I recently had a friend visit who within a few hours of arrival became very ill. Symptoms consisted of a pounding headache, fatigue, nausea, lack of hunger and the nail in the coffin…traveling from Ohio to Colorado aka a rapid change in altitude. Bingo, he was suffering from high-altitude sickness.
What exactly is high-altitude sickness? Well, there are three types from which individuals can suffer. First is acute mountain sickness, this is the most common and most mild version with individuals presenting with headache, nausea/vomiting, fatigue, and dizziness. Second is high altitude cerebral edema (HACE) which results in severe brain swelling and presents with confusion, lethargy, ataxia, altered consciousness and possible death. Third is high altitude pulmonary edema (HAPE) where there’s a severe fluid accumulation around the lungs presenting with shortness of breath, a dry cough that can progress to a pinkish expectoration, chest tightness, decreased physical performance and possibly death. Scary.
Now why does this happen? As you come to higher altitude, the atmospheric pressure decreases and can result in high altitude hypoxia. While the relative concentration of oxygen remains constant, the partial pressure decreases in the ambient air, inspired air, alveolar air, and arterial blood. This hypoxia can significantly affect cellular processes and can trigger a cascade of issues. The body tries to acutely adapt by increasing respiratory rate (increase oxygen) and increase heart rate (pump more oxygen ‘rich’ blood). Problem is, hypoxia is a powerful factor to increase microvascular permeability induced by interactions between fluid mechanics and biohumoral response, together with impaired compensatory mechanisms leads to cerebral vasogenic edema (HACE and swelling of the brain) and pulmonary hydrostatic edema (HAPE). Overall, very troublesome, so what does one do about it?
Acclimatization is a man’s best friend and least invasive option to prevent high altitude sickness. Beyond that, medications like acetazolamide, dexamethasone, and nifedipine are available. The general treatment option is to descend from the high altitude but if not, available oxygen therapy may help, and hyperbaric chambers used to simulate decent.
To further expand on acclimatization, individuals can adapt to living at high altitudes. Within a few weeks, the body will alter itself to affect the oxyhemoglobin dissociation curve via persistent respiratory alkalosis and increased BPG production. Evolutionary adaptations have occurred for certain populations such as Tibetans who chronically hyperventilate to breathe more air per time unit while individuals from the Andes have increased hemoglobin levels.
Reference:
Savioli, G., Ceresa, I. F., Gori, G., Fumoso, F., Gri, N., Floris, V., Varesi, A., Martuscelli, E., Marchisio, S., Longhitano, Y., Ricevuti, G., Esposito, C., Caironi, G., Giardini, G., & Zanza, C. (2022). Pathophysiology and Therapy of High- Altitude Sickness: Practical Approach in Emergency and Critical Care. Journal of Clinical Medicine 2022, Vol. 11, Page 3937, 11(14), 3937. https://doi.org/10.3390/JCM11143937
Taylor, A. T. (2011). High-Altitude Illnesses: Physiology, Risk Factors, Prevention, and Treatment. Rambam
Maimonides Medical Journal, 2(1), e0022. https://doi.org/10.5041/RMMJ.10022
At what point is oxygen therapy actually helpful as opposed to placebo? I often hear that most of the oxygen containers you can buy at the airport are generally unnecessary and aren't actually that helpful, but you mention that in some cases oxygen therapy may help. I understand that oxygen therapy and the oxygen containers at the airport are not the same thing, however I imagine it is a similar concept in that a person is receiving more oxygen than is otherwise available. Is that only the case in more severe cases of altitude sickness or hypoxia, or could oxygen therapy be useful for less severe cases as well?
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