CARDIOPULMONARY RESPONSES OF RESTING MAN DURING EARLY EXPOSURE TO HIGH ALTITUDE,
Abstract
Sixteen young male subjects were exposed to simulated altitudes of 2,000, 11,000 and 15,000 ft in a hypobaric chamber and measured at sitting rest after 10, 20, 30 and 40 hours of exposure. Of those measurements made, only Pa O2 changed significantly with time of exposure. Cardiac output rose from 71 at 2,000 ft to 84 and 123 ml/min/kg at 11,000 and 15,000 ft, respectively. This was due to a significant increases in heart rate at both higher elevations with no alteration in stroke volume. Mean arterial blood pressure was unaltered and, therefore, peripheral resistance fell concomitant with the rise in cardiac output. Mean Pa O2 for the three altitudes was 94, 63 and 44 mm Hg; and for % Sa O2: 99 92 and 79. Largest changes in Pa CO2 and pH were observed between 2,000 and 11,000 ft and much less between 11,000 and 15,000 ft. Changes in cardiac output appeared best related to alterations in arterial O2 content or saturation rather than tension, suggesting a peripheral rather than a central origin for the stimulus of the cardiovascular response to high altitude. Most observed circulatory responses appear to follow an exponential relationship with altitude. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Jan 31, 1967
- Accession Number
- AD0651328
Entities
People
- Charles W. Harris
- James A. Vogel