cmH2O + PEEP 10 cmH2O vs CPAP 40 cmH2O + PEEP 15 cmH2O, CPAP 40 + PEEP 15 achieved better gas exchange p = 0.003 (MD 36.00) and compliance p = 0.0003 (MD 3.00). Conclusion: There is some evidence that the alveolar recruitment maneuvers associated with PEEP lead to better oxygenation and higher compliance. There is no evidence of differences between pressure control ventilation (PCV) and Volume control ventilation (VCV).
... 14 For instance, recruitment maneuvers only lead to physiologic and radiographic improvement in obese patients or during pneumoperitoneum when associated with increased PEEP. 14,91, 193 In clinical trials, periodic recruitment maneuvers failed to improve postoperative pulmonary outcomes even when combined to high PEEP after abdominal or cardiac surgery (table 2). 102,188,194,195 Accordingly, current recommendations limit the use of recruitment maneuvers to patients presenting a respiratory dysfunction suggestive of atelectasis according to an individual risk-benefit assessment and always combined with PEEP ( fig. 6). ...
... 197 This occurs either with mere application of PEEP to normal lungs, 3 or when PEEP follows lung recruitment maneuvers in highrisk settings for atelectasis (e.g., obesity). 14,91, 193 Besides those beneficial physiologic effects, PEEP can also prevent the mechanical and biologic lung injuries associated with atelectasis 26 and, consequently, improve postoperative pulmonary outcomes. Such protection has been implied by the observation of better postoperative pulmonary outcomes with moderate PEEP (5 to 8 cm H 2 O) than with lower to no or high PEEP in large registry-based studies in noncardiothoracic surgery, 157,198 and worse outcomes when PEEP of approximately 0 is associated with low V T . ...
Article
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The development of pulmonary atelectasis is common in the surgical patient. Pulmonary atelectasis can cause various degrees of gas exchange and respiratory mechanics impairment during and after surgery. In its most serious presentations, lung collapse could contribute to postoperative respiratory insufficiency, pneumonia, and worse overall clinical outcomes. A specific risk assessment is critical to allow clinicians to optimally choose the anesthetic technique, prepare appropriate monitoring, adapt the perioperative plan, and ensure the patient’s safety. Bedside diagnosis and management have benefited from recent imaging advancements such as lung ultrasound and electrical impedance tomography, and monitoring such as esophageal manometry. Therapeutic management includes a broad range of interventions aimed at promoting lung recruitment. During general anesthesia, these strategies have consistently demonstrated their effectiveness in improving intraoperative oxygenation and respiratory compliance. Yet these same intraoperative strategies may fail to affect additional postoperative pulmonary outcomes. Specific attention to the postoperative period may be key for such outcome impact of lung expansion. Interventions such as noninvasive positive pressure ventilatory support may be beneficial in specific patients at high risk for pulmonary atelectasis (e.g., obese) or those with clinical presentations consistent with lung collapse (e.g., postoperative hypoxemia after abdominal and cardiothoracic surgeries). Preoperative interventions may open new opportunities to minimize perioperative lung collapse and prevent pulmonary complications. Knowledge of pathophysiologic mechanisms of atelectasis and their consequences in the healthy and diseased lung should provide the basis for current practice and help to stratify and match the intensity of selected interventions to clinical conditions.
... 34 Intraoperative Ventilation Strategies Tidal volumes used on the basis of TBW instead of ideal body weight may be overestimated by 20%-50%, 35 and potentially increase postoperative pulmonary complications. 36 In patients undergoing laparoscopic surgery, pressure control ventilation has been shown to result in better intraoperative oxygenation when compared to volume-controlled ventilation. 37 Positive end-expiratory pressure (PEEP) carefully titrated up to 10 cm H 2 O can mitigate atelectasis after laparoscopic bariatric surgery. ...
... 37 Positive end-expiratory pressure (PEEP) carefully titrated up to 10 cm H 2 O can mitigate atelectasis after laparoscopic bariatric surgery. 36 In nonobese patients undergoing laparoscopic or open abdominal surgery, tidal volumes of 6-8 mL/kg of predicted body weight, PEEP of 6-8 cm H 2 O, and lung recruitment in the form of 30 seconds of CPAP at 30 cm H 2 O improved the incidence of postoperative pulmonary and extrapulmonary complications. 38 More recently, however, high levels of PEEP (12 cm H 2 O) and alveolar recruitment maneuvers during intraoperative mechanical ventilation did not reduce postoperative pulmonary complications in obese patients, when compared to low levels of PEEP (4 cm H 2 O) although hypoxia was more frequent in the latter. ...
Article
Obesity hypoventilation syndrome (OHS) is considered as a diagnosis in obese patients (body mass index [BMI] ≥30 kg/m2) who also have sleep-disordered breathing and awake diurnal hypercapnia in the absence of other causes of hypoventilation. Patients with OHS have a higher burden of medical comorbidities as compared to those with obstructive sleep apnea (OSA). This places patients with OHS at higher risk for adverse postoperative events. Obese patients and those with OSA undergoing elective noncardiac surgery are not routinely screened for OHS. Screening for OHS would require additional preoperative evaluation of morbidly obese patients with severe OSA and suspicion of hypoventilation or resting hypoxemia. Cautious selection of the type of anesthesia, use of apneic oxygenation with high-flow nasal cannula during laryngoscopy, better monitoring in the postanesthesia care unit (PACU) can help minimize adverse perioperative events. Among other risk-reduction strategies are proper patient positioning, especially during intubation and extubation, multimodal analgesia, and cautious use of postoperative supplemental oxygen.
... When the lung is allowed to collapse below normal FRC, atelectatic, and edema-filled resting tissue (1) does not exchange gas; (2) is susceptible to the development of pneumonia (Huynh et al., 2019;Li Bassi et al., 2019); (3) will become fibrotic if not reopened (Burkhardt, 1989;Cabrera-Benitez et al., 2014;Lutz et al., 2015); (4) initiates patient-ventilator dyssynchrony, which is caused by the firing of mechanical stretch, PO 2 , PCO 2 , and pH receptors (Solomon et al., 2000;Manning and Mahler, 2001;Widdicombe, 2001;Mellott et al., 2009;Burki and Lee, 2010;Yu, 2016;Yoshida et al., 2017) and which is associated with high mortality (Blanch et al., 2015); and (5) creates a stress-focus in the adjacent open alveoli and alveolar ducts, greatly amplifying the forces applied to these parenchymal tissues during tidal ventilation (Mead et al., 1970;Gattinoni et al., 2012;Cressoni et al., 2014;Makiyama et al., 2014;Retamal et al., 2014). It has been shown that letting the lung rest in obese bariatric surgery patients is associated with worse oxygenation, longer post-anesthesia care unit stay, and more post-operative pulmonary complications as compared with patients in which the atelectatic resting lung was opened and ventilated (Talab et al., 2009). Although, the phrase resting the lung sounds protective, the lung is not meant to function in a deflated state, and as listed above, such a state is associated with numerous pathologies. ...
Article
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Acute respiratory distress syndrome (ARDS) causes a heterogeneous lung injury and remains a serious medical problem, with one of the only treatments being supportive care in the form of mechanical ventilation. It is very difficult, however, to mechanically ventilate the heterogeneously damaged lung without causing secondary ventilator-induced lung injury (VILI). The acutely injured lung becomes time and pressure dependent, meaning that it takes more time and pressure to open the lung, and it recollapses more quickly and at higher pressure. Current protective ventilation strategies, ARDSnet low tidal volume (LVt) and the open lung approach (OLA), have been unsuccessful at further reducing ARDS mortality. We postulate that this is because the LVt strategy is constrained to ventilating a lung with a heterogeneous mix of normal and focalized injured tissue, and the OLA, although designed to fully open and stabilize the lung, is often unsuccessful at doing so. In this review we analyzed the pathophysiology of ARDS that renders the lung susceptible to VILI. We also analyzed the alterations in alveolar and alveolar duct mechanics that occur in the acutely injured lung and discussed how these alterations are a key mechanism driving VILI. Our analysis suggests that the time component of each mechanical breath, at both inspiration and expiration, is critical to normalize alveolar mechanics and protect the lung from VILI. Animal studies and a meta-analysis have suggested that the time-controlled adaptive ventilation (TCAV) method, using the airway pressure release ventilation mode, eliminates the constraints of ventilating a lung with heterogeneous injury, since it is highly effective at opening and stabilizing the time- and pressure-dependent lung. In animal studies it has been shown that by “casting open” the acutely injured lung with TCAV we can (1) reestablish normal expiratory lung volume as assessed by direct observation of subpleural alveoli; (2) return normal parenchymal microanatomical structural support, known as alveolar interdependence and parenchymal tethering, as assessed by morphometric analysis of lung histology; (3) facilitate regeneration of normal surfactant function measured as increases in surfactant proteins A and B; and (4) significantly increase lung compliance, which reduces the pathologic impact of driving pressure and mechanical power at any given tidal volume.
... The usefulness of positive end expiratory pressure (PEEP) in improving arterial oxygenation during laparoscopy was evaluated by many authors. [1][2][3] However there seems to be no consensus on the amount of PEEP required. A ventilatory strategy should aim to improve the blood gas changes and prevent atelectasis associated with laparoscopy. ...
Article
Full-text available
Respiratory dynamics are significantly altered during laparoscopic surgeries. Anesthesiologists should be well versed with the benefits as well as limitations of positive end expiratory pressure (PEEP) during laparoscopy. They can then judiciously use the same in different patient populations. In this study we have compared the effects of ventilation with and without PEEP of 10 cm on blood gases, airway pressures and hemodynamic parameters during laparoscopy. 60 patients, from American Society of Anesthesiologists (ASA) physical status I and II, in the age group of 18 to 60, posted for laparoscopic cholecystectomy were enrolled. They were randomized into two groups of 30 each. Group P received PEEP of 10 cm during laparoscopy and group C did not receive any PEEP. The vital parameters, arterial blood gases, and airway pressures were compared in both groups. The oxygenation, (PaO2/FiO2 ratio) was significantly higher in PEEP group (446. 4 ± 113.32 mm of Hg) as compared to the control group (404 ± 51.4 mm of Hg) after one hour of laparoscopy (P= 0.0037). The control group had higher arterial carbon dioxide tension (42.84 ± 2.38 mm of Hg) as compared to PEEP group (41.86 ± 2.33 mm of Hg), (P < 0.001). Both the findings suggest better ventilation perfusion matching in PEEP group. There was a no significant variation in mean arterial pressure and heart rate due to PEEP in our patient population. However the peak airway pressures were significantly higher in PEEP group. 10 cm of PEEP helped in better oxygenation with no significant hemodynamic alterations, in otherwise healthy patients undergoing laparoscopic cholecystectomy.
... The effects of intraoperative intermittent positive pressure ventilation (IPPV) regimens on physiological variables are reported in bariatric patients. [24][25][26][27][28] Currently, the translation of these data into effects on postoperative pulmonary complications and outcomes is lacking for the bariatric population. A using of positive end expiratory pressure (PEEP) and recruitment improved intraoperative oxygenation and pulmonary mechanics. ...
... In adults, lung recruitment ventilation has been demonstrated as effective in reducing pulmonary complications after cardiac surgery, 6 surgery in obese patients 7,8 and endoscopic surgery, 9,10 as well as in increasing oxygenation 11,12 However, adequate positive end-expiratory pressure (PEEP) was demonstrated as sufficient to minimise atelectasis in patients undergoing nonabdominal surgery without the need for lung recruitment. 13 Additionally, compared with low PEEP ( 2 cm H 2 O), high PEEP (12 cm H 2 O) combined with lung recruitment during open abdominal surgery does not protect against PPCs. ...
