Maximal O2 Uptake Limitation in Contracting Skeletal Muscle During Carbon Monoxide Hypoxia
Previous studies have shown that at levels of approximately 20% carboxyhemoglobin (COHb), O2 uptake (VO2) during maximal exercise in humans, was preserved at normoxic levels (Ekblom and Huot, 1972; Pirnay et al., 1971; Vogel and Gleser, 1972). However, when severe carbon monoxide hypoxia (COH) (COHb-60%) was superimposed on submaximal contractions of the canine gastrocnemius muscle preparation, VO2 fell below normoxic levels (King et al., 1987). Maximal O2 uptake (MVO2) is limited even at levels as low as 7% COHb (Horvath et al., 1975). At levels of 20% COHb, MVO2 has been shown to be reduced by approximately 20% in both exercising humans (Ekblom and Huot, 1972; Pirnay et al., 1971; Vogel and Gleser, 1972) and dogs (Horst-man et al., 1974). It would appear that the limitation of VO2 during COH is dependent upon both the magnitude of the O2 demnd (%MVO2) and severity of COH. The purpose of the present experiments, therefore, was to define the mechanisms of the VO2 responses of the canine gastrocnemius muscle at rest, submaximal, and maximal contractions during normoxia and COH.
KeywordsPopliteal Artery Extraction Ratio Contracting Muscle Muscle Blood Flow Muscle Preparation
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