Dynamic Model of Ventilatory Response to Changes in Po2 at the Carotid Body Chemoreceptors

Much of the recent work evaluating the role of the carotid body chemoreceptors in the control of ventilation has involved the application of transient stimuli. The response of ventilation to a sustained step decrease in Po2 from 90 mm Hg to 32 mm Hg of blood perfusing the carotid bodies of dogs indicated an abrupt increase in ventilation to nearly the final steady-state levels. The similarity of this response to the classic linear second-order system response prompted the investigation of a mathematical model that could be used to simulate the ventilatory control loop. It has been determined that the response of the ventilatory system of the dog to step, ramp, pulse, and pulse train inputs of hypoxia can be simulated with good accuracy by a nonlinear closed-loop feedback system that contains linear second-order dynamics. The input to this system is proportional to the magnitude and the rate of change of Po2 at the carotid bodies.