Article
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Background: Atelectasis is a common postoperative complication. Peri-operative lung protection can reduce atelectasis; however, it is not clear whether this persists into the postoperative period. Objective: To evaluate to what extent lung-protective ventilation reduces peri-operative atelectasis in children undergoing nonabdominal surgery. Design: Randomised, controlled, double-blind study. Setting: Single tertiary hospital, 25 July 2019 to 18 January 2020. Patients: A total of 60 patients aged 1 to 6 years, American Society of Anesthesiologists physical status 1 or 2, planned for nonabdominal surgery under general anaesthesia (≤2 h) with mechanical ventilation. Interventions: The patients were assigned randomly into either the lung-protective or zero end-expiratory pressure with no recruitment manoeuvres (control) group. Lung protection entailed 5 cmH2O positive end-expiratory pressure and recruitment manoeuvres every 30 min. Both groups received volume-controlled ventilation with a tidal volume of 6 ml kg-1 body weight. Lung ultrasound was conducted before anaesthesia induction, immediately after induction, surgery and tracheal extubation, and 15 min, 3 h, 12 h and 24 h after extubation. Main outcome measures: The difference in lung ultrasound score between groups at each interval. A higher score indicates worse lung aeration. Results: Patients in the lung-protective group exhibited lower median [IQR] ultrasound scores compared with the control group immediately after surgery, 4 [4 to 5] vs. 8 [4 to 6], (95% confidence interval for the difference between group values -4 to -4, Z = -6.324) and after extubation 3 [3 to 4] vs. 4 [4 to 4], 95% CI -1 to 0, Z = -3.161. This did not persist from 15 min after extubation onwards. Lung aeration returned to normal in both groups 3 h after extubation. Conclusions: The reduced atelectasis provided by lung-protective ventilation does not persist from 15 min after extubation onwards. Further studies are needed to determine if it yields better results in other types of surgery. Trial registration: Chictr.org.cn (ChiCTR2000033469).
... The application of positive end-expiratory pressure (PEEP) is effective against atelectasis in general anaesthesia [8]. In spontaneously breathing awake patients, PEEP can be provided using EzPAP® [9,10]. ...
Article
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Introduction: Spinal anaesthesia, supine position and higher BMI are risk factors for pulmonary atelectasis. NIV, PEEP and CPAP are employed in ICU's to treat atelectasis postoperatively. However, we wanted to investigate whether CPAP was protective against atelectasis when used intraoperatively, in high risk patients. Material and methods: This study was a randomized controlled trial. Overweight patients, who were to undergo surgeries under spinal anesthesia were included in the study. After informed consent, 126 patients underwent preoperative pulmonary function tests (PFT: FEV1, FVC, PEFR). Following the onset of spinal anaesthesia patients were randomised into group E (n = 63, received CPAP) and control group, group C ( n =63, received nil intervention). Postoperative PFT was done at 20 minutes, 1 hour, 2 hours and 3 hours after surgery. Patients were followed up till discharge for pulmonary complications. Results: We observed significant reduction in pulmonary function (FEV1, FVC and PEFR) postoperatively compared to base-line. CPAP group had better pulmonary function when compared to control group, the difference being significant 20 minu-tes after the surgery(p < 0.05). No postoperative pulmonary complication was reported among the 126 patients studied. Conclusion: Intraoperative use of CPAP in overweight patients undergoing surgeries under spinal anaesthesia could be beneficial in improving pulmonary function in the immediate post-operative period.
... Postoperative pulmonary complications within the hospital stay occurred in 8 patients (40%) in the C group compared with 7 patients (35.0%) in the RM group. The rate of pulmonary disorders was higher than that reported in previous studies [28,29]. The causes for this may be related to the higher number of male patients, smokers, and underlying pulmonary diseases in our population, which could have had a poor effect on lung function [30]. ...
Article
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BACKGROUND Atelectasis occurs in patients of all ages during various surgeries. Previous studies have mainly focused on perioperative atelectasis in infants. However, research on the incidence of atelectasis among elderly patients, particularly those undergoing laparoscopic surgeries, is limited. Therefore, this prospective study aimed to investigate the effect of lung recruitment maneuvers (LRMs) on the reduction of atelectasis determined by lung ultrasound in patients more than 60 years old undergoing laparoscopic surgery for colorectal carcinoma. MATERIAL AND METHODS In this evaluator-blinded clinical study, 42 patients more than 60 years old diagnosed with colorectal carcinoma were randomly grouped either into a lung recruitment maneuver (RM) group or control (C) group. All patients were scheduled for laparoscopic surgery under general anesthesia using the lung-protective ventilation strategy. Lung ultrasonography was carried out at 3 predetermined time intervals. Patients in the RM group received ultrasound-guided recruitment maneuvers once atelectasis was discovered by lung ultrasound. Scores of lung ultrasound were used for assessing the severity of lung atelectasis. RESULTS At the end of the operation, the occurrence of atelectasis was 100% in the RM group and 95% in the C group. After RMs, the frequency of atelectasis in the RM group and C group was 50% and 95%, respectively (P<0.01). Postoperative pulmonary complications were not different between the 2 groups. CONCLUSIONS At a single center, patients more than 60 years old undergoing laparoscopic surgery for colorectal carcinoma had a prevalence of lung atelectasis of 100% and although LRMs significantly reduced the incidence of pulmonary atelectasis, they did not improve postoperative pulmonary complications.
... We used PEEP and the RM together. Talab et al. [29] stated there was better oxygenation, less atelectasis, and less postoperative respiratory complications with no barotrauma encountered in the group with 10 cmH 2 O PEEP and 40 cmH 2 O recruitment procedure for 7-8 s. Golparvar et al. [30] performed in their study in 3 groups; multiple deep breathing maneuvers, PEEP, and both. ...
Article
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PurposeLSG surgery is used for surgical treatment of morbid obesity. Obesity, anesthesia, and pneumoperitoneum cause reduced pulmoner functions and a tendency for atelectasis. The alveolar “recruitment” maneuver (RM) keeps airway pressure high, opening alveoli, and increasing arterial oxygenation. The aim of our study is to research the effect on respiratory mechanics and arterial blood gases of performing the RM in LSG surgery.Materials and Methods Sixty patients undergoing LSG surgery were divided into two groups (n = 30) Patients in group R had the RM performed 5 min after desufflation with 100% oxygen, 40 cmH2O pressure for 40 s. Group C had standard mechanical ventilation. Assessments of respiratory mechanics and arterial blood gases were made in the 10th min after induction (T1), 10th min after insufflation (T2), 5th min after desufflation (T3), and 15th min after desufflation (T4). Arterial blood gases were assessed in the 30th min (T5) in the postoperative recovery unit.ResultsIn group R, values at T5, PaO2 were significantly high, while PaCO2 were significantly low compared with group C. Compliance in both groups reduced with pneumoperitoneum. At T4, the compliance in the recruitment group was higher. In both groups, there was an increase in PIP with pneumoperitoneum and after desufflation this was identified to reduce to levels before pneumoperitoneum.Conclusion Adding the RM to PEEP administration for morbidly obese patients undergoing LSG surgery is considered to be effective in improving respiratory mechanics and arterial blood gas values and can be used safely.
... 7 It is notable that there was minimum variability in the levels of PEEP used in these subjects, most of them who received only 5 cm H 2 O. Several studies, which used physiologic and radiologic outcomes, support the use of higher levels of PEEP in this population. 9,[22][23][24] Nonetheless, the PROBESE trial showed that a higher PEEP strategy did not improve clinical outcomes among patients who are obese. 25 The most significant finding among the ventilatory parameters was that V T /IBW was significantly better correlated to P ETCO 2 than to V T alone. ...
Article
Background: The patient who is morbidly obese is not adequately represented in the evidence recommending intraoperative low tidal volume (VT) ventilation. We aimed to explore the association between VT adjusted for ideal body weight (IBW) and the occurrence of postoperative pulmonary complications in subjects who were morbidly obese and undergoing abdominal surgery, as well as its implications on intraoperative ventilatory variables. Methods: We included 734 subjects with a body mass index of at least 40 kg/m2, undergoing open or laparoscopic abdominal surgery that lasted for at least 120 min. Clinical variables were obtained to estimate the preoperative pulmonary risk as well as intraoperative ventilator data to perform associations. Outcomes were defined by medical billing code diagnoses and oxygen use. All data were collected electronically by using Structured Query Language. Results: The subjects received a mean VT/IBW of 9.41 mL/kg IBW, and postoperative pulmonary complications occurred in 7.5% of the subjects. The occurrence of complications was correlated with the presence of several preoperative risk factors for postoperative pulmonary complications. VT/IBW was not associated with postoperative pulmonary complications. This finding remained present after separating different levels of VT/IBW. In a multivariate analysis, only laparoscopic surgery was an independent protective factor against postoperative pulmonary complications (odds ratio 0.07, 95% CI 0.01-0.55). Conclusions: VT/IBW was not associated with the occurrence of postoperative pulmonary complications in subjects who were morbidly obese and undergoing prolonged abdominal surgery. Future prospective studies are indicated to guide the optimum ventilation strategy for patients who are morbidly obese.
... 10,11 Several different ventilatory strategies have been proposed to optimize both oxygenation and respiratory mechanics during laparoscopy. [12][13][14][15][16] Application of PEEP increases functional residual capacity by reducing the cranial shift of the diaphragm during laparoscopic and robotic surgery. 16,17 Moreover, a ventilatory strategy using lungrecruitment maneuvers followed by the application of PEEP is effective in improving respiratory mechanics and oxygenation during laparoscopy in normal-weight and obese subjects. ...
Article
Background: Pneumoperitoneum and Trendelenburg position affect respiratory system mechanics and oxygenation during elective pelvic robotic surgery. The primary aim of this randomized pilot study was to compare the effects of a conventional low tidal volume ventilation with PEEP guided by gas exchange (VGas-guided) versus low tidal volume ventilation tailoring PEEP according to esophageal pressure (VPes-guided) on oxygenation and respiratory mechanics during elective pelvic robotic surgery. Methods: This study was conducted in a single-center tertiary hospital between September 2017 and January 2019. Forty-nine adult patients scheduled for elective pelvic robotic surgery were screened; 28 subjects completed the full analysis. Exclusion criteria were American Society of Anesthesiologists physical status ≥ 3, contraindications to nasogastric catheter placement, and pregnancy. After dedicated naso/orogastric catheter insertion, subjects were randomly assigned to VGas-guided ([Formula: see text] and PEEP set to achieve [Formula: see text] > 94%) or VPes-guided (PEEP tailored to equalize end-expiratory transpulmonary pressure). Oxygenation ([Formula: see text]/[Formula: see text]) was evaluated (1) at randomization, after pneumoperitoneum and Trendelenburg application; (2) at 60 min; (3) at 120 min following randomization; and (4) at end of surgery. Respiratory mechanics were assessed during the duration of the study. Results: Compared to VGas-guided, oxygenation was higher with VPes-guided at 60 min (388 ± 90 vs 308 ± 95 mm Hg, P = .02), at 120 min after randomization (400 ± 90 vs 308 ± 81 mm Hg, P = .008), and at the end of surgery (402 ± 95 vs 312 ± 95 mm Hg, P = .009). Respiratory system elastance was lower with VPes-guided compared to VGas-guided at 20 min (24.2 ± 7.3 vs 33.4 ± 10.7 cm H2O/L, P = .001) and 60 min (24.1 ± 5.4 vs 31.9 ± 8.5 cm H2O/L, P = .006) from randomization. Conclusions: Oxygenation and respiratory system mechanics were improved when applying a ventilatory strategy tailoring PEEP to equalize expiratory transpulmonary pressure in subjects undergoing pelvic robotic surgery compared to a VGas-guided approach. (ClinicalTrials.gov registration NCT03153592).
... In addition, many of the interventions often employed to minimize hypoxemia during general anesthesia, such as positive pressure ventilation and recruitment maneuvers, are often not readily available without an airway device. [15][16][17] Patients with a constellation of comorbidities known to elevate risk including OSA, asthma, CAD, smoking, and obesity represent the highest risk for elective endoscopic and colonoscopic procedures and deserve the greatest consideration for risk assessment and risk mitigation. 18,19 Fentanyl use has been advocated to decrease overall propofol dosage requirement and decrease airway reflexes for upper endoscopy. ...
