Effects of Carbonic Anhydrase Inhibition During Acute Hypoxia

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Abstract
The effects of exposure to a simulated altitude of 20,000 feet in a decompression chamber before and after a single intravenous injection of a carbonic anhydrase inhibitor were observed in five trained unanesthetized dogs. The pulmonary ventilation, alveolar gas exchange and composition and pH, gas tensions and CO2 content of the arterial blood were observed. The drug, in a single dose of 100 mg/kg, produced the following effects when combined with acute hypoxia: a) hyperventilation greater than that resulting from hypoxia alone, b) a smaller decrement in the alveolar and arterial Po2 following ascent to altitude, c) a subsequent rise in alveolar and arterial Po2 if administered after attaining altitude, d) a greater decrement in alveolar Pco2 following ascent to 20,000 feet, e) a higher arterial blood H-ion concentration than that associated with hypoxia alone and f) a greater decrease in plasma CO2 content during adjustment to acute hypoxia. Theoretical calculations were made which indicated that the pulmonary capillary blood has a higher pH and a lower plasma CO2 content than the peripheral arterial blood after administration of the inhibitor. Submitted on March 6, 1957