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Introduction: We assessed rates and predictive factors of non-invasive ventilation (NIV) failure in patients admitted to the intensive care unit (ICU) for non-hypercapnic acute hypoxemic respiratory failure (AHRF)., Methods: This is an observational cohort study using data prospectively collected over a three-year period in a medical ICU of a university hospital., Results: Among 113 patients receiving NIV for AHRF, 82 had acute respiratory distress syndrome (ARDS) and 31 had non-ARDS. Intubation rates significantly differed between ARDS and non-ARDS patients (61% versus 35%, P = 0.015) and according to clinical severity of ARDS: 31% in mild, 62% in moderate, and 84% in severe ARDS (P = 0.0016). In-ICU mortality rates were 13% in non-ARDS, and, respectively, 19%, 32% and 32% in mild, moderate and severe ARDS (P = 0.22). Among patients with moderate ARDS, NIV failure was lower among those having a PaO2/FiO2 >150 mmHg (45% vs. 74%, p = 0.04). NIV failure was associated with active cancer, shock, moderate/severe ARDS, lower Glasgow coma score and lower positive end-expiratory pressure level at NIV initiation. Among intubated patients, ICU mortality rate was 46% overall and did not differ according to the time to intubation., Conclusions: With intubation rates below 35% in non-ARDS and mild ARDS, NIV stands as the first-line approach; NIV may be attempted in ARDS patients with a PaO2/FiO2 > 150. By contrast, 84% of severe ARDS required intubation and NIV did not appear beneficial in this subset of patients. However, the time to intubation had no influence on mortality.

Purpose: Pulmonary vascular dysfunction is common during acute respiratory distress syndrome (ARDS), but there is controversy concerning prevalence and prognosis of cor pulmonale during protective ventilation for ARDS., Methods: This was a prospective observational study in an academic medical intensive care unit in France. Two hundred and twenty-six consecutive patients with moderate to severe ARDS (Berlin definition) ventilated with plateau pressure limited at 30 cmH₂O (mean PEEP of 8.8 ± 3.6 cmH₂O) underwent transesophageal echocardiography (TEE) within the first 3 days after the diagnosis of ARDS. Cor pulmonale was defined as a dilated right ventricle associated with septal dyskinesia., Results: Cor pulmonale was detected in 49 patients (prevalence of 22%; 95% confidence interval, 16-27%). Multivariate logistic regression identified infectious causes of lung injury and higher driving pressures as independent factors associated with cor pulmonale. Patients with cor pulmonale exhibited a higher incidence of shock (need for vasoactive drug) at the time of TEE and were more often managed with prone positioning and/or nitric oxide as adjunctive therapy for severe hypoxemia during ARDS course. The 28-day mortality rate was significantly higher in the group with cor pulmonale (60 vs. 36%, p < 0.01). Multivariate logistic regression identified McCabe and Jackson class, lung injury not related to pneumonia, aspiration, or sepsis, lactic acidosis, driving pressure, and cor pulmonale as independent risk factors for 28-day mortality., Conclusion: Cor pulmonale occurrence is not negligible in ARDS patients ventilated with airway pressure limitation. Cor pulmonale was associated with sepsis and higher values of driving pressure and was an independent risk factor for 28-day mortality in our series.

Objectives: During proportional assist ventilation with load-adjustable gain factors, peak respiratory muscle pressure can be estimated from the peak airway pressure and the percentage of assistance (gain). Adjusting the gain can, therefore, target a given level of respiratory effort. This study assessed the clinical feasibility of titrating proportional assist ventilation with load-adjustable gain factors with the goal of targeting a predefined range of respiratory effort., Design: Prospective, multicenter, clinical observational study., Settings: Intensive care departments at five university hospitals., Patients: Patients were included after meeting simple criteria for assisted mechanical ventilation., Interventions: Patients were ventilated in proportional assist ventilation with load-adjustable gain factors. The peak respiratory muscle pressure, estimated in cm H2O as (peak airway pressure-positive end-expiratory pressure)×[(100-gain)/gain], was calculated from a grid at the bedside. The gain adjustment algorithm was defined to target a peak respiratory muscle pressure between 5 and 10 cm H2O. Additional recommendations were available in case of hypoventilation or hyperventilation., Results: Fifty-three patients were enrolled. Median time spent under proportional assist ventilation with load-adjustable gain factors was 3 days (interquartile range, 1-5). Gain was adjusted 1.0 (0.7-1.8) times per day, according to the peak respiratory muscle pressure target range in 91% of cases and because of hypoventilation or hyperventilation in 9%. Thirty-four patients were ventilated with proportional assist ventilation with load-adjustable gain factors until extubation, which was successful in 32. Eighteen patients required volume assist-controlled reventilation because of clinical worsening and need for continuous sedation. One patient was intolerant to proportional assist ventilation with load-adjustable gain factors., Conclusions: This first study assessing the clinical feasibility of titrating proportional assist ventilation with load-adjustable gain factors in an attempt to target a predefined range of effort showed that adjusting the level of assistance to maintain a predefined boundary of respiratory muscle pressure is feasible, simple, and often sufficient to ventilate patients until extubation.