Article
PurposeWe sought to quantify the severity and duration of hypoxemic events in morbidly obese patients during outpatient endoscopy procedures performed under deep sedation.Methods This was a retrospective cohort study using intraprocedural pulse oximetry readings from 11,595 American Society of Anesthesiologists physical status score I–III adult patients who underwent deep sedation for elective endoscopy at free standing ambulatory centres between June 2015 and June 2016. Unadjusted and risk-adjusted logistic regression analyses explored the relationship between increasing categories of body mass index (BMI) and intraoperative hypoxemia, severe hypoxemia, and prolonged hypoxemia.ResultsHypoxemia occurred in 600 (13%) patients with normal BMI, 314 (18%) with class I obesity, 159 (27%) with class II obesity, and 24 (19%) with class III obesity. Adjusted odds ratio (AOR) for any occurrence of intraoperative hypoxemia increased from 1.61 (95% confidence interval [CI], 1.35 to 1.90; P < 0.001) in the class I obesity group to 2.61 (95% CI, 2.05 to 3.30; P < 0.001) in patients with class II obesity, when compared with patients with normal BMI. Adjusted odds ratio of severe hypoxemia were significant in the class I obesity group (AOR, 1.47; 95% CI, 1.13 to 1.89; P = 0.003), and the class II obesity group (AOR, 2.59; 95% CI, 1.86 to 3.57; P < 0.001). Adjusted odds ratio of prolonged hypoxemia increased with each category of BMI from 1.97 (95% CI, 1.08 to 3.69) in the overweight group to 9.20 (95% CI, 4.74 to 18.03) in patients with class III obesity.Conclusions The incidence of severe hypoxemia increased nearly six-fold in obese patients and 8.5-fold in class III obese patients when compared with those of normal BMI. Intravenous fentanyl was associated with intraoperative hypoxemia independent of BMI. Patients who represent the highest risk for hypoxia should be stratified to procedure locations with adequate resources for the safest care.
... Reinius et al. [44] found that the application of a RM followed by PEEP 10 improved oxygenation in morbidly obese patients, which comes in accordance with the results obtained in this study. Those results were corroborated by many other studies [45][46][47]. ...
... The documents indicated that inverse ratio ventilation (IRV) could improve oxygenation and reduce peak airway pressure compared with conventional ventilation mode. [2][3][4][5][6] Moreover, it was reported that the optimal I: E ratio was 2:1 when using IRV. [7] So we investigated the effect of pressure-controlled IRV (PC-IRV) with inspiratory/expiratory (I: E) ratio of 2:1 on respiratory function in children undergoing laparoscopic surgery. ...
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Background High end-tidal carbon dioxide tension (P ET CO 2 ) and respiratory acidosis occurs frequently in patients undergoing laparoscopic surgery. The aim of this study is to be investigate the effect of pressure-controlled inverse ratio ventilation (IRV) with inspiratory to expiratory ratio (I: E) of 2:1 on children undergoing laparoscopic surgery. Methods Eighty children undergoing elective laparoscopic surgery were allocated randomly to the IRV group (1: E=2:1) and the control group (I: E=1:2). Children received pressure-controlled ventilation with I: E ratio of 2:1 or 1:2. Hemodynamic parameters and respiratory mechanics were recorded. Side effects were also recorded. ResultsAt 30 min after CO 2 pneumoperitoneum, tidal volume (Vt) and arterial partial pressure of oxygen (PaO 2 ) were greater in the IRV group than the control group (100.6 ± 6.6 vs. 95.1±7.9 ml, 282.7 ± 45.6 vs.246.5 ± 40.1mmHg, respectively) ( P < 0.01), but PaCO 2 was lower than the control group (43.9 ± 5.45 vs. 46.7 ± 4.90 mmHg, P = 0.013). The incidence of intra-operative hypercapnia was lower in the IRV group (25% vs. 42.5%, P = 0.03). ConclusionIRV may reduce the incidence of intra-operative hypercapnia as well as increasing Vt and thus improving CO 2 elimination in children undergoing laparoscopy. (Registration number: ChiCTR2000035589)
... Prolongation of inspiratory to expiratory ratio has become an alternative strategy for improving gas exchange and respiratory mechanics. This strategy is used in surgical patients with reduced lung compliance due to surgical factors during general anesthesia as well as critical patients with acute respiratory syndrome (Talab et al. 2009). ...
Article
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Background Obesity has become a global epidemic problem affecting every system and is associated with many consequences including coronary artery disease, hypertension, diabetes mellitus, dyslipidemia, obstructive sleep apnea, and socioeconomic and psychosocial impairment. Laparoscopic sleeve gastrectomy is one of the best and most commonly done operations for weight loss. Elevated peak airway pressure and hypoxemia are common problems that anesthesiologists face during laparoscopic surgeries with conventional volume-controlled ventilation. This study aimed at the use of the prolonged I:E ratio as an alternative strategy to improve gas exchange and the respiratory mechanics of obese patients undergoing laparoscopic sleeve gastrectomy. Results The study was a prospective randomized controlled trial and was performed between April 2019 and March 2020. After the approval of the departmental ethical committee and the informed written consent had been taken from the patients, fifty-two obese patients undergoing laparoscopic sleeve gastrectomy were enrolled in this study. After endotracheal intubation, the patients were randomly divided into the IRV group ( n =26) and the VCV group ( n =26). Respiratory parameters were adjusted as tidal volume (Vt) 8mL/kg ideal body weight, respiratory rate 12 breaths/min, positive-end expiratory pressure (PEEP) 0, fractional inspired oxygen (FiO 2 ) 0.6, and I:E ratio 1:2 for the VCV group and 2:1 for the IRV group; hemodynamics and respiratory mechanics were monitored and recorded after intubation (0 min), before pneumoperitoneum (10 mins), and after pneumoperitoneum (20 mins), 30, 40, 50, and 60 mins. IRV significantly improves the respiratory mechanics during pneumoperitoneum in the form of decreasing the peak pressure (Ppeak) and plateau pressure (Pplat) and improving the dynamic compliance, but the mean pressure (Pmean) was increased; it also increased the partial pressure of oxygen (arterial PO 2 ) significantly. No statistical significance was found regarding the demographic data or the hemodynamics. Conclusion IRV is superior to conventional VCV in morbidly obese patients undergoing laparoscopic sleeve gastrectomy as it improves respiratory mechanics and oxygenation.
... In addition, the use of ORi is suitable for surgeries that have a high probability of leading to atelectasis, such as surgeries on obese patients [42,43], surgeries in the Trendelenburg position, and laparoscopic surgeries [43][44][45]. Other studies also suggested that ORi is useful in situations in which awake intubation is performed [22]. ...
Article
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In the perioperative period, hypoxemia and hyperoxia are crucial factors that require attention, because they greatly affect patient prognoses. The pulse oximeter has been the only noninvasive monitor that can be used as a reference of oxygenation in current anesthetic management; however, in recent years, a new monitoring method that uses the oxygen reserve index (ORi™) has been developed by Masimo Corp. ORi is an index that reflects the state of moderate hyperoxia (partial pressure of arterial oxygen [PaO2] between 100 and 200 mmHg) using a non-unit scale between 0.00 and 1.00. ORi monitoring performed together with percutaneous oxygen saturation (SpO2) measurements may become an important technique in the field of anesthetic management, for measuring oxygenation reserve capacity. By measuring ORi, it is possible to predict hypoxemia and to detect hyperoxia at an early stage. In this review, we summarize the method of ORi, cautions for its use, and suitable cases for its use. In the near future, the monitoring of oxygen concentrations using ORi may become increasingly common for the management of respiratory function before, after, and during surgery.
... have proven that a low TV does not prevent postoperative respiratory complications without adequate PEEP even though a low TV is an important component of the lung-protective ventilation strategy. Pressure-controlled inverse ratio ventilation has been reported to have successfully recruited collapsed alveoli and improved oxygenation at lower peak airway pressure (Ppeak) [9,[12][13][14]. ...
Article
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Objective To investigate the effects of inverse ratio ventilation combined with lung-protective ventilation on pulmonary function and inflammatory factors in severe burn patients undergoing surgery. Populations and Methods: Eighty patients with severe burns undergoing elective surgery were divided randomly into two groups: control (CG, n = 40) and experiment (EG, n = 40). The CG had conventional ventilation, whereas the EG were ventilated with tidal volume (TV) of 6–8 ml/kg, I (inspiration): E (expiration) of 2:1, and positive end-expiratory pressure (PEEP) 5 cm H2O. The following variables were evaluated before (T0), 1 h after start of surgery (T1) and after surgery (T2): oxygenation index (OI), partial pressure of carbon dioxide (PaCO2), TV, peak airway pressure (Ppeak), mean airway pressure (Pmean), PEEP, pulmonary dynamic compliance (Cdyn), alveolar–arterial difference of oxygen partial pressure D(A-a)O2, lactic acid (Lac), interleukin (IL)-6 and IL-10, and lung complications. Results: At T1 and T2 time points, the OI, Pmean and Cdyn were significantly greater in the EG than in the CG while the TV, Ppeak, D(A-a)O2, IL-6 and IL-10 were significantly smaller in the EG than in the CG. At the end of the surgery, the Lac was significantly smaller in the EG than in the CG (1.28 ± 0.19 vs. 1.40 ± 0.23 mmol/L). Twenty-four hours after the surgery, significantly more patients had hypoxemia (27.5 vs. 10.0%), increased expectoration (45.0 vs. 22.5%), increased lung texture or exudation (37.5 vs. 17.5%) in the CG than in the EG. Conclusions: Inverse ratio ventilation combined with lung-protective ventilation can reduce Ppeak, increase Pmean and Cdyn, improve the pulmonary oxygenation function, and decrease ILs in severe burn surgery patients.
... The BMI is divided into five categories: <25 kg/m2 = normal, 25-30 kg/m2 =overweight, >30 kg/m2 = obese, >35 kg/m2 = morbid obesity, >55 kg/m2 = super morbid obesity (26). Obese women (BMI > 30) have a greater risk of complications than non-obese patients (27). Morbidity and mortality increases when the BMI is >30 kg/m2 and consequently, postoperative risks of hypoxemia and pulmonary complications are high in such women (28)(29)(30). ...
Article
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Background: The purpose of the study was to evaluate the effectiveness and safety of thermal balloon ablation in women with high anesthetic and surgical risk compared to invulnerable women according to the American Society of Anesthesia (ASA) physical status stratification. Methods: This report was based on a retrospective cohort study of women with heavy menstrual bleeding (HMB) who were eligible for treatment with CavatermTM plus during 2012-2017. Women were classified as high-risk (HR) or low-risk (LR) cohorts based on ASA physical status stratification. The primary outcome includes amenorrhea in the twelfth months after the treatment. Risk adjustments were performed using regression models. Results: This research study consisted of 63 women with mean age 44.42±5.48. Mean of body mass index (BMI) in the HR cohort was higher than the LR cohort (31.48±6.22 vs 26.83± 3.51, P=0.005) and results were also similar considering the uterine length (mm) between HR and LR women (58.27±35.70 vs 30.92± 35.30, P=0.01). The primary outcome of treatment after a one-year follow-up in the two groups (HR and LR) was 31 (93.9%) and 15 (78.9%), respectively. After adjusting for known confounders including age, uterine length, parity, dysmenorrheal, the adjusted odds ratio was 0.94 (95% CI, 0.14- 2.5; P= 0.60). Conclusion: For women with high anesthetic and surgical risks derived from serious underlying co morbidities, endometrial ablation can provide a minimally invasive, safe, and effective therapy for heavy menstrual bleeding.
... Several ventilatory strategies have been proposed to improve gas exchange and outcome in obese patient [12]. The RM "a strategy of reopening atelectatic lung areas present during anesthesia" is recommended to reverse anesthesia induced atelectasis in the healthy lungs [13]. ...
Article
Background: Maintaining satisfactory ventilation for obese patients undergoing bariatric surgery frequently poses a challenge for anesthetists. The optimal ventilation strategy during pneumoperitoneum remains obscure in obese patients. In this study, we investigated the effect of conventional ventilation, inverse ratio ventilation (IRV) and alveolar recruitment maneuver (RM) on arterial oxygenation, lung mechanics and hemodynamics in morbid obese patients undergoing laparoscopic bariatric surgery. Methods: 105 adult obese patients scheduled for elective laparoscopic bariatric surgery were randomly allocated into three groups: Conventional ratio ventilation (I:E ratio was 1:2, PEEP 5 cmH2O and no RM), Inverse Ratio Group (IRVG) (I:E ratio was 2:1 and PEEP 5 cmH2O and No RM ) and Recruitment Maneuver Group (RMG) ( RM was done and I:E ratio was 1:2). Arterial blood gases and respiratory mechanics were recorded after induction of anesthesia (T1), 5 minutes (T2), 30 minutes (T3), 60 minutes (T4) after the beginning of pneumoperitoneum and at the end of the surgery (T5). Cardiac output was recorded at (T1), (T2), (T3) and (T5). Results: At T3, T4 and T5, arterial oxygen tension was higher in RMG than IRVG than CG (P ˂ 0.05). At T3, T4 and T5, the mean airway pressure and dynamic compliance (Cdyn) were significantly higher in IRVG and RMG compared with CG (P ˂ 0.05) while at those times, the mean air way pressure and Cdyn in IRVG and RMG were comparable. Cardiac output result were comparable between all groups throughout the study period (P ˃ 0.05). Conclusions: RM and IRV had provided better arterial oxygenation and respiratory mechanics compared to conventional ventilation in morbid obese patients undergoing laparoscopic bariatric surgery. However, RM had better gas exchange than IRV.
