OBJECTIVE: 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). PATIENTS: Fourteen consecutive patients with ALI were studied. INTERVENTIONS: 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. MEASUREMENT AND RESULTS: 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. CONCLUSION: In mechanically ventilated patients with ALI the breathing of pure oxygen leads to derecruitment, which is prevented by high PEEP.

Adult↗

PubMed2006

Benefits and risks of success or failure of noninvasive ventilation.

OBJECTIVE: 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. SETTINGS: 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%). DESIGN AND ANALYSIS: 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. RESULTS: 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). CONCLUSION: 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.

Aged↗

PubMed2006

B-type natriuretic peptide and weaning from mechanical ventilation.

OBJECTIVE: Cardiac function and volume status could play a critical role in the setting of weaning failure. B-type natriuretic peptide (BNP) is a powerful marker of cardiac dysfunction. We assessed the value of BNP during the weaning process. DESIGN, SETTING AND PATIENTS: One hundred and two consecutive patients considered ready to undergo a 1-h weaning trial (T-piece or low-pressure support level) were prospectively included in a medical intensive care unit of a university hospital. Weaning was considered successful if the patient passed the trial and sustained spontaneous breathing for more than 48 h after extubation. INTERVENTIONS: Plasma BNP was measured just before the trial in all patients, and at the end of the trial in the first 60 patients. RESULTS: Overall, 42 patients (41.2%) failed the weaning process (37 patients failed the trial and 5 failed extubation). Logistic regression analysis identified high BNP level before the trial and the product of airway pressure and breathing frequency during ventilation as independent risk factors for weaning failure. BNP values were not different at the end of the trial. In nine of the patients in whom the weaning process failed, it succeeded on a later occasion after diuretic therapy. Their BNP level before weaning decreased between the two attempts (517 vs 226 pg/ml, p=0.01). In survivors, BNP level was significantly correlated to weaning duration (rho=0.52, p<0.01). CONCLUSIONS: Baseline plasma BNP level before the first weaning attempt is higher in patients with subsequent weaning failure and correlates to weaning duration.

Aged↗

PubMed2006

Relation between PaO2/FIO2 ratio and FIO2: a mathematical description.

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Humans↗

PubMed2006

Effects of vertical positioning on gas exchange and lung volumes in acute respiratory distress syndrome.

OBJECTIVE: Supine position may contribute to the loss of aerated lung volume in patients with acute respiratory distress syndrome (ARDS). We hypothesized that verticalization increases lung volume and improves gas exchange by reducing the pressure surrounding lung bases. DESIGN AND SETTING: Prospective observational physiological study in a medical ICU. SUBJECTS AND INTERVENTION: In 16 patients with ARDS we measured arterial blood gases, pressure-volume curves of the respiratory system recorded from positive-end expiratory pressure (PEEP), and changes in lung volume in supine and vertical positions (trunk elevated at 45 degrees and legs down at 45 degrees ). MEASUREMENTS AND RESULTS: Vertical positioning increased PaO(2) significantly from 94+/-33 to 142+/-49 mmHg, with an increase higher than 40% in 11 responders. The volume at 20 cmH(2)O measured on the PV curve from PEEP increased using the vertical position only in responders (233+/-146 vs. -8+/-9 1ml in nonresponders); this change was correlated to oxygenation change (rho=0.55). End-expiratory lung volume variation from supine to vertical and 1 h later back to supine, measured in 12 patients showed a significant increase during the 1-h upright period in responders (n=7) but not in nonresponders (n=5; 215+/-220 vs. 10+/-22 ml), suggesting a time-dependent recruitment. CONCLUSIONS: Vertical positioning is a simple technique that may improve oxygenation and lung recruitment in ARDS patients.

Blood Gas Analysis↗

PubMed2006

Patient-ventilator asynchrony during assisted mechanical ventilation.

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.

Aged↗

PubMed2006

A multicenter randomized trial of computer-driven protocolized weaning from mechanical ventilation.

RATIONALE AND OBJECTIVES: Duration of weaning from mechanical ventilation may be reduced by the use of a systematic approach. We assessed whether a closed-loop knowledge-based algorithm introduced in a ventilator to act as a computer-driven weaning protocol can improve patient outcomes as compared with usual care. METHODS AND MEASUREMENTS: We conducted a multicenter randomized controlled study with concealed allocation to compare usual care for weaning with computer-driven weaning. The computerized protocol included an automatic gradual reduction in pressure support, automatic performance of spontaneous breathing trials (SBT), and generation of an incentive message when an SBT was successfully passed. One hundred forty-four patients were enrolled before weaning initiation. They were randomly allocated to computer-driven weaning or to physician-controlled weaning according to local guidelines. Weaning duration until successful extubation and total duration of ventilation were the primary endpoints. MAIN RESULTS: Weaning duration was reduced in the computer-driven group from a median of 5 to 3 d (p=0.01) and total duration of mechanical ventilation from 12 to 7.5 d (p=0.003). Reintubation rate did not differ (23 vs. 16%, p=0.40). Computer-driven weaning also decreased median intensive care unit (ICU) stay duration from 15.5 to 12 d (p=0.02) and caused no adverse events. The amount of sedation did not differ between groups. In the usual care group, compliance to recommended modes and to SBT was estimated, respectively, at 96 and 51%. CONCLUSIONS: The specific computer-driven system used in this study can reduce mechanical ventilation duration and ICU length of stay, as compared with a physician-controlled weaning process.

Aged↗

PubMed2006

Pressure-volume curves with and without muscle paralysis in acute respiratory distress syndrome.

