[Show abstract][Hide abstract] ABSTRACT: The use of heat and moisture exchangers (HME) during noninvasive ventilation (NIV) can increase the work of breathing, decrease alveolar ventilation, and deliver less humidity in comparison with heated humidifiers (HH). We tested the hypothesis that the use of HH during NIV with ICU ventilators for patients with acute respiratory failure would decrease the rate of intubation (primary endpoint) as compared with HME.
We conducted a multicenter randomized controlled study in 15 centers. After stratification by center and type of respiratory failure (hypoxemic or hypercapnic), eligible patients were randomized to receive NIV with HH or HME.
Of the 247 patients included, 128 patients were allocated to the HME group and 119 to the HH group. Patients were comparable at baseline. The intubation rate was not significantly different: 29.7 % in the HME group and 36.9 % in the HH group (p = 0.28). PaCO2 did not significantly differ between the two arms, even in the subgroup of hypercapnic patients. No significant difference was observed for NIV duration, ICU and hospital LOS, or ICU mortality (HME 14.1 vs. HH 21.5 %, p = 0.18).
In this study, the short-term physiological benefits of HH in comparison with HME during NIV with ICU ventilators were not observed, and no difference in intubation rate was found. The physiologic effects may have been obscured by leaks or other important factors in the clinical settings. This study does not support the recent recommendation favoring the use of HH during NIV with ICU ventilators.
Full-text · Article · Nov 2013 · Intensive Care Medicine
[Show abstract][Hide abstract] ABSTRACT: During invasive mechanical ventilation, inspired gases must be humidified. We previously showed that high ambient temperature greatly impaired hygrometric performances of heated wire heated humidifiers. The aim of this bench and clinical study was to assess the humidification performances of passive and active heat and moisture exchangers (HME) and the impact of ambient temperature and ventilator settings.
We first tested on bench a device with passive and active humidification properties (Humid-Heat, Hudson), and two passive hydrophobic/hygroscopic HMEs (Hygrobac and Hygrobac-S, Mallinkrodt). The devices were tested at three different ambient temperature (from 22 to 30°C), and at two minute ventilations (10 and 20L/min). Inspired gas hygrometry was measured at Y-piece with the psychrometric method. In addition to the bench study, we measured hygrometry of inspired gases in two different clinical studies. In 15 mechanically ventilated patients, we evaluated Humid-Heat at different settings. Additionnaly, we evaluated Humid-Heat and compared it with Hygrobac in a cross-over study in 10 patients.
On bench, with the Hygrobac and Hygrobac S, inspired absolute humidity was around 30 mgH2O/L and with the Humid-Heat, slightly below 35 mgH2O/L. Ambient temperature and minute ventilation did not have a clinically significant difference on the performances of the tested devices. During the clinical evaluation, Humid-Heat provided inspired humidity in a range from 28.5 mgH2O/L to 42.0 mgH2O/L, depending on settings, and was only weakly influenced by patient's body temperature.
in this study, both passive and active HME had stable humidification performances with negligible influence of ambient temperature and minute ventilation. This contrasts with previous findings with heated wire heated humidifiers. Although there is no clear data demonstrating that higher humidification impact outcomes, it is worth noting that humidity was significantly higher with the active HME.
[Show abstract][Hide abstract] ABSTRACT: Purpose:
The influence of posture on breathing effort in patients with difficult weaning is unknown. We hypothesized that posture could modulate the breathing effort in difficult-to-wean patients.
A prospective, crossover, physiologic study was performed in 24 intubated patients breathing with pressure support who had already failed a spontaneous breathing trial or an extubation episode. Their median duration of mechanical ventilation before measurements was 25 days. Breathing pattern, occlusion pressure (P (0.1)), intrinsic PEEP (PEEP(i)), and inspiratory muscle effort evaluated by the pressure-time product of the respiratory muscles and the work of breathing were measured during three postures: the seated position in bed (90°LD), simulating the position in a chair, the semi-seated (45°), and the supine (0°) positions consecutively applied in a random order. A comfort score was obtained in 17 cooperative patients. The influence of position on chest wall compliance was measured in another group of 11 sedated patients.