... Although different intra-operative ventilation strategies have been evaluated in several studies, the ideal ventilation strategy for obese patients undergoing surgery has yet to be defined [9,10]. Pressure-controlled ventilation (PCV) decelerates the inspiratory flow. ...
Article
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Background: Mechanical ventilation may be particularly challenging in obese patients undergoing laparoscopic bariatric surgery. The present study aimed to compare the effects of pressure-controlled ventilation (PCV) with those of volume-controlled ventilation (VCV) on peripheral tissue oxygenation (PTO), respiratory function, hemodynamic status, and ventilation-related complications in patients undergoing laparoscopic bariatric surgery. Methods: A total of 100 patients with obesity who underwent gastric plication or sleeve gastrectomy were recruited for the study, and 60 patients (n=32, in group PCV; n=28, in group VCV) were ultimately enrolled. Data on peri-operative PTO (arterial blood gas [ABG] analysis and tissue oxygen saturation [StO2]) and respiratory functions were recorded for each patient, along with post-operative hemodynamic status, fluid intake, urinary output, Numeric Pain Rating Scale (NPRS) score , and complications. Results: The two groups were similar in pH, partial pressure of oxygen, partial pressure of carbon dioxide, oxygen saturation, and lactate values at baseline, intra-operative and post-operative periods. The perioperative StO2 values were also similar between the two groups at all times. The two groups were identical in terms of preoperative values for respiratory function tests and post-operative hemodynamic status, fluid intake, urinary output, pain scores, and complication rates. Conclusions: In conclusion, the choice of the mechanical ventilation mode did not appear to influence oxygen delivery, respiratory function, hemodynamic status, post-operative pain, or ventilation-related complications in obese patients undergoing laparoscopic bariatric surgery.
... However, when the alveoli have been collapsed, the isolated application of a PEEP alone will not reopen them, when recruitment manoeuvres will allow them to be reopened (recruitment). It is therefore recommended to apply at the beginning of the mechanical ventilation and during the whole ventilation period a PEEP of approximately 10 cmH2O, associated with a TV of 6 to 8 ml/kg of IBW [57,71] and regular recruitment manoeuvres [57]. Recruitment manoeuvre using bag squeezing should be avoided, as it was recently found to be associated with postoperative pulmonary complications [72]. ...
Article
The obese patient is at risk of perioperative complications including difficult airway access (intubation, difficult or impossible ventilation), and postextubation acute respiratory failure due to the formation of atelectases or to airway obstruction. The association of obstructive sleep apnoea syndrome (OSA) with obesity is very common, and induces a high risk of per and postoperative complications. Preoperative OSA screening is crucial in the obese patient, as well as its specific management: use of continuous positive pre-, per- and postoperative pressure. For any obese patient, the implementation of difficult intubation protocols and the use of protective ventilation (low tidal volume 6-8 ml/Kg of ideal body weight, moderate positive end-expiratory pressure of 10 cmH20, recruitment manoeuvres in absence of contra-indications), with morphine sparing and semi-seated positioning as much as possible is recommended, associated with a close postoperative monitoring. The dosage of anaesthetic drugs is usually based on the ideal body weight or the adjusted body weight and then titrated, except for succinylcholine that is dosed according to the total body weight. Monitoring of neuromuscular blockers should be used where appropriate, as well as monitoring of the depth of anaesthesia, especially when total intravenous anaesthesia is used in association with neuromuscular blockers. The occurrence of intraoperative awareness is indeed more frequent in the obese patient than in the non-obese patient. Appropriate prophylaxis against venous thromboembolism and early mobilisation are recommended, if possible included in an early rehabilitation protocol, to further reduce postoperative complications.
... Such results were consistent with the findings of Jakobsen et al. (19), which showed that preoperative general anesthesia and hypoventilation can reduce the resistance of patients during surgery. In 5 articles (14)(15)(16)(17)(18), there were slight differences in preoperative interventional methods, but all treatments had the effect of shortening the patient's blood loss, pleural expansion, and hospital stay. In addition, in the same study, the surgical method in the control group and the restorative drugs in the treatment group were the same. ...
Article
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Background: In clinical general thoracic surgery, the prevalence of atelectasis is relatively high. Perioperative interventions can affect the probability of patients with atelectasis after surgery. Therefore, the incidence of perioperative intervention to prevent atelectasis after thoracic surgery was discussed using meta-analysis in this study. Methods: The articles were searched in the English database PubMed and Chinese databases including China National Knowledge Infrastructure (CNKI), VIP, and China Journal Full-text Database (CJFD). The duration for publication time of the articles was from the database inception to March 2021, and the articles were required to be randomized controlled trials (RCTs) using interventions [such as changing the dose of general anesthesia, continuous positive end expiratory pressure (PEEP), non-invasive pressure support ventilation, and physical therapy] after thoracic surgery (such as pulmonary lobectomy, sternum surgery, and lung cancer surgery) for the treatment of atelectasis. The software RevMan 5.3 provided by the Cochrane Collaboration was used for meta-analysis. Results: A total of 5 articles were obtained, including 375 cases in the control group and 268 cases in the intervention treatment group. A meta-analysis was performed on the included articles, combined effect model analysis results showed that compared with the control group, the use of PEEP during mechanical ventilation can significantly reduce the incidence of atelectasis [odds ratio (OR) =0.46; 95% confidence interval (CI): 0.31-0.67; Z=3.94; P<0.0001]. Discussion: Perioperative intervention was more effective for postoperative atelectasis and other complications.
... However, laparoscopic procedures are operated under general anesthesia that decreases functional residual capacity (FRC) and enhances atelectasis [5]. Also, it is performed in conjunction with intraabdominal CO 2 insufflations and subsequent increase in the intra-abdominal pressure [6,7]. This CO 2 pneumoperitoneum together with the steep Trendelenburg position, which is maintained for long period in LSG, results in cephalic displacement of the diaphragm leading to several respiratory changes as decreased FRC and vital capacity (VC) [8,9], decrease pulmonary compliance, consequently resulting in atelectasis formation in the dependent lung regions [10,11]. ...
Article
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Purpose The aim of this study was to evaluate the effect of recruitment maneuvers (RMs) and positive end expiratory pressure (PEEP) on diaphragmatic function and atelectasis areas during pneumoperitoneum and the trendelenburg position in laparoscopic sleeve gastrectomy (LSG) patients. Methods This prospective double-blinded randomized clinical study was conducted on 69 obese patients undergoing LSG. Patients were randomly allocated to one of the three groups, Group I (control group) patients were mechanically ventilated without PEEP or RM, Group II received PEEP of 5 cmH2O, and Group III received 5 cmH2O PEEP, and intermittent four times RM consisting of maintaining airway pressure 40 cmH2O for 40 s. Primary outcome was diaphragmatic excursion (DE). Secondary outcomes were atelectasis area, Forced Vital Capacity (FVC), Forced Expiratory Volume in 1 s (FEV1), Peak Inspiratory Pressure (PIP), and any complications. Results DE decreased in all investigated groups after anesthesia induction till the end of procedure compared to pre-induction values, and it was statistically significant lower in control group compared to the two interventional groups with no significant difference between PEEP and PEEP+RM groups. Atelectasis volume according to lung aeration score was significantly increased in control group compared to the other two groups, while there was no statistical significant difference in PEEP+RM compared to PEEP in all the times except before induction of anesthesia there was no significant difference among the three groups. Conclusion The application of RM and PEEP are helpful for preserving DE and improving lung aeration during laparoscopic sleeve gastrectomy.
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Objective To identify, appraise, and synthesise the best available evidence on the efficacy of perioperative interventions to reduce postoperative pulmonary complications (PPCs) in adult patients undergoing non-cardiac surgery. Design Systematic review and meta-analysis of randomised controlled trials. Data sources Medline, Embase, CINHAL, and CENTRAL from January 1990 to December 2017. Eligibility criteria Randomised controlled trials investigating short term, protocolised medical interventions conducted before, during, or after non-cardiac surgery were included. Trials with clinical diagnostic criteria for PPC outcomes were included. Studies of surgical technique or physiological or biochemical outcomes were excluded. Data extraction and synthesis Reviewers independently identified studies, extracted data, and assessed the quality of evidence. Meta-analyses were conducted to calculate risk ratios with 95% confidence intervals. Quality of evidence was summarised in accordance with GRADE methods. The primary outcome was the incidence of PPCs. Secondary outcomes were respiratory infection, atelectasis, length of hospital stay, and mortality. Trial sequential analysis was used to investigate the reliability and conclusiveness of available evidence. Adverse effects of interventions were not measured or compared. Results 117 trials enrolled 21 940 participants, investigating 11 categories of intervention. 95 randomised controlled trials enrolling 18 062 participants were included in meta-analysis; 22 trials were excluded from meta-analysis because the interventions were not sufficiently similar to be pooled. No high quality evidence was found for interventions to reduce the primary outcome (incidence of PPCs). Seven interventions had low or moderate quality evidence with confidence intervals indicating a probable reduction in PPCs: enhanced recovery pathways (risk ratio 0.35, 95% confidence interval 0.21 to 0.58), prophylactic mucolytics (0.40, 0.23 to 0.67), postoperative continuous positive airway pressure ventilation (0.49, 0.24 to 0.99), lung protective intraoperative ventilation (0.52, 0.30 to 0.88), prophylactic respiratory physiotherapy (0.55, 0.32 to 0.93), epidural analgesia (0.77, 0.65 to 0.92), and goal directed haemodynamic therapy (0.87, 0.77 to 0.98). Moderate quality evidence showed no benefit for incentive spirometry in preventing PPCs. Trial sequential analysis adjustment confidently supported a relative risk reduction of 25% in PPCs for prophylactic respiratory physiotherapy, epidural analgesia, enhanced recovery pathways, and goal directed haemodynamic therapies. Insufficient data were available to support or refute equivalent relative risk reductions for other interventions. Conclusions Predominantly low quality evidence favours multiple perioperative PPC reduction strategies. Clinicians may choose to reassess their perioperative care pathways, but the results indicate that new trials with a low risk of bias are needed to obtain conclusive evidence of efficacy for many of these interventions. Study registration Prospero CRD42016035662.
With the increasing prevalence of obesity worldwide, it is inevitable that anesthesiologists will encounter patients with metabolic syndrome. Metabolic syndrome encompasses multiple diseases, which include central obesity, hypertension, dyslipidemia, and hyperglycemia. Given the involvement of multiple diseases, metabolic syndrome involves numerous complex pathophysiological processes that negatively impact several organ systems. Some of the organ systems that have been well-documented to be adversely affected include the cardiovascular, pulmonary, and endocrine systems. Metabolic syndrome also leads to prolonged hospital stays, increased rates of infections, a greater need for care after discharge, and overall increased healthcare costs. Several interventions have been suggested to mitigate these negative outcomes ranging from lifestyle modifications to surgeries. Therefore, anesthesiologists should understand metabolic syndrome and formulate management strategies that may modify perianesthetic and surgical risks.
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Background: The debate on lung-protective ventilation strategies for surgical patients is ongoing. Evidence suggests that the use of low tidal volume VT improves clinical outcomes. However, the optimal levels of PEEP and recruitment manoeuvre (RM) strategies incorporated into low VT ventilation remain unclear. Methods: Several electronic databases were searched to identify RCTs that focused on comparison between low VT strategy and conventional mechanical ventilation (CMV), or between two different low VT strategies in surgical patients. The primary outcome was postoperative pulmonary complications (PPCs). The secondary outcomes were atelectasis, pneumonia, acute respiratory distress syndrome, and short-term mortality. Bayesian network meta-analyses were performed using WinBUGS. The odds ratios (ORs) and corresponding 95% credible intervals (CrIs) were estimated. Results: Compared with CMV, low VT ventilation with moderate-to-high PEEP reduced the risk of PPCs (moderate PEEP [5-8 cm H2O]: OR 0.50 [95% CrI: 0.28, 0.89]; moderate PEEP+RMs: 0.39 [0.19, 0.78]; and high PEEP [≥9 cm H2O]+RMs: 0.34 [0.14, 0.79]). Low VT ventilation with moderate-to-high PEEP and RMs also specifically reduced the risk of atelectasis compared with CMV (moderate PEEP+RMs: OR 0.36 [95% CrI: 0.16, 0.87]; and high PEEP+RMs: 0.41 [0.15, 0.97]), whilst low VT ventilation with moderate PEEP was superior to CMV in reducing the risk of pneumonia (OR 0.46 [95% CrI: 0.15, 0.94]). Conclusions: The combination of low VT ventilation and moderate-to-high PEEP (≥5 cm H2O) seems to confer lung protection in surgical patients undergoing general anaesthesia. Clinical trial registration: PROSPERO (CRD42019144561).
