From the Guidelines
Preventing and treating altitude illness requires a combination of gradual ascent, medication, and appropriate response to symptoms, with the most effective prevention strategy being gradual acclimatization, ascending no more than 300-500 meters per day above 2500 meters, with a rest day every 1000 meters, as recommended by recent studies 1. The primary preventive medication is acetazolamide (Diamox), taken at 125mg twice daily starting 1-2 days before ascent and continuing for 2-3 days at maximum altitude 1. For treatment, descending at least 500-1000 meters is crucial when symptoms develop. Dexamethasone (4mg every 6 hours) can treat severe symptoms, particularly cerebral edema, while nifedipine (10mg every 8 hours) may help with high altitude pulmonary edema 1. Supplemental oxygen, if available, provides immediate relief at flow rates of 2-4 liters per minute. Portable hyperbaric chambers can temporarily simulate descent when immediate physical descent isn't possible. These interventions work by addressing the underlying pathophysiology of altitude illness, which involves hypoxia-induced changes in cerebral blood flow, increased capillary permeability, and pulmonary vasoconstriction. Some key points to consider include:
- Staying well-hydrated and avoiding alcohol and sedatives during acclimatization further reduces risk.
- Sex-dependent physiological reactions to hypoxia may contribute to an increased acute mountain sickness vulnerability in some women, and adequate acclimatisation, slow ascent speed and/or preventive medication (e.g. acetazolamide) are solutions 1.
- Targeted training of the respiratory musculature could be a valuable preparation for altitude training in women 1.
- Sex hormones influence hypoxia responses and hormonal-cycle and/or menstrual-cycle phases therefore may be factors in acclimatisation to altitude and efficiency of altitude training 1.
From the Research
Prevention of Altitude Illness
- The major preventive measure for altitude illness is slow ascent 2, 3, 4, 5
- Acetazolamide is effective in preventing acute mountain sickness (AMS) and can be used as a prophylactic measure 2, 6, 5
- Dexamethasone can also be used to prevent AMS 2, 3
- Nifedipine is effective in preventing high-altitude pulmonary edema (HAPE) 2, 3, 5
- Gradual ascent to a high altitude leads to acclimatization, which includes changes in the respiratory, cardiovascular, hematologic systems and cellular adaptations that enhance oxygen delivery to the tissues and augment oxygen uptake 3
Treatment of Altitude Illness
- Immediate descent and/or the administration of oxygen is the treatment of choice for both AMS and HAPE 2, 3
- Dexamethasone may be given for severe AMS 2, 3
- Nifedipine may be given for HAPE 2, 3, 5
- Acetazolamide can be used to treat AMS, with doses of 500-750 mg/day appearing to be the most effective for minimizing symptoms of AMS during rapid ascents to altitudes >3,500 m 6
Acclimatization
- Acclimatization can be achieved by a slow ascent at a climbing rate of 300 to 600 m in one day 5
- Climbers should spend at least nine or more nights at an altitude higher than 2500 m a.s.l. in the last 30 days before ascent to improve performance at high altitude and significantly decrease symptoms of AMS 5
- Individual concept of optimal acclimatization to altitude is crucial, taking into account typical health restrictions and developing a personalized plan 4