The 45° position was associated with the lowest levels of effort (p ≤ 0.01) and occlusion pressure (p < 0.05), and tended to be more often comfortable. Respiratory effort was the lowest at 45° in 18/24 patients. PEEP(i) and PEEP(i)-related work were slightly higher in the supine position (p ≤ 0.01), whereas respiratory effort, heart rate, and P (0.1) values were increased in the seated position (p < 0.05).
A 45° position helps to unload the respiratory muscles, moderately reduces PEEP(i), and is often considered as comfortable. The semi-seated position may help the weaning process in ventilator-dependent patients.
Full-text · Article · Oct 2012 · Intensive Care Medicine
[Show abstract][Hide abstract] ABSTRACT: BACKGROUND: The impact of the humidification devices on ventilatory and arterial blood gases parameters during noninvasive ventilation (NIV) remains controversial. The aim of the study was to compare the short term impact of heat and moisture exchangers (HME) and heated humidifiers (HH) during NIV for either hypercapnic or hypoxemic acute respiratory failure. METHODS: Consecutive patients receiving NIV were successively treated with HME and HH in randomized order for 30 minutes each. At the end of each period, arterial blood gases were measured and ventilatory parameters were recorded. RESULTS: Eighty-one patients were enrolled, of which 52 were hypercapnic (with or without acidosis) and 29 hypoxemic. Minute-ventilation was greater with the HME in comparison with the HH (15.5 ± 6.4 vs. 13.7 ± 5.8 l/min, P<0.001), while PaCO₂ was increased when using HME, indicating a dead space effect. This effect was observed in all patients, but was more pronounced in hypercapnic patients (PaCO₂ 63 ± 18 mmHg with HME vs. 57 ± 14 with HH, P<0.001). In a subgroup of 19 patients with respiratory acidosis, alveolar hypoventilation improved only with the HH. The amplitude of the dead space impact was a function of the degree of hypercapnia. CONCLUSION: Use of an HME decreased CO₂ elimination during noninvasive ventilation despite increased minute ventilation, especially in hypercapnic patients.
No preview · Article · Mar 2012 · Respiratory care
[Show abstract][Hide abstract] ABSTRACT: To test the short-term physiologic effects (indexes of respiratory effort, ventilation, and gas exchange), leaks, patient-ventilator asynchrony, and comfort of four noninvasive ventilation (NIV) facial, oronasal, or oral interfaces with major differences in internal volume.
Prospective, short-term, crossover randomized physiologic study.
Medical intensive care unit in a university hospital.
Fourteen consecutive patients receiving NIV for either hypoxemic (n = 7) or hypercapnic (n = 7) acute respiratory failure.
Four interfaces, tested randomly over consecutive sequences, had very high (977 mL), high (163 mL), moderate (84 mL), or virtually no internal volume (mouthpiece). The pressure level was increased in two patients with the larger mask, and was decreased in all patients when using the mouthpiece.
Despite differences in internal volume, no apparent dead space effect was observed on minute ventilation, work of breathing, or arterial CO2 levels. Compared with baseline, NIV was uniformly successful in reducing indexes of respiratory effort: the pressure-time product of the respiratory muscles decreased from a median (25th-75th interquartile range) of 179 (158-285) cm H2O.sec.min to values between 91 and 111 during NIV, with no differences between masks (p = 0.84). Few differences were observed in terms of arterial blood gases and breathing pattern. Leaks and patient-ventilator asynchronies were greater with the mouthpiece, and comfort with this interface was deemed poor for most patients.
The internal volume of the masks had no apparent short-term dead space effect on gas exchange, minute ventilation, or patient's effort, suggesting that, with the exception of mouthpiece, interfaces may be interchangeable in clinical practice provided adjustment of the ventilatory device parameters are performed.
No preview · Article · Apr 2009 · Critical care medicine
[Show abstract][Hide abstract] ABSTRACT: No clear recommendation exists concerning humidification during non-invasive ventilation (NIV) and high flow CPAP, and few hygrometric data are available.
We measured hygrometry during NIV delivered to healthy subjects with different humidification strategies: heated humidifier (HH), heat and moisture exchanger, (HME) or no humidification (NoH). For each strategy, a turbine and an ICU ventilator were used with different FiO(2) settings, with and without leaks. During CPAP, two different HH and NoH were tested. Inspired gases hygrometry was measured, and comfort was assessed. On a bench, we also assessed the impact of ambient air temperature, ventilator temperature and minute ventilation on HH performances (with NIV settings).