OBJECTIVE: Pressure-volume (PV) curves are recorded after induction of complete muscle paralysis, which may limit their clinical use. The feasibility of recording PV curves without paralysis has not been tested. In 19 patients with acute respiratory distress syndrome (ARDS) and no hemodynamic instability we prospectively evaluated whether PV curves can be safely and reliably recorded under deep sedation without neuromuscular blockade. METHODS: After standardized sedation (continuous infusion of midazolam and fentanyl) PV curves were recorded during apneic sedation, defined as absence of respiratory effort during a 6-s expiratory pause and during paralysis induced by cis-atracurium. MEASUREMENTS AND RESULTS: Agreement between PV curve parameters in the two conditions was evaluated. Curves were obtained from 10 cmH2O and from zero end-expiratory pressure in all patients under apneic sedation. In five patients propofol was given in addition to midazolam and fentanyl, and in two of them fluid resuscitation was needed. A strong agreement was found for respiratory system compliance and the lower inflection point and for chest wall compliance in the five patients whose esophageal pressure was measured. The variability of the measurements, however, should be taken into account in clinical practice. CONCLUSION: Neuromuscular blockade can be dispensed with when recording PV curves in many ARDS patients. Reliable PV curves can be obtained under anesthesia alone, with no serious adverse effects.

Adult↗

PubMed2006

Increased use of noninvasive ventilation in French intensive care units.

OBJECTIVES: 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. SETTINGS: Patients were enrolled in a prospective survey in 70 French ICUs. METHODS: Three-week survey, with prospective inclusion of all patients requiring ventilatory support. MEASUREMENTS AND RESULTS: 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. CONCLUSIONS: 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).

Acute Disease↗

PubMed2006

Under-humidification and over-humidification during moderate induced hypothermia with usual devices.

OBJECTIVE: 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. DESIGN: Prospective, cross-over randomized study. SETTINGS: Medical Intensive Care Unit in a University Hospital. PATIENTS AND PARTICIPANTS: Nine adult patients hospitalized after cardiac arrest in whom moderate hypothermia was induced (33 degrees C for 24[Symbol: see text]h). INTERVENTIONS: 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. MEASUREMENTS AND RESULTS: 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. CONCLUSIONS: 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.

Adult↗

PubMed2006

Constant flow insufflation of oxygen as the sole mode of ventilation during out-of-hospital cardiac arrest.

BACKGROUND: Constant flow insufflation of oxygen (CFIO) through a Boussignac multichannel endotracheal tube has been reported to be an efficient ventilatory method during chest massage for cardiac arrest. METHODS: Patients resuscitated for out-of-hospital cardiac arrest were randomly assigned to standard endotracheal intubation and mechanical ventilation (MV; n =457) or use of CFIO at a flow rate of 15 l/min (n=487). Continuous chest compressions were similar in the two groups. Pulse oximetry level was recorded every 5[Symbol: see text]min. Outcome of initial resuscitation, hospital admission, complications, and discharge from the intensive care unit (ICU) were analyzed. The randomization scheme was changed during the study, but the in-depth analysis was performed only on the first cohort of 341 patients with CFIO and 355 with MV, because of randomization problems in the second part. RESULTS: No difference in outcome was noted regarding return to spontaneous circulation (CFIO 21%, MV 20%), hospital admission (CFIO 17%, MV 16%), or ICU discharge (CFIO 2.4%, MV 2.3%). The level of detectable pulse saturation and the proportion of patients with saturation above 70% were higher with CFIO. Ten patients with MV but only one with CFIO had rib fractures. CONCLUSIONS: CFIO is a simplified alternative to MV, with favorable effects regarding oxygenation and fewer complications, as observed in this group of patients with desperate prognosis.

Adult↗

PubMed2006

Year in review in intensive care medicine, 2005. III. Nutrition, pediatric and neonatal critical care, and experimental.

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Child↗

PubMed2006

Year in review in intensive care medicine, 2005. II. Infection and sepsis, ventilator-associated pneumonia, ethics, haematology and haemostasis, ICU organisation and scoring, brain injury.

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Brain Injuries↗

PubMed2006

Relationship between pressure-volume curve and markers for collagen turn-over in early acute respiratory distress syndrome.

OBJECTIVE: In acute respiratory distress syndrome, the relationships between changes in the elastic behavior of the respiratory system and biological markers of extra-cellular matrix or surfactant turn-over could give some insights into its pathophysiological determinants. DESIGN AND MEASUREMENTS: In 17 patients with acute respiratory distress syndrome, we assessed the relationship between chord compliance measured on pressure-volume curves obtained at two levels of positive end-expiratory pressure (0 and 10[Symbol: see text]cm[Symbol: see text]H(2)O) and biological markers of collagen turn-over or surfactant degradation in bronchoalveolar lavage fluid obtained simultaneously in the early phase of the disease (first 4 days). MAIN RESULTS: The compliance of the respiratory system obtained from the pressure-volume curves was significantly correlated with markers for collagen turn-over (type III procollagen peptide and matrix metalloproteinase 2) and with markers of surfactant degradation (type-IIA secretory phospholipase A2). The correlations were stronger when the curve was traced from positive end-expiratory pressure, suggesting that this condition may improve the assessment of tissue mechanics. A logarithmic relationship best described the correlation between compliance and type III procollagen peptide, in agreement with a collagen-dependent model of maximal distension. The marker for surfactant degradation was associated with ongoing alveolar inflammation (cellularity of bronchoalveolar lavage fluid and tumor necrosis factor-alpha concentration). Interleukin-10, an anti-inflammatory mediator, showed no correlation with compliance. CONCLUSION: These preliminary data suggest that a severe reduction in compliance in the early phase of acute respiratory distress syndrome is associated with both collagen deposition and surfactant degradation.

Adult↗