The study included 17 consecutive ARDS patients placed on baseline ventilation with standardized ventilatory parameters. Pressure-controlled ventilation RM was then applied for 2 minutes and consisted of: peak inspiratory pressure = 45 mbar, respiratory rate = 10/min, I:E = 1:1, positive end-expiratory pressure (PEEP) = 20 mbar for the first minute, 25 mbar for the remaining time. Predefined safety criteria were used for premature RM termination. Patients with a minimum of 30% PaO2/FiO2 increment on the fifth minute after the RM completion were judged responders. Those with prematurely terminated RM and non-responders were excluded from the subsequent study. In the remaining group, a decremental PEEP trial was then conducted. ECG, SpO2, invasive systemic arterial pressures, Paw, exhaled Vt/MV and total respiratory system compliance (Ctot) were continuously monitored and their representative values were recorded for different time periods. Arterial blood samples for blood gas analysis were taken immediately before the RM, on the fifth minute and on the sixth hour after the RM completion. Twenty-four hours after the RM, a bedside chest X-ray was conducted for extraalveolar air detection.