effect of prone positioning on mortality in patients with mild to moderate acute respiratory distress syndrome.

Conditions: ARDS; Acute Respiratory Distress Syndrome; Intensive Care Unit; Mechanical Ventilation

Summary: acute respiratory distress syndrome (ards) accounts for almost 10% of intensive care units (icu) admissions. three ards stages have been defined, based on the pao2/fio2 ratio measured with positive end-expiratory pressure (peep) ≥5 cmh2o: mild (201-300 mmhg), moderate (200-101 mmhg), and severe (≤100mmhg). they represent 30.0%, 46.6%, and 23.4% of ards, respectively. mechanical invasive ventilation (mv), the cornerstone of ards patient care, has a primary goal to protect the lung from ventilator-induced lung injury (vili). delivering mv in a prone position (pp) has been shown to improve oxygenation, protect the lung through a better homogenization of lung stress/strain, and stabilize hemodynamics. a meta-analysis of four randomized controlled trials showed beneficial effect of pp vs. supine position (sp) in the most hypoxemic patients. a fifth randomized controlled trial further showed a significant reduction in mortality with pp in ards patients with pao2/fio2 \<150 mmhg, when neuromuscular blockade and long prone positioning sessions were used. therefore, pp has since been strongly recommended for ards patients with pao2/fio2 \<150 mmhg. yet, there is limited evidence in patients with mild to moderate ards. there are, however, strong arguments supporting the need for a new trial in ards patients with pao2/fio2 in the range 150-300 mmhg: 1. there is no trial that has specifically tested pp in this ards subset; 2. pp is safe and has become a standard of care in icu; 3. should vili prevention be a mechanism through which pp improves survival, this should be involved in all ards patients; 4. the mortality at hospital discharge in this subset of ards remains significant, amounting to 34.9% (95% confidence intervals 31.4-38.5%) in mild and 40.3% (37.4-43.3) in moderate stages; 5. among 580 patients with mild ards at admission to the icu, in-hospital mortality was 10%, 30%, and 37% for those who improved, persisted, and worsened ards, respectively. 6. finally, pp has been shown to be cost-effective under commonly accepted thresholds. the hypothesis is that in patients within the 150-300mmhg pao2/fio2 range at the time of ards diagnosis, pp can reduce mortality as compared to a similar group left in the sp.


Eligibility criteria:
inclusion criteria: * age of 18 years or more admitted to icu. * ards patients meeting the berlin criteria under invasive mechanical ventilation within the first 24h. * mechanically ventilated patients with standard settings: peep of 5 cmh2o or more and vt 6 ml/kg pbw and pplat equal to or below 28-30 cmh2o after intubation. * pao2/fio2 between 150 and 300 mmhg under previous settings within 12 hours after mechanical ventilation standardization. * written informed consent obtained from the patient, next of kin/proxy or emergency consent. the patient will be asked to give his consent for the continuation of the trial when his condition will allow. exclusion criteria: * contra-indication to pp: spine instability; intracranial pressure greater than 20 mmhg; severe facial trauma; hemodynamic instability * non-inclusion criteria related to medical condition: lung transplant; burns over more than 20% of body surface; chronic respiratory failure requiring home oxygen supplementation and/or non-invasive ventilation; underlying disease with death expectancy within one year; * other non-inclusion criteria: therapeutic limitation; inclusion into another interventional study in intubated and ventilated patients with mortality as primary end-point in the last 30 days; previously included in the same study; prone positioning before inclusion. * individuals referred to in articles l. 1121-5 à l. 1121-7 (pregnant women, persons deprived of freedom, minors), adult individuals under protection of law (l. 1121-8 and l. 1122-1-2) (emergency situations) of public health regulation in france * patients not affiliated to social security insurance regimen

Keywords: ards acute respiratory distress syndrome intensive care unit icu prone position