Rationale: Baseline characteristics and management have changed over time in patients requiring mechanical ventilation; however, the impact of these changes on patient outcomes is unclear., Objectives: To estimate whether mortality in mechanically ventilated patients has changed over time., Methods: Prospective cohort studies conducted in 1998, 2004, and 2010, including patients receiving mechanical ventilation for more than 12 hours in a 1-month period, from 927 units in 40 countries. To examine effects over time on mortality in intensive care units, we performed generalized estimating equation models., Measurements and Main Results: We included 18,302 patients. The reasons for initiating mechanical ventilation varied significantly among cohorts. Ventilatory management changed over time (P < 0.001), with increased use of noninvasive positive-pressure ventilation (5% in 1998 to 14% in 2010), a decrease in tidal volume (mean 8.8 ml/kg actual body weight [SD = 2.1] in 1998 to 6.9 ml/kg [SD = 1.9] in 2010), and an increase in applied positive end-expiratory pressure (mean 4.2 cm H2O [SD = 3.8] in 1998 to 7.0 cm of H2O [SD = 3.0] in 2010). Crude mortality in the intensive care unit decreased in 2010 compared with 1998 (28 versus 31%; odds ratio, 0.87; 95% confidence interval, 0.80-0.94), despite a similar complication rate. Hospital mortality decreased similarly. After adjusting for baseline and management variables, this difference remained significant (odds ratio, 0.78; 95% confidence interval, 0.67-0.92)., Conclusions: Patient characteristics and ventilation practices have changed over time, and outcomes of mechanically ventilated patients have improved. Clinical trials registered with www.clinicaltrials.gov (NCT01093482).

Background: Diffuse alveolar damage is the histological hallmark of acute respiratory distress syndrome (ARDS). However, the chronology of histological lesions is not well established. We aimed to determine the time to onset of exudative or proliferative changes and end-stage fibrosis in ARDS., Methods: We analysed all patients who died between Jan 1, 1991, and Dec 31, 2010, in the intensive-care unit at the Hospital Universitario de Getafe, Madrid, Spain, and who had a clinical autopsy. Patients had to have clinical criteria for ARDS at time of death and histological features of diffuse alveolar damage at autopsy examination. Capillary congestion and intra-alveolar oedema characterised the exudative phase whereas proliferation of alveolar cell type 2 or fibroblasts, or fibrosis characterised the proliferative phase., Findings: We analysed 159 patients. The prevalence of exudative changes decreased over time, being reported in 74 (90%) of 82 patients with ARDS of less than 1 week duration, 40 (74%) of 54 patients with disease of 1-3 week duration, and only four (17%) of 23 patients with disease of longer than 3 weeks' duration (p<0·0001). The incidence of proliferative changes increased over time, and was reported in 44 (54%) of 82 patients with ARDS of less than 1-week duration, 42 (78%) of 54 patients with disease duration of 1-3 weeks, and 23 (100%) of 23 patients with disease duration longer than 3 weeks (p<0·0001). Fibrosis was noted in three (4%) of 82 patients with disease of less than 1 week duration, 13 (24%) of 54 patients with disease of 1-3-weeks' duration, and 14 (61%) of 23 patients with disease longer than 3-week duration (p<0·0001). Fibrosis was more frequent in ARDS of pulmonary origin than in that of extrapulmonary origin., Interpretation: Histological features of the lungs were related to duration of ARDS. Within the first week of evolution, exudative changes were predominant and fibrosis was rarely noted. Beyond the third week of evolution, proliferative changes were noted in all patients and fibrosis in two-thirds of them. Treatments with a potential effect on inflammation or fibrosis, or both, should probably focus on the first week after the onset of ARDS., Funding: None., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

Background: In mechanically ventilated patients under mechanical ventilation in the ICU, ventilatory mode or settings may influence sleep quality. The aim of this study was to evaluate the direct impact of mechanical ventilation per se on sleep quantity and quality in patients who were able to tolerate separation from mechanical ventilation over prolonged periods., Design and Setting: Randomized crossover clinical trial in a medical ICU., Patients: Sixteen conscious patients, free of sedation and tracheostomized because of prolonged weaning from mechanical ventilation, were included in the study when able to tolerate at least 5 hours of spontaneous ventilation., Interventions: Patients were randomized to receive either spontaneous ventilation or mechanical ventilation at low levels of pressure support for two crossover periods of 5-hour duration each, from 22:00 to 08:00. Polysomnography was performed throughout the study., Measurements and Results: Total sleep time was higher during mechanical ventilation than during spontaneous ventilation (183 min vs 132 min, p = 0.04). No significant differences between mechanical ventilation and spontaneous ventilation were observed in slow wave sleep time (45 min vs 28 min), rapid eye movement sleep time (11 min vs 3 min), or the fragmentation index (25 vs 23 arousals and awakenings per hr). In four patients, however, our analysis of patient-ventilator interaction suggested that the ventilatory settings were suboptimal and could have been improved to potentially improve sleep., Conclusions: In difficult-to-wean tracheostomized patients, sleep quality was similar with or without the ventilator. Sleep quantity was higher during mechanical ventilation. Reconnection to the ventilator during the night period may favor sleep efficiency in tracheostomized patients in prolonged weaning.

