Abstract
Oxygen transport is believed to primarily occur via capillaries and depends on the oxygen tension gradient between the vessels and tissues. As blood flows along branching arterioles, the O2saturation drops, indicating either consumption or diffusion. The blood flow rate, the O2concentration gradient, and Krogh’s O2diffusion constant (K) of the vessel wall are parameters affecting O2delivery. We devised a method for evaluatingKof arteriolar wallin vivousing phosphorescence quenching microscopy to measure the partial pressure of oxygen in two areas almost simultaneously. TheKvalue of arteriolar wall (inner diameter, 63.5 ± 11.9 μm; wall thickness, 18.0 ± 1.2 μm) was found to be 6.0 ± 1.2 × 10−11(cm2/s)(ml O2·cm−3tissue·mmHg−1). The arteriolar wall O2consumption rate (M) was 1.5 ± 0.1 (ml O2·100 cm−3tissue·min−1), as calculated using Krogh’s diffusion equation. These results suggest that the arteriolar wall consumes a considerable proportion of the O2that diffuses through it.
