Journal of Applied Physiology, Vol 65, Issue 6 2696-2708, Copyright © 1988 by American Physiological Society
Maximal aerobic capacity at several ambient concentrations of CO at several altitudes
S. M. Horvath, J. F. Bedi, J. A. Wagner and J. Agnew
Institute of Environmental Stress, University of California, Santa Barbara 93106.
To assess the nature of the combined effect of the hypoxias of altitude
(ALT) and CO exposure, 11 men and 12 women nonsmokers served as subjects in
a double-blind experiment. The exposure conditions were four ambient CO
levels (0, 50, 100, and 150 ppm) at each of four ALT (55, 1,524, 2,134, and
3,048 m). Each subject, after attaining the required ALT and ambient CO
level, performed a maximal aerobic capacity test (VO2max). Blood samples
were obtained before, at 50-W, 100-W, 150-W, and maximum work loads and at
the 5th min of recovery. Blood were analyzed for hemoglobin, hematocrit,
plasma proteins, lactates, and carboxyhemoglobin (HbCO). VO2max was similar
at 55 and 1,524 m and decreased by 4 and 8% from the 55-m value at 2,134
and 3,048 m, respectively. On the basis of all statistical analyses, we
concluded that VO2max values measured in men were only slightly diminished
due to increased ambient CO. HbCO attained at maximum was highest at 55 m
and lowest at 3,048 m. Women's HbCO concentrations were lower than men's.
At maximal work loads CO shifted into extravascular spaces and returned to
the vascular space within 5 min after exercise stopped. The independence of
altitude and CO hypoxias on parameters of the maximum aerobic capacity test
and a decrease in the CO to HbCO uptake with increasing altitude were
demonstrated and attributed in part to the decrease in driving pressure of
CO at altitude.
