Influence of mixed venous PO2 on diffusion of O2 across the pulmonary blood: gas barrier

Wiley - Tập 2 Số 2 - Trang 105-115 - 1982
Peter D. Wagner1
1Department of Medicine, M-023, University of California, San Diego, La Jolla, California, 92093

Tóm tắt

Summary. Analyses of diffusion limitation of pulmonary O2 exchange have stressed that alveolar PO2 (PAO2) is one of the most important factors to consider, but recent reports suggest that PAO2 is important only insofar as it determines the effective slope of the O2 dissociation curve. If this slope is the critical factor, mixed venous PO2 (Pv̄o2) should also be important. This notion was examined in theoretical calculations of oxygenation along the capillary in a homogeneous lung model of normal diffusing capacity. For PAO2= 100 torr, half‐time of rise of PO2, between PV̄O2, and PAO2 (T1/2) increased from 0·09 s (PV̄;O2= 50) to 0·32 s (PV̄;O2=10), while for PAO2= 60, T1/2 increased from 0·18 s (Pv̄O2= 50) to 0·43 s (PV̄;O= 10). At PAO2= 60, diffusion equilibration after 0·75 s was virtually complete if PV̄;O2⋙ 40 torr, but was only 80% complete for PV̄;O2= 10. These calculations show that at any given PAO2, PV̄;O2, has considerable influence on the rate of diffusion equilibration of O2. Thus, situations in which PV̄;O2 is low (e.g. when cardiac output is low in relation to O2 uptake) are associated with considerably increased vulnerability of O2 exchange to diffusion limitation, other factors remaining unchanged.

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Wiley

Tập 2 Số 2

105-115

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