We investigate the effects on arterial PCO2 and on arterial-end tidal PCO2 difference of six different ventilation patterns of equal tidal volume, and also of various combinations of tidal volume and respiratory rate that maintain a constant alveolar ventilation. We use predictions from three different mathematical models. Models 1 (distributed) and 2 (compartmental) include combined convection and diffusion effects. Model 3 incorporates a single well-mixed alveolar compartment and an anatomical dead-space in which plug flow occurs. We found that: (i) breathing patterns with longer inspiratory times yield lower arterial PCO2; (ii) varying tidal volume and respiratory rate so that alveolar ventilation is kept constant may change both PACO2 and the PACO2-PETCO2 difference; (iii) the distributed model predicts higher end-tidal and arterial PCO2 than the compartmental models under similar conditions; and (iv) PCO2 capnograms predicted by the distributed model exhibit longer phase I and steeper phase II than other models.
- Carbon dioxide, arterial-end tidal P difference
- Mammals, humans
- Models, CO expirogram
- Pattern of breathing, CO expirogram