EFFECT OF BLOOD FLOW AND HAEMATOCRIT ON THE RELATIONSHIP BETWEEN MUSCLE VENOUS Po2 AND OXYGEN UPTAKE IN DOG MAXIMALLY CONTRACTING GASTROCNEMIUS IN SITU |
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| Authors: | H Kohzuki Y Enoki Y Ohga S Sakata S Shimizu T Morimoto T Kishi M Takaki |
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| Institution: | Department Physiology II, Nara Medical University, Kashihara, Nara, Japan |
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| Abstract: | 1. To clarify the limiting factors for peak V?o2 (V?o2peak)> we measured muscle venous Po2 (Pvo2) and V?o2, peak under various O2 delivery conditions (arterial O2 concentration X flow) via the alteration of blood flow and haematocrit (Hct) in anaesthetized dog gastrocnemius muscle (n= 11) stimulated by 1 Hz isometrically and tetanically. 2. Two levels of flow (high and moderate) were maintained by using a pump (ISO and 100 mL/min per 100 g, respectively). Haematocrit was adjusted to 45 and 30% by isovolaemic haemodilution with dextran (MW 40 000). 3. The decrease in Hct induced a 31% decrease in O2 delivery (P<0.05), a 9–12% decrease in Pvo2, a 23% decrease in V?o2, peak(P<0.05) and a 12–14% increase in O2 extraction (V?o2/O2delivery) at both flow levels. The decrease in flow induced a 24–25% decrease in O2 delivery (P<0.05), a 15–17% decrease in Pvo2 (P<0.05), a 9% decrease in V?o2,peak (P<0.05) and a 19–22% increase in O2 extraction (P<0.05) at both Hct levels. 4. The results suggest that the limiting factor of V?o2peak, unrelated to O2 diffusion limitation (i.e. the change in the heterogeneity of V?o2 to O2 delivery ratio among capillaries), due to lowering Hct may be different from that due to lowering blood flow in maximally contracting muscle. |
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| Keywords: | O2 supply O2 transport Pvo2-̇o2 diagram skeletal muscle |
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