AJP - Heart and Circulatory Physiology, Vol 240, Issue 2 177-H184, Copyright © 1981 by American Physiological Society
Effects of small changes of blood volume on oxygen delivery and tissue oxygenation
I. H. Sarelius and J. D. Sinclair
Circulatory effects of small (approximately 10%) changes in blood volume
were examined in resting and exercising dogs: controls; group A (-200 ml
blood); group B (+200 ml blood); group C (+200 ml 6% dextran). In exercise,
cardiac output (Q) increased more in Group A than controls (510.4 ml . kg-1
. min-1 compared to 429.6 ml . kg-1 . min-1; P less than 0.05); oxygen
delivery (cardiac output x arterial O2 content) and mixed venous oxygen
tension (PVO2) were unchanged from exercising controls. Hypervolemia (group
B) did not change Q or O2 delivery compared to controls, but caused a
greater reduction in exercise PVO2 (29.3 mmHg compared to 33.1 mmHg in
controls; P less than 0.01). Resting PVO2 as raised in group C (50.0 mmHg
compared to 46.3 mmHg; P less than 0.05) and exercise PVO2 was reduced less
(35.5 mmHg compared to 33.1 mmHg in controls; P less than 0.05). O2
delivery in exercise was higher than in controls (123.4 ml . kg-1 . min-1
compared to 94.3 ml . kg-1 . min-1; P less than 0.001). During exercise, O2
consumption was raised from base line to 34.9 ml . kg-1 . min-1 in controls
and raised further to 41.4 ml . kg-1 . min-1 in group A, 44.4 ml . kg-1 .
min-1 in group B, and 41.2 ml . kg-1 . min-1 in group C (P less than 0.01).
Changes of blood volume that lie within physiological limits thus
significantly modify the circulatory response to changed O2 requirements,
and also change the metabolic cost of exercise.
