Oxygen transport and cardiovascular function at extreme altitude: lessons from Operation Everest II

• Published in: International journal of sports medicine 1992-10, Vol.13 Suppl 1 (S 1), p.S13-S18
• Main Authors: Sutton, J. R., Reeves, J. T., Groves, B. M., Wagner, P. D., Alexander, J. K., Hultgren, H. N., Cymerman, A., Houston, C. S.
• Format: Article
• Language: English
• Subjects: Adult; Aerospace Medicine; Altitude; Applied physiology; Biological and medical sciences; Cardiac Output - physiology; Cardiovascular Physiological Phenomena; Heart Rate - physiology; Human physiology applied to population studies and life conditions. Human ecophysiology; Humans; Lactates - blood; Male; Medical sciences; Mountaineering - physiology; Muscles - physiology; Oxygen - metabolism; Oxygen Consumption - physiology; Physical Endurance - physiology; Respiratory Physiological Phenomena; Space life sciences; Transports. Aerospace. Diving. Altitude
• ISSN: 0172-4622; 1439-3964
• DOI: 10.1055/s-2007-1024580

Operation Everest II was designed to examine the physiological responses to gradual decompression simulating an ascent of Mt Everest (8,848 m) to an inspired PO2 of 43 mmHg. The principal studies conducted were cardiovascular, respiratory, muscular-skeletal and metabolic responses to exercise. Eight healthy males aged 21-31 years began the "ascent" and six successfully reached the "summit", where their resting arterial blood gases were PO2 = 30 mmHg and PCO2 = 11 mmHg, pH = 7.56. Their maximal oxygen uptake decreased from 3.98 +/- 0.2 L/min at sea level to 1.17 +/- 0.08 L/min at PIO2 43 mmHg. The principal factors responsible for oxygen transport from the atmosphere to tissues were (1) Alveolar ventilation--a four fold increase. (2) Diffusion from the alveolus to end capillary blood--unchanged. (3) Cardiac function (assessed by hemodynamics, echocardiography and electrocardiography)--normal--although maximum cardiac output and heart rate were reduced. (4) Oxygen extraction--maximal with PvO2 14.8 +/- 1 mmHg. With increasing altitude maximal blood and muscle lactate progressively declined although at any submaximal intensity blood and muscle lactate was higher at higher altitudes.