The pleasures of hiking and climbing high mountain altitudes cannot be understated. It can be quite the experience and accomplishment. When planning or thinking about these trips, we have to understand what is considered high altitude and how does this affect our physiology and health?
When we talk about high altitudes we are talking about the following heights:
2,500 to 4,000 metres
|8,000 to 13,000 feet|
|4,000 to 5,500 metres||13,000 to 18,000 feet|
|Extremely High||over 5,500 metres||
over 18,000 feet
High altitude destinations include: Cuzco, Peru (11,150ft), La Paz, Bolivia (12,400ft), Lhasa, Tibet (12,000ft), Everest Base Camp in Nepal (17,598 ft), and Kilimanjaro in Tanzania (19,341ft).
At these high altitude environment, the body will undergo the stresses of cold, low humidity, increased ultraviolet radiation, decreased air pressure, and the main concern hypoxia (a lack of oxygen). Hypoxia can have drastic effects on us. For example at 10,000 ft (3000m), we breathe in only 69% of what we would breathe in at sea level. With changes in concentration of oxygen available, the body needs to adjust and minimize the amount of hypoxic stress on the body. Hypoxic stress depends on three factors:
- Rate of ascent
- Duration of exposure
When trekking through the high altitude destinations, you can control two of these factors: rate of ascent, and duration of exposure. The human body does adjust well to higher altitudes but needs some time in the time it takes to ascend and sleep exposure at high altitudes.
Altitude Sickness is divided into three stages:
- Acute Mountain Sickness (AMS): this is the most common form which starts at ~ 8000ft (2500m). Symptoms are similar to an alcohol hangover: headache (starts 2-12 hours after landing), fatigue, loss of appetite, nausea, occasional vomiting. This usually resolves around 24-72 hours later (1-3 days). AMS can be mild, moderate or severe.
- The next stage is referred to as High Altitude Cerebral Edema. This is rare, but severe. Signs you are looking for here include AMS symptoms and profound lethargy, drowsiness, confusion, and ataxia. This requires immediate descent.
- High Altitude Pulmonary Edema: This can occur on its own or with HACE and can occur at altitudes of > 14,000ft. Signs you are looking for include: breathlessness with exertion, and eventual breathlessness at rest with weakness and cough. In this case you need oxygen or need to descent.
What can I do for excursion to ensure I don’t get sick?
There isn’t anything guaranteed, but there are a few key tips that can prevent or minimize the side effects of AMS.
- Drink water throughout your flight and as soon as you land drink 1L of water immediately.
- Drink 3-4L or water per day. With exercise and lack of moisture in the air, your body loses a lot of water so it is essential to stay hydrated.
- Notice signs and symptoms early.
- Ideally, you would want to take 3-5 days at each interval of climb. Meaning it will take some time to acclimatize to 8000-9000ft before proceeding to the next higher altitude. A general rule is once at >9000ft, move sleeping altitude no higher than 1600ft per day, and plan an extra day for acclimatization every 3300 ft.
- Descend if symptoms are getting worse.
- Avoid depressants: alcohol, and medications if possible (barbituratse, tranquilzers, sleeping pills, opiates).
- Avoid vasoconstrictors: Tobacco and caffeine.
This post is dedicated to my sister. She will be climbing Everest within the next month- Good Luck and Be Well Miranda!