Physiologic and pathologic effects of a systematic regimen of movement were compared with immobility in anesthetized, over-hydrated dogs. Immobile animals suffered early loss of oxygenating capability of the dependent lung that developed extensive atelectasis, hemorrhage, and pulmonary edema. A regimen of movement to alternate lateral positions every 30 minutes preserved oxygenating ability of both lungs, while hourly changes restored lost function and minimized the extent of pathologic findings in random zones of the lungs.
Active regimens of movement were observed to prevent or relieve the arteriovenous shunting in patients. Pathophysiology was exaggerated in the dependent lung and reduced by change to the alternate position. Immobility, a critical factor in the genesis of hypoxemia, must be replaced by planned, systematic antigravity changes in position to maintain optimal lung mechanics and airway resistance and to prevent wasted work of the heart.