EFFECTS OF CHRONIC HYPERCAPNIA ON ELECTROLYTE AND ACID-BASE EQUILIBRIUM. I. ADAPTATION*

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Abstract
Balance studies were carried out in 11 dogs exposed to an atmosphere of 11 to 13% carbon dioxide for periods of 6 to 15 days. A consistent pattern of response was found, characterized by a sharp rise in plasma bicarbonate concentration during the first day of exposure, and a subsequent slower rise over the next 5 or 6 days to final concentrations ranging from 35 to 38 mEq per 1. During the first day, when approximately one-half of the total rise in plasma bicarbonate occurred, there was often little or no increase in renal acid excretion, indicating that tissue buffers, played a major role in the initial defense of the extracellular pH. The plasma bicarbonate approached a plateau which fell short, by 5 to 10 mEq per 1, of the level necessary for full compensation of the acidosis. The sodium chloride content of the diet appeared to exert no significant effect on the adaptive process. The plasma chloride concentration varied in a virtually reciprocal fashion with the plasma bicarbonate concentration throughout the study. In each dog there was a chloruresis and a cumulative chloride loss of sufficient magnitude readily to account for the degree of hypochloremia. On the first day in the CO2 atmosphere there was a marked increase in the excretion of potassium and-phosphorus and a variable sodium diuresis. Subsequently, both sodium and potassium excretion returned toward or to the control level. At the end of the study there usually remained a slight deficit of sodium, but in most instances, after correction for changes in nitrogen balance, there was no evidence of potassium deficiency.