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Physiology of Extreme Altitude

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Abstract

The sections in this article are:

1 Barometric Pressure
2 Pulmonary Gas Exchange
2.1 Alveolar Gas Composition
2.2 Blood Gases and Acid‐Base Status
3 Maximal Oxygen Consumption
4 Cardiovascular System
5 Other Features
5.1 Central Nervous System
5.2 Sleep
5.3 Metabolic Changes
Figure 1. Figure 1.

Barometric pressure–altitude relationships. Upper line shows measurements made on Mt. Everest during AMREE. Lower line shows the relationship for the Standard Atmosphere . From .

Figure 2. Figure 2.

Mean monthly pressures for 8,848 m altitude obtained from weather balloons released from New Delhi, India. Note increase during summer months. Mean monthly standard deviation (SD) also shown. Barometric pressure measured on the Everest summit on October 24, 1981 (*) was unusually high. From .

Figure 3. Figure 3.

Oxygen–carbon dioxide diagram showing alveolar gas values collated by Rahn and Otis together with values obtained at extreme altitudes by the AMREE expedition (triangles). From .

Figure 4. Figure 4.

Oxygen‐carbon dioxide diagram showing the two lines drawn by Rahn and Otis for unacclimatized and acclimatized subjects at high altitude (compare Fig. . Alveolar gas failures for OEI, OEII, and AMREE are shown together with corresponding barometric pressures. Note that OEI subjects appeared to be poorly acclimatized at extreme altitudes, whereas OEII subjects had intermediate values. From .

Figure 5. Figure 5.

Maximum oxygen consumptions plotted against inspired Po2 for OEII and AMREE. Note that, although AMREE values were higher at sea level, values measured at the summit Po2 were essentially identical. From .

Figure 6. Figure 6.

Sensitivity of calculated maximal oxygen consumption to changes in several variables for a climber on the summit of Mt. Everest. Each variable was increased by 5%, leaving all others constant. From .

Figure 7. Figure 7.

Blood lactate concentrations measured at rest or shortly after maximal exercise at various altitudes. Most of the data are redrawn from Cerretelli . Filled circles and triangles show data for acclimatized Caucasians (C); open circles and triangles are for high‐altitude natives (N). Data for 6,300 m are from AMREE for acclimatized lowlanders. From .

Figure 8. Figure 8.

Cardiac output (by thermodilution) and stroke volume plotted against oxygen uptake and heart rate at barometric pressures of 760, 347, 282, and 240 mm Hg during OEII. For measurements at 240 mm Hg, subjects breathed an oxygen mixture to give an inspired Po2 of 43 mm Hg. From .

Figure 9. Figure 9.

Left ventricular ejection fractions at rest on the cycle ergometer and during peak exercise at sea level and at a simulated altitude of about 8,010 m. Note that ejection fraction was well preserved. From .

Figure 10. Figure 10.

Mean pulmonary artery pressure minus mean pulmonary wedge pressure plotted against cardiac output by thermodilution at various barometric pressures (PB) during OEII. For measurements at 240 mm Hg, subjects breathed an oxygen mixture to give an inspired Po2 of 43 mm Hg. From .

Figure 11. Figure 11.

Example of periodic breathing at altitude 6,300 m (barometric pressure 351 mm Hg). From .



Figure 1.

Barometric pressure–altitude relationships. Upper line shows measurements made on Mt. Everest during AMREE. Lower line shows the relationship for the Standard Atmosphere . From .



Figure 2.

Mean monthly pressures for 8,848 m altitude obtained from weather balloons released from New Delhi, India. Note increase during summer months. Mean monthly standard deviation (SD) also shown. Barometric pressure measured on the Everest summit on October 24, 1981 (*) was unusually high. From .



Figure 3.

Oxygen–carbon dioxide diagram showing alveolar gas values collated by Rahn and Otis together with values obtained at extreme altitudes by the AMREE expedition (triangles). From .



Figure 4.

Oxygen‐carbon dioxide diagram showing the two lines drawn by Rahn and Otis for unacclimatized and acclimatized subjects at high altitude (compare Fig. . Alveolar gas failures for OEI, OEII, and AMREE are shown together with corresponding barometric pressures. Note that OEI subjects appeared to be poorly acclimatized at extreme altitudes, whereas OEII subjects had intermediate values. From .



Figure 5.

Maximum oxygen consumptions plotted against inspired Po2 for OEII and AMREE. Note that, although AMREE values were higher at sea level, values measured at the summit Po2 were essentially identical. From .



Figure 6.