Article
Background: Obesity has become an increasing problem worldwide during the past few decades. Hence, surgeons and anaesthetists will care for an increasing number of obese patients in the foreseeable future, and should be prepared to provide optimal management for these individuals. This review provides an update of recent evidence regarding perioperative strategies for obese patients. Methods: A search for papers on the perioperative care of obese patients (English language only) was performed in July 2019 using the PubMed, Scopus, Web of Science and Cochrane Library electronic databases. The review focused on the results of RCTs, although observational studies, meta-analyses, reviews, guidelines and other reports discussing the perioperative care of obese patients were also considered. When data from obese patients were not available, relevant data from non-obese populations were used. Results and conclusion: Obese patients require comprehensive preoperative evaluation. Experienced medical teams, appropriate equipment and monitoring, careful anaesthetic management, and an adequate perioperative ventilation strategy may improve postoperative outcomes. Additional perioperative precautions are necessary in patients with severe morbid obesity, metabolic syndrome, untreated or severe obstructive sleep apnoea syndrome, or obesity hypoventilation syndrome; patients receiving home ventilatory support or postoperative opioid therapy; and obese patients undergoing open operations, long procedures or revisional surgery.
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Obesity is considered a major comorbidity, and it is imperative for an anesthesiologist to put increased emphasis on preoperative evaluation and perioperative management. A multidisciplinary team approach is the key for a successful outcome. This article encompasses basic tenets like pathophysiology and pharmacology pertaining to obesity. The authors also talk about important aspects of anesthesia care starting from preoperative assessment and optimization, intraoperative challenges and care, to recovery and discharge of these patients.
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Background The effect of inverse inspiration:expiration (I:E) ratio on functional residual capacity (FRC) during pneumoperitoneum is unclear. We hypothesised that volume-targeted pressure-controlled inverse ratio ventilation (vtPC-IRV) would increase FRC by increasing the level of auto-PEEP in low respiratory compliance situations. Methods During robot-assisted laparoscopic radical prostatectomy, 20 obese patients were sequentially ventilated with four different settings for 30 min in each setting: (1) control, I:E ratio of 1:2 and baseline airway pressure (BAP) of 5 cm H2O; (2) IRV2, I:E ratio of 2:1 and BAP off; (3) IRV3, I:E ratio of 3:1 and BAP off; and (4) IRV4, I:E ratio of 4:1 and BAP off. The changes in FRC were identified and compared among these settings. Results The FRC significantly increased as the I:E ratio increased. The FRC values expressed as median (inter-quartile range) during control, IRV2, IRV3, and IRV4 were 1149 (898–1386), 1485 (1018–1717), 1602 (1209–1775), and 1757 (1337–1955) ml, respectively. Auto-PEEP increased significantly as the I:E ratio increased and correlated with FRC (rho=0.303; P=0.006). Shunt and physiological dead space were significantly lower in all IRV groups than in the control group; however, there were no significant differences among the IRV groups. Conclusions vtPC-IRV with shortened expiratory time and increased auto-PEEP effectively increases FRC during robot-assisted laparoscopic radical prostatectomy in obese patients. FRC increases progressively as the I:E ratio increases from 1:2 to 4:1; however, an I:E ratio higher than 2:1 does not further improve the dead space. Clinical trial registration UMIN000038989.
Conference Paper
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UČBENIK Zdravniška zbornica Slovenije Slovensko združenje za anesteziologijo in intenzivno medicine (SZAIM) Klinični oddelek za anesteziologijo in intenzivno terapijo operativnih strok Oddelek za anesteziologijo, intenzivno terapijo in terapijo bolečin Katedra za anesteziologijo, Medicinska fakulteta
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Perioperative ventilation is an important challenge of anaesthesia, especially in obese patients: body mass index is correlated with reduction of the pulmonary volume and they develop significantly more perioperative atelectasis and pulmonary complications. The alveolar recruitment manoeuvre is the most effective technique to reverse atelectasis. However, the clinical benefit on lung function in the perioperative period is not clear. The aim of the present study is to assess the perioperative clinical results of systematic alveolar recruitment manoeuvre associated with protective ventilation in patients undergoing laparoscopic bariatric surgery. It was a single-centre, randomised, double blind, superiority trial: control group with standard protective ventilation and recruitment group with protective ventilation and systematic recruitment manoeuvre. The primary outcome was a composite clinical criterion of pulmonary dysfunction including oxygen saturation, oxygen needs and dyspnoea in recovery room and at day 1. Secondary outcomes were recruitment manoeuvre tolerance, pulmonary and non-pulmonary complications, length of hospital stay and proportion of Intensive Care Unit admission. Two hundred and thirty patients were included: 115 in the recruitment manoeuvre group and 115 in the control group, 2 patients were excluded from the analysis in the control group. Patients in the recruitment manoeuvre group had significantly lower rate of pulmonary dysfunction in the recovery room (73% versus 84% (p = 0.043) and 77% versus 88% at postoperative day 1 (p = 0.043)). No significant differences were found for secondary outcomes. No patient was excluded from the recruitment manoeuvre group for intolerance to the manoeuvre. Recruitment Manoeuvre is safe and effective in reducing early pulmonary dysfunction in obese patients undergoing bariatric surgery.
Chapter
Respiratory failure affects approximately 1:500 pregnancies. Causes include pregnancy-specific and pregnancy-aggravated conditions, as well as those causes also observed in the general population. Management issues include the altered maternal respiratory physiology, the increased risk of endotracheal intubation, and ensuring that maternal interests are prioritized. Noninvasive ventilation may be considered for short-term ventilator support. Limited data exist to inform on prolonged management of invasive mechanical ventilation in pregnancy. Hypoxemia is likely harmful to the fetus (targets unknown). Hypocapnia should be avoided, but some hypercapnia is acceptable. Delivery for fetal benefit should only be considered if maternal benefit/lack of harm is also anticipated.
Article
Background: The optimal ventilation strategy during general anesthesia is unclear. This systematic review investigated the relationship between ventilation targets or strategies (eg, positive end-expiratory pressure [PEEP], tidal volume, and recruitment maneuvers) and postoperative outcomes. Methods: PubMed and Embase were searched on March 8, 2021, for randomized trials investigating the effect of different respiratory targets or strategies on adults undergoing noncardiac surgery. Two investigators reviewed trials for relevance, extracted data, and assessed risk of bias. Meta-analyses were performed for relevant outcomes, and several subgroup analyses were conducted. The certainty of evidence was evaluated using Grading of Recommendations Assessment, Development and Evaluation (GRADE). Results: This review included 63 trials with 65 comparisons. Risk of bias was intermediate for all trials. In the meta-analyses, lung-protective ventilation (ie, low tidal volume with PEEP) reduced the risk of combined pulmonary complications (odds ratio [OR], 0.37; 95% confidence interval [CI], 0.28-0.49; 9 trials; 1106 patients), atelectasis (OR, 0.39; 95% CI, 0.25-0.60; 8 trials; 895 patients), and need for postoperative mechanical ventilation (OR, 0.36; 95% CI, 0.13-1.00; 5 trials; 636 patients). Recruitment maneuvers reduced the risk of atelectasis (OR, 0.44; 95% CI, 0.21-0.92; 5 trials; 328 patients). We found no clear effect of tidal volume, higher versus lower PEEP, or recruitment maneuvers on postoperative pulmonary complications when evaluated individually. For all comparisons across targets, no effect was found on mortality or hospital length of stay. No effect measure modifiers were found in subgroup analyses. The certainty of evidence was rated as very low, low, or moderate depending on the intervention and outcome. Conclusions: Although lung-protective ventilation results in a decrease in pulmonary complications, randomized clinical trials provide only limited evidence to guide specific ventilation strategies during general anesthesia for adults undergoing noncardiac surgery.
Article
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Background: High tidal volume leads to inflammation, and low tidal volume leads to atelectasia and hypoxemia. This study was conducted to compare the effect of 6 mL/kg with positive end-expiratory pressure (PEEP) and 8 mL/kg without PEEP on pulmonary shunt and dead space volume. Methods: This clinical trial was done on 36 patients aged 20 to 65 years old with ASA I-II. They were candidates for upper abdominal surgery and divided randomly into 2 groups. One group were ventilated with the tidal volume = 8 mL/kg without PEEP (TV8). The other group received the tidal volume = 6 mL/kg with low PEEP = 5 cm H2O (TV6). Arterial and central venous blood gases were taken after intubation and 2 hours later. Additionally, the vital signs of the patients were checked every 30 minutes. Data analysis was performed using t test, chi-square test, and repeated measures analysis of variance with SPSS software, version 16 (SPSS Inc). P value less than.05 were meaningful. Results: There was no significant difference on the preanesthesia parameters. The pulmonary shunt was 13.5±0.1% and 18.6±0.2% in the groups TV6 and TV8, respectively (p=0.132), which slightly decreased after 2 hours in both groups without any significant difference (p=0.284). Prior to the ventilation, the ratios of dead space to tidal volume were 0.25±0.2 and 0.14±0.1 in the TV6 and TV8 groups, respectively (p=0.163), and after 2 hours, they were 0.23±0.11 and 0.16±0.1 in the TV6 and TV8 groups, respectively (p=0.271). There was no significant difference between the groups for blood pressure and peripheral and arterial oxygenation changes. Conclusion: The tidal volume of 6 mL/kg with the PEEP of 5 mmHg was similar to the tidal volume of 8 mL/kg without PEEP for hemodynamic and pulmonary changes (oxygenation, shunt, and dead space).
Article
A severely obese 42-year-old man (height 184 cm, weight 192 kg, and body mass index (BMI) 56.7 kg/m²) presented at another clinic with abdominal pain four days earlier. He did not improve with antibiotic treatment and was referred to our department. Blood tests showed a severe inflammatory response with a white blood cell count of 10,800/μl and a C-reactive protein of 20.35 mg/dl. Abdominal computed tomography showed that the appendix was enlarged, with signs suggesting abscess formation. Localized peritonitis due to acute appendicitis was diagnosed, and laparoscopic appendectomy was performed. The patient was placed in the ramp position, and his body was immobilized with a negative-pressure postural fixation device and a fixation support device. The first port was inserted by the optical method 10 cm above the umbilicus via the left rectus abdominis. Insufflation pressure was set at 15 mmHg, and further ports were added to secure the field of view. Because the inflamed fatty appendices were difficult to distinguish from the appendix itself, rapid intraoperative diagnosis was performed to confirm that the resected tissue was the appendix. The patient's postoperative course was uneventful, and the patient was discharged improved on postoperative Day 10. Our use of laparoscopic appendectomy to treat acute appendicitis in a severely obese patient with a BMI of 56.7 kg/m² is reported.
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Morbidly and super obese patients are a unique patient population that presents critical care transport providers with unique clinical and logistical challenges in the setting of respiratory distress and failure. These patients are more likely to have chronic respiratory issues at baseline, unique anatomic and physiologic abnormalities, and other comorbidities that leave them poorly able to tolerate respiratory illness or injury. This requires specialized understanding of their respiratory mechanics as well as how to tailor standard treatment modalities, such as noninvasive ventilation, to meet their needs. Also, careful and deliberate planning is required to address the specific anatomic and physiologic characteristics of this population if intubation and mechanical ventilation are needed. Finally, their dimensions and weight also have distinct consequences on transport vehicle considerations. This article reviews the pathophysiology, management, and critical care transport considerations for this unique patient population in respiratory distress and failure.
