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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.

The weaning process concerns all patients receiving mechanical ventilation. A previous classification into simple, prolonged, and difficult weaning ignored weaning failure and presupposed the use of spontaneous breathing trials. To describe the weaning process, defined as starting with any attempt at separation from mechanical ventilation and its prognosis, according to a new operational classification working for all patients under ventilation. This was a multinational prospective multicenter observational study over 3 months of all patients receiving mechanical ventilation in 36 intensive care units, with daily collection of ventilation and weaning modalities. Pragmatic definitions of separation attempt and weaning success allowed us to allocate patients in four groups. A total of 2,729 patients were enrolled. Although half of them could not be classified using the previous definition, 99% entered the groups on the basis of our new definition as follows: 24% never started a weaning process, 57% had a weaning process of less than 24 hours (group 1), 10% had a difficult weaning of more than 1 day and less than 1 week (group 2), and 9% had a prolonged weaning duration of 1 week or more (group 3). Duration of ventilation, intensive care unit stay, and mortality (6, 17, and 29% for the three groups, respectively) all significantly increased from one group to the next. The unadjusted risk of dying was 19% after the first separation attempt and increased to 37% after 10 days. A new classification allows us to categorize all weaning situations. Every additional day without a weaning success after the first separation attempt increases the risk of dying.

The use of ultrasonography has become increasingly popular in the everyday management of critically ill patients. It has been demonstrated to be a safe and handy bedside tool that allows rapid hemodynamic assessment and visualization of the thoracic, abdominal and major vessels structures. More recently, M-mode ultrasonography has been used in the assessment of diaphragm kinetics. Ultrasounds provide a simple, non-invasive method of quantifying diaphragmatic movement in a variety of normal and pathological conditions. Ultrasonography can assess the characteristics of diaphragmatic movement such as amplitude, force and velocity of contraction, special patterns of motion and changes in diaphragmatic thickness during inspiration. These sonographic diaphragmatic parameters can provide valuable information in the assessment and follow up of patients with diaphragmatic weakness or paralysis, in terms of patient–ventilator interactions during controlled or assisted modalities of mechanical ventilation, and can potentially help to understand post-operative pulmonary dysfunction or weaning failure from mechanical ventilation. This article reviews the technique and the clinical applications of ultrasonography in the evaluation of diaphragmatic function in ICU patients.

Esophageal manometry is the clinically available method to estimate pleural pressure, thus enabling calculation of transpulmonary pressure (Pl). However, many concerns make it uncertain in which lung region esophageal manometry reflects local Pl. To determine the accuracy of esophageal pressure (Pes) and in which regions esophageal manometry reflects pleural pressure (Ppl) and Pl; to assess whether lung stress in nondependent regions can be estimated at end-inspiration from Pl. In lung-injured pigs (n = 6) and human cadavers (n = 3), Pes was measured across a range of positive end-expiratory pressure, together with directly measured Ppl in nondependent and dependent pleural regions. All measurements were obtained with minimal nonstressed volumes in the pleural sensors and esophageal balloons. Expiratory and inspiratory Pl was calculated by subtracting local Ppl or Pes from airway pressure; inspiratory Pl was also estimated by subtracting Ppl (calculated from chest wall and respiratory system elastance) from the airway plateau pressure. In pigs and human cadavers, expiratory and inspiratory Pl using Pes closely reflected values in dependent to middle lung (adjacent to the esophagus). Inspiratory Pl estimated from elastance ratio reflected the directly measured nondependent values. These data support the use of esophageal manometry in acute respiratory distress syndrome. Assuming correct calibration, expiratory Pl derived from Pes reflects Pl in dependent to middle lung, where atelectasis usually predominates; inspiratory Pl estimated from elastance ratio may indicate the highest level of lung stress in nondependent \"baby\" lung, where it is vulnerable to ventilator-induced lung injury.

Despite their controversial role, corticosteroids are often administered to patients with adult respiratory distress syndrome (ARDS) secondary to viral pneumonia. To analyze the impact of corticosteroid therapy on outcomes of patients having ARDS associated with influenza A/H1N1 pneumonia. Patients from the French registry of critically ill patients with influenza A/H1N1v 2009 infection were selected if fulfilling criteria for ARDS, excluding patients having other indication for corticosteroids, or decompensated underlying disease as the primary cause for intensive care unit admission. Survival to hospital discharge was analyzed using Cox regression, accounting for the time to administration of steroids, and after adjustment on the propensity for receiving steroid therapy. Of 208 patients with ARDS, 83 (39.9%) received corticosteroids (median initial dose of 270 mg equivalent hydrocortisone per day for a median of 11 d). Steroid therapy was associated with death, both in crude analysis (33.7 vs. 16.8%; hazard ratio, 2.4; 95% CI, 1.3-4.3; P = 0.004) and after propensity score-adjusted analysis (adjusted hazard ratio, 2.82; 95% CI, 1.5-5.4; P = 0.002), controlling for an admission severity Simplified Acute Physiology Score, version 3, greater than 50, initial administration of vasopressors, and immunodepression. Early therapy (≤ 3 d of mechanical ventilation) appeared more strongly associated with mortality than late administration. Patients receiving steroids had more acquired pneumonia and a trend to a longer duration of ventilation. Our study provides no evidence of a beneficial effect of corticosteroids in patients with ARDS secondary to influenza pneumonia, but suggests that very early corticosteroid therapy may be harmful.

