Affiliation:
1. Departments of Pediatrics and Physiology and Biophysics, University of Alabama at Birmingham, Birmingham, Alabama 35294
Abstract
Curtis, Scott E., Thomas A. Walker, W. E. Bradley, and Stephen M. Cain. Raising P50increases tissue [Formula: see text] in canine skeletal muscle but does not affect critical O2 extraction ratio. J. Appl. Physiol. 83(5): 1681–1689, 1997.—Affinity of hemoglobin (Hb) for O2 determines in part the rate of O2 diffusion from capillaries to myocytes by altering capillary [Formula: see text]. We hypothesized that a decrease in Hb O2 affinity (increased P50) would increase capillary and tissue [Formula: see text](P[Formula: see text]) and improve O2 consumption during ischemia. To test this hypothesis, blood flow to the pump-perfused left hindlimb of 18 anesthetized and paralyzed dogs was progressively decreased over 90 min while hindlimb O2 consumption and O2 delivery (Q˙o 2) and P[Formula: see text] were measured at the muscle surface. Arterial[Formula: see text] was maintained at 150 ± 10 Torr in all dogs. We increased P50by 12.3 ± 0.9 (SE) Torr in nine dogs with RSR-13, an allosteric modifier of Hb. This decreased arterial O2 saturation to 90–92% but increased mean P[Formula: see text] from 35.5 ± 11.6 to 44.1 ± 15.2 (SD) Torr ( P < 0.05) with no change in controls ( n = 9). O2 extraction ratio at criticalQ˙o 2was 74 ± 2% in controls and 79 ± 1% in RSR-13-treated dogs ( P = not significant). P[Formula: see text] was 30–40% higher in the RSR-13-treated group at anyQ˙o 2above critical but did not differ between groups below criticalQ˙o 2. Perfusion heterogeneity and convergence of the dissociation curves near criticalQ˙o 2may have mitigated any effect of increased P50 on O2 diffusion. Still, increasing P50 by 12 Torr with RSR-13 significantly increased P[Formula: see text] atQ˙o 2values above critical.
Publisher
American Physiological Society
Subject
Physiology (medical),Physiology
Cited by
18 articles.
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