During NIV, with NoH, gas humidity was very low when an ICU ventilator was used (5 mgH(2)O/l), but equivalent to ambient air hygrometry with a turbine ventilator at minimal FiO(2) (13 mgH(2)O/l). HME and HH had comparable performances (25-30 mgH(2)O/l), but HME's effectiveness was reduced with leaks (15 mgH(2)O/l). HH performances were reduced by elevated ambient air and ventilator output temperatures. During CPAP, dry gases (5 mgH(2)O/l) were less tolerated than humidified gases. Gases humidified at 15 or 30 mgH(2)O/l were equally tolerated.
This study provides data on the level of humidity delivered with different humidification strategies during NIV and CPAP. HH and HME provide gas with the highest water content. Comfort data suggest that levels above 15 mgH(2)O/l are well tolerated. In favorable conditions, HH and HMEs are capable of providing such values, even in the presence of leaks.
Full-text · Article · Apr 2009 · Intensive Care Medicine
[Show abstract][Hide abstract] ABSTRACT: Heat and moisture exchangers (HMEs) are increasingly used in the ICU for gas conditioning during mechanical ventilation. Independent assessments of the humidification performance of HMEs are scarce. The aim of the present study was thus to assess the humidification performance of a large number of adult HMEs.
We assessed 48 devices using a bench test apparatus that simulated real-life physiologic ventilation conditions. Thirty-two devices were described by the manufacturers as HMEs, and 16 were described as antibacterial filters. The test apparatus provided expiratory gases with an absolute humidity (AH) of 35 mg H(2)O/L. The AH of inspired gases was measured after steady state using the psychrometric method. We performed three hygrometric measurements for each device, measured their resistance, and compared our results with the manufacturer data.
Of the 32 HMEs tested, only 37.5% performed well (>or= 30 mg H(2)O/L), while 25% performed poorly (< 25 mg H(2)O/L). The mean difference (+/- SD) between our measurements and the manufacturer data was 3.0 +/- 2.7 mg H(2)O/L for devices described as HMEs (maximum, 8.9 mg H(2)O/L) [p = 0.0001], while the mean difference for 36% of the HMEs was > 4 mg H(2)O/L. The mean difference for the antibacterial filters was 0.2 +/- 1.4 mg H(2)O/L. The mean resistance of all the tested devices was 2.17 +/- 0.70 cm H(2)O/L/s.
Several HMEs performed poorly and should not be used as HMEs. The values determined by independent assessments may be lower than the manufacturer data. Describing a device as an HME does not guarantee that it provides adequate humidification. The performance of HMEs must be verified by independent assessment.
[Show abstract][Hide abstract] ABSTRACT: High fractions of inspired oxygen (FIO(2)) used in acute lung injury (ALI) may promote resorption atelectasis. The impact of derecruitment related to high FIO(2) in ALI is debated. We evaluated derecruitment with 100% vs. 60% FIO(2) at two levels of positive end-expiratory pressure (PEEP).
Fourteen consecutive patients with ALI were studied.
Recruited volume at two PEEP levels was computed from two pressure-volume curves, recorded from PEEP and from zero end-expiratory pressure, using the sinusoidal flow modulation method. PEEP-induced recruitment was measured during prolonged expiration as the difference between the two curves at a given pressure. PaO(2)/FIO(2) was also measured. PEEP was 5 +/- 1 or 14 +/- 3 cmH(2)O and FIO(2) was 60% or 100%, yielding four combinations. We looked for differences between the beginning and end of a 30-min period with each combination.
With low PEEP and 100% FIO(2), recruited volume decreased significantly from 68 +/- 53 to 39 +/- 43 ml and PaO(2)/FIO(2) from 196 +/- 104 to 153 +/- 83 mmHg. With the three other combinations (low PEEP and 60% FIO(2) or high PEEP and 60% or 100% FIO(2)) none of the parameters decreased significantly.
In mechanically ventilated patients with ALI the breathing of pure oxygen leads to derecruitment, which is prevented by high PEEP.
