Analyses of breath-by-breath responses of ventilation to CO 2 employing V-PCO 2 loops.

Computer techniques were employed to construct a respiratory control model in which the variables treated were programmed according to a series of mathematical equations, with the purpose of eliciting the relationship of V-PCO2 (minute ventilation-partial pressure of carbon dioxide) on a transient time basis. It was discovered that the transient V-PCO2 relationship has the shape of a loop half of which is for on-CO2 and the other half for off-CO2. Breath-by-breath ventilation was calculated by means of a home-made computer and the V-PCO2 relationship was monitored on an XY plotter. The transient V-PCO2 course also showed a loop which was quite similar in the general shape to the one traced employing theoretical analysis with an analog computer. This V-PCO2 loop may have potential usefulness to reveal mechanisms of respiratory control which may not be shown by the conventional V-PCO2 response curves.