I have been there a time to two: miserably hunched over my trekking poles, desperately sucking in seemingly non-existent oxygen and trying to not vomit on my hiking boots. Altitude sickness is no fun.
Before my Kilimanjaro trek, I spent several months researching altitude sickness prevention, symptoms, and remedies. Previously, I had climbed mountains in the western U.S. that were pretty high, but none in the year before my trip to Africa. I was stuck on the East Coast and not able to train for Kilimanjaro on any elevation higher than 6,000 feet.
Even so, hiking above 6,000 feet was pretty rare too since I was only able to squeeze in a couple of hiking trips to the mountains of North Carolina in that year before my trip. Most of my workouts were in the gym, or walking on flat ground.
The information presented here is gathered from several sources which include outdoor training manuals, hiking and trekking outfitters, medical journals, and personal experience. This information is not meant as a definitive source but instead, gives the reader a basic understanding of the environment and reactions the human body may experience at high altitude.
Please seek medical consultation prior to embarking on high altitude hikes. This article is not intended in any way to serve as medical advice.
Definitions of Altitude
- High: 8,000 – 12,000 feet (2438 – 3658 meters)
- Very High: 12,000 – 18,000 feet (3658 – 5487 meters)
- Extremely High: 18,000 + feet (5487 + meters)
The 7-day Machame Route that I took to the summit of Kilimanjaro climbed from high altitude on the first day all the way to extremely high at the summit.
The effects of the altitude on the human body at the summit of Kilimanjaro and mountains in its altitude class can be seriously brutal.
Environmental Changes at Altitude
As hikers ascend Kilimanjaro toward the summit, the barometric pressure of the surrounding atmosphere decreases. The air temperature also drops – for every 1,000 feet gained, approximately 5 degrees Fahrenheit are lost (10 degrees C lost per 1,000 meters).
The air becomes less dense, so essentially, there is less air to breathe. Many hikers refer to this feeling of less air and its associated breathing difficulties as “thin air.” While the percentage of oxygen in the atmosphere remains constant at around 21% there are fewer oxygen molecules for the given volume of air that you breathe in.
When ascending to high altitude, your body needs to deal with, and adjust to, the reduced amount of oxygen available for breathing with every inhalation. The changes that your body goes through to function on reduced oxygen is the process called acclimatization. The primary changes that can occur within the body include:
- Depth of breathing increases
- Pressure in the pulmonary arteries increase, which assists the body in delivering blood flow into parts of the lungs not always utilized at lower altitudes
- The body produces more red blood cells which aids the hemoglobin (oxygen carrier)
- Production of certain enzymes facilitate the release of oxygen from hemoglobin
- Urine production increases
Rate of Acclimatization
How quickly your body responds to the acclimatization process is affected by several factors. Primarily, how quickly a hiker ascends can determine whether the summit attempt is successful or not. The ideal target rate is to climb just 1,000 feet per day (305 meters per day), and for every 3,000 feet gained, it is recommended to spend an entire day at that altitude without going any higher.
If it is at all possible, spend an extra day at altitude before continuing to ascend. A good maxim to follow is to climb high and sleep low.
The physical condition of your body is also an important factor to successful acclimatization. Ensure your body is well-prepared from prior physical training and aerobic conditioning. Resting often while on the hike also helps give your body the best chance of reacting positively to the acclimatization process and changes in the environment. I trained for an entire year before my Kilimanjaro trek with aerobic conditioning classes three times a week and strength training at least twice a week.
Staying well hydrated and consuming a diet high in carbohydrates will help give your body the nutrients it requires for high altitude endeavors. (While I was training, I primarily followed a low carb, high protein diet which is the exact opposite of what is required at altitude. Once I reached 12,000 feet, our hiking team was served several options of high carbohydrate laden foods and very little protein.)
