Altitude Sickness

You will learn to respect Mother Nature in Nepal. Resistance is futile! Actually, it’s fatal! Perhaps the greatest danger to even casual trekkers in the Himalayan region is the human body’s struggle to adapt to the diminished oxygen levels at higher altitudes. The ratio of oxygen remains constant in the air (21%) but the barometric pressure decreases, providing less oxygen volume with each breath As you may have learned by now, the body relies on oxygen as the single most immediately critical element for its survival. The body is capable of adjusting to the constrained oxygen supply, but only given a fair amount of time to acclimatize. A telling analogy is like the g-forces of going from zero to the speed of sound in one second. Yes, they’d have to scrape you out of the cockpit. You can expect comparable consequences if you dash up the mountains for a 15,000-foot elevation gain and then get cozy for the night.

The medical term for this catastrophe is Acute Mountain Sickness, a result of the body’s adverse reaction to hypoxia. At higher elevations (between five and ten thousand feet) the body normally shows signs of shortness of breath from light physical exertion and difficulty sleeping at night. Symptoms of a more serious condition are confusion, staggering, persistent headache, deep fatigue, and nausea. An experienced mountain guide will [continually watch#Pema-Watch] for these signs and treat them seriously. The rule is that any illness at high elevations is presumed to be altitude sickness until proven otherwise. At the first signs the guide will begin to take actions to mitigate the effects. The guide will make sure that hiker stays at that elevation or lower until the symptoms are completely cleared. One common drug used for treatment to help the body adapt to the decreased oxygen is acetazolamide (Diamox®). This inhibits an enzyme in the blood, making it more acidic and better able to properly absorb oxygen. It can also relieve some of the swelling. This is often given at the first sign of symptoms, along with other sensible treatments.

For those who dare to venture upward with these symptoms, things will get worse. As the body fights to adapt it shuts down ‘less vital’ systems, such as digestion, and fluid will leak from cell membrane throughout the body. A severe result of the latter condition is a buildup of fluid around the lungs, and ultimately around the brain. The former is known as High Altitude Pulmonary Edema (HAPE), and the latter is High Altitude Cerebral Edema (HACE). These conditions are a dope slap to you from your body telling you to stop – drop – and roll (down hill, ASAP). The first order of business is to get the afflicted hiker to a lower elevation, or cheat and put them in a portable hyperbaric chamber, also known as a Gamow bag or Personal Altitude Chamber. This is a tightly sealed, person-sized inflatable bag that simulates the conditions of immediately being at lower elevation. This is not considered to be a cure, only a holdover until the suffering hiker can really be evacuated to lower elevation and to proper medical facilities, such as by an [emergency helicopter #Pema-Bushes]. The Gamow bag is an extra expense, but guides will often recommend renting one for the trek. They are also available at some medical stations along common trekking trails. Just consider that renting a Gamow bag (~US $100 per week) is cheaper than calling for a helicopter (~US $4,000).

The reality is that anyone, regardless of their previous physical conditioning, is susceptible to the effects of elevation. Hikers may feel just fine during the day, but that can change drastically during the night. When trekking in the mountains you must understand that you will be taking your time to acclimatize. Stop and smell the yak dung! Give your body a fair chance at acclimatizing by making only a gradual daily elevation gain, generally 1,000 feet per day (contingent on being free of any symptoms of altitude sickness). A well-established practice is to climb high during the day, and sleep low at night. Pushing the envelope during the day (as long as you have absolutely no symptoms of altitude sickness) takes advantage of the fact that the exertion of hiking keeps your respiration up. Since your body is at a great disadvantage during the night due to the lower respiration rate of sleep it is imperative that you allow the greater level of oxygen at a lower elevation. Some hikers choose to take acetazolamide tablets to help the acclimatize faster, and it does help in many cases, but since it is a prescription medication it would be wise to use it only under experienced medical supervision, and that doesn’t mean a fellow hiker saw it in a movie once. A Sherpa guide will make sure you get lots of fluids, in the form of his Tibetan tea and Sherpa garlic soup.

Here is a table showing the relative volume of oxygen at various elevations as compared to sea level (100%).

Elevation (feet)	Relative Volume (%)	Notes
29,035	33	Mt. Everest Summit
26,000	37
23,000	41
20,000	47
18,000	50
14,800	57
13,000	61	Hotel Everest View
9,300	70	Lukla Airfield
3,200	88
-0-	100	Sea Level