Academic Medical Center (Amsterdam, Netherlands), European Society of Anaesthesiology.

PURPOSE:Mechanical power (MP) may unify variables known to be related with development of ventilator-induced lung injury. The aim of this study is to examine the association between MP and mortality in critically ill patients receiving invasive ventilation for at least 48 hours. METHODS:This is an analysis of data stored in the databases of the MIMIC-III, and eICU. Critically ill patients receiving invasive ventilation for at least 48 hours were included. The exposure of interest was MP. The primary outcome was in-hospital mortality. RESULTS:In total, 8,207 patients were analyzed. Median MP during the second 24 hours was 21.4 (16.2 to 28.1) J/min in MIMIC-III and 16.0 (11.7 to 22.1) J/min in eICU. MP was independently associated with in-hospital mortality (odds ratio per 5 J/min increase [OR] 1.06 [95% confidence interval [CI] 1.01 to 1.11]; p = 0.021 in MIMIC-III, and 1.10 [1.02 to 1.18]; p = 0.010 in eICU). MP was also associated with ICU-mortality, 30-day mortality, and with ventilator-free days, ICU and hospital length of stay. Even at low tidal volume, high MP was associated with in-hospital mortality (OR 1.70 [1.32 to 2.18]; p < 0.001) and other secondary outcomes. Finally, there is a consistent increase in the risk of death with MP higher than 17.0 J/min. CONCLUSION:High MP of ventilation is independently associated with higher inhospital mortality and several other outcomes in ICU patients receiving invasive ventilation for at least 48 hours.

Postoperative pulmonary complications (PPCs) occur frequently and are associated with substantial morbidity and mortality. Evidence suggests that reduction of PPCs can be accomplished by using lung-protective ventilation strategies intraoperatively, but a consensus on perioperative management has not been established. We sought to determine recommendations for lung protection for the surgical patient at an international consensus development conference. Seven experts produced 24 questions concerning preoperative assessment and intraoperative mechanical ventilation for patients at risk of developing PPCs. Six researchers assessed the literature using questions as a framework for their review. The modified Delphi method was utilised by a team of experts to produce recommendations and statements from study questions. An expert consensus was reached for 22 recommendations and four statements. The following are the highlights: (i) a dedicated score should be used for preoperative pulmonary risk evaluation; and (ii) an individualised mechanical ventilation may improve the mechanics of breathing and respiratory function, and prevent PPCs. The ventilator should initially be set to a tidal volume of 6e8 ml kg À1 predicted body weight and positive end-expiratory pressure (PEEP) 5 cm H 2 O. PEEP should be individualised thereafter. When recruitment manoeuvres are performed, the lowest effective pressure and shortest effective time or fewest number of breaths should be used.

A large number of postoperative pulmonary outcome measures have been used, but most are poorly defined. Our four recommended outcome measures include a new definition of postoperative pulmonary complications, incorporating an assessment of severity. These definitions will meet the needs of most clinical effectiveness trials of treatments to improve postoperative pulmonary outcomes.

IMPORTANCE An intraoperative higher level of positive end-expiratory positive pressure (PEEP) with alveolar recruitment maneuvers improves respiratory function in obese patients undergoing surgery, but the effect on clinical outcomes is uncertain. OBJECTIVE To determine whether a higher level of PEEP with alveolar recruitment maneuvers decreases postoperative pulmonary complications in obese patients undergoing surgery compared with a lower level of PEEP. DESIGN, SETTING, AND PARTICIPANTS Randomized clinical trial of 2013 adults with body mass indices of 35 or greater and substantial risk for postoperative pulmonary complications who were undergoing noncardiac, nonneurological surgery under general anesthesia. The trial was conducted at 77 sites in 23 countries from July 2014-February 2018; final follow-up: May 2018. INTERVENTIONS Patients were randomized to the high level of PEEP group (n = 989), consisting of a PEEP level of 12 cm H 2 O with alveolar recruitment maneuvers (a stepwise increase of tidal volume and eventually PEEP) or to the low level of PEEP group (n = 987), consisting of a PEEP level of 4 cm H 2 O. All patients received volume-controlled ventilation with a tidal volume of 7 mL/kg of predicted body weight. MAIN OUTCOMES AND MEASURES The primary outcome was a composite of pulmonary complications within the first 5 postoperative days, including respiratory failure, acute respiratory distress syndrome, bronchospasm, new pulmonary infiltrates, pulmonary infection, aspiration pneumonitis, pleural effusion, atelectasis, cardiopulmonary edema, and pneumothorax. Among the 9 prespecified secondary outcomes, 3 were intraoperative complications, including hypoxemia (oxygen desaturation with SpO 2 Յ92% for >1 minute). RESULTS Among 2013 adults who were randomized, 1976 (98.2%) completed the trial (mean age, 48.8 years; 1381 [69.9%] women; 1778 [90.1%] underwent abdominal operations). In the intention-to-treat analysis, the primary outcome occurred in 211 of 989 patients (21.3%) in the high level of PEEP group compared with 233 of 987 patients (23.6%) in the low level of PEEP group (difference, −2.3% [95% CI, −5.9% to 1.4%]; risk ratio, 0.93 [95% CI, 0.83 to 1.04]; P = .23). Among the 9 prespecified secondary outcomes, 6 were not significantly different between the high and low level of PEEP groups, and 3 were significantly different, including fewer patients with hypoxemia (5.0% in the high level of PEEP group vs 13.6% in the low level of PEEP group; difference, −8.6% [95% CI, −11.1% to 6.1%]; P < .001). CONCLUSIONS AND RELEVANCE Among obese patients undergoing surgery under general anesthesia, an intraoperative mechanical ventilation strategy with a higher level of PEEP and alveolar recruitment maneuvers, compared with a strategy with a lower level of PEEP, did not reduce postoperative pulmonary complications.

Postoperative pulmonary complications are associated with increased morbidity, length of hospital stay, and mortality after major surgery. Intraoperative lung-protective mechanical ventilation has the potential to reduce the incidence of postoperative pulmonary complications. This review discusses the relevant literature on definition and methods to predict the occurrence of postoperative pulmonary complication, the pathophysiology of ventilator-induced lung injury with emphasis on the noninjured lung, and protective ventilation strategies, including the respective roles of tidal volumes, positive end-expiratory pressure, and recruitment maneuvers. The authors propose an algorithm for protective intraoperative mechanical ventilation based on evidence from recent randomized controlled trials.

Writing Group for the PReVENT Investigators IMPORTANCE It remains uncertain whether invasive ventilation should use low tidal volumes in critically ill patients without acute respiratory distress syndrome (ARDS).OBJECTIVE To determine whether a low tidal volume ventilation strategy is more effective than an intermediate tidal volume strategy.

In the surfactant depletion model of acute lung injury, the new noisy PSV increased the variability of the respiratory pattern and improved oxygenation by a redistribution of perfusion toward the ventilated nondependent lung regions with simultaneous lower mean airway pressure, comparable minute ventilation, and no increase in the inspiratory effort or cardiac output.