The day of extubation is a critical time during an intensive care unit (ICU) stay. Extubation is usually decided after a weaning readiness test involving spontaneous breathing on a T-piece or low levels of ventilatory assist. Extubation failure occurs in 10 to 20% of patients and is associated with extremely poor outcomes, including high mortality rates of 25 to 50%. There is some evidence that extubation failure can directly worsen patient outcomes independently of underlying illness severity. Understanding the pathophysiology of weaning tests is essential given their central role in extubation decisions, yet few studies have investigated this point. Because extubation failure is relatively uncommon, randomized controlled trials on weaning are underpowered to address this issue. Moreover, most studies evaluated patients at low risk for extubation failure, whose reintubation rates were about 10 to 15%, whereas several studies identified high-risk patients with extubation failure rates exceeding 25 or 30%. Strategies for identifying patients at high risk for extubation failure are essential to improve the management of weaning and extubation. Two preventive measures may prove beneficial, although their exact role needs confirmation: one is noninvasive ventilation after extubation in high-risk or hypercapnic patients, and the other is steroid administration several hours before extubation. These measures might help to prevent postextubation respiratory distress in selected patient subgroups.

Rationale: A revised definition of clinical criteria for acute respiratory distress syndrome (ARDS), the Berlin definition, was recently established to classify patients according to their severity., Objective: To evaluate the accuracy of these clinical criteria using diffuse alveolar damage (DAD) at autopsy as the reference standard., Methods: All patients who died and had a clinical autopsy in our intensive care unit over a 20-year period (1991-2010) were included. Patients with clinical criteria for ARDS were identified from the medical charts and were classified as mild, moderate, or severe according to the Berlin definition using PaO2/FiO2 oxygenation criteria. Microscopic analysis from each pulmonary lobe was performed by two pathologists., Measurements and Main Results: Among 712 autopsies analyzed, 356 patients had clinical criteria for ARDS at time of death, classified as mild (n = 49, 14%), moderate (n = 141, 40%), and severe (n = 166, 46%). Sensitivity was 89% and specificity 63% to identify ARDS using the Berlin definition. DAD was found in 159 of 356 (45%) patients with clinical criteria for ARDS (in 12, 40, and 58% of patients with mild, moderate, and severe ARDS, respectively). DAD was more frequent in patients who met clinical criteria for ARDS during more than 72 hours and was found in 69% of those with severe ARDS for 72 hours or longer., Conclusions: Histopathological findings were correlated to severity and duration of ARDS. Using clinical criteria the revised Berlin definition for ARDS allowed the identification of severe ARDS of more than 72 hours as a homogeneous group of patients characterized by a high proportion of DAD.

Purpose of Review: The decision to extubate is a crucial moment for intubated patients. In most cases, the transition to spontaneous breathing is uneventful, but in some patients, it implies a more challenging decision. Both extubation delay and especially the need for reintubation are associated with poor outcomes. We aim to review the recent literature on weaning and to clarify the role of certain interventions intending to help in this process., Recent Findings: Cardiac dysfunction is probably one of the most common causes of weaning failure. Several studies have evaluated the ability of B-natriuretic peptides and echocardiographic tools to predict weaning outcome due to cardiac origin, attempting to prevent its failure. Noninvasive ventilation may have a potential benefit in preventing respiratory failure after extubation of hypercapnic patients, although more studies are needed to define a target population., Summary: Current research is focusing on preventing extubation failure, especially in the most challenging cases. The use of weaning protocols - written or computerized - attempts to early identify patients who are able to breathe spontaneously and to hasten extubation, resulting in better outcomes. Nevertheless, individualized care is needed in the most vulnerable patients, trying to prompt weaning without exposing patients to unnecessary risks.

Objective: To compare sleep quality between two types of ventilators commonly used for noninvasive ventilation: conventional ICU ventilators and dedicated noninvasive ventilators; and to evaluate sleep during and between noninvasive ventilation sessions in critically ill patients., Design: Physiological sleep study with a randomized assessment of the ventilator type., Setting: Medical ICU in a university hospital., Patients: Twenty-four patients admitted for acute hypercapnic respiratory failure requiring noninvasive ventilation., Interventions: Patients were randomly assigned to receive noninvasive ventilation with either an ICU ventilators (n = 12) or a dedicated noninvasive ventilators (n = 12), and their sleep and respiratory parameters were recorded by polysomnography from 4 PM to 9 AM on the second, third, or fourth day after noninvasive ventilation initiation., Measurements and Main Results: Sleep architecture was similar between ventilator groups, including sleep fragmentation (number of arousals and awakenings/hr), but the dedicated noninvasive ventilators group showed a higher patient-ventilator asynchrony-related fragmentation (28% [17-44] vs. 14% [7.0-22]; p = 0.02), whereas the ICU ventilators group exhibited a higher noise-related fragmentation. Ineffective efforts were more frequent in the dedicated noninvasive ventilators group than in the ICU ventilators group (34 ineffective efforts/hr of sleep [15-125] vs. two [0-13]; p < 0.01), possibly as a result of a higher tidal volume (7.2 mL/kg [6.7-8.8] vs. 5.8 [5.1-6.8]; p = 0.04). More sleep time occurred and sleep quality was better during noninvasive ventilation sessions than during spontaneous breathing periods (p < 0.05) as a result of greater slow wave and rapid eye movement sleep and lower fragmentation., Conclusions: There were no observed differences in sleep quality corresponding to the type of ventilator used despite slight differences in patient-ventilator asynchrony. Noninvasive ventilation sessions did not prevent patients from sleeping; on the contrary, they seem to aid sleep when compared with unassisted breathing.

