Physiology and Medicine at High Altitude: The Exposure and the Stress

Abstract

<p>Increase in altitude causes decrease in atmospheric barometric pressure that results in decrease of inspired<br />partial pressure of oxygen, a source for stress and pose a challenge to climbers/trekkers or persons posted on<br />high altitude areas. This review discusses about the high altitude sickness, their incidence rates, pathophysiology<br />and the classic model of acclimatisation, which explains about how oxygen requirement in extreme environment<br />is achieved by complex interplay among pulmonary, hematological and cardiovascular processes. The acute<br />high altitude illness (AHAI) is basically composed of two syndromes: cerebral and pulmonary that can afflict<br />un-acclimatised climbers/trekkers. The cerebral syndrome includes acute mountain sickness (AMS) and high<br />altitude cerebral oedema (HACO) and pulmonary syndrome typically refers to high altitude pulmonary oedema<br />(HAPO). The core physiological purpose, according to the classic model is centered upon the optimisation of<br />increased delivery of oxygen to the cells through a coherent response involving increased ventilation, cardiac<br />output and hemoglobin concentration with aim to increase the oxygen flux across the oxygen cascade, which<br />will help in preventing the development of majority of high altitude illness.</p>