Preview · Article · Jan 2007 · Intensive Care Medicine
[Show abstract][Hide abstract] ABSTRACT: A prospective survey of French intensive care units (ICUs) in 1997 showed moderate and variable use of noninvasive ventilation (NIV). This study examined changes in NIV use in French ICUs after the intervening 5years.
Patients were enrolled in a prospective survey in 70 French ICUs.
Three-week survey, with prospective inclusion of all patients requiring ventilatory support.
Overall 1,076 patients received ventilatory support (55% of admissions). First-line NIV was significantly more common than 5years earlier, overall (23% vs. 16%) and especially in patients not intubated before ICU admission (52% vs. 35%). Reasons for respiratory failure were coma (33%), cardiogenic pulmonary edema (8%), acute-on-chronic respiratory failure (17%), and de novo respiratory failure (41%). Significant increases in NIV use were noted for acute-on-chronic respiratory failure (64% vs. 50%) and de novo respiratory failure (22% vs. 14%). Among patients given NIV, 38% subsequently required endotracheal intubation (not significantly different). Independent risk factors for NIV failure were high SAPS II and de novo respiratory failure, whereas factors associated with success were good NIV tolerance and high body mass index.
NIV use has significantly increased in French ICUs during the past 5years, and the success rate has remained unchanged. In patients not previously intubated, NIV is the leading first-line ventilation modality. The proportion of patients successfully treated with NIV increased significantly over the 5-year period (13% vs. 9% of all patients receiving ventilatory support).
No preview · Article · Dec 2006 · Intensive Care Medicine
[Show abstract][Hide abstract] ABSTRACT: Noninvasive ventilation (NIV) fails more frequently for de novo acute respiratory failure (de novo) than for cardiogenic pulmonary edema (CPE) or acute-on-chronic respiratory failure (AOC). The impact of NIV failure and success was compared between de novo and CPE or AOC after adjustment for disease severity.
Patients requiring ventilatory support were enrolled in a prospective survey in 70 French ICUs. Of 1076 patients requiring ventilatory support, 524 were eligible, including 299 de novo (NIV use, 30%) and 225 CPE-AOC (NIV use, 55%).
Independent risk factors associated with mortality and length of stay were identified by logistic regression analysis. The adjusted outcome of NIV success or failure was compared to that with endotracheal intubation without NIV.
NIV success was independently associated with survival in both de novo, adjusted OR 0.05 (95% CI 0.01-0.42), and CPE-AOC OR 0.03 (CI 0.01-0.24). NIV failure was associated with ICU mortality in the de novo group (OR 3.24, CI 1.61-6.53) but not in the CPE-AOC group. Nosocomial pneumonia was less common in patients successful with NIV. NIV failure was associated with a longer ICU stay in CPE-AOC only. The overall use of NIV was independently associated with a better outcome only in CPE-AOC patients (OR 0.33, CI 0.15-0.73).
The effect of NIV differs between de novo and CPE-AOC patients because NIV failure is associated with increased mortality for de novo patients. This finding should raise a note of caution when applying NIV in this indication.
Full-text · Article · Dec 2006 · Intensive Care Medicine
[Show abstract][Hide abstract] ABSTRACT: In mechanically ventilated patients with induced hypothermia, the efficacy of heat and moisture exchangers and heated humidifiers to adequately humidify the airway is poorly known. The aim of the study was to assess the efficacy of different humidification devices during moderate hypothermia.
Prospective, cross-over randomized study.
Medical Intensive Care Unit in a University Hospital.
Nine adult patients hospitalized after cardiac arrest in whom moderate hypothermia was induced (33 degrees C for 24[Symbol: see text]h).
Patients were ventilated at admission (period designated "normothermia") with a heat and moisture exchanger, and were randomly ventilated during hypothermia with a heat and moisture exchanger, a heated humidifier, and an active heat and moisture exchanger.
Core temperature, inspired and expired gas absolute and relative humidity were measured. Each system demonstrated limitations in its ability to humidify gases in the specific situation of hypothermia. Performances of heat and moisture exchangers were closely correlated to core temperature (r (2)[Symbol: see text]=[Symbol: see text]0.84). During hypothermia, heat and moisture exchangers led to major under-humidification, with absolute humidity below 25[Symbol: see text]mgH(2)O/l. The active heat and moisture exchanger slightly improved humidification. Heated humidifiers were mostly adequate but led to over-humidification in some patients, with inspiratory absolute humidity higher than maximal water content at 33 degrees C with a positive balance between inspiratory and expiratory water content.
