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EFFECT OF BLOOD FLOW AND HAEMATOCRIT ON THE RELATIONSHIP BETWEEN MUSCLE VENOUS Po 2 AND OXYGEN UPTAKE IN DOG MAXIMALLY CONTRACTING GASTROCNEMIUS IN SITU
Author(s) -
Kohzuki H.,
Enoki Y.,
Ohga Y.,
Sakata S.,
Shimizu S.,
Morimoto T.,
Kishi T.,
Takaki M.
Publication year - 1997
Publication title -
clinical and experimental pharmacology and physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.752
H-Index - 103
eISSN - 1440-1681
pISSN - 0305-1870
DOI - 10.1111/j.1440-1681.1997.tb01805.x
Subject(s) - blood flow , chemistry , gastrocnemius muscle , limiting , medicine , oxygen delivery , endocrinology , zoology , oxygen , anesthesia , skeletal muscle , biology , mechanical engineering , organic chemistry , engineering
SUMMARY 1. To clarify the limiting factors for peak V̇o 2 (V̇o 2peak )> we measured muscle venous Po 2 (Pvo 2 ) and V̇o 2, peak under various O 2 delivery conditions (arterial O 2 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 O 2 delivery ( P <0.05), a 9–12% decrease in Pvo 2 , a 23% decrease in V̇o 2, peak ( P <0.05) and a 12–14% increase in O 2 extraction (V̇o 2 /O 2 delivery) at both flow levels. The decrease in flow induced a 24–25% decrease in O 2 delivery ( P <0.05), a 15–17% decrease in P vo2 ( P <0.05), a 9% decrease in V̇o 2,peak ( P <0.05) and a 19–22% increase in O 2 extraction ( P <0.05) at both Hct levels. 4. The results suggest that the limiting factor of V̇o 2peak , unrelated to O 2 diffusion limitation (i.e. the change in the heterogeneity of V̇o 2 to O 2 delivery ratio among capillaries), due to lowering Hct may be different from that due to lowering blood flow in maximally contracting muscle.