Analysis of respiratory models at different levels of exercise, hypercapnia and hypoxia

The purpose of this work is to evaluate characteristics of five respiratory models under different levels of exercise, hypercapnia and hypoxia. Two of them, RS1 and RS2, have permitted the implementation of a respiratory control system much more complex than the other ones. RS1 considers the integration of cardiorespiratory and mechanical systems. The most important difference in RS2 is the presence of respiratory frequency (f) that changes depending on the level of stimulus as it happens in fact. Tidal volume (V_T) vs. f plots which are very interesting for the physiologists are obtained. A comparative study of the steady-state and transient responses between the five models is performed by simulation analyzing some interesting respiratory variables: expired ventilation, V_T, f and arterial CO₂ and O₂ pressures. Finally, the influence of f and the ratio between inspiration and expiration intervals is evaluated.