Rationale and Background: Alveolar recruitment is a major goal of mechanical ventilatory support for patients with ARDS. Various forms of recruitment maneuvers have been established in human or animal subjects. Sustained inflation within the range of 30-45 cmH2O applied for 15-40 seconds have been found effective in improving oxygenation and respiratory mechanics. Objectives: Our aim was to evaluate the effect of repeated ARM on gas exchange, respiratory mechanics and hemodynamic variables and to study the impact of repeated ARM on the weaning process. Patients and Methods: Fourty patients were studied. Patients were initially ventilated according to the ARDSNet protective ventilatory strategy using a pressure controlled ventilation mode. Following 2 hours of conventional pressure cotrolled ventilation, each patient was evaluated and ARM was considered indicated when PEEP level of 15 cmH2O and FiO2 0.6 fail to achieve the minimum SpO2 (90%), PaO2 (60 mmHg) and PaO2/FiO2 ratio (200). FiO2 was increased to 1.0 and maintained for 10 minutes prior to recruitment maneuver. Recruitment maneuver (RM) was then performed (40 cmH2O CPAP for 40 seconds). PEEP was then decreased immediately to 20 cmH2O. Post recruitment PEEP was determined by decreasing PEEP gradually by 1 cmH2O decrements aiming to keep SpO2 between 92% to 95%. If SpO2 level fell to < 92%, postinflation PEEP level was then set at the next to the last value. All patients requiring ARM receive at least three maneuvers performed at O (first ARM), 8 and 24 hours. Following the second RM (done 8 hours after the first one), PEEP was decreased immediately to the level at which the patient was maintained after 15 minutes of the first RM. Following the third RM, PEEP was decreased immediately to the level at which the patient was maintained after 15 minutes of the second maneuver. FiO2 was kept unchanged (1.0) till 15 minutes after RM, thereafter it was gradually decreased (0.1 every 10 minutes) with an objective to keep SpO2 above 92%.ABGs, plateau and mean airway pressures were recorded at baseline (before recruitment), 2mintues, and at 15 minutes after the RM. Static respiratory compliance was also calculated. Heart rate, CVP and direct mean arterial blood pressure were recorded at the same time intervals for respiratory parameters assessment. Total duration of mechanical ventilation and the duration of ICU stay and survival rate were recorded. Results: RM did not result in any significant hemodynamic changes. Alveolar recruitment maneuver resulted in a remarkable increase in tidal volume and static compliance of the lung. These two parameters were significantly increased (p < 0.0001) 2 and 15 minutes after each of the 3 ARMs compared with pre-ARMs values. Also, ARM allowed reduction of PEEP and plateau pressures. ARM resulted also in a remarkable improvement of oxygenation. There was a highly significant increase in PaO2 following each of the three ARMs (p < 0.0001), both at 2 and 15 minutes following the maneuver. Many patients were hypercapnic at the beginning of the study, because not enough tidal volumes were achieved with a Pplat limit of 30 cmH2O. Fifteen minutes after the first ARM, PaCO2 was significantly reduced (p < 0.0001) to almost normal, but some patients remained slightly hypercapnic. Fifteen minutes following the second ARM, PaCO2 was again significantly reduced (p < 0.05) to normal and remained as such till the end of the study. Out of the fourty patients, 8 patients (20%) died and the remaining 32 survived. Conclusion: From the results we can conclude that repetitive high pressure (CPAP) alveolar recruitment maneuvers proved to be safe and effective in recruiting and maintaining lung recruitment with consequent improvement in oxygenation, easier weaning from mechanical ventilation and improvement in the overall outcome.