Acute altitude illness

Updated February 22, 2024

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Updated 2024 WMS guidelines for the prevention and management of acute altitude illness.

Background

Overview

Definition

Acute altitude illness is a group of conditions that can develop when non-acclimatized individuals ascend to high altitudes (> 2,500 meters) too quickly. These conditions include acute mountain sickness, high-altitude cerebral edema, and high-altitude pulmonary edema.

Pathophysiology

The pathophysiology of acute altitude illness is not completely understood, but it is known to be related to the body's response to hypoxia, or lack of oxygen, at high altitudes. This hypoxic environment can lead to tissue hypoxia, which can then trigger a series of physiological changes that result in the symptoms of acute altitude illness.

Epidemiology

The prevalence of acute altitude illness in the US is estimated at 65,000 per 100,000 population.

Disease course

The clinical manifestations of acute altitude illness can vary depending on the specific condition. Symptoms of acute mountain sickness include headache, dizziness, nausea, and vomiting. High-altitude pulmonary edema is characterized by orthopnea, breathlessness at rest, cough, and pink frothy sputum. High-altitude cerebral edema can lead to ataxia, decreased consciousness, and in severe cases, coma and brain herniation.

Prognosis and risk of recurrence

The prognosis of acute altitude illness is generally good if the individual descends to a lower altitude.

Guidelines

Key sources

The following summarized guidelines for the management of acute altitude illness are prepared by our editorial team based on guidelines from the Wilderness Medical Society (WMS 2024) and the European Respiratory Society (ERS 2017)....

Respiratory support

Supplemental oxygen

As per WMS 2024 guidelines:

Consider administering ongoing supplemental oxygen when available to raise SpO2 to > 90% or relieve symptoms while waiting to initiate descent or when descent is impractical.

Administer supplemental oxygen when available to achieve SpO2 of > 90% or relieve symptoms while waiting to initiate descent when descent is not feasible and during descent in severely ill patients.

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Medical management

Acetazolamide: as per WMS 2024 guidelines, Consider administering acetazolamide for the treatment of patients with acute mountain sickness.

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Nonpharmacologic interventions

Descent: as per WMS 2024 guidelines, Advise descent in patients with severe acute mountain sickness, high-altitude cerebral edema, or high-altitude pulmonary edema.

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Specific circumstances

Patients with high altitude-induced central sleep apnea

As per ERS 2017 guidelines:

Recognize that healthy lowlanders travelling to altitudes > 1,600 m may experience central sleep apnea (high-altitude periodic breathing), with severity increasing as altitude increases.

Consider offering oxygen-enriched air or acetazolamide to reduce high-altitude periodic breathing and improve nocturnal oxygen saturation in healthy lowlanders staying at altitude. Offer combined treatment with acetazolamide and automatic positive airway pressure to prevents central apneas and improve nocturnal oxygen saturation.

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Preventative measures

Gradual ascent: as per WMS 2024 guidelines, Advise gradual ascent (a slow increase in sleeping elevation) for the prevention of acute mountain sickness and high-altitude pulmonary edema.

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