Background

Acute high altitude illness, also known as acute mountain sickness, may present with a variety of symptoms. It is caused by the decreasing level of oxygen at increasingly high altitudes; and it can be experienced when reaching a high altitude when travelling, hiking or climbing mountains or other elevated areas. People going to altitudes over 4000 metres, females, people younger than mid-adulthood , and people with a history of migraine are at greater risk of suffering from altitude sickness. The most common symptoms are headache, loss of appetite , insomnia, and nausea. However, severe forms can include confusion, difficulty walking, progressive cough, shortness of breath, and even death.

Review question

What are the benefits and risks of different treatments for people suffering from high altitude illness?

Study characteristics

We included 13 studies with a total of 468 participants. Most studies included participants with mild or moderate forms of mountain sickness, and only one study included the severe neurological (disorder of the nervous system) form. Follow-up was usually less than one day. We also identified two ongoing studies.

Key results

We found studies evaluating the following interventions: simulated descent with a hyperbaric chamber (medical use of oxygen in a special chamber at greater than atmospheric pressure to increase the availability of oxygen in the body); oxygen; medicines: acetazolamide, dexamethasone, ibuprofen, paracetamol, gabapentin, sumatriptan, nitric oxide, and magnesium sulphate. None of the studies reported the effects of these interventions on all-cause mortality. The report of complete relief from acute mountain sickness symptoms, and adverse events was infrequent. Studies related to simulated descent with the use of a hyperbaric chamber did not find additional benefits or harms related to this intervention (3 studies, 124 participants). In addition, studies related to administration of medicines found some benefits in terms of reduction of symptoms with the use of acetazolamide (2 studies, 25 participants), and dexamethasone (1 study, 35 participants), without an increase in side effects.

Quality of the evidence

The quality of the evidence we found was low, and thus our certainty in the findings is limited. There was insufficient information on how the studies were conducted, and in some cases there was evidence of tampering at some stages of the trials. Furthermore, the number of persons in each study was very small (< 30 participants), and therefore the results were not clear (imprecise). Some studies were not blinded (that is, participants knew what experimental treatment they were receiving), and this could have affected how the participants evaluated their own symptoms.