Study Objective: The aim of the study was to compare the effectiveness of drainage via a single-lumen (5F catheter) central venous catheter (CVC) to a conventional (14-20 F catheter) chest tube (CT) for the management of pneumothoraces, including primary spontaneous pneumothorax (PSP), secondary spontaneous pneumothorax (SSP), and traumatic and iatrogenic pneumothoraces., Patients: All consecutive patients admitted to the intermediate intensive care unit of a university hospital for pneumothorax were retrospectively screened over an 8-year period. Patients were preferentially treated using CT from 2003 to 2007 and using CVC from 2008 to 2010. Drainage failure was defined as the need for a second drainage procedure or for surgery., Results: Of 212 patients included, 117 (55%) had PSP, 28 (13%) had SSP associated with chronic obstructive pulmonary disease, 19 (9%) had traumatic pneumothorax, and 48 (23%) had iatrogenic pneumothorax. The failure rate was 23% in PSP, 36% in SSP, 16% in traumatic pneumothorax, and only 2% in iatrogenic pneumothorax. After adjustment, iatrogenic pneumothorax was the only factor that had an influence on drainage failure. The failure rate was similar between the 112 patients treated using CVC and the 100 patients treated using CT (18% vs 21%, P = .60). However, the durations of drainage (3.3 ± 1.9 vs 4.6 ± 2.6 days, P < .01) and of hospital stay were significantly shorter in patients treated using CVC as compared with CT., Conclusion: Our findings suggest that drainage via a catheter or via a CT is similarly effective in the management of pneumothorax. We recommend considering drainage via a small-bore catheter as a first-line treatment in patients with pneumothorax, whatever its cause., (Copyright © 2012 Elsevier Inc. All rights reserved.)

Background: Different kinds of ventilators are available to perform noninvasive ventilation (NIV) in ICUs. Which type allows the best patient-ventilator synchrony is unknown. The objective was to compare patient-ventilator synchrony during NIV between ICU, transport—both with and without the NIV algorithm engaged—and dedicated NIV ventilators., Methods: First, a bench model simulating spontaneous breathing efforts was used to assess the respective impact of inspiratory and expiratory leaks on cycling and triggering functions in 19 ventilators. Second, a clinical study evaluated the incidence of patient-ventilator asynchronies in 15 patients during three randomized, consecutive, 20-min periods of NIV using an ICU ventilator with and without its NIV algorithm engaged and a dedicated NIV ventilator. Patient-ventilator asynchrony was assessed using flow, airway pressure, and respiratory muscles surface electromyogram recordings., Results: On the bench, frequent auto-triggering and delayed cycling occurred in the presence of leaks using ICU and transport ventilators. NIV algorithms unevenly minimized these asynchronies, whereas no asynchrony was observed with the dedicated NIV ventilators in all except one. These results were reproduced during the clinical study: The asynchrony index was significantly lower with a dedicated NIV ventilator than with ICU ventilators without or with their NIV algorithm engaged (0.5% [0.4%-1.2%] vs 3.7% [1.4%-10.3%] and 2.0% [1.5%-6.6%], P < .01), especially because of less auto-triggering., Conclusions: Dedicated NIV ventilators allow better patient-ventilator synchrony than ICU and transport ventilators, even with their NIV algorithm. However, the NIV algorithm improves, at least slightly and with a wide variation among ventilators, triggering and/or cycling off synchronization.

Purpose: Ultrasonography allows the direct observation of the diaphragm. Its thickness variation measured in the zone of apposition has been previously used to diagnose diaphragm paralysis. We assessed the feasibility and accuracy of this method to assess diaphragmatic function and its contribution to respiratory workload in critically ill patients under non-invasive ventilation., Methods: This was a preliminary physiological study in the intensive care unit of a university hospital. Twelve patients requiring planned non-invasive ventilation after extubation were studied while spontaneously breathing and during non-invasive ventilation at three levels of pressure support (5, 10 and 15 cmH(2)O). Diaphragm thickness was measured in the zone of apposition during tidal ventilation and the thickening fraction (TF) was calculated as (thickness at inspiration - thickness at expiration)/thickness at expiration. Diaphragmatic pressure-time product per breath (PTP(di)) was measured from oesophageal and gastric pressure recordings., Results: PTP(di) and TF both decreased as the level of pressure support increased. A significant correlation was found between PTP(di) and TF (ρ = 0.74, p < 0.001). The overall reproducibility of TF assessment was good but the coefficient of repeatability reached 18% for inter-observer reproducibility., Conclusions: Ultrasonographic assessment of the diaphragm TF is a non-invasive method that may prove useful in evaluating diaphragmatic function and its contribution to respiratory workload in intensive care unit patients.

