Changes in blood gases and acid-base balance in the exercising dog

¹ Department of Anatomy and Physiology, Indiana University, Bloomington, Indiana

Effects of varying rates of treadmill work on blood gases and hydrogen ion concentrations of four healthy young dogs were determined by analyses of blood for O₂ and CO₂ contents, Po₂, Pco₂, and pH. Changes in these parameters were also observed during 30-min recovery periods from hard work. Arterial and mixed venous blood samples were obtained simultaneously during work through a polyethylene catheter in the right ventricle and an indwelling needle in an exteriorized carotid artery. Mixed venous O₂ content, Po₂ and O₂ saturation fell with increased work, whereas arterial values showed little or no change. Mixed venous CO₂ content, Pco₂, and hydrogen ion concentration exhibited little change from resting levels in two dogs but increased significantly in two others during exercise. These values always decreased in the arterial blood during exercise, indicating the presence of respiratory alkalosis. On cessation of exercise, hyperventilation increased the degree of respiratory alkalosis, causing it to be reflected on the venous side of the circulation.