This analysis of previously reported trials shows that low tidal volumes, a key component of safer ventilation strategies, confer a protective effect against complications only if the lower volume results in a lower pulmonary driving pressure. Mechanical-ventilation strategies that use lower end-inspiratory (plateau) airway pressures, lower tidal volumes (V T ), and higher positive end-expiratory pressures (PEEPs) — collectively termed lung-protective strategies — have been associated with survival benefits in randomized clinical trials involving patients with the acute respiratory distress syndrome (ARDS). 1 – 4 The different components of lung protection in those strategies, such as lower V T , lower plateau pressure, and higher PEEP, can all reduce mechanical stresses on the lung, which are thought to induce ventilator-induced lung injury. 5 – 9 Clinical trials, however, have reported conflicting responses to the manipulation of separate components of lung . . .

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 H 2 O), with and without positive end-expiratory pressure (5 cm H 2 O). 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.

BackgroundThe electrical activity of the crural diaphragm (Eadi), a surrogate of respiratory drive, can now be measured at the bedside in mechanically ventilated patients with a specific catheter. The expected range of Eadi values under stressed or assisted spontaneous breathing is unknown. This study explored Eadi values in healthy subjects during unstressed (baseline), stressed (with a resistance) and assisted spontaneous breathing. The relation between Eadi and inspiratory effort was analyzed.MethodsThirteen healthy male volunteers were included in this randomized crossover study. Eadi and esophageal pressure (Peso) were recorded during unstressed and stressed spontaneous breathing and under assisted ventilation delivered in pressure support (PS) at low and high assist levels and in neurally adjusted ventilatory assist (NAVA). Overall eight different situations were assessed in each participant (randomized order). Peak, mean and integral of Eadi, breathing pattern, esophageal pressure–time product (PTPeso) and work of breathing (WOB) were calculated offline.ResultsMedian [interquartile range] peak Eadi at baseline was 17 [13–22] μV and was above 10 μV in 92% of the cases. Eadimax defined as Eadi measured at maximal inspiratory capacity reached 90 [63 to 99] μV. Median peak Eadi/Eadimax ratio was 16.8 [15.6–27.9]%. Compared to baseline, respiratory rate and minute ventilation were decreased during stressed non-assisted breathing, whereas peak Eadi and PTPeso were increased. During unstressed assisted breathing, peak Eadi decreased during high-level PS compared to unstressed non-assisted breathing and to NAVA (p = 0.047). During stressed breathing, peak Eadi was lower during all assisted ventilation modalities compared to stressed non-assisted breathing. During assisted ventilation, across the different conditions, peak Eadi changed significantly, whereas PTPeso and WOB/min were not significantly modified. Finally, Eadi signal was still present even when Peso signal was suppressed due to high assist levels.ConclusionEadi analysis provides complementary information compared to respiratory pattern and to Peso monitoring, particularly in the presence of high assist levels.Trial registration The study was registered as NCT01818219 in clinicaltrial.gov. Registered 28 February 2013

Background In pressure-controlled (PC) ventilation, tidal volume ( V T ) and transpulmonary pressure ( P L ) result from the addition of ventilator pressure and the patient’s inspiratory effort. PC modes can be classified into fully, partially, and non-synchronized modes, and the degree of synchronization may result in different V T and P L despite identical ventilator settings. This study assessed the effects of three PC modes on V T , P L , inspiratory effort (esophageal pressure–time product, PTP es ), and airway occlusion pressure, P 0.1 . We also assessed whether P 0.1 can be used for evaluating patient effort. Methods Prospective, randomized, crossover physiologic study performed in 14 spontaneously breathing mechanically ventilated patients recovering from acute respiratory failure (1 subsequently withdrew). PC modes were fully (PC-CMV), partially (PC-SIMV), and non-synchronized (PC-IMV using airway pressure release ventilation) and were applied randomly; driving pressure, inspiratory time, and set respiratory rate being similar for all modes. Airway, esophageal pressure, P 0.1 , airflow, gas exchange, and hemodynamics were recorded. Results V T was significantly lower during PC-IMV as compared with PC-SIMV and PC-CMV (387 ± 105 vs 458 ± 134 vs 482 ± 108 mL, respectively; p  < 0.05). Maximal P L was also significantly lower (13.3 ± 4.9 vs 15.3 ± 5.7 vs 15.5 ± 5.2 cmH 2 O, respectively; p  < 0.05), but PTP es was significantly higher in PC-IMV (215.6 ± 154.3 vs 150.0 ± 102.4 vs 130.9 ± 101.8 cmH 2 O × s × min −1 , respectively; p  < 0.05), with no differences in gas exchange and hemodynamic variables. PTP es increased by more than 15% in 10 patients and by more than 50% in 5 patients. An increased P 0.1 could identify high levels of PTP es . Conclusions Non-synchronized PC mode lowers V T and P L in comparison with more synchronized modes in spontaneously breathing patients but can increase patient effort and may need specific adjustments. Clinical Trial Registration Clinicaltrial.gov # NCT02071277

Patients with acute hypoxemic respiratory failure were assigned to standard oxygen therapy, high-flow oxygen therapy, or noninvasive ventilation. The intubation rate did not differ significantly among the groups, but 90-day mortality was lower in the high-flow–oxygen group. Noninvasive positive-pressure ventilation (hereafter, noninvasive ventilation) reduces the need for endotracheal intubation and mortality among patients with acute exacerbations of chronic obstructive pulmonary disease 1 – 3 or severe cardiogenic pulmonary edema. 4 The physiological effects of noninvasive ventilation include a decrease in the work of breathing and improvement in gas exchange. In patients with acute hypoxemic respiratory failure, the need for mechanical ventilation is associated with high mortality, 5 but data on the overall effects of noninvasive ventilation with respect to the prevention of intubation and improvement in outcome are conflicting. 6 – 10 Previous studies have often included a heterogeneous population of patients with . . .