Background: Noninvasive ventilation (NIV) is frequently used for the management of acute respiratory failure (ARF) in very old patients (≥ 80 years), often in the context of a do-not-intubate order (DNI). We aimed to determine its efficacy and long-term outcome., Methods: Prospective cohort of all patients admitted to the medical ICU of a tertiary hospital during a 2-year period and managed using NIV. Characteristics of patients, context of NIV, and treatment intensity were compared for very old and younger patients. Six-month survival and functional status were assessed in very old patients., Results: During the study period, 1,019 patients needed ventilatory support and 376 (37%) received NIV. Among them, 163 (16%) very old patients received ventilatory support with 60% of them managed using NIV compared with 32% of younger patients (p < 0.0001). Very old patients received NIV more frequently with DNI than in younger patients (40% vs. 8%). Such cases were associated with high mortality for both very old and younger patients. Hospital mortality was higher in very old than in younger patients but did not differ when NIV was used for cardiogenic pulmonary edema or acute-on-chronic respiratory failure (20% vs. 15%) and in postextubation (15% vs. 17%) out of a context of DNI. Six-month mortality was 51% in very old patients, 67% for DNI patients, and 77% in case of NIV failure and endotracheal intubation. Of the 30 hospital survivors, 22 lived at home and 13 remained independent for activities of daily living., Conclusions: Very old patients managed using NIV have an overall satisfactory 6-month survival and functional status, except for endotracheal intubation after NIV failure.

Background: Patients in intensive care units (ICUs) experience severe sleep alterations and conventional sleep scoring rules are difficult to use in these patients. In a previous study, we showed that abnormal sleep EEG and wake EEG patterns could predict the outcome of noninvasive ventilation in a group of patients treated for acute respiratory failure. Our aims were to assess the prevalence of these abnormal sleep/wake EEG patterns in a larger group and search for objective parameters to help their identification., Methods: We reviewed sleep studies previously performed with full polysomnography during 17-h in conscious nonsedated ICU patients receiving invasive ventilation during weaning or noninvasive ventilation for acute respiratory failure., Results: We included 57 patients. Sleep scoring using conventional rules was not feasible in 16 (28%) patients due to the absence of stage-2 markers. Wake EEG in these 16 patients, although recognizable, showed abnormal features, including decreased reactivity to eye opening and slower peak EEG frequency compared to patients with normal sleep-wake EEGs., Conclusion: In almost one third of awake mechanically ventilated ICU patients, sleep cannot be classified with standard criteria. Two new states, atypical sleep and pathologic wakefulness, need to be added. We suggest rules for scoring these states. The origin and links with outcomes of these abnormal EEG patterns deserve investigation., (Copyright © 2011 Elsevier B.V. All rights reserved.)

Objective: Extubation failure is associated with a poor prognosis, but the respective roles for reintubation per se and underlying disease severity remain unclear. Our objectives were to evaluate the impact of failed extubation, whether planned or unplanned, on patient outcomes and to identify a patient subset at risk for extubation failure., Design: Prospective 1-yr observational study with daily data collection., Setting: : Thirteen-bed medical intensive care unit in a teaching hospital., Patients: Consecutive patients requiring invasive mechanical ventilation were screened and followed until discharge or death., Interventions: None., Measurements and Main Results: Of 168 planned extubations in 340 patients, 26 (15%) failed. Of these 26 patients, seven (27%) had pneumonia and 13 (50%) died after reintubation. Compared with successfully extubated patients, the patients with failed extubation were not significantly different regarding disease severity, mechanical ventilation duration, or blood gas values. Age and underlying diseases were the only factors associated with extubation failure, and extubation failure occurred in 34% of patients >65 yrs with chronic cardiac or respiratory disease compared with only 9% of other patients (p < .01). Unplanned extubation occurred in 9% of patients, and inadequate endotracheal tube position was a risk factor. Failure of both planned and unplanned extubation was specifically associated with significant rapid worsening of daily organ dysfunction scores., Conclusions: Patients >65 yrs with underlying chronic cardiac or respiratory disease are at high risk for extubation failure and subsequent pneumonia and death. Contrasting with successful extubation, failed planned or unplanned extubation was followed by marked clinical deterioration, suggesting a direct and specific effect of extubation failure and reintubation on patient outcomes.

Background: A simple method for effective bronchodilator aerosol delivery while administering continuing continuous positive airway pressure (CPAP) would be useful in patients with severe bronchial obstruction., Objective: To assess the effectiveness of bronchodilator aerosol delivery during CPAP generated by the Boussignac CPAP system and its optimal humidification system., Methods: First we assessed the relationship between flow and pressure generated in the mask with the Boussignac CPAP system. Next we measured the inspired-gas humidity during CPAP, with several humidification strategies, in 9 healthy volunteers. We then measured the bronchodilator aerosol particle size during CPAP, with and without heat-and-moisture exchanger, in a bench study. Finally, in 7 patients with acute respiratory failure and airway obstruction, we measured work of breathing and gas exchange after a β(2)-agonist bronchodilator aerosol (terbutaline) delivered during CPAP or via standard nebulization., Results: Optimal humidity was obtained only with the heat-and-moisture exchanger or heated humidifier. The heat-and-moisture exchanger had no influence on bronchodilator aerosol particle size. Work of breathing decreased similarly after bronchodilator via either standard nebulization or CPAP, but P(aO(2)) increased significantly only after CPAP aerosol delivery., Conclusions: CPAP bronchodilator delivery decreases the work of breathing as effectively as does standard nebulization, but produces a greater oxygenation improvement in patients with airway obstruction. To optimize airway humidification, a heat-and-moisture exchanger could be used with the Boussignac CPAP system, without modifying aerosol delivery.

