Submarine Base, Groton, Conn. REPORT NUMBER 598 DISPLACEMENT OF OXYGEN DISSOCIATION CURVES AND RED CELL CATION EXCHANGE IN CHRONIC HYPERCAPNIA by

Guinea pigs were exposed to 15% C02 in 21% 02 for periods up to seven days. Two separate oxygen dissociation curves were determined at a PC02 of 40 mm Hg and a Pco2 of 115 mm Hg on pooled blood samples. Red cell pH and cation concentrations were also measured. Pr(0 fell from 27.8 mm Hg to 18.6 at one day exposure and rose again to 24.7 after seven days of exposure to 15% C02. Blood oxygen capacity decreased significantly with the return shift of the oxygen dissociation curve. In spite of the increase in oxygen affinity during the uncompensated phase of respiratory acidosis, delivery of oxygen to the tissues was not reduced due an increase in the Bohr effect, resulting in a higher oxygen delivery to the tissues than at normal conditions. Commensurate with the increase and decrease in oxygen affinity, cation concentrations of the red cells exhibited corresponding decreases and increases. The potassium concentrations showed a larger fall, while red cell content increased slightly during the uncompensated phase of respiratory acidosis. These changes were reversed during the compensated phase of respiratory acidosis without returning to control levels. The ratio of red cell cations/Hb showed a close correlation with the changes in P50 values. The pH gradients across the red cell were found to decrease during the uncompensated phase of respiratory acidosis and increase again during the compensated phase of respiratory acidosis. DISPLACEMENT OF OXYGEN DISSOCIATION CURVES AND RED CELL CATION EXCHANGE IN CHRONIC HYPERCAPNIA