Relation of respiratory alkalosis to hypokalemia in anesthetized dogs during altitude stress

¹ Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland

Results of this investigation confirm the hypothesis that respiratory alkalosis is directly related to hypokalemia in dogs during their exposure to moderate altitude stress. Anesthetized animals were placed in a decompression chamber and subjected to a simulated altitude of 30,000 ft for 30 min. Arterial blood samples were obtained prior to and during the decompression period. In one series of 14 experiments in which animals breathed room air, the mean plasma K⁺ concentration declined from 3.9 to 3.4 mEq/ liter after 30 min. Respiratory alkalosis was demonstrated by a marked rise in blood pH (from 7.37 to 7.56) and fall in pCO₂ (from 40 to 23 mm Hg) which appeared after 5 min. In a second series of 15 experiments in which dogs breathed a gas mixture containing 20% CO₂ (partial pressure = 45 mm Hg at 30,000 ft), 21% O₂, and 59% N₂, respiratory alkalosis was effectively prevented and the characteristic hypokalemia failed to occur. It appears that potassium ions leave the plasma and enter the tissues as a secondary response to alkalosis.