Role of acid-base balance in the chemoreflex control of breathing

This paper uses a steady- state modeling approach to describe the effects of changes in acid- base balance on the chemoreflex control of breathing. First, a mathematical model is presented, which describes the control of breathing by the respiratory chemoreflexes; equations express the dependence of pulmonary ventilation on P-CO2 and P-O2 at the central and peripheral chemoreceptors. These equations, with P-CO2 values as inputs to the chemoreceptors, are transformed to equations with hydrogen ion concentrations [ H+] in brain interstitial fluid and arterial blood as inputs, using the Stewart approach to acid- base balance. Examples illustrate the use of the model to explain the regulation of breathing during acid- base disturbances. They include diet- induced changes in sodium and chloride, altitude acclimatization, and respiratory disturbances of acid- base balance due to chronic hyperventilation and carbon dioxide retention. The examples demonstrate that the relationship between P-CO2 and [ H+] should not be neglected when modeling the chemoreflex control of breathing. Because pulmonary ventilation controls P-CO2 rather than the actual stimulus to the chemoreceptors, [ H+], changes in their relationship will alter the ventilatory recruitment threshold P-CO2, and thereby the steady- state resting ventilation and P-CO2.