Types of Altitude Sickness
If your body is not able to deal with the change in altitude, there are three main types of altitude sickness that may become apparent:
- Acute Mountain Sickness: common symptoms that indicate you are not acclimatized to the current altitude include headache combined with loss of appetite, tiredness (even when at rest), dizziness, mild swelling of hands, feet, and ankles, and disturbed sleep. Fluid leakage on the brain is the primary cause of the headache and severe forms can lead to HACE.
- High Altitude Cerebral Edema (HACE): Excess fluid leakage causes mental impairment, and level of illness can be fatal. The symptoms include severe headache and impaired ability to walk. Ataxia, or the loss of coordination, is an easy sign to recognize. Descent is the ONLY cure.
- High Altitude Pulmonary Edema (HAPE): Fluid builds up in the lungs and triggers the warning signs of breathlessness even at rest, a cough (possibly with frothy or pinkish sputum), rattle-sounding breaths, extremely pale extremities, and drowsiness. HAPE can be confused with pneumonia but rapid descent from altitude quickly differentiates between the two. Pneumonia will not improve with decreased altitude.
Most of the hikers on my Kilimanjaro trek experienced mild forms of Acute Mountain Sickness, myself included. With many rest stops, a very slow ascent pace, and an extra day at high camp, all of us developed a tolerance for the increased altitude so we were able to continue up the mountain. Only one team member out of seven of us hikers did not make it to Uhuru Peak.
One of the freakishly scary things that happened to me beginning on about day 3 of the Kilimanjaro hike, when we were above 12,600 feet, was that I developed periodic breathing patterns, called Cheyne-Stokes respirations. This is not considered mountain illness, but it was still quite disturbing and frightening.
The Cheyne-Stokes breathing occurred most nights and resulted in wildly fluctuating breathing cycles during sleep. Often, I would startle myself awake and it felt like I might have momentarily stopped breathing. I had heard of others experiencing this, so I somewhat expected it to happen. I knew from my research that this is not considered to be abnormal at high altitudes and I took acetazolamide (Diamox) to help with this.
Diamox / Acetazolamide
Diamox is the brand name of a sulfa-based medication that is a carbonic anhydrase inhibitor. Essentially, its effect is to act as a respiratory stimulant. This impacts breathing, especially at night, and can eliminate the Cheyne-Stokes periodic breathing. Clinical trials have not been conclusive, but the drug is widely thought to increase the rate of acclimatization. This is not a wonder drug! It does not work for everyone in the same way, and it may not help you at all. Some key things to consider:
- Some people may be allergic to it and a prescription from your physician is required to get it.
- It is a diuretic.
- Side effects include tingling in the fingers, toes, and lips. Additionally, you may experience altered taste when eating and drinking and possibly ringing in the ears.
I elected to take Diamox for the entire duration of my Kilimanjaro hike. I reduced the prescribed dosage of 125 mg per tablet by cutting the tablet in half for the first days of the trip. Once we reached 13,000 feet, I took the entire 125 mg. dose twice a day. I still experienced the mild Cheyne-Stokes breathing patterns at night but did not feel significant effects of the altitude until summit night.
Summit night, even with the Diamox, was brutal. I wrote about my entire trip in a memoir titled Solo to Seven Six More in the Wind: A Memoir of Kilimanjaro that is available on Amazon. In the book, I describe summit night in great detail and the effects of the altitude on my body. For more information on my book, click here: Solo to Seven
Consult your physician for the best and most accurate advice regarding altitude medications. Most people who take Diamox find that an effective dose is 125 mg, taken twice a day, at breakfast and dinner. Consult your doctor and discuss your individual needs so you can do what is right for you.
This article is not intended to take the place of professional medical advice. Consult your physician for advice and information specific to your needs. If you follow the advice of your doctor, get physically fit, go on training hikes and acclimatize as much as possible, you might very well eliminate suffering from altitude sickness altogether.
Do you have any other tips for minimizing the effects of altitude sickness? Let us know in a comment below.
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