A new device, the Roto-Rest bed, has been used in critically ill patients to effect lateral to lateral position changes and continuous rotation to influence distribution of pulmonary blood flow. Selection of extreme lateral position can be made particularly in cases of respiratory failure with primarily unilateral involvement. Dependent positioning of the uninvolved lung to match ventilation and perfusion can be accomplished simply. Rapid resolution of a large pulmonary contusion serves to illustrate the clinical use of the apparatus.