Blood-Gas Transfer of O2 and CO2 in the Lungs: New Models Measurements and Conclusions
Three simultaneous differential equations for O2, CO2 and HCO 3 - diffusion in the red blood cell (RBC) were solved numerically, taking the Bohr and Haldane effects into account (Mochizuki and Kagawa, 1986). Then, from the numerical solution the relationship of the gas exchange ratio (R) to alveolar PCO2 (PACO2) during rebreathing was derived (Kagawa and Mochizuki, 1987). R in rebreathing air is linearly related to PACO2. Since CO2 diffusion in the RBC accompanies HCO 3 - shift and partly results from the Haldane effect, the CO2 reactions are generally slower than the O2 reactions. Therefore, the slope of R-CO2 line (θ) depends not only on the true venous PCO2 (trPvCO2) and arterial-venous O2 content difference (C(a-v)O2), but also on the contact time (tc). Using the theoretical equation for the R-PCO2 line as a gas exchange model, the relationship between tc and C(a-v)O2 is obtained from the experimental data of rebreathing in normal subject (Shibuya et al, 1987).
KeywordsContact Time Dissociation Curve Content Difference Lung Capillary Pulmonary Diffuse Capacity
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