Climbers sometimes develop Acute Mountain Sickness (AMS) when ascending too rapi

Question

Climbers sometimes develop Acute Mountain Sickness (AMS) when ascending too rapidly without allowing their bodies time to acclimate to the lower oxygen concentrations in air at high elevations. One physiological response to high altitude is hyperventilation. Taking acetazolamide (trade name: Diamox) prior to and during ascent can help prevent the nausea, dizziness, fatigue, and headaches associated with AMS. Acetazolamide inhibits carbonic anhydrase functions. 1. What effect does hyperventilation have on blood pH and how would acetazolamide act to counteract this?

Explanation / Answer

Efect of hyperventilation: Blood pH is tightly regulated by a system of buffers that continuously maintain it in a normal range of 7.35 to 7.45 (slightly alkaline). Blood pH drop below 7 can lead to a coma and even death due to severe acidosis. This causes depression of the central nervous system. High blood pH (above 7.45) is called alkalosis. Severe alkalosis (when blood pH is more than 8) can also lead to death, as it often happens during last days or hours of life in most people who are chronically and terminally ill. Hyperventilation is the most common cause of respiratory alkalosis. acetazolamide did not change the CO2 sensitivities and time constants of both chemoreflex loops. However, mean ( ± SD) resting ventilation increased from 12.22 ± 2.41 to 14.01 ± 1.85 L · min- 1, resulting in a decrease in end-tidal PCO 2 from 40.0 ± 4.7 to 33.3 ± 3.5 mm Hg. Base excess decreased from - 0.08 ± 1.20 to - 7.48 ± 2.07 mmol · L- 1, indicating metabolic acidosis and explaining a leftward shift of the CO2 response curve by 7.3 mm Hg. Possible clinical implications of these results are discussed. Teppema LJ, Dahan A. Acetazolamide and breathing: does a clinical dose alter peripheral and central CO2 sensitivity?

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