Purpose: During volume-controlled ventilation, part of the volume delivered is compressed into the circuit. To correct for this phenomenon, modern ventilators use compensation algorithms. Humidity and temperature also influence the delivered volume., Methods: In a bench study at a research laboratory in a university hospital, we compared nine ICU ventilators equipped with compensation algorithms, one with a proximal pneumotachograph and one without compensation. Each ventilator was evaluated under normal, obstructive, and restrictive conditions of respiratory mechanics. For each condition, three tidal volumes (V (T)) were set (300, 500, and 800 ml), with and without an inspiratory pause. The insufflated volume and the volume delivered at the Y-piece were measured independently, without a humidification device, under ambient temperature and pressure and dry gas conditions. We computed the actually delivered V (T) to the lung under body temperature and pressure and saturated water vapour conditions (BTPS)., Results: For target V (T) values of 300, 500, and 800 ml, actually delivered V (T) under BTPS conditions ranged from 261 to 396 ml (-13 to +32%), from 437 to 622 ml (-13 to +24%), and from 681 to 953 ml (-15 to +19%), respectively (p < 0.01). Respiratory system mechanics and application of an inspiratory pause significantly affected actually delivered V (T). Assuming a set V (T) of 6 ml/kg of predicted body weight, a difference of 1-2 ml/kg with actually delivered V (T) would be commonly observed., Conclusion: The difference between preset V (T) and actually delivered V (T) is clinically meaningful and differs across modern ICU ventilators.

Purpose: To compare cardiovascular and respiratory responses to different spontaneous breathing trials (SBT) in difficult-to-wean patients using T-piece and pressure support ventilation (PSV) with or without positive end-expiratory pressure (PEEP)., Methods: Prospective physiological study. Fourteen patients who were monitored with a Swan-Ganz catheter and had failed a previous T-piece trial were studied. Three SBTs were performed in random order in all patients: PSV with PEEP (PSV-PEEP), PSV without PEEP (PSV-ZEEP), and T-piece. PSV level was 7 cmH(2)O, and PEEP was 5 cmH(2)O. Inspiratory muscle effort was calculated, and hemodynamic parameters were measured using standard methods. RESULTS [MEDIAN (AND INTERQUARTILE RANGE)]: Most patients succeeded in the PSV-PEEP (11/14) and PSV-ZEEP (8/14) trials, but all failed the T-piece trial. Patient effort was significantly higher during T-piece than during PSV with or without PEEP [esophageal pressure-time product was 292 (238-512), 128 (58-299), and 148 (100-465) cmH(2)O x s/min, respectively, p < 0.05]. Left ventricular heart failure was observed in 11 of the 14 patients during the T-piece trial. Pulmonary artery occlusion pressure and respiratory rate were significantly higher during T-piece than with PSV-PEEP [21 (18-24) mmHg versus 17 (14-22) mmHg, p < 0.05 and 27 (21-35) breaths/min versus 19 (16-29) breaths/min, p < 0.05 respectively]. Tidal volume was significantly lower during the T-piece trial., Conclusion: In this selected population of difficult-to-wean patients, PSV and PSV plus PEEP markedly modified the breathing pattern, inspiratory muscle effort, and cardiovascular response as compared to the T-piece. Caregivers should be aware of these differences in SBT as they may play an important role in weaning decision-making.

Objective: To determine whether sleep quality helps to predict noninvasive ventilation outcome in patients with acute hypercapnic respiratory failure. Despite an initial clinical improvement, nearly one fourth of patients may fail noninvasive ventilation after several days. Because late intubation is associated with a poor prognosis, it may be useful to identify factors that may predict or explain late noninvasive ventilation failure., Patients: We prospectively studied 27 hypercapnic patients in a medical intensive care unit who required noninvasive ventilation for >48 hrs., Interventions: A 17-hr sleep polysomnography (3 PM-8 AM) was recorded 2 days to 4 days after noninvasive ventilation initiation. Late noninvasive ventilation failure was defined as death, endotracheal intubation, or persistent need for noninvasive ventilation on day 6., Measurements and Main Results: An abnormal electroencephalographic pattern that eluded analysis by standard sleep-scoring criteria was noted in seven (50%) of the 14 patients with late noninvasive ventilation failure compared with one (8%) of the 13 patients successfully treated with noninvasive ventilation (p = .03). No clinical or laboratory variables explained the electroencephalographic differences. Patients failing noninvasive ventilation had poorer sleep quality with greater circadian sleep-cycle disruption and less nocturnal rapid eye movement sleep (6 mins [range, 0-12] vs. 26 mins [range, 6-49], p = .03), compared with patients successfully treated with noninvasive ventilation. Noninvasive ventilation failure was associated with delirium during the intensive care unit stay (64% vs. 0%)., Conclusions: Late noninvasive ventilation failure in elderly patients with acute hypercapnic respiratory failure was associated with early sleep disturbances including an abnormal electroencephalographic pattern, disruption of the circadian sleep cycle, and decreased rapid eye movement sleep.

