The effects of ventilation pattern on carbon dioxide transfer in three computer models of the airways.
We investigate the effects on arterial P(CO(2)) and on arterial-end tidal P(CO(2)) 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 P(CO(2)); (ii) varying tidal volume and respiratory rate so that alveolar ventilation is kept constant may change both PA(CO(2)) and the PA(CO(2))-PET(CO(2)) difference; (iii) the distributed model predicts higher end-tidal and arterial P(CO(2)) than the compartmental models under similar conditions; and (iv) P(CO(2)) capnograms predicted by the distributed model exhibit longer phase I and steeper phase II than other models.
Department of Anaesthetics, University of Sydney, Royal Prince Alfred Hospital, Building 92, Missenden Road, Camperdown, NSW 2050, Australia.
J P
JP
Whiteley
M J
MJ
Turner
A B
AB
Baker
D J
DJ
Gavaghan
C E W
CE
Hahn
D000818:Animals; D002245:Carbon Dioxide / Q000378:metabolism*; D003198:Computer Simulation; D006801:Humans; D008168:Lung / Q000502:physiology*; D008954:Models, Biological; D011659:Pulmonary Gas Exchange / Q000502:physiology*; D012119:Respiration
D002245:Carbon Dioxide