![]() ![]() Preventing the occurrence of HAI should be a priority over treatment. After a few days, cardiac output decreases due to diuresis which is also defined as high altitude diuresis so that maximum oxygen delivery to the tissues reduces. In high altitude, cardiac output and systemic blood pressure were increased due to increased sympathetic nervous tone. 10, 16 The individual's adaptation capacity to hypobaric hypoxia which is termed as acclimatization lasting from hours to weeks, depends on both the magnitude and the rate of onset of hypoxia. 13, 14, 15 In case of inadequate acclimatization, cerebral and pulmonary edema may develop consequently due to overperfusion of the microvascular beds, elevated hydrostatic capillary pressure and leakage in both the blood-brain barrier and blood-gas barrier in the lungs. 2, 11, 12 This stressful situation is accompanied by specific adaptations, which depend on the level of altitude and duration of exposure. 10 These environmental changes may trigger a series of physiological responses including respiratory alkalosis which develops due to higher alveolar paO 2 and lower alveolar paCO 2 caused by increased minute ventilation, higher red blood cell aggregation and hematocrit levels, increased cerebral blood flow to compensate for the reduced arterial oxygen content. This make it difficult for oxygen to diffuse in to the pulmonary capillaries although the proportion of oxygen in the air remains the same. 8 Hypobaric hypoxemia in high altitude is caused by low air pressure which decreases partial oxygen pressure. The barometric pressure at sea level is 760 mmHg and 370 mmHg at 5791 m. As altitude increases, temperature and humidity decreases, ultraviolet radiation increases, more importantly, barometric pressure and partial pressure of oxygen decreases. 3, 4, 5, 6, 7 At high altitudes, environmental features differ from the ones at sea level. In this review it is intended to provide detailed information about pathophysiology, clinical features, prevention and treatment strategies for HAI according to current literature.Ģ. The pathophysiology of high-altitude illnessĪlthough some prior studies report that AMS and potentially HAPE can be seen at lower elevations (2000–2500 m), HAI is more common above 2500 m. The pathophysiology of HAI is partially well understood while prevention and treatment strategies are mostly based on low quality evidences. 2 HAI has three forms acute mountain sickness (AMS), high-altitude cerebral edema (HACE) and high-altitude pulmonary edema (HAPE). High-altitude illness is a group of syndromes that results from hypoxia which is the major parameter causing a series of physiological alterations. If the time of high elevation is faster than the process of acute acclimatization, then high-altitude illness (HAI) occurs. ![]() 1 The adaptability of the human body to hypobaric hypoxia is quite successful but requires time to do so. In high altitudes, usually accepted as above 2500 m, travelers are faced with decreased partial pressure of oxygen along with decreased barometric pressure. People are increasingly interested in travelling to high altitudes for several purposes for fun, for work or sportive activities. ![]()
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