The general issue of weaning can be viewed as composed of three different groups of patients. First, simple or easy weaning, represents 60% to 70% of patients whose first trial of spontaneous breathing is successful. The main objective of the weaning process is to detect weaning readiness as early as possible, which is best achieved using a systematic approach. The percentage of patients in this group in a given intensive care unit represents the pretest probability of weaning. A second group is made of patients who experience failure of the first spontaneous breathing trial and in whom up to 7 days from the first trial may be required to achieve weaning. This group represents 20% to 25% of patients who undergo weaning from mechanical ventilation. Muscle weakness contributes to the prolongation of weaning in many of these patients. The last group is made of patients who are characterized by a prolonged or very difficult weaning process (about 5% to 15% of patients undergoing weaning). Muscle weakness is likely to be a major contributing factor. Early use of spontaneous breathing, well-controlled use of sedation, and early mobilization may help in reducing muscle weakness and hasten the weaning process. The postextubation period may be particularly at risk in these patients. More research is needed to guide clinicians regarding the best ventilatory management.

Objective: To compare 13 commercially available, new-generation, intensive-care-unit (ICU) ventilators in terms of trigger function, pressurization capacity during pressure-support ventilation (PSV), accuracy of pressure measurements, and expiratory resistance., Design and Setting: Bench study at a research laboratory in a university hospital., Methods: Four turbine-based ventilators and nine conventional servo-valve compressed-gas ventilators were tested using a two-compartment lung model. Three levels of effort were simulated. Each ventilator was evaluated at four PSV levels (5, 10, 15, and 20 cm H2O), with and without positive end-expiratory pressure (5 cm H2O). Trigger function was assessed as the time from effort onset to detectable pressurization. Pressurization capacity was evaluated using the airway pressure-time product computed as the net area under the pressure-time curve over the first 0.3 s after inspiratory effort onset. Expiratory resistance was evaluated by measuring trapped volume in controlled ventilation., Results: Significant differences were found across the ventilators, with a range of triggering delays from 42 to 88 ms for all conditions averaged (P < 0.001). Under difficult conditions, the triggering delay was longer than 100 ms and the pressurization was poor for five ventilators at PSV5 and three at PSV10, suggesting an inability to unload patient's effort. On average, turbine-based ventilators performed better than conventional ventilators, which showed no improvement compared to a bench comparison in 2000., Conclusion: Technical performance of trigger function, pressurization capacity, and expiratory resistance differs considerably across new-generation ICU ventilators. ICU ventilators seem to have reached a technical ceiling in recent years, and some ventilators still perform inadequately.

Objective: To determine the prevalence of patient-ventilator asynchrony in patients receiving non-invasive ventilation (NIV) for acute respiratory failure., Design: Prospective multicenter observation study., Setting: Intensive care units in three university hospitals., Methods: Patients consecutively admitted to ICU were included. NIV, performed with an ICU ventilator, was set by the clinician. Airway pressure, flow, and surface diaphragmatic electromyography were recorded continuously for 30 min. Asynchrony events and the asynchrony index (AI) were determined from visual inspection of the recordings and clinical observation., Results: A total of 60 patients were included, 55% of whom were hypercapnic. Auto-triggering was present in 8 (13%) patients, double triggering in 9 (15%), ineffective breaths in 8 (13%), premature cycling 7 (12%) and late cycling in 14 (23%). An AI > 10%, indicating severe asynchrony, was present in 26 patients (43%), whose median (25-75 IQR) AI was 26 (15-54%). A significant correlation was found between the magnitude of leaks and the number of ineffective breaths and severity of delayed cycling. Multivariate analysis indicated that the level of pressure support and the magnitude of leaks were weakly, albeit significantly, associated with an AI > 10%. Patient comfort scale was higher in pts with an AI < 10%., Conclusion: Patient-ventilator asynchrony is common in patients receiving NIV for acute respiratory failure. Our results suggest that leaks play a major role in generating patient-ventilator asynchrony and discomfort, and point the way to further research to determine if ventilator functions designed to cope with leaks can reduce asynchrony in the clinical setting.

Objective: To identify ventilatory setting adjustments that improve patient-ventilator synchrony during pressure-support ventilation in ventilator-dependent patients by reducing ineffective triggering events without decreasing tolerance., Design and Setting: Prospective physiological study in a 13-bed medical intensive care unit in a university hospital., Patients and Participants: Twelve intubated patients with more than 10% of ineffective breaths while receiving pressure-support ventilation., Interventions: Flow, airway-pressure, esophageal-pressure, and gastric-pressure signals were used to measure patient inspiratory effort. To decrease ineffective triggering the following ventilator setting adjustments were randomly adjusted: pressure support reduction, insufflation time reduction, and change in end-expiratory pressure., Measurements and Results: Reducing pressure support from 20.0 cm H(2)O (IQR 19.5-20) to 13.0 (12.0-14.0) reduced tidal volume [10.2ml /kg predicted body weight (7.2-11.5) to 5.9 (4.9-6.7)] and minimized ineffective triggering events [45% of respiratory efforts (36-52) to 0% (0-7)], completely abolishing ineffective triggering in two-thirds of patients. The ventilator respiratory rate increased due to unmasked wasted efforts, with no changes in patient respiratory rate [26.5 breaths/min (23.1-31.9) vs. 29.4 (24.6-34.5)], patient effort, or arterial PCO(2). Shortening the insufflation time reduced ineffective triggering events and patient effort, while applying positive end-expiratory pressure had no influence on asynchrony., Conclusions: Markedly reducing pressure support or inspiratory duration to reach a tidal volume of about 6 ml/kg predicted body weight eliminated ineffective triggering in two-thirds of patients with weaning difficulties and a high percentage of ineffective efforts without inducing excessive work of breathing or modifying patient respiratory rate.

