Experimental and theoretical studies of human hypercapnic ventilatory response with the use of mathematical modeling of gas exchange

Abstract

A mathematical model of the biotechnical system integrating the human cardiorespiratory system with a hard- and software suite (HSS) was designed to investigate breathing control. The model describes the dynamics of carbon dioxide and oxygen in three biotechnical system compartments in the course of rebreathing tests. The tests do not require tanks with compressed gas and, hence, can be performed in space flights. The results of simulated modeling of the ventilation response in two breath tests, i.e., to hypercapnia due to rebreathing hyperoxic gas mixture (HGM) and to hypercapnia combined with hypoxia due to air rebreathing are presented. The model validity was verified by comparison between the modeling and experimental data. The mathematical model made it evident that CO₂ partial pressures in tissues, the lungs, and the breathing circuit equalize very fast when the initial carbon dioxide concentration in the respiration circuit is equal to the end-tidal CO₂ concentration in humans at rest.