Article
In general anaesthesia, early collapse of poorly ventilated lung segments with low alveolar ventilation–perfusion ratios occurs and may lead to postoperative pulmonary complications after abdominal surgery. An ‘open lung’ ventilation strategy involves lung recruitment followed by ‘individualised’ positive end-expiratory pressure titrated to maintain recruitment of low alveolar ventilation–perfusion ratio lung segments. There are limited data in laparoscopic surgery on the effects of this on pulmonary gas exchange. Forty laparoscopic bowel surgery patients were randomly assigned to standard ventilation or an ‘open lung’ ventilation intervention, with end-tidal target sevoflurane of 1% supplemented by propofol infusion. After peritoneal insufflation, stepped lung recruitment was performed in the intervention group followed by maintenance positive end-expiratory pressure of 12–15 cmH 2 O adjusted to maintain dynamic lung compliance at post-recruitment levels. Baseline gas and blood samples were taken and repeated after a minimum of 30 minutes for oxygen and carbon dioxide and for sevoflurane partial pressures using headspace equilibration. The sevoflurane arterial/alveolar partial pressure ratio and alveolar deadspace fraction were unchanged from baseline and remained similar between groups (mean (standard deviation) control group = 0.754 (0.086) versus intervention group = 0.785 (0.099), P = 0.319), while the arterial oxygen partial pressure/fractional inspired oxygen concentration ratio was significantly higher in the intervention group at the second timepoint (control group median (interquartile range) 288 (234–372) versus 376 (297–470) mmHg in the intervention group, P = 0.011). There was no difference between groups in the sevoflurane consumption rate. The efficiency of sevoflurane uptake is not improved by open lung ventilation in laparoscopy, despite improved arterial oxygenation associated with effective and sustained recruitment of low alveolar ventilation–perfusion ratio lung segments.
Article
Résumé La période intraopératoire est associée à de profondes modifications de la fonction respiratoire consécutives aux effets cumulés de l’anesthésie générale et de la chirurgie. Ces modifications se traduisent par le développement d’une hétérogénéité dans la distribution régionale de l’aération et de la ventilation pulmonaire. Destinée à maintenir des échanges gazeux physiologiques, la ventilation mécanique peut insuffisamment corriger, voire, en cas de réglages inadaptés, aggraver les anomalies d’aération pulmonaire. L’exposition de régions pulmonaires à des niveaux pathologiques d’expansion (surdistension ou atélectasie) participe aux lésions pulmonaires induites par la ventilation mécanique et favorise une morbidité pulmonaire spécifique altérant le pronostic postopératoire. L’impact d’une optimisation des réglages du ventilateur sur les complications postopératoires a été largement étudié, aboutissant à de réelles modifications dans la prise en charge ventilatoire du patient chirurgical. Néanmoins, de nombreuses incertitudes persistent concernant l’identification des populations à risque, la contribution respective des différents types de lésions pulmonaires induites par la ventilation mécanique, et la pertinence de stratégies individualisées au sein d’une population chirurgicale particulièrement inhomogène. Les objectifs de ce texte sont d’introduire les principaux aspects physiopathologiques de la ventilation mécanique intraopératoire, de présenter les différents points de consensus et d’exposer les questionnements persistants afin de guider les anesthésiologistes cliniciens dans leur pratique clinique, mais également les investigateurs dans la conception de leurs futurs travaux.
Article
Introduction Positive end-expiratory pressure (PEEP) following alveolar recruitment manoeuvre (RM) can effectively prevent anaesthesia-induced atelectasis in children. We aimed to evaluate the individual effect of PEEP following RM on atelectasis at the end of laparoscopic surgery in infants and small children. Methods Children undergoing laparoscopic inguinal hernia repair aged 5 weeks to 2 years were randomly allocated to either the PEEP or control group. A progressive RM was performed after intubation in all cases. The PEEP group received PEEP of 5 cmH2O until the end of mechanical ventilation, while the control group did not receive any PEEP. Lung ultrasonography was performed to compare the number of atelectatic regions between the two groups after anaesthesia induction, after RM, and at the end of surgery in 12 thoracic regions. Results Overall, 432 ultrasonographic images were acquired from 36 children. At the end of surgery, the number of atelectatic regions (median [interquartile range]) was significantly lower in the PEEP group compared to the control group (2.0 [1.0 – 3.0] versus 4.0 [3.0 – 4.0] out of 12 regions, respectively; p = 0.02). While no difference was observed between the number of atelectatic regions after induction and at the end of surgery in the control group (p = 0.30), a decrease was observed in the PEEP group (3.0 [2.0 – 4.0] to 2.0 [1.0 – 3.0], respectively; p = 0.02). Conclusion RM followed by a PEEP of 5 cmH2O can effectively reduce the regions of pulmonary atelectasis at the end of laparoscopic surgery in infants and small children.
Article
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Background and aim: Postoperative hypoxemia is common after general anesthesia in obese patients. We investigated if early application of high-flow nasal oxygen (HFNO) improved postoperative oxygenation in obese patients compared with standard oxygen therapy following general anesthesia for laparoscopic bariatric surgery. Methods: This was an open labeled randomized controlled trial conducted at a university hospital in Sweden between October 23, 2018 and February 11, 2020. The study was performed as a substudy within a previously published trial. After ethics committee approval and written informed consent, 40 obese patients (body mass index [BMI] ≥ 35 kg m-2) scheduled for laparoscopic bariatric surgery were randomized to receive oxygen using a standard low-flow nasal cannula (NC group) or HFNO at 40 L min-1 (HF group) immediately upon arrival to the post-anesthesia care unit. Flow rate (NC group) or FiO2 (HF group) was titrated to reach an initial SpO2 of 95%-98% after which settings were left unchanged. The primary outcome was PaO2 at 60 min following postoperative baseline values. Secondary outcomes included PaCO2, SpO2, hemodynamic variables, and patient self-assessed discomfort. Results: Thirty-four patients were available for analysis. PaO2 was similar between groups at postoperative baseline. After 60 min, PaO2 had increased to 12.6 ± 2.8 kPa in the NC group (n = 15) and 14.0 ± 2.7 kPa in the HF group (n = 19); (mean difference 1.4 kPa, 95% confidence interval -0.6 to 3.3; p = 0.16). There were no differences in PaCO2, hemodynamic variables, or self-assessed discomfort between groups after 60 min. Conclusion: In obese patients, HFNO did not improve postoperative short-term oxygenation compared with standard low-flow oxygen following general anesthesia for laparoscopic bariatric surgery.
Article
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Postoperative pulmonary complications (PPCs) occur frequently and are associated with substantial morbidity and mortality. Evidence suggests that reduction of PPCs can be accomplished by using lung-protective ventilation strategies intraoperatively, but a consensus on perioperative management has not been established. We sought to determine recommendations for lung protection for the surgical patient at an international consensus development conference. Seven experts produced 24 questions concerning preoperative assessment and intraoperative mechanical ventilation for patients at risk of developing PPCs. Six researchers assessed the literature using questions as a framework for their review. The modified Delphi method was utilised by a team of experts to produce recommendations and statements from study questions. An expert consensus was reached for 22 recommendations and four statements. The following are the highlights: (i) a dedicated score should be used for preoperative pulmonary risk evaluation; and (ii) an individualised mechanical ventilation may improve the mechanics of breathing and respiratory function, and prevent PPCs. The ventilator should initially be set to a tidal volume of 6-8 ml kg-1 predicted body weight and positive end-expiratory pressure (PEEP) 5 cm H2O. PEEP should be individualised thereafter. When recruitment manoeuvres are performed, the lowest effective pressure and shortest effective time or fewest number of breaths should be used.
Article
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The incidence, degree, and duration of acute hypoxemia were evaluated with continuous arterial hemoglobin oxygen saturation monitoring by pulse oximetry in 100 postoperative patients during 40 percent oxygen administration by aerosol face tent from postanesthetic recovery room admission to discharge. Saturations were recorded by pulse oximeters (Nellcor-N 200) with desaturations of < or = 92 percent for > or = 30 s considered significant. On recovery room admission, 15 percent of patients were experiencing episodes of desaturation. Low admission saturations correlated positively with patient age and body weight, American Society of Anesthesiologists class, patients having received general anesthesia, and with greater volumes of intraoperative intravenous fluids, particularly > 1,500 ml. Later desaturations to 86.7 +/- 4.6 percent (72 to 91 percent) at 32 +/- 54 min after admission for 5.2 +/- 12.6 min occurred in 25 percent of patients and correlated positively with peripheral surgical procedures, low oxygen saturation on admission, duration of anesthesia, and volume of intraoperative intravenous fluids. Desaturation durations were longer for female subjects and correlated positively with body weight and intravenous fluid volume. Significant arterial hemoglobin oxygen desaturations occurred despite prophylactic oxygen administration by aerosol face tent during short-term postoperative recovery room care.
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A major cause of impaired gas exchange during general anaesthesia is atelectasis, causing pulmonary shunt. A 'vital capacity' (VC) manoeuvre (i.e. inflation of the lungs up to 40 cm H2O, maintained for 15 s) may re-expand atelectasis and improve oxygenation. However, such a manoeuvre may cause adverse cardiovascular effects. Reducing the time of maximal inflation may improve the margin of safety. The aim of this study was to analyse the change over time in the amount of atelectasis during a VC manoeuvre in 12 anaesthetized adults with healthy lungs. I.v. anaesthesia with controlled mechanical ventilation (VT 9 (SD 1) ml kg-1) was used. For the VC manoeuvre, the lungs were inflated up to an airway pressure (Paw) of 40 cm H2O. This pressure was maintained for 26 s. Atelectasis was assessed by analysis of computed x-ray tomography. The amount of atelectasis, measured at the base of the lungs, was 4.0 (SD 2.7) cm2 after induction of anaesthesia. The decrease in the amount of atelectasis over time during the VC manoeuvre was described by a negative exponential function with a time constant of 2.6 s. At an inspired oxygen concentration of 40%, PaO2 increased from 17.2 (4.0) kPa before to 22.2 (6.0) kPa (P = 0.013) after the VC manoeuvre. Thus in anaesthetized adults undergoing mechanical ventilation with healthy lungs, inflation of the lungs to a Paw of 40 cm H2O, maintained for 7-8 s only, may re-expand all previously collapsed lung tissue, as detected by lung computed tomography, and improve oxygenation. We conclude that the previously proposed time for a VC manoeuvre may be halved in such subjects.
Article
Background: Laparoscopic surgery has been reported to be associated with greater incidence of postoperative atelectasis. Studies have been lacking regarding quantifying atelectasis produced and methods to guard against increase in atelectasis. Methods: In this study we compared 30 healthy patients scheduled for laparoscopic cholecystectomy and randomized them into two groups (Group A, n=15) receiving 5 cm H2O PEEP during intraoperative mechanical ventilation and (Group B, n=15) receiving zero end expiratory pressure (ZEEP). Measurements were performed 10 minutes following induction of anaesthesia, 10 minutes following pneumoperitonium, and 1 hour following admission to recovery room. Measurements included mean arterial blood pressure (MAP), Heart rate (HR), SPO2 and arterial blood gases, Also CT chest examinations were performed 2 hours postoperative to evaluate atelectasis. Results: Group A had better oxygenation than Group B (P<0.0001), however there were no significant difference among the two study groups in MAP, SPO 2 and heart rate. Also Group A had less atelectasis score than Group B by CT scan performed 2 hours postoperative (p<0.0001). Conclusion: The use of PEEP prevents deoxygenation during pneumoperitoneum and leads to lower atelectasis score on CT scan examination up to two hours postoperative.
Article
Continuous monitoring of important respiratory indices has the potential for predicting catastrophes and for providing an opportunity for the timely institution of lifesaving measures. Pulmonary gas exchange can be assessed by indices derived from arterial blood gas measurements, but these are limited by their invasive and intermittent nature. Intra-arterial electrodes that provide a continuous recording of blood gases are under development and appear very promising. Specially designed pulmonary artery catheters permit continuous recording of mixed venous O2 saturation, whereas continuous, non-invasive recordings of arterial oxygenation can be obtained with pulse oximetry and transcutaneous electrodes. A satisfactory method of monitoring CO2 tension does not exist. Measurements of respiratory drive can be obtained at the bedside, but their clinical usefulness remains unknown. Assessment of respiratory muscle strength is helpful in determining the need for mechanical ventilation, but a practical method of diagnosing respiratory muscle fatigue remains elusive. Recordings of the airway pressure waveform, calculation of thoracic compliance, and detailed examination of the pattern of breathing are helpful in assessing pulmonary mechanics. Although respiratory monitoring provides much useful information, it does not substitute for careful bedside examination.
