It’s May and as every climber knows it’s the season for summiting Mount Everest. Unfortunately, since the mid 90’s Everest has seemed to capture the public’s attention more for the crowds, characters, deaths, and occasional scandals rather than the grandeur, inspiration, and astounding stories of remarkable people surviving and occasionally thriving in “the death zone”. Bold explorers and climbers such as Shipton, Mallory and Irvine, Hillary and Norgay, Messner, and Hargreaves once personified these sublime stories.
To this day scientists still have many unanswered questions about the effects of extreme altitude on the human body. However, there is a small, highly educated cadre of scientists working hard to uncover answers. My good friend, Dale Wagner, Ph.D., is one of them and summited Everest four years ago. Below is his brief summary about the effects of extreme altitude on the bodies of those hardy folks who climb the flanks of Everest for a chance to stand “on top of the world”.
What are the consequences of exercising in “thin air”? The most noticeable change is a decrease in one’s cardio respiratory exercise capacity (VO2max). At moderate altitudes (e.g., 10,000’) you might notice only a slight decrease in performance. However, at higher altitudes the decrement is much more dramatic. The body makes immediate adjustments, like increased breathing and increased heart rate. As altitude increases there is a greater reduction in VO2max and a higher resting heart rate. Thus, at extreme altitude, maximum exercise capacity may be only slightly greater! This is one explanation why some climbers never make it out of the death zone – it requires a huge (near maximal) effort just to keep moving.
In addition to the decrease in exercise capacity, high altitude climbers must contend with a multitude of other challenges. As altitude increases, air temperature plummets. Thus, frostbite and hypothermia become a major concern. Despite the cold, sunburn is common due to strong UV rays. Additionally, the strong reflection of the light off of the snow can lead to snow blindness for climbers not wearing protective eyewear.
High altitude environments are also very dry. Breathing in cold dry air often contributes to the “high altitude hack”, a persistent dry cough that can be debilitating and even lead to fractured ribs. Dry air combined with a fast breathing rate and the body’s natural response to urinate more at altitude all contribute to an increased risk of dehydration, and climbers have to conscientiously consume fluids. The added risks imposed by the hostile environment continue into the night. Climbers often experience irregular breathing patterns while sleeping, which contributes to restlessness.
Finally, there are several illnesses specific to high altitude. The most common is acute mountain sickness (AMS). AMS is a self-limiting syndrome characterized by headaches with one or more additional symptoms including nausea, fatigue, lightheadedness, and/or difficulty sleeping. It occurs when climbers ascend too high too fast, and it can be avoided with proper acclimatization. Although AMS is an annoyance and can disrupt climbing plans, recovery is fast and complete with descent to a lower altitude and rest. However, if the symptoms are ignored and a climber continues to ascend, the risk of developing high altitude cerebral edema (HACE), or swelling in the brain, increases.
Another altitude illness is high altitude pulmonary edema (HAPE). One of the body’s adaptations to high altitude is increasing pressure in the blood vessels that supply your lungs. However, if the body overcompensates and the pressure increases too much, the pulmonary capillaries (small vessels in the lungs) can burst and fluid fills the lungs. Both HACE and HAPE are medical emergencies and can kill a climber quickly if he or she is unable to rapidly descend.
That being said, altitude poses a “double whammy” – a reduction in exercise capacity makes it difficult to perform well and time is needed for the body to acclimatize, but the longer someone is exposed to extreme altitude the greater the risk of developing hypothermia, frostbite, sunburn, snow blindness, dehydration, a debilitating cough, sleep disturbances, and altitude illnesses.
We’re entering into the “summit season” for big mountains, as May is the most common month for reaching a Himalayan summit while June-August being the climbing season for the high Andes. The best high altitude climbers in the world make it look easy by moving seemingly effortlessly and quickly in the thin air. However, every year there are stories of climbers (both novice and elite) who succumb to the elements or “make mistakes” and do not return to their homes.
It’s easy to be critical of climbers when watching a televised ascent of Everest from the comfort of your living room, or when scanning Facebook reports and YouTube posts while sitting in a climate-controlled, oxygen-rich office. But keep in mind that the high altitude world is a hostile one, wrought with many physiological challenges. As the saying goes, “walk a mile in their crampons before making a snap judgment about their performance or actions in this extreme environment.”
Play safe out there!