Effect of different pressure breathing patterns on alveolar-arterial gradients in dogs

¹ Division of Anesthesiology, University of Utah College of Medicine, and Veterans Administration Hospital, Salt Lake City, Utah

Arterial end-tidal carbon dioxide gradients were measured and alveolar-arterial oxygen gradients were estimated in dogs during intermittent positive pressure ventilation at constant inflating pressure using four curves having differing pressure profiles. The smallest gradients for both oxygen and carbon dioxide occurred when mean pressure during respiratory cycles was high and decreases in mean pressure were consistently associated with increases in both oxygen and carbon dioxide gradients. Profile of the applied pressure curve per se did not influence magnitude of the gradients. It is concluded that during intermittent positive pressure breathing, relative distribution of pulmonary capillary blood flow and inspired gas may vary with mean pressure during the respiratory cycle and is more uniform when mean pressure during the respiratory cycle is high.

Submitted on December 13, 1962