Prone position augments recruitment and prevents alveolar overinflation in acute lung injury

Rationale: Mechanical ventilation in the prone position may be an effective means of recruiting nonaerated alveolar units and minimizing ventilation-induced lung injury. Objectives: To evaluate and quantify regional lung volume alterations when patients with lobar or diffuse acute lung injury (ALI) were turned prone after a recruitment maneuver. Methods: In 21 patients with ALI, a recruitment maneuver was applied in the supine position followed by a multislice spiral computed tomography (CT) scan; then, patients were turned prone and a second CT scan was performed. Main Results: Both the recruitment maneuver and prone position resulted in improved oxygenation in patients with lobar ALI. Prone position also resulted in increased respiratory system compliance and decreased Pa-CO2 in lobar ALI. In lobar ALI, the proportion of overinflated and nonaerated areas declined, whereas the proportion of well-aerated areas increased in the prone position. The decrease in overinflated areas was observed mainly in the ventral areas. The dorsal regions showed a decrease in nonaerated areas and an increase in well-aerated areas. Recruitment maneuver and prone position improved oxygenation but had no effect either on Pa-CO2 or on the respiratory system compliance of patients with diffuse ALI. These patients responded to prone position with a decrease in nonaerated areas. Conclusions: Prone position recruited the edematous lung further than recruitment maneuvers and reversed overinflation, resulting in a more homogeneous distribution of aeration. The effects of the prone position were more pronounced in patients with lobar ALI.