Experimental analyses of pulmonary gas exchange in a standing position at rest and during treadmill exercise.

Abstract

Quantitative relations between 02 uptake (V02), arterial-venous 02 content difference ((a-v)C02), and contact time (ta) were measured at rest and during exercise in 7 normal subjects, using a rebreathing technique. By injecting a known amount of pure 02 into a rebreathing circuit, the V02 was measured from the time interval during which the injected 02 volume was consumed. From the 02 and C02 concentrations in rebreathing air the gas exchange ratio (R), which was linearly related to the PC02, was determined. By using the slope of the R-P02 relation, the (av)C02 was evaluated from the slope of the C02 dissociation curve between the true-and oxygenated-venous PC02. These two venous PC02 were estimated from the R-P02 relation by use of the Haldane effect coefficient and by extrapolating it to the abscissa, where R =0. Furthermore, t~ was evaluated by inserting the above two venous PC0 2 together with the alveolar PC02 into a contact time equation. The mean (a-v)C0 2 and t~ had consistent relations to the V0 2 and (a-v)C02, respectively:

Theoretical analyses for arterial-venous O2 content difference and Haldane effect during rebreathing.

“…(1) and (2), respectively. The above standardization was derived from the experimental data obtained at rest and during exercise in normal subjects (UCHIDA et al, 1986;SHIBUYA et al, 1987). Therefore, F(avCo2) and F(H) may not be used, when the P'co2 and t~ widely deviated from the normal relations given by Eqs.…”

“…Because of such complicated variation in dpH~, it was difficult to derive a general mathematical formula that included all the initial and boundary conditons. For clarifying the PA~o 2-dependency of the (a-v) Cot, the relations of the (av)Co2* to the t~ and trP02 were standardized by referring to the experimental data of SHIBUYA et al (1987). The t~ thereof was given by the following hyperbolic equation as shown in Fig.…”