An Early PEEP/FiO2 Trial IdentifiesDifferent Degrees of Lung Injury in ARDS patients. [Am J Respir Crit Care Med] Journal article

Rationale and
OBJECTIVE: Current American-European Consensus Conference (AECC) definitions for ALI and ARDS are inadequate for inclusion into clinical trials due to the lack of standardization for measuring the oxygenation defect. We questioned whether an early assessment of oxygenation on specific ventilator settings would identify patients with established ARDS (persisting over 24h). Methods. At the time of meeting ARDS criteria (Day 0) and 24 hours later (Day 1), arterial blood gases were obtained on standard ventilator settings, VT7 mL/kg PBW plus the following PEEP and FiO2 settings in sequence: (1) PEEP>/=5 cmH2O and FiO2>/=0.5, (2) PEEP>/=5 cmH2O and FiO2 1.0, (3) PEEP>/=10 cmH2O and FiO2>/=0.5, and (4) PEEP>/=10 cmH2O and FiO21.0.
MEASUREMENTS AND MAIN RESULTS: 170 patients meeting ARDS criteria (PaO2/FiO2 128+/-33 mmHg) were enrolled. Overall hospital mortality was 34.1%. The standard ventilator settings that best identified established ARDS patients and predicted differences in ICU mortality were PEEP>/=10 cmH2O and FiO2>/=0.5 at Day 1 (p=0.0001). Only 99 (58.2%) patients continued to meet ARDS criteria (PaO2/FiO2 155.8 +/- 29.8 mmHg, ICU mortality 45.5%) while 55 patients were reclassified as ALI (PaO2/FiO2 246.5 +/- 25.6 mmHg, ICU mortality 20%) and 16 patients as acute respiratory failure (ARF) (PaO2/FiO2 370 +/- 54 mmHg, ICU mortality 6.3%) (p=0.0001) on these settings.
CONCLUSIONS: Patients meeting current AECC ARDS criteria may have highly variable levels of lung injury and outcomes. A systematic method of assessing severity of lung injury is required for enrollment of ARDS patients into randomized controlled trials. www.clinicaltrials.gov NCT00435110.

Am J Respir Crit Care Med