![]() Usually, arterial oxygen saturation ( S aO 2) and tension ( P aO 2) are on average slightly lower compared to healthy controls at a given altitude, and the alveolar–arterial oxygen tension difference slightly greater ( table 1). Without appropriate treatment, HACE usually leads to death, sometimes within 24 h of onset.Ĭlinical and routine laboratory examinations do not reveal abnormal findings in AMS. Absence of preceding or concurrent headache does not exclude the diagnosis of HACE. The leading signs of HACE are truncal ataxia and clouded consciousness. Progression of symptoms including nausea and headache not responding to first-line antiemetics and analgesics and increasing lassitude may point to progression of AMS to HACE. These are all nonspecific, and insomnia, in particular, is very prevalent in healthy individuals at high altitude. Additional symptoms are loss of appetite or nausea, dizziness, fatigue or lassitude and insomnia. However, this has been questioned by those who argue, based on anecdotal reports, that some individuals (probably ∼5% ) with symptoms clearly attributable to high altitude will be missed by having headache as a compulsory symptom. The leading symptom is headache, which is required for the diagnosis of AMS by the most frequently used scoring system. The symptoms are usually most pronounced after the first night spent at a new altitude and resolve spontaneously when appropriate measures are taken. For the purposes of this review, we will consider high altitude as elevations ≥2500 m, although it should be recognised that the physiological responses to hypobaric hypoxia start at lower elevations, and thus some individuals who are highly susceptible to acute altitude illness may become sick at altitudes <2500 m.ĪMS consists of nonspecific symptoms that occur at altitudes of ≥2500 m in unacclimatised individuals with a usual delay of 4–12 h after arrival at a new altitude. We then review the primary pharmacological and nonpharmacological approaches to the management of each form of acute altitude illness and provide practical recommendations for both prevention and treatment. ![]() For each disease, we review the clinical features, epidemiology and the current understanding of their pathophysiology. The review is intended to provide detailed information about each of these entities. These diseases can develop at any time from several hours to 5 days following ascent to a given elevation and can range in severity from mild with minimal effect on the planned travel itinerary to life-threatening illness. However, in other cases, maladaptive responses occur, that in turn cause one of three forms of acute altitude illness, acute mountain sickness (AMS), high-altitude cerebral oedema (HACE) and high-altitude pulmonary oedema (HAPE). Altitude sickness treatment series#This hypobaric hypoxia triggers a series of physiological responses, which, in most cases, help the individual tolerate and adapt to the low oxygen conditions. Among other important changes, such as decreases in temperature and ambient humidity, the defining environmental feature at high altitude is a drop in barometric pressure, which causes a decrease in the partial pressure of oxygen at every point along the oxygen transport cascade from ambient air to cellular mitochondria. ![]() Large numbers of people are ascending to high altitudes for the purposes of pleasure, work and athletic competition. ![]()
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