Medicine for the Outdoors
Medicine for the Outdoors

Dr. Paul Auerbach is the world's leading outdoor health expert. His blog offers tips on outdoor safety and advice on how to handle wilderness emergencies.

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Brain Oxygenation During Exercise at High Altitude Improves with Acetazolamide

It’s well known that barometric (atmospheric) pressure, and therefore the amount of available oxygen, decreases with altitude, such that at an altitude of 18,000 feet, only half the amount of oxygen is available for breathing in inspired air as that available at sea level. This diminished oxygen is the main reason why it is essential to ascend slowly enough for one’s body to acclimatize and, hopefully, avoid the ravages of high altitude associated afflictions, such as acute mountain sickness, high altitude cerebral edema, high altitude pulmonary edema, and so forth.

Acetazolamide (Diamox) is a drug that helps the body mimic and accelerate the physiological changes that accompany the acclimatization process. It is used quite often by persons who ascend to high altitudes to assist with acclimatization in order to avoid becoming ill. It is also useful to a lesser degree for the treatment of the early stages of altitude-related illnesses. It’s precise mechanisms of action may include promotion of urinary excretion of bicarbonate (which boosts acclimatization), diminution in the production of cerebrospinal fluid (thus decreasing fluid accumulation in the central nervous system that might contribute to brain swelling or other deleterious effects), and stimulation of breathing, which improves general oxygenation, particularly during sleep.

In the most recent issue of the journal High Altitude Medicine & Biology, Jaap Vuyk and colleagues studied members of the Dutch 2005 Cho Oyu (a 8201 meter peak in Tibet) expedition. They were interested specifically on the influence of acetazolamide and exercise on heart rate and oxygen saturation (limbs and brain), the presence and severity of acute mountain sickness, and psychomotor function. They were able to demonstrate that acetazolamide diminished the exercise-reduced reduction in brain oxygenation that is normally observed under these conditions. They further observed that after several weeks at high altitude, all climbers showed the same physiological measurements, which was attributed to the climbers not taking acetazolamide becoming acclimatized and therefore no longer at a relative disadvantage. This study provides more support for the contention that acetazolamide is a useful drug for climbers, trekkers, and others who sojourn to high altitude.

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photo by Mathias Schar
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Dr. Paul S. Auerbach is the world’s leading authority on wilderness medicine.