Article
Atelectasis occurs in the dependent parts of the lungs of most patients who are anesthetized. Development of atelectasis is associated with decreased lung compliance, impairment of oxygenation, increased pulmonary vascular resistance, and development of lung injury. The adverse effects of atelectasis persist into the postoperative period and can impact patient recovery. This review article focuses on the causes, nature, and diagnosis of atelectasis. The authors discuss the effects and implications of atelectasis in the perioperative period and illustrate how preventive measures may impact outcome. In addition, they examine the impact of atelectasis and its prevention in acute lung injury.
Article
Techniques to monitor the respiratory system during mechanical ventilation have evolved significantly over the years. When integrated with the physical examination, these tools aid the management of respiratory disease, ultimately leading to safer and more effective care for all mechanically ventilated children. This review will focus on readily available methods of respiratory monitoring for children undergoing mechanical ventilation. In particular, there will be a brief discussion on gas exchange, capnography, respiratory plethysmography and oesophageal manometry, as well as a more substantial discussion on pressure–volume and flow–volume loops. Finally, we discuss using all these tools to help determine optimal ventilator support for a variety of pulmonary disease states.
Article
Formation of atelectasis is one mechanism of impaired gas exchange during general anaesthesia. We have studied manoeuvres to re-expand such atelectasis in 16 consecutive, anaesthetized adults with healthy lungs. In group 1 (10 patients), the lungs were inflated stepwise to an airway pressure (Paw) of 10, 20, 30 and 40 cm H2O. In group 2 (six patients), three repeated inflations up to Paw = 30 cm H2O were followed by one inflation to 40 cm H2O. Atelectasis was assessed by analysis of computed x-ray tomography (CT). In group 1 the mean area of atelectasis in the CT scan at the level of the right diaphragm was 6.4 cm2 at Paw = 0 cm H2O, 5.9 cm2 at 20 cm H2O, 3.5 cm2 at 30 cm H2O and 0.8 cm2 at 40 cm H2O. A Paw of 20 cm H2O corresponds approximately to inflation with twice the tidal volume. In group 2 the mean area of atelectasis was 9.0 cm2 at Paw = 0 cm H2O and 4.2 cm2 after the first inflation to 30 cm H2O. Repeated inflations did not add to re-expansion of atelectasis. The final inflation (Paw = 40 cm H2O) virtually eliminated the atelectasis. We conclude that, after induction of anaesthesia, the amount of atelectasis was not reduced by inflation of the lungs with a conventional tidal volume or with a double tidal volume ("sigg"). An inflation to vital capacity (Paw = 40 cm H2O), however, re-expanded virtually all atelectatic lung tissue.
Article
Breathing mechanics and gas exchange were studied in 10 extremely obese subjects (average weight 138 kg) prior to and during anaesthesia with mechanical ventilation. Breathing mechanics were analysed from measurements of transpulmonary pressure (during anaesthesia, trans-chest wall pressure as well) inspiratory gas flow and tidal volume. Gas exchange was studied by analysing inspired and from the Bohr equation, and the division into anatomical and alveolar dead space was arrived at by capnography. The patients were anaesthetised with neuroltpt agents and ventilated with an air-oxygen mixture. Lung compliance during spontaneous breathing was below normal and decreased further during artificial ventilation. Chest wall compliance measured during anaesthesia was within normal limits. Lung resistance was above normal during spontaneous breathing and increased further during mechanical ventilation. Total dead space was normal during spontaneous breathing and increased moderately during artificial ventilation, the increment coming mainly from alveolar dead space. A moderate hypoxaemia was recorded during spontaneous breathing, and the alveolar-arterial oxygen tension difference was slightly elevated. During anaesthesia this difference was markedly greater. It is concluded that the most probable reason for the relative hypoxaemia is right-to-left shunting.
Article
The anatomical basis of gas exchange impairment in the anaesthetised horse was studied by computerised tomography (CT; three shetland ponies) and morphological analysis (one pony and three horses). By means of CT, densities were seen in dependent lung regions early during anaesthesia, both with spontaneous breathing and with mechanical ventilation. The densities remained for some time where they had initially been created when the animal was turned from dorsal to sternal recumbency. Deep insufflation of the lungs reduced the dense area. Gas exchange was impaired roughly in proportion to the dense area. On histological analysis, the densities were atelectatic and congested with blood. Gravimetry showed no more extravascular water per unit lung tissue in the atelectatic than in the 'normal' regions, and the blood content was increased only slightly. It is concluded that the horse develops atelectasis in dependent lung regions early during anaesthesia in dorsal recumbency, and that atelectasis is the most likely explanation for the large shunt and impaired arterial oxygenation regularly seen during anaesthesia.
Article
The nature of dense areas in dependent lung regions regularly seen in anaesthetized humans was examined in a sheep model. During anaesthesia with muscle paralysis and mechanical ventilation dense areas in dependent lung regions could be seen by means of computerized tomography (CT). They had the same location and the same attenuation as in anaesthetized humans. Gas exchange impairment tended to increase in proportion to the size of the dense area on the CT scan. Microscopy showed that the densities in the sheep were atelectatic lung regions, with no or little interstitial oedema and only minor vascular congestion. The atelectatic lung tissue was sharply demarcated and the lung tissue in the immediate vicinity was well aerated, or even hyperinflated. Gravimetry showed the same amount of extravascular fluid and blood per unit lung weight in the atelectatic lung and in the aerated lung region. It is concluded that the densities appearing in dependent lung regions during anaesthesia are caused by atelectasis.
Article
Twenty patients (23-76 yr) were studied with regard to lung tissue changes prior to and following induction of general anesthesia with muscular relaxation, and another four subjects were studied for a longer period awake. The transverse thoracic area and the structure of the lung tissue were determined by computerized tomography. No abnormalities in the lung tissue were noted before anesthesia. Within 5 min after induction, including muscular relaxation, all subjects had developed crest-shaped changes of increased density in the dependent regions of both lungs. They were largest in the most caudal segment (4.8 +/- 0.8% of the transverse lung area, mean +/- SE) and smaller in the cephalad exposures (3.4 +/- 0.7% of the transverse area). The size of the densities showed no correlation to age. The densities did not increase after a further 20 min of anesthesia and were not affected by the inspiratory oxygen fraction. When the subjects were moved from the supine to the lateral position, the crest-shaped densities disappeared in the nondependent lung and remained in the dorsal part of the dependent lung. The application of positive end-expiratory pressure of 10 cmH2O eliminated or reduced the densities. The four awake subjects showed no lung densities after 90 min in the supine position. It is suggested that these crest-shaped densities represent atelectases, which develop by compression of lung tissue rather than by resorption of gas.
Article
Postmortem examination was performed in 15 patients who had plate atelectasis (PA) on their last antemortem radiograph. In 10 patients, corresponding abnormalities were found in the lungs. In all 10, there was peripheral subpleural linear collapse combined with invagination of the overlying pleura; prominent interlobular septa were observed within or bordering the linear atelectasis in nine. The atelectasis and the invaginated pleura both contributed to the linear radiographic density. The bronchi supplying the areas of PA showed no obstruction nor rearrangement. Despite a frequent association with pulmonary embolism (6/10), there was no evidence that PA directly represented thrombosed vessels or infarcts. The findings suggest that PA represents one (radiographically visible) form of peripheral atelectasis. In persisting low-volume states, the dependent subpleural lung appears to buckle and fold in. The frequent association of PA with congenital pleural clefts, indentations, scars, and incomplete fissures suggests that this process may preferentially occur at sites of pre-existing pleural invagination. PA frequently indicates more widespread peripheral atelectasis than is radiologically apparent; it also may indicate the presence of some other (more serious) abnormality in the chest or abdomen.
Article
Formation of atelectasis is one mechanism of impaired gas exchange during general anaesthesia. We have studied manoeuvres to re-expand such atelectasis in 16 consecutive, anaesthetized adults with healthy lungs. In group 1 (10 patients), the lungs were inflated stepwise to an airway pressure (Paw) of 10, 20, 30 and 40 cm H2O In group 2 (six patients), three repeated inflations up to Paw = 30 cm H2O were followed by one inflation to 40 cm H2O. Atelectasis was assessed by analysis of computed x-ray tomography (CT). In group 1 the mean area of atelectasis in the CT scan at the level of the right diaphragm was 6.4 cm2 at Paw = 0 cm H2O, 5.9 cm2 at 20 cm H2O, 3.5 cm 2 at 30 cm H2O and 0.8 cm2 at 40 cm H2O, A Paw of 20 cm H2O corresponds approximately to inflation with twice the tidal volume. In group 2 the mean area of atelectasis was 9.0 cm2 at Paw = 0 cm H2O and 4.2 cm2 after the first inflation to 30 cm H2O. Repeated inflations did not add to re-expansion of atelectasis. The final inflation (Paw = 40 cm H2O) virtually eliminated the atelectasis. We conclude that, after induction of anaesthesia, the amount of atelectasis was not reduced by inflation of the lungs with a conventional tidal volume or with a double tidal volume (“sigh”). An inflation to vital capacity (Paw = 40 cm H2O, however, re-expanded virtually all atelectatic lung tissue. (Br. J. Anaesth. 1993; 71: 788–795)
Article
Spiral computed tomography (CT) allows volumetric analysis of formation of atelectasis and aeration of the lungs during anaesthesia. We studied 26 premedicated patients undergoing elective surgery allocated to group 1 (conscious, spontaneous breathing, investigating inspiration and expiration), group 2 (general anaesthesia with mechanical ventilation, investigating inspiration and expiration) or group 3 (general anaesthesia with mechanical ventilation, investigating changes over time). Using spiral CT, the lungs were studied either before or during general anaesthesia. CT scans were grouped into the following areas: overaeration, normal aeration, reduced aeration, poor aeration and atelectasis. The mechanism of atelectasis appeared to be both gravitational forces and a diaphragm-related force that acts regionally in caudal lung regions. Mean atelectasis formation and poorly aerated regions comprised approximately 4% of the total lung volume between the diaphragm and carina, giving a mean value of 16-20% of the normal aerated lung tissue being either collapsed or poorly aerated. The vertical ventilation distribution was more even during anaesthesia than in the awake state.
Article
Sometimes a high intrapulmonary shunt occurs after cardiac surgery, and impairment of lung function and oxygenation can persist for 1 week after operation. Animal studies have shown that postoperative shunt can be explained by atelectasis. In this study the authors tried to determine if atelectasis can explain shunt in patients who have had cardiac surgery. Nine patients having coronary artery bypass graft surgery and nine patients having mitral valve surgery were examined using the multiple inert gas elimination technique before and after operation. On the first postoperative day, computed tomography scans were made at three levels of the thorax. Before anesthesia, the average shunt was low (2+/-3%; range, 0-13%), but on the first postoperative day shunt had increased to 12+/-60% (range, 3-28%). The computed tomography scans showed bilateral dependent densities in all patients but one. The mean area of the densities was 8+/-8% (range, 0-37%) of total lung area, corresponding to a calculated fraction of collapsed lung tissue of 20+/-14% (range, 0-59%). In the basal region, the calculated amount of collapsed tissue was 28+/-19% (range, 0-73%). One mitral valve patient was an outlier and had a large shunt both before and after the operation. Large atelectasis in the dorsal part of the lungs was found on the first postoperative day after cardiac surgery. However, there was no clear correlation between atelectasis and measured shunt fraction.
Article
Unlabelled: We investigated the effects of body mass index (BMI) on functional residual capacity (FRC), respiratory mechanics (compliance and resistance), gas exchange, and the inspiratory mechanical work done per liter of ventilation during general anesthesia. We used the esophageal balloon technique, together with rapid airway occlusion during constant inspiratory flow, to partition the mechanics of the respiratory system into its pulmonary and chest wall components. FRC was measured by using the helium dilution technique. We studied 24 consecutive and unselected patients during general anesthesia, before surgical intervention, in the supine position (8 normal subjects with a BMI < or = 25 kg/m2, 8 moderately obese patients with a BMI >25 kg/m2 and <40 kg/m2, and 8 morbidly obese patients with a BMI > or = 40 kg/m2). We found that, with increasing BMI: 1. FRC decreased exponentially (r = 0.86; P < 0.01) 2. the compliance of the total respiratory system and of the lung decreased exponentially (r = 0.86; P < 0.01 and r = 0.81; P < 0.01, respectively), whereas the compliance of the chest wall was only minimally affected (r = 0.45; P < 0.05) 3. the resistance of the total respiratory system and of the lung increased (r = 0.81; P < 0.01 and r = 0.84; P < 0.01, respectively), whereas the chest wall resistance was unaffected (r = 0.06; P = not significant) 4. the oxygenation index (PaO2/PAO2) decreased exponentially (r = 0.81; P < 0.01) and was correlated with FRC (r = 0.62; P < 0.01), whereas PaCO2 was unaffected (r = 0.06; P = not significant) 5. the work of breathing of the total respiratory system increased, mainly due to the lung component (r = 0.88; P < 0.01 and r = 0.81; P < 0.01, respectively). In conclusion, BMI is an important determinant of lung volumes, respiratory mechanics, and oxygenation during general anesthesia with patients in the supine position. Implications: The aim of this study was to investigate the influence of body mass on lung volumes, respiratory mechanics, and gas exchange during general anesthesia.