Sensitivity of calculated maximal oxygen consumption to changes in several variables for a climber on the summit of Mt. Everest. Each variable was increased by 5%, leaving all others constant. From .



Figure 7.

Blood lactate concentrations measured at rest or shortly after maximal exercise at various altitudes. Most of the data are redrawn from Cerretelli . Filled circles and triangles show data for acclimatized Caucasians (C); open circles and triangles are for high‐altitude natives (N). Data for 6,300 m are from AMREE for acclimatized lowlanders. From .



Figure 8.

Cardiac output (by thermodilution) and stroke volume plotted against oxygen uptake and heart rate at barometric pressures of 760, 347, 282, and 240 mm Hg during OEII. For measurements at 240 mm Hg, subjects breathed an oxygen mixture to give an inspired Po2 of 43 mm Hg. From .



Figure 9.

Left ventricular ejection fractions at rest on the cycle ergometer and during peak exercise at sea level and at a simulated altitude of about 8,010 m. Note that ejection fraction was well preserved. From .



Figure 10.

Mean pulmonary artery pressure minus mean pulmonary wedge pressure plotted against cardiac output by thermodilution at various barometric pressures (PB) during OEII. For measurements at 240 mm Hg, subjects breathed an oxygen mixture to give an inspired Po2 of 43 mm Hg. From .



Figure 11.

Example of periodic breathing at altitude 6,300 m (barometric pressure 351 mm Hg). From .

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 109. West, J. B. The safety of trekking at high altitude after coronary bypass surgery. JAMA 260: 2218–2219, 1988.
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 112. West, J. B., S. J. Boyer, D. J. Graber, P. H. Hackett, K. H. Maret, J. S. Milledge, R. M. Peters, Jr., C. J. Pizzo, M. Samaja, F. H. Sarnquist, R. B. Schoene, and R. M. Winslow. Maximal exercise at extreme altitudes on Mount Everest. J. Appl. Physiol.: Respir. Environ. Exerc. Physiol. 55: 688–698, 1983.
 113. West, J. B., P. H. Hackett, K. H. Maret, J. S. Milledge, R. M. Peters, Jr., C. J. Pizzo, and R. M. Winslow. Pulmonary gas exchange on the summit of Mt. Everest. J. Appl. Physiol.: Respir. Environ. Exerc. Physiol. 55: 678–687, 1983.
 114. West, J. B., S. Lahiri, M. B. Gill, J. S. Milledge, L. G. C. E. Pugh, and M. P. Ward. Arterial oxygen saturation during exercise at high altitude. J. Appl. Physiol. 17: 617–621, 1962.
 115. West, J. B., S. Lahiri, K. H. Maret, R. M. Peters, Jr., and C. J. Pizzo. Barometric pressures at extreme altitudes on Mt. Everest: physiological significance. J. Appl. Physiol.: Respir. Environ. Exerc. Physiol. 54: 1188–1194, 1983.
 116. West, J. B., R. M. Peters, Jr., G. Aksnes, K. H. Maret, J. S. Milledge, and R. B. Schoene. Nocturnal periodic breathing at altitudes of 6,300 and 8,050 m. J. Appl. Physiol.: Respir. Environ. Exerc. Physiol. 61: 280–287, 1986.
 117. Winslow, R. M., C. C. Monge, E. G. Brown, H. G. Klein, F. Sarnquist, N. J. Winslow, and S. S. McKneally. Effects of hemodilution of O2 transport in high‐altitude polycythemia. J. Appl. Physiol.: Respir. Environ. Exerc. Physiol. 59: 1495–1502, 1985.
 118. Young, P. M., M. S. Rose, J. R. Sutton, H. J. Green, A. Cymerman, and C. S. Houston. Operation Everest II: plasma lipid and hormonal responses during a simulated ascent of Mt. Everest. J. Appl. Physiol.: Respir. Environ. Exerc. Physiol. 66: 1430–1435, 1989.
 119. Zuntz, N., A. Loewy, F. Muller, and W. Caspari. Atmospheric pressure at high altitudes. In: Höhenklima und Bergwanderungen in ihrer Wirkung auf den Menschen. Berlin: Bong, 1906. (Translation of relevant pages in: High Altitude Physiology, edited by J. B. West. Stroudsburg, PA: Hutchins Ross, 1981).

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John B. West. Physiology of Extreme Altitude. Compr Physiol 2011, Supplement 14: Handbook of Physiology, Environmental Physiology: 1307-1325. First published in print 1996. doi: 10.1002/cphy.cp040257