Objectives: To compare the influence of three ventilatory modes on sleep., Design: Prospective, comparative, crossover study., Setting: Medical intensive care unit in a university hospital., Patients: Fifteen conscious, nonsedated, mechanically ventilated patients., Interventions: Patients were successively ventilated with assist-control ventilation, clinically adjusted pressure support ventilation (cPSV), and automatically adjusted pressure support ventilation (aPSV). Sleep polysomnography was performed during three consecutive 6-hr periods, one with each mode in random order. Airway pressure and thorax and abdomen plethysmography were used to diagnose central apneas and ineffective efforts., Measurements and Main Results: The main abnormalities were a low percentage of rapid eye movement (REM) sleep counting, for a median (25th-75th percentiles) of 10% (3.5-12.5) of total sleep, and a highly fragmented sleep with 29 arousals and awakenings per hour of sleep. REM sleep duration was similar in the three ventilatory modes, 7% in assist-control, 4% in aPSV, and 1% during cPSV (p = .54), as well as in the fragmentation index, 31 arousals and awakenings per hour in assist-control, 32 in aPSV, and 34 during cPSV (p = .62). Ineffective efforts occurred similarly with the three modes (seven per hour of sleep in assist-control, 16 in aPSV, and 12 during cPSV) or central apneas during PSV (five in aPSV, seven during cPSV). Minute ventilation was similar with the three modes., Conclusions: In conscious, mechanically ventilated patients, sleep architecture was highly abnormal, with a short REM stage and a high degree of fragmentation. The ventilatory mode did not influence sleep pattern, arousals, awakenings, and ineffective efforts.

Background: Alveolar recruitment in response to positive end-expiratory pressure (PEEP) may differ between pulmonary and extrapulmonary acute respiratory distress syndrome (ARDS), and alveolar recruitment values may differ when measured by pressure-volume curve compared with static compliance., Methods: The authors compared PEEP-induced alveolar recruitment in 71 consecutive patients identified in a database. Patients were classified as having pulmonary, extrapulmonary, or mixed/uncertain ARDS. Pressure-volume curves with and without PEEP were available for all patients, and pressure-volume curves with two PEEP levels were available for 44 patients. Static compliance was calculated as tidal volume divided by pressure change for tidal volumes of 400 and 700 ml. Recruited volume was measured at an elastic pressure of 15 cm H2O., Results: Volume recruited by PEEP (10 +/- 3 cm H2O) was 223 +/- 111 ml in the pulmonary ARDS group (29 patients), 206 +/- 164 ml in the extrapulmonary group (16 patients), and 242 +/- 176 ml in the mixed/uncertain group (26 patients) (P = 0.75). At high PEEP (14 +/- 2 cmH2O, 44 patients), recruited volumes were also similar (P = 0.60). With static compliance, recruitment was markedly underestimated and was dependent on tidal volume (226 +/- 148 ml using pressure-volume curve, 95 +/- 185 ml for a tidal volume of 400 ml, and 23 +/- 169 ml for 700 ml; P < 0.001)., Conclusion: In a large sample of patients, classification of ARDS was uncertain in more than one third of patients, and alveolar recruitment was similar in pulmonary and extrapulmonary ARDS. PEEP levels should not be determined based on cause of ARDS.

Objective: The incidence, pathophysiology, and consequences of patient-ventilator asynchrony are poorly known. We assessed the incidence of patient-ventilator asynchrony during assisted mechanical ventilation and we identified associated factors., Methods: Sixty-two consecutive patients requiring mechanical ventilation for more than 24 h were included prospectively as soon as they triggered all ventilator breaths: assist-control ventilation (ACV) in 11 and pressure-support ventilation (PSV) in 51., Measurements: Gross asynchrony detected visually on 30-min recordings of flow and airway pressure was quantified using an asynchrony index., Results: Fifteen patients (24%) had an asynchrony index greater than 10% of respiratory efforts. Ineffective triggering and double-triggering were the two main asynchrony patterns. Asynchrony existed during both ACV and PSV, with a median number of episodes per patient of 72 (range 13-215) vs. 16 (4-47) in 30 min, respectively (p=0.04). Double-triggering was more common during ACV than during PSV, but no difference was found for ineffective triggering. Ineffective triggering was associated with a less sensitive inspiratory trigger, higher level of pressure support (15 cmH(2)O, IQR 12-16, vs. 17.5, IQR 16-20), higher tidal volume, and higher pH. A high incidence of asynchrony was also associated with a longer duration of mechanical ventilation (7.5 days, IQR 3-20, vs. 25.5, IQR 9.5-42.5)., Conclusions: One-fourth of patients exhibit a high incidence of asynchrony during assisted ventilation. Such a high incidence is associated with a prolonged duration of mechanical ventilation. Patients with frequent ineffective triggering may receive excessive levels of ventilatory support.