Homoiostase des arteriellen CO2-Drucks und Anpassung der Lungenventilation an den Stoffwechsel als Leistungen eines Regelsystems

Abstract

The effect of alveolar ventilation changes upon alveolar CO2 partial pressure is described by the alveolar equation which is the formula of a hyperbolic function. The effect of changes of alveolar CO2 partial pressure upon lung ventilation if inspiratory CO2 is varied is approximated by a linear relationship called the CO2 response curve. The alveolar CO2 partial pressure and the corresponding alveolar ventilation in a given situation are determined as the intercept of both functions and can be found either graphically or by combination of both equations. An assumption on the relationship of total ventilation to alveolar ventilation must be made for this purpose. The derived formulae (4, 5 and 6) allow to predict alveolar CO2 partial pressure, alveolar ventilation and total ventilation for any given inspired CO2 partial pressure and for any given CO2 output. The formulae describe a regulating system which serves CO2-homeostasis as well as adaptation of ventilation to metabolic needs. The influences of pH and of oxygen partial pressure are considered as modifying the system. The pH influence acts on the intercept of the CO2 response curve with the\(p_{CO_2 } \) axis and the\(p_{O_2 } \) influence acts on the slope of this curve. The additional influence of muscular work and of other influences on the drive of ventilation can be considered by their effect on the same parameters of the CO2 response curve.