Altitude Medicine (HAP 11)

Talk by Rich Jeavons

Notes by Tim Slade


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NB: For education only. Double check prior to any clinical use.

  • High altitude 1500-3500 m
  • Very High Altitude 3500 -5500 m
  • Extreme altitude > 5500 m

Note: A plane cabin is normally pressurised to around  2750m so still high altitude.

Normal symptoms with increased altitude:

  • Hyperventilation
  • Increased urination
  • Waking at night
  • Periodic Breathing

pO2 decreases due to drop in pressure but percentage of oxygen in air remains the same, therefore it is not possible to achieve normal oxygen saturations at altitude. 

Acute mountain sickness (AMS):

  • Gastrointestinal upset
  • Fatigue
  • Dizziness and nausea
  • Headache
  • Insomnia


  • Descent to where symptoms started.
  • Acetazolaminde (Diamox) 250 mg BD – carbonic anhydrase inhibitor. Respiratory stimulant and sleeping tablet. Side effects include parasthesia of lips, hands and feet and blurred vision. Can continue to climb when symptoms improve.
  • Dexamethasone 4 mg – but cannot continue to climb
  • Gingko Biloba – needs to be taken pre-ascent as prevention.

High Altitude Cerebral Oedema (HACE):

  • Symptoms of AMS + Gait ataxia or altered mental status.
  • Or both gait ataxia and mental status changes without features of AMS.
  • Ataxia assessed by heel toe – N.B. not finger nose as this is unaffected. N.B. should assess heel toe before ascent as some people cannot do this anyway!


  • Descent
  • Dexamathosone 4mg
  • Oxygen
  • Hyperbaric oxygen if available.

High Altitude Pulmonary Oedema (HAPE):

  • Pathologically different mechanism to HACE
  • Hypoxic vasoconstriction to pulmonary vasculature, high pressure leads to fluid leak.

Diagnostic criteria:

  • 2 Symptoms from: dyspnoea, cough, decreased exercise tolerance, tight chest, congestion.
  • 2 Signs from: crackles, wheeze, hypoxia – exertion reduced saturations, tachycardia.


  • Descent
  • Nifedapine 20 mg
  • Oxygen
  • Hyperbaric oxygen if available.

Linked Resources

Environmental Emergencies HAP 11
Environmental Emergencies HAP 11

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