Encompasses acute mountain sickness, high-altitude pulmonary oedema, and high-altitude cerebral oedema that occurs in lowland residents following an ascent to altitude.
Acute mountain sickness is self-limiting and resolves over a number of days at altitude.
High-altitude pulmonary oedema and cerebral oedema are often fatal if left untreated.
Descent is the most effective form of treatment for all three conditions.
The diagnosis is usually clinical. However, the combination of a remote and hostile environment together with the potential for other medical conditions sometimes makes confirmation of the diagnosis difficult to achieve.
New symptoms at altitude should be assumed to be those of a high-altitude illness until proved otherwise.
High-altitude illness (HAI) encompasses acute mountain sickness, high-altitude pulmonary oedema, and high-altitude cerebral oedema that occurs in lowland residents following an ascent to altitude.
History and exam
Key diagnostic factors
- presence of risk factors
- change in mental state: for example, tired, irritable, confused, forgetful, irrational
- abnormal tone, power, and reflexes
Other diagnostic factors
- nausea, vomiting, and loss of appetite
- fatigue and weakness
- dizziness or lightheadedness
- difficulty sleeping
- visual disturbance
- shortness of breath
- cough with or without sputum
- peripheral oedema
- accentuated pulmonary second sound
- elevated respiratory rate
- elevated heart rate
- low arterial oxygen saturation
- urinary incontinence or retention
- retinal haemorrhages and papilloedema on fundoscopy
- chest pain
- cranial nerve palsies (III, IV, and VI)
- visual and auditory hallucinations, seizures, tinnitus, vertigo, tremors, speech disturbance, and deafness
- high altitude
- rapid ascent
- low-altitude residence
- history of previous altitude illness
- younger age
- poor awareness of high-altitude illness prior to travel
Investigations to consider
- arterial blood gases
- chest radiography
- chest ultrasound and echocardiography
- WBC count
- lumbar puncture
- CT head
- MRI head
high-altitude ascent planned
concurrent HAPO and HACO
Jeremy S. Windsor, MBChB, DCH, FCARCSI
Anaesthetics and Intensive Care Medicine
University College Hospital
JSW is an author of a number of references cited in this topic.
David Hillebrandt, MBBS, MRCGP, FIMC RCS (Edin), MFTM RCPS (Glas), Dip Mt Med (UIAA and Leics)
Mountain Medicine & Pre Hospital Care
DH is paid to advise a commercial high altitude company. DH is a member of the FPHC RCS (Edin) Diploma of Mountain Medicine, and has received some expenses and an honorarium. DH is an unpaid medical advisor to the British Mountain Guides and British Mountaineering Council.
James S. Milledge, MBBS
Department of Physiology
University College London
JSM declares that he has no competing interests.
Mike Grocott, MD
Intensive Care Medicine
University College Hospital
MG declares that he has no competing interests.
Haibo Wang, MD, PhD
LSU Health Sciences Center
HW declares that he has no competing interests.
- Acute exacerbation asthma
- Community-acquired pneumonia
- Acute exacerbation of chronic heart failure (CHF)
- CDC health information for international travel (yellow book): the pre-travel consultation - altitude illness
- Wilderness Medical Society practice guidelines for the prevention and treatment of acute altitude illness: 2014 update
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