From Jim McEachen, M.D., (USAF) Mayo Aerospace Medicine Fellow
If you have no plans to go mountain climbing, then you are probably thinking why does this expedition matter? The results of this journey could impact a large segment of our population who every year encounter situations of reduced oxygenation without really knowing it. Whether flying in an airplane with a cabin altitude of 8,000 feet, skiing down a high mountain, or hiking on a mountain-top as part of a vacation, the unseen stressors that hypoxia imposes on our bodies can have both an immediate and long-term impact. Studying healthy high-altitude climbers becomes an excellent analog for assessing hypoxic and cognitive adaptive processes.
You also may be wondering what could happen at such altitudes? ‘High-altitude illness’ is near the top of the list. This refers to a group of medical conditions that can have profound effects on the brain and/or lungs. Acute Mountain Sickness (AMS) and High Altitude Cerebral Edema (HACE) are associated with cerebral issues, while High Altitude Pulmonary Edema (HAPE) affects the lungs. As noted by the New England Journal of Medicine, AMS is a public health problem with significant economic implications, especially for the ski industry. The exact mechanism of AMS is unknown, but many believe that hypoxia-induced vasodilatation within the brain leads to an excruciating headache and/or concomitant nausea. Though much less common in occurrence, both HACE and HAPE are potentially fatal. Depending on individual physiology, the speed of ascent, and the altitude, these illnesses can rapidly develop in unacclimated climbers. Treatment options are based on the severity of symptoms and may include any of the following: descending in altitude (at least 500m), oxygen therapy, further acclimatization at a lower altitude, medications (i.e. acetazolamide, dexamethasone) and in exceptional circumstances hyperbaric oxygen treatment