A Method for Estimating Contact Time of Red Cells in Lung Capillaries from O2 and CO2 Concentrations in Rebreathing Air in Man
In a previous paper (Mochizuki et al., 1986) we described the relation between alveolar- and venous-Pco2 and the contact time (tc). However, at that time, Pco2-dependency of the arterio-venous difference in O2 content ((a-v)Co2), the contact-time-dependency of the Haldane effect, and linearity of the relation between the experimental gas exchange ratio and Pco2 (R-Pco2 line) in rebreathing air were not taken into account. Recently, we have precisely analysed the above correlations from the numerical solutions of the simultaneous O2 and CO2 diffusions in the red blood cell (RBC). Based upon the results we have derived a corrected contact time equation. When the time constant of the reaction rate of the extracellular dehydration reaction was less than 0.2 sec, good agreement was observed between the contact time obtained from the pulmonary diffusing capacity for CO (Uchida, Shibuya and Mochizuki, 1986) and that from the present method.
KeywordsTime Constant Contact Time Dehydration Reaction Lung Capillary Pulmonary Diffuse Capacity
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