Article
Unlabelled: To determine the influence of the surgical sites on early postoperative hypoxemia, we studied postoperative hypoxemia in 994 patients, ASA physical status I or II, aged 18-68 yr, scheduled for various types of elective surgery. Patients were divided into three groups on the basis of the surgical sites: Group 1 = elective superficial plastic surgery (n = 288); Group 2 = upper abdominal surgery (n = 452); and Group 3 = thoracoabdominal surgery (n = 254). Anesthesia was maintained with 1%-2% enflurane and 67% nitrous oxide in oxygen; thiopental or fentanyl was given IV as required. SpO2 levels were recorded while patients breathed room air shortly after arrival in the recovery room (0 min) and 5, 10, 15, 20, 30, 40, 50, 60, 120, and 180 min thereafter. The results showed that during the early postoperative period, the degree of arterial desaturation and the incidences of hypoxemia (SpO2 86%-90%) and severe hypoxemia (SpO2 85%) were closely related to the operative sites and were greatest for thoracoabdominal operations, less for the upper abdominal operation, and least for the peripheral surgery. The incidence of hypoxemia and severe hypoxemia in the recovery room was 7% and 0.7%, respectively, in Group 1, 38% and 3% in Group 2, and 52% and 20% in Group 3. Mild airway obstruction and hypothermia in the postanesthesia recovery unit (PAR) were the predictive factors of early postoperative hypoxemia. We conclude that during the early postoperative period, there were significant differences in SpO2 levels and incidences of hypoxemia and severe hypoxemia among the three groups. Implications: We found that the severity of arterial desaturation and the incidence of hypoxemia during the early postoperative period are closely related to the surgical sites and are strongest for thoracoabdominal surgery, less for upper abdominal surgery, and least for peripheral surgery.
Article
Unlabelled: A vital capacity maneuver (VCM) (inflating the lungs to 40 cm H(2)O for 15 s) is effective in relieving atelectasis during general anesthesia or after cardiopulmonary bypass (CPB). The study was undertaken to investigate the safety of one or repeated VCM. Five groups of six pigs were studied. Two groups had general anesthesia for 6 h and one group received a VCM every hour. Three other groups received CPB. VCM was performed after CPB in two of these groups. VCM was then repeated every hour in one of the groups. Lung damage was evaluated by extravascular lung water (EVLW) measurement, light microscopy, and the half-time (T(1/2)) of disappearance from the lung of a nebulized aerosol containing (99m)Tc-DTPA. No changes were noted in extravascular lung water. The pigs subjected to VCM decreased their T(1/2). In the groups exposed to repeated VCM, T(1/2) remained lowered (CPB pigs) or decreased over time (non-CPB pigs). No lung damage could be seen on the morphology study. These results suggest that one VCM is a safe procedure. The increase in lung clearance of (99m)Tc-DTPA not associated with an increase in lung water when VCM is repeated may have been caused by an increase in lung volume. Therefore, repeated VCM also appears to be safe. Implications: This study demonstrates in an animal model that inflating the lung once or repeatedly to the vital capacity is a safe procedure. This maneuver, also called the vital capacity maneuver, can be used to relieve lung collapse which occurs in all patients during general anesthesia.
Article
Unlabelled: We compared outpatients transported to the postanesthesia care unit (PACU) while breathing room air to 2-4 L/min nasal cannula oxygen (O2) to test the hypothesis that routine supplemental O2 during transport is not required after general anesthesia in an ambulatory surgery center. We also examined whether the arbitrary arrival PACU O2 saturations of > 92% may be used to predict an infrequent incidence of subsequent significant desaturations (< 90%) in the PACU. One-hundred-ninety patients were randomized to receive either room air or 2-4 L/min nasal cannula for transport to PACU after receiving general anesthesia. O2 saturations were recorded before surgery, just before leaving the operating room, and upon arrival in the PACU. The lowest O2 saturation occurring in the PACU was also recorded. The mean arrival PACU O2 saturation was 95.0 in the Room Air group, compared with 97.2 for the Nasal Cannula (NC) group, a statistically significant difference (P < 0.001). In the Room Air group, 20% had arrival O2 saturations < or = 92%, and half of these (10%) had O2 saturations < 90%. In the NC group, 6% had O2 saturations < or = 92%, of which one third (2%) were < 90% on arrival in the PACU. All of these initial desaturations were easily corrected with face-tent O2 administration, deep breathing, or both. Subgroup analysis revealed that patients whose ages were 60 yr or older or those weighing 100 kg or more had lower arrival room air saturations than their younger or slimmer counterparts. In the Room Air group, only three (3.9%) of the patients that arrived in PACU with O2 saturations > 92% had subsequent desaturations < 90%, compared with seven (7.9%) in the NC group. We conclude that most adult patients undergoing ambulatory surgery can be transported safely to the PACU breathing room air after general anesthesia. However, patients whose age was > or = 60 yr or weight was > or = 100 kg, or for whom transient O2 desaturation on transport may be harmful, should be transported while breathing nasal O2 via nasal cannula. Implications: Most adult patients undergoing ambulatory surgery can be transported safely to the PACU breathing room air after general anesthesia. However, patients whose age was > or = 60 yr or weight > or = 100 kg, or for whom transient O2 desaturation on transport may be harmful, should be transported while breathing oxygen via nasal cannula.
Article
Perturbation of respiratory mechanics produced by general anesthesia and surgery is more pronounced in morbidly obese (MO) patients. Because general anesthesia induces pulmonary atelectasis in nonobese patients, we hypothesized that atelectasis formation would be particularly significant in MO patients. We investigated the importance and resorption of atelectasis after general anesthesia in MO and nonobese patients. Twenty MO patients were anesthetized for laparoscopic gastroplasty and 10 nonobese patients for laparoscopic cholecystectomy. We assessed pulmonary atelectasis by computed tomography at three different periods: before the induction of general anesthesia, immediately after tracheal extubation, and 24 h later. Already before the induction of anesthesia, MO patients had more atelectasis, expressed in the percentage of the total lung area, than nonobese patients (2.1% versus 1.0%, respectively; P < 0.01). After tracheal extubation, atelectasis had increased in both groups but remained significantly more so in the MO group (7.6% for MO patients versus 2.8% for the nonobese; P < 0.05). Twenty-four hours later, the amount of atelectasis remained unchanged in the MO patients, but we observed a complete resorption in nonobese patients (9.7% versus 1.9%, respectively; P < 0.01). General anesthesia in MO patients generated much more atelectasis than in nonobese patients. Moreover, atelectasis remained unchanged for at least 24 h in MO patients, whereas atelectasis disappeared in the nonobese. IMPLICATIONS: We compared the resolution over time of pulmonary atelectasis after a laparoscopic procedure by performing computed tomography scans in two different groups of patients: 1 group had 10 nonobese patients, and in the other group there were 20 morbidly obese patients.
Article
Factors influencing oxygenation of the arterial blood were studied, during routine anaesthesia, in thirty-six patients anaesthetized with halothane and allowed to breathe spontaneously, with a mean minute volume of 5 l./min. There was evidence of an unsteady respiratory state during the first hour of anaesthesia. Oxygen consumption was 87 per cent of basal. Physiological deadspace amounted to 33 per cent of the expired tidal volume (all patients intubated). At high levels of inspired oxygen concentration, the mean alveolar-arterial Po, gradient was 184 mm Hg, corresponding to a shunt of 14 per cent of pulmonary bloodflow. At lower levels of alveolar Po2, the alveolar-arterial Po, gradient diminished but was above the value which would be caused by a shunt of 14 per cent. This was probably due to uneven ventilation perfusion ratios (maldistribution) corresponding to a calculated venous admixture rising as high as 30 per cent. It is concluded that, to ensure the maintenance of a normal arterial Poa in the majority of patients, the alveolar Po, is required to be as high as 200 mm Hg and this needs an inspired oxygen concentration of 35 per cent under the conditions investigated in this study.
Article
Unlabelled: Atelectasis caused by general anesthesia is increased in morbidly obese patients. We have shown that application of positive end-expiratory pressure (PEEP) during the induction of anesthesia prevents atelectasis formation in nonobese patients. We therefore studied the efficacy of PEEP in morbidly obese patients to prevent atelectasis. Twenty-three adult morbidly obese patients (body mass index >35 kg/m(2)) were randomly assigned to one of two groups. In the PEEP group, patients breathed 100% oxygen (5 min) with a continuous positive airway pressure of 10 cm H(2)O and, after the induction, mechanical ventilation via a face mask with a PEEP of 10 cm H(2)O. In the control group, the same induction was applied but without continuous positive airway pressure or PEEP. Atelectasis, determined by computed tomography, and blood gas analysis were measured twice: before the induction and directly after intubation. After endotracheal intubation, patients of the control group showed an increase in the amount of atelectasis, which was much larger than in the PEEP group (10.4% +/- 4.8% in control group versus 1.7% +/- 1.3% in PEEP group; P < 0.001). After intubation with a fraction of inspired oxygen of 1.0, PaO(2) was significantly higher in the PEEP group compared with the control group (457 +/- 130 mm Hg versus 315 +/- 100 mm Hg, respectively; P = 0.035) We conclude that in morbidly obese patients, atelectasis formation is largely prevented by PEEP applied during the anesthetic induction and is associated with a better oxygenation. Implications: Application of positive end-expiratory pressure during induction of general anesthesia in morbidly obese patients prevents atelectasis formation and improves oxygenation. Therefore, this technique should be considered for anesthesia induction in morbidly obese patients.
Article
NCREASED alveolar to arterial oxygen gradients occur in most patients after the induction of anesthesia. Mild hypoxemia (saturation not below 85%) is noted in up to half of patients under general anesthesia and more severe hypoxemia (saturation below 85%) in up to 20%. The cause of this hypoxemia is an increase in low ventilation to perfusion areas which can become absolute shunts (i.e., no ventilation but persistent perfusion to collapsed alveoli as airways close). The loss of aerated alveoli (atelectasis) occurs as functional residual capacity is reduced below closing capacity and is a consequence of alveolar oxygen re-absorption, dependent lung compression, and loss of surfactant. Atelectasis under general anesthesia routinely involves 5 to 6% of the lung predominantly in dependent areas, can increase up to 50% of the lung in cardiothoracic operations, and can persist for multiple postoperative days. 1 Atelectasis and airway closure explain as much as 74% of gas exchange impairment noted during routine general anesthesia as these poorly ventilated regions are relatively overperfused. 2 Atelectasis may be associated with longer length of hospitals stays, 3,4 pneumonia, initiation of the inflammatory cascade by activating macrophages, and decrease in surfactant production.
Article
Atelectasis occurs in the dependent parts of the lungs of most patients who are anesthetized. Development of atelectasis is associated with decreased lung compliance, impairment of oxygenation, increased pulmonary vascular resistance, and development of lung injury. The adverse effects of atelectasis persist into the postoperative period and can impact patient recovery. This review article focuses on the causes, nature, and diagnosis of atelectasis. The authors discuss the effects and implications of atelectasis in the perioperative period and illustrate how preventive measures may impact outcome. In addition, they examine the impact of atelectasis and its prevention in acute lung injury.
Morbid obesity and postoperative pulmonary atelectasis: an underestimated problem.
  • Eichenberger
The safety of one, or repeated, vital capacity maneuvers during general anesthesia.
  • Magnusson
Pulmonary atelectasis: a pathogenic perioperative entity.
  • Michelle
The effects of body mass on lung volumes, respiratory mechanics, and gas exchange during general anesthesia.
  • Pelosi