Individual patient data analysis of tidal volumes used in three large randomized control trials involving patients with acute respiratory distress syndrome.

BACKGROUND.: The acute respiratory distress syndrome (ARDS) is a condition with a high mortality and morbidity. Mechanical ventilation prevents immediate mortality but may further damage patients' lungs. Low tidal volume lung-protective strategies have been shown to increase survival by reducing this iatrogenic damage. Current guidelines recommend tidal volumes of 6-8 ml kg -1 of predicted body weight. We used data from three large randomized controlled trials of treatments for ARDS to determine compliance with these recommendations.

METHODS.: We used the tidal volume recorded at randomization for all patients in the OSCAR, HARP-2, and BALTI-2 studies. In addition, we used the ventilation data for control arm patients in OSCAR and all patients in HARP-2 at days 1 and 7 after randomization.

RESULTS.: The three trials enrolled 1660 patients, with tidal volume data available at least at one time point in 1412 patients. Compliance with the 6-8 ml kg -1 recommendation for tidal volume ranged from 20 to 39% of patients across all time points in all three trials.

CONCLUSION.: Poor compliance with the guidelines for tidal volume in patients with ARDS has been demonstrated before in case series, but not in clinical trials where the patient population is specifically selected against standard ARDS diagnostic criteria and the investigators were encouraged to use low tidal volumes. This study may indicate a need to improve implementation and compliance with protective lung ventilation.