MODEL OF RESPIRATORY SENSATION AND WILLFUL CONTROL OF VENTILATION

A mathematical model has been developed that includes sensations of br eathlessness and a dynamic CO2 respiratory controller. Breathing sensa tions, which are represented as a discomfort index, are assumed to dep end on arterial PCO2 level, automatic and wilful motor commands and me chanoreceptor feedback. Wilful control is assumed to arise from cortic al centres of the brain and is independent of the reflex control syste m. The bulbopontine respiratory controller produces the automatic moto r command, which is determined by chemical and mechanical feedback. Si mulations demonstrate how the controller output and breathing sensatio ns change when wilful motor commands disturb spontaneous breathing. Si mulations include isocapnic hyper- and hypoventilation and deliberate hypoventilation during CO2 rebreathing. Simulations are compared with experimental data from human subjects. Simulations predict that the di scomfort index intensifies when ventilation is either voluntarily rais ed or lowered from the optimal level; and discomfort is greater when v entilation is lowered than when it is raised at a given level of PCO2. The simulated results agree with those obtained experimentally. The s imulations suggest that respiratory drive Integration may depend not o nly on the direct effects of chemical and mechanical feedback, but als o on the perceptual consequences of these stimuli.