High mountain ranges such as the Rockies, Andes and Himalaya offer some of the most spectacular hiking opportunities on the planet.
However, walking at high altitude brings with it certain inherent risks, the most common of which is altitude sickness, also known as acute mountain sickness (AMS).
Whilst the dangers of AMS are very real, it is a malady which is almost entirely preventable, so long as some basic precautions are followed before and during your hike.
What is Altitude Sickness?
- Altitude sickness is the name given to the collection of symptoms which can occur, when a person attempts to ascend too quickly at altitudes above 2,500 m (8,202 ft).
- Why does it happen? As altitude increases, atmospheric pressure decreases. As a result, less oxygen is available to the body’s tissues, which in turn means that the heart and lungs need to work overtime in order to compensate. If a person has ascended at such a rate that their body has not had sufficient time to acclimatize to the change in atmospheric conditions, altitude sickness may result.
- Initial symptoms of AMS include headache, dizziness, nausea, shortness of breath, difficulty sleeping and extreme lethargy.
- Advanced or severe symptoms include rapid pulse, irrational behaviour, loss of balance and coordination, severe headache, vomiting and persistent cough.
Prevention of AMS
The key is to acclimatize gradually. Keep in mind that there is no universal yardstick by which each and every hiker can gauge their tolerance to high altitude conditions. Everyone acclimatizes at different rates. If you take the necessary precautions and listen to your body, chances are you will be fine.
- If you fly directly into a high altitude city, be sure to take it easy for the first few days. Gradually increase your exercise workload. Factor in some touristy activities that involve walking. Going straight from the airport to the start of your trek is potentially putting yourself at risk of AMS.
- From the time you arrive drink at least 3 litres of water per day. The air is drier and thinner at high altitude, and due to cooler temperatures many hikers make the mistake of not drinking enough water.
- As the initial symptoms of AMS are similar to those of dehydration, people often assume they have AMS when in actual fact they are simply dehydrated. Either way, keep drinking. You will be peeing like a racehorse, but you will feel better for it. A good indicator as to whether or not you are sufficiently hydrated is your urine. The clearer the better.
- Note that both alcohol and caffeine increase dehydration. Limit your intake of both when hiking at high altitudes. This particularly holds true during the first few days of your hike.
- Don’t overexert in the initial stages of your hike. Pace yourself. Aim at becoming progressively stronger as the trek continues. Think tortoise rather than hare.
Climb High, Sleep Low
- Climb high, sleep low is the strategy by which you sleep at a lower elevation to which you have ascended during the day. It is said that when hiking above 3,000 m (9,843 ft), you should not increase your sleeping altitude (i.e. the altitude at which you make camp) by any more than 300 m (984 ft) per day. This is a conservative estimate, but considering the potential dangers of AMS, nonetheless represents a useful benchmark for people who are new to high altitude trekking. In the beginning, it is always better to err on the side of caution.
- In regards to the use of Diamox as a prophylactic for mild symptoms of AMS, I personally prefer the natural methods described above. However, if you have been particularly susceptible to AMS in the past and/or have a limited time frame in which to complete your trek (not advisable), then Diamox may help as a preventative measure. Consult your doctor if you are considering the use of Diamox or any other drug whilst trekking at altitude.
If mild AMS symptoms occur:
- Don’t ascend any higher.
- Drink lots of water.
- If necessary, take a couple of ibuprofen or paracetamol for headache.
- Once symptoms have subsided, which could take up to two or three days, it should be ok to start ascending again. Do so slowly and with awareness.
In case of severe AMS symptoms:
- Descend immediately (at least 500 m / 1,640 ft).
- Seek medical attention ASAP.
- Note that if your symptoms are severe, you are beyond the point at which Diamox or or any other medication (such as Dexamethasone) can provide relief. Your only option is to descend.
Other Altitude Illnesses
Less common, but more serious forms of altitude illness occur when fluid accumulates on the lungs (High-Altitude Pulmonary oedema or HAPE) and brain (High-Altitude Cerebral Oedema or HACE). For information on these conditions and other altitude related issues, see Traveldoctor.co.uk and Base Camp MD.