Alveolar-Arterial Oxygen Tension Differences in Open-Chest Dogs

¹ From the Department of Cardiorespiratory Diseases, Army Medical Service Graduate School, Walter Reed Army Medical Center, Washington, D. C.

The alveolar-arterial oxygen tension difference has been measured in open-chest dogs both with the lung inflated and collapsed after expiration. In dogs with the lung inflated after expiration the tension differences varied with the magnitude of the alveolar ventilation and were similar to those seen in spontaneously breathing dogs and in intact dogs with positive-pressure respiration. Collapse of the lung resulted in an increase of the alveolar-arterial oxygen tension difference and appreciable tension differences were present during the inspiration of 12% and of 8% oxygen. The tension differences measured at three levels of oxygenation could be caused by the presence of different ventilation/perfusion ratios in various parts of the lung.