These results suggest that in the case of moderate hypothermia, heat and moisture exchangers should be used cautiously and that heated humidifiers may lead to over-humidification with the currently recommended settings.
No preview · Article · Aug 2006 · Intensive Care Medicine
[Show abstract][Hide abstract] ABSTRACT: A prospective, crossover, physiologic study was performed in 10 patients with acute lung injury to assess the respective short-term effects of noninvasive pressure-support ventilation and continuous positive airway pressure. We measured breathing pattern, neuromuscular drive, inspiratory muscle effort, arterial blood gases, and dyspnea while breathing with minimal support and the equipment for measurements, with two combinations of pressure-support ventilation above positive end-expiratory pressure (10-10 and 15-5 cm H2O), and with continuous positive airway pressure (10 cm H2O). Tidal volume was increased with pressure support, and not with continuous positive airway pressure. Neuromuscular drive and inspiratory muscle effort were lower with the two pressure-support ventilation levels than with other situations (p < 0.05). Dyspnea relief was significantly better with high-level pressure-support ventilation (15-5 cm H2O; p < 0.001). Oxygenation improved when 10 cm H2O positive end-expiratory pressure was applied, alone or in combination. We conclude that, in patients with acute lung injury (1) noninvasive pressure-support ventilation combined with positive end-expiratory pressure is needed to reduce inspiratory muscle effort; (2) continuous positive airway pressure, in this setting, improves oxygenation but fails to unload the respiratory muscles; and (3) pressure-support levels of 10 and 15 cm H2O provide similar unloading but differ in their effects on dyspnea.
Full-text · Article · Dec 2005 · American Journal of Respiratory and Critical Care Medicine
[Show abstract][Hide abstract] ABSTRACT: To evaluate the ability of a computer-driven system (CDS) to manage pressure-support ventilation over prolonged periods and to predict weaning readiness compared to intensivists. The system continuously adapts pressure support, gradually decreases ventilatory assistance when possible, and indicates weaning readiness.
A two-center, prospective, open, clinical, pilot study in medical ICUs of two university hospitals.
42 consecutive mechanically ventilated patients (60+/-14 years, SAPS II 39+/-15), 9 of whom were excluded.
As soon as patients could tolerate pressure support, they were ventilated with the CDS. The times of weaning readiness determined by the intensivists and CDS were compared.
Weaning was successful in 25 patients and failed in 7; unplanned extubation occurred in 1 patient. Time on CDS ventilation was 3+/-3 days (maximum, 12 days). The CDS detected weaning readiness earlier than the intensivists in 17 patients, and intensivists earlier than the CDS in 4; in 11 patients detection times coincided.
A CDS was successful in fully managing pressure-support ventilation over prolonged periods and often proposed weaning readiness earlier than the intensivists did. Use of this CDS may reduce the duration of mechanical ventilation.
Full-text · Article · Nov 2005 · Intensive Care Medicine
[Show abstract][Hide abstract] ABSTRACT: Objectif. – Tester, comparer et classer les performances de huit ventilateurs d'anesthésie proposés au choix d'un appel d'offres ouvert communautaire.
Type d'étude. – Évaluation sur banc d'essai du monitorage et des performances pneumatiques par rapport aux utilisations revendiquées.
Matériel. – i) Un banc de test, configurable en deux versions : adulte et nouveau-né, utilisant un modèle de poumon passif, des capteurs de débit et pression, un logiciel d'acquisition et de traitement des données. ii) huit ventilateurs (A, B, C, D, E, F, G, H) proposés par quatre sociétés (Dräger, Datex-Ohméda, Siemens, Taema) dont deux fonctionnant avec un moteur électrique et utilisant la technologie du piston et six utilisant la technologie classique du « bag in bottle ».
Méthodes. – Les tests effectués, selon les revendications d'utilisation des appareils, évaluaient l'exactitude de la spirométrie, des mesures de pressions et la stabilité de la pression en mode pression contrôlée (PC) dans différentes conditions de ventilation. Le modèle de poumon adulte du banc possédait une compliance et des résistances ajustables. Le modèle de poumon nouveau-né du banc était composé de deux poumons à compliance fixe et des résistances ajustables. Les mesures effectuées étaient les débits et pressions.
