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 O
2saturation drops, indicating either consumption or diffusion. The blood flow rate, the O
2concentration gradient, and Krogh’s O
2diffusion constant (
K) of the vessel wall are parameters affecting O
2delivery. We devised a method for evaluating
Kof arteriolar wall
in vivousing phosphorescence quenching microscopy to measure the partial pressure of oxygen in two areas almost simultaneously. The
Kvalue 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(cm
2/s)(ml O
2·cm
−3tissue·mmHg
−1). The arteriolar wall O
2consumption rate (
M) was 1.5 ± 0.1 (ml O
2·100 cm
−3tissue·min
−1), as calculated using Krogh’s diffusion equation. These results suggest that the arteriolar wall consumes a considerable proportion of the O
2that diffuses through it.
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