Altitude and Travel
Introduction
Travelling to destinations at high altitude can be exciting, challenging and rewarding. Travellers going on high altitude excursions, treks or expeditions must research thoroughly, plan and prepare carefully (in some instances may include physical training) well in advance of travel, particularly if inexperienced in high altitude travel.
High Altitude
Between 2400-3658m
Cochabamba, Bolivia - 2550m
Bogota, Colombia - 2645m
Quito, Ecuador - 2879m
Cuzco, Peru - 3225m
Very High Altitude
Between 3658-5500m
La Paz, Bolivia - 3658m
Lhaza, Tibet - 3685m
Everest Base Camp - 5500m
Extreme Altitude
Between 5500-8848m
Mt Everest summit - 8850m
Mt Aconcagua - 6962m
Mt Kilimanjaro - 5895m
Good medical insurance that covers medical evacuation and repatriation is strongly recommended for those travelling to area of high altitude.
There are risks associated with high altitude including exposure to ultraviolet (UV) radiation, cold and the risk of developing altitude Sickness.
Climate Considerations
Sun Protection
The higher the altitude, the higher the exposure to UV radiation.
Protection against UV light should include:
wearing clothing that covers the skin and is impermeable to ultraviolet light
a facemask or balaclava may be required to protect against cold and sun at very high and extreme altitude
using a sunscreen that protects against UVA, UVB and UVC with a high sun protection factor (at least SPF15)
lips, ears and nose should be protected with a high protection sunblock
wearing sunglasses which filter out UV light.
Cold Protection
In areas at very high altitude, low temperatures combined with lower blood oxygen levels increases the risk of frostbite. The risk is even greater in those who already have poor circulation. To help prevent injury from the cold:
wear correctly fitting clothes that are approved for cold climates; gloves, hats, socks, boots
a facemask or balaclava may be required to protect against cold and sun at very high and extreme altitude
keep hands and feet dry, change wet socks and gloves promptly
wear goggles at very high altitudes.
Acclimatisation
At altitude the air pressure is lower than at sea level and gets lower as you climb higher. This means that although the amount of oxygen in the air remains constant, the amount of absolute oxygen in the lungs and the blood is less.
Oxygen is necessary for energy and for the body to function normally. The body will adapt to lower oxygen levels and responds by breathing faster and deeper and making more red blood cells to carry oxygen around. This response, called acclimatisation, takes around 3-5 days to occur but will vary between individuals and environmental conditions.
Pre-existing Medical Conditions
If appropriate care is taken, most people can travel to high altitude destinations. However, travellers with certain medical conditions should seek expert medical advice pre-travel to ensure their condition is stable and will not be worsened by altitude. These conditions do not predispose to altitude sickness.
These include:
diabetes
epilepsy
heart conditions
lung conditions including chronic obstructive pulmonary disease and moderate/severe asthma
sickle cell disease.
Pregnancy
Pregnancy is not thought to increase the risk of altitude sickness, but if it occurs it can cause reduced oxygen levels in the placenta, which may be dangerous to the fetus. Travel to altitudes up to 2500m is considered safe; the World Health Organization advises avoiding sleeping at altitudes > 3000m during pregnancy. Pregnant women travelling to altitude should consult their obstetrician and a specialist travel advisor pre-travel.
Altitude Sickness
Altitude sickness occurs if the body fails to, or has not had enough time to, acclimatise to altitude, the exact mechanism for this remains unclear. The risk of altitude sickness increases with altitude; up to 25% will suffer at 2500m, whilst up to 75% will suffer > 4500m.
Altitude sickness at best is unpleasant; at worst it is a life-threatening condition that develops rapidly. There are three forms of altitude sickness:
Acute Mountain Sickness (AMS)
High Altitude Pulmonary Oedema (HAPE)
High Altitude Cerebral Oedema (HACE)
Acute Mountain Sickness
AMS is more likely to occur in those who do not take time to acclimatise properly or arrive directly at areas of high altitude e.g. Cusco in Peru (3300m). The higher and faster the ascent, the more likely that AMS will occur. Anyone can suffer from AMS regardless of age, gender, level of fitness or training.
Signs and Symptoms of AMS
Symptoms of AMS do not usually develop immediately upon arrival but occur between the first 4 - 36 hours at altitude. There is a wide variation in the rate of onset and the height at which they occur. Early, mild symptoms are similar to that of a hangover:
headache
loss of appetite
nausea or vomiting
fatigue, flu like symptoms
dizziness
poor sleep and irregular breathing during sleep.
AMS can be diagnosed in adults using the a self assessment Lake Louise Symptom Score:
anyone who has recently ascended to over 2500m and has a score of 3 or more should be considered to have AMS
Treatment of AMS
be aware of the signs and symptoms of AMS and recognise them early. Let someone know that you are beginning to feel unwell
if early signs and symptoms of AMS are noticed then stop and rest at that level
do not go any higher
take analgesics to treat any headache e.g. ibuprofen or paracetamol
maintain a good fluid intake
once fully recovered ascent can begin again with care
if the symptoms of AMS do not improve over a day then descent of 500-1000m is necessary.
Acclimatisation and Prevention of AMS
There is no guaranteed way to prevent AMS but acclimatisation and slow ascent are strongly advised. Recommended rate of ascent at altitude according to expert guidelines are:
Daily Assent: 300-500m
Rest Day: Every 600m-900m /Every 3-4 days
Maximum Daily Gain: 800m
Gradual ascent is the most important preventive measure:
the major cause of altitude sickness is going too high too quickly
Those travelling in a group/tour are more at risk of AMS as the tour follows a set itinerary which may not suit all participants:
choose a trip with time for gradual acclimatisation built in
ideally avoid flying directly to areas of high altitude
take 2-3 days to acclimatise before going above 3000m
maintain a good intake (not