Résultats. – a) Tests adultes : les performances des appareils testés sont globalement homogènes et de très bonne qualité. Un classement, tout item confondu, a été impossible. b) Tests nouveau-nés : les résultats obtenus ont permis un classement discriminant notamment sur la fiabilité de la spirométrie et de la mesure des pressions.
Conclusions. – Les progrès technologiques et l'intégration de l'informatique ont amélioré le monitorage et les performances pneumatiques des ventilateurs d'anesthésie. Ceci est particulièrement mis en évidence sur les tests adultes. Une évaluation clinique et ergonomique protocolée doit nécessairement compléter une évaluation sur banc pour obtenir un jugement objectif et permettre le meilleur choix d'appareil. La systématisation du mode PC et l'introduction du mode aide inspiratoire (AI) permettant aux constructeurs de revendiquer une plus large gamme d'utilisation demande à être évaluées de façon plus approfondie.
[Show abstract][Hide abstract] ABSTRACT: Although heated humidifiers are considered the most efficient humidification devices for mechanical ventilation, endotracheal tube occlusion caused by dry secretions has been reported with heated-wire humidifiers. We tested the hypothesis that inlet chamber temperature, influenced by ambient air and ventilator output temperatures, may affect humidifier performance, as assessed by hygrometry. Hygrometry was measured with three different humidifiers under several conditions, varying ambient air temperatures (high, 28-30 degrees C; and normal, 22-24 degrees C), ventilators with different gas temperatures, and two VE levels. Clinical measurements were performed to confirm bench measurements. Humidifier performance was strongly correlated with inlet chamber temperature in both the bench (p < 0.0001, r2 = 0.93) and the clinical study. With unfavorable conditions, absolute humidity of inspired gas was much lower than recommended (approximately 20 mg H2O/L). Performance was improved by specific settings or new compensatory algorithms. Hygrometry could be evaluated from condensation on the wall chamber only when ambient air temperature was normal but not with high air temperature. An increase in inlet chamber temperature induced by high ambient temperature markedly reduces the performance of heated-wire humidifiers, leading to a risk of endotracheal tube occlusion. Such systems should be avoided in these conditions unless automatic compensation algorithms are used.
Full-text · Article · Dec 2004 · American Journal of Respiratory and Critical Care Medicine
[Show abstract][Hide abstract] ABSTRACT: Randomized controlled trials have shown that the use of noninvasive ventilation (NIV) reduces the need for endotracheal intubation and invasive mechanical ventilation and reduces complication rates and mortality in selected groups of patients. But whether these benefits translate to a clinical setting is unclear.
To evaluate longitudinally the routine implementation of NIV and its effect on patients admitted to the intensive care unit (ICU) with acute exacerbation of chronic obstructive pulmonary disease (COPD) or severe cardiogenic pulmonary edema (CPE).
Retrospective, observational cohort study using prospectively collected data from January 1, 1994, through December 31, 2001.
A 26-bed medical intensive care unit (ICU) of a French university referral hospital.
A cohort of 479 consecutive patients ventilated for acute exacerbation of COPD or CPE.
The ICU mortality and incidence rates of ICU-acquired infections.
A significant increase in NIV use and a concomitant decrease in mortality and ICU-acquired infection rates were observed over the study years. With adjustment for relevant covariates and propensity scores, NIV was identified as an independent factor linked with a reduced risk of death in the cohort (odds ratio [OR], 0.37; 95% confidence interval [CI], 0.18-0.78), whereas a high severity score on admission (OR, 1.05; 95% CI, 1.01-1.10) and the occurrence of a nosocomial infection (OR, 3.08; 95% CI, 1.62-5.84) were independently associated with death. Rates of ICU-acquired pneumonia decreased from 20% in 1994 to 8% in 2001 (P =.04).
Implementing routine use of NIV in critically ill patients with acute exacerbation of COPD or severe CPE was associated with improved survival and reduction of nosocomial infections.
Full-text · Article · Jan 2004 · JAMA The Journal of the American Medical Association