Additive effects of acetazolamide and fat emulsion on alveolar-arterial Pco₂ difference

¹ Physiology-Biophysics Branch, School of Aerospace Medicine, Brooks Air Force Base, Texas

Alveolar and arterial gas tensions were measured in anesthetized dogs during a control period, after intravenous injections of a carbonic anhydrase inhibitor, and after rapid intravenous infusion of fat emulsion. These were carried out in sequence. The alveolar-arterial (A-a) Pco₂ difference increased from about 6 mm Hg during the control to 26 mm Hg after carbonic anhydrase inhibition. A further increase took place after fat emulsion when the A-a Pco₂ difference averaged 35 mm Hg. There was no increase in the A-a Po₂ difference between carbonic anhydrase inhibition and fat emulsion. The additive increase in the A-a Pco₂ difference strongly suggested that fat emulsion did not further interfere with the interconversion of CO₂ and bicarbonate.