The End-Points of the Oxygen Path: Transport Resistance in Red Cells and Mitochondria
The variation of oxygen pressure from red cell to mitochondrion is, for a given oxygen flux, determined by the distribution of transport resistance over the oxygen path. The total drop in oxygen pressure may be resolved into several component drops: (1) the red cell drop, from cell center to cell surface, (2) the transcapillary drop, from red cell surface to outer capillary wall, (3) the tissue drop, from the capillary wall to an interior point in the tissue, and (4) the mitochondrial drop, from tissue to mitchondrial interior. The frequently used Krogh model, as usually formulated, deals only with the tissue drop. The other components have received somewhat less attention in the literature. The transcapillary drop, which depends on hematocrit, blood flow rate, red cell geometry, capillary geometry, and other things, is by far the most complex. Some recent progress in the theory of this drop has been made — for example, the work of Federspiel and Sarelius (1984) on the effect of red cell spacing on oxygen delivery. Nevertheless, the transcapillary drop probably will be the last component to be understood quantitatively. The red cell drop and the mitochondrial drop, on the other hand, are readily amenable to analysis, and we summarize here our recent theoretical results on these parts of the oxygen path.
KeywordsOxygen Pressure Oxygen Transport Oxygen Flux Oxygen Gradient Transport Resistance
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