High altitude sickness: Physiological basis, Prevention and Treatment

Abstract

High altitude sickness is a clinical condition that occur in non-acclimatized individuals after rapid ascent to high altitude (>2500 meter). The clinical manifestations of high altitude sickness usually appear within a few hours to two days of ascent and typically consists of headache accompanied by loss of appetite, nausea, vomiting, disturbed sleep, fatigue, and dizziness. Major risk factors include rate of ascent, maximum altitude achieved and sleeping altitude. The initial body response to reduced partial pressure of oxygen at high altitude is the increase ventilation. This is brought about by hypoxic stimulation of the peripheral chemoreceptors which sense the low PaO₂ in the arterial blood. As ventilation increases, CO₂ is washed out and PaCO₂ drops and blood becomes alkaline. Slow ascent is the key to prevent high altitude sickness and rapid descend is the most effective treatment measure. Oxygen therapy and acetazolamide (carbonic anhydrase inhibitors) might be effective for both prevention and treatment. The aim of this article is to discuss clinical manifestations, prevention, and treatment options on the basis of body responses to hypoxia at high altitude.