Prone Position Augments Recruitment and Prevents Alveolar Overinflation in Acute Lung Injury

Mechanical ventilation in the prone position may be an effective means of recruiting nonaerated alveolar units and minimizing ventilation-induced lung injury. 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. 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. 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(CO(2)) 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(CO(2)) or on the respiratory system compliance of patients with diffuse ALI. These patients responded to prone position with a decrease in nonaerated areas. 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.