[20] AMS normally resolves within 2 to 4 days, but may be ameliorated by drug therapy (see below). HACE is thought to be a progression of AMS representing the final encephalopathic, Venetoclax life-threatening stage of cerebral altitude effects.[7, 11] It is characterized by ataxia, hallucinations, confusion, vomiting, and decreased activity[3] and is mostly but

not necessarily accompanied by severe, unbearable headache.[21] Ataxia is the key sign, manifested by a positive Romberg test.[22] HACE requires immediate treatment (see below). HAPE symptoms are dyspnea at rest and especially when attempting to exercise, bothersome cough, weakness, and chest tightness. The signs include central cyanosis, frothy sputum, and crackles/wheezing in at least one lung field, tachypnea and tachycardia.[21, 23] HAPE is most often misdiagnosed or mistreated as pneumonia. If the conditions worsen, the extreme oxygen desaturation may also lead to HACE. Early treatment is of utmost importance (see below). Sleep disturbances and/or HAH are experienced by 60% to 80% of high-altitude selleck compound travelers.[7] AMS has a prevalence of ∼10% for those going from sea level to 2,500 m[3] and 30% to 40% when ascending to mountain huts at ∼3,500 m in the Alps or Tibet.[24, 25] One could expect similar rates of HAH and AMS on same-day car trips to the Hawaiian volcano summits (eg, Mauna Kea at 4,100 m)

or Colorado mountain passes or lookouts (3,000–4,300 m). HACE is usually not encountered below 3,000 m. HAPE is rare below 3,000 m,[3, 6, 7] but can present as low as 1,400 m.[26] Among 14,000 railroad workers (age range 20–62 years; 98% men) moved from lowland China to Tibet (3,500–5,000 m), the Baricitinib prevalence of AMS was 51%, whereas that of HACE

0.28% and HAPE 0.49%.[25] HACE prevalence of 1.0% has been reported for all trekkers between altitudes of 4,243 and 5,500 m in Nepal, but HACE increased to 3.4% in those who suffered from AMS.[27] Prevalence data for HAPE vary from 0.2% in individuals ascending to an altitude of 4,559 m in the Alps to 15% in Indian troops that were flown to 3,500 m.[28] A very recent study reported an incidence of severe AMS in 23.7%, HAPE in 1.7%, and HACE in 0.98% of 1,326 subjects sojourning to 4,000 m.[29] AMS is usually benign, whereas HACE and HAPE have mortality rates up to 40% where there is limited medical care.[2, 3, 6, 30] High-altitude illnesses occur when the rate of ascent to high altitude overcomes the ability of the individual to acclimatize.[3, 11] A recent study suggests not to exceed an ascent rate of 400 m per day.[29] In regard to AMS, the major determinants for its occurrence are a previous history of AMS (ie, individual susceptibility), a history of migraine, a lack of recent exposures to altitude (ie, no acclimatization), faster rate of ascent, and a higher altitude attained.[24, 31] Other factors found to contribute to AMS development were physical exertion,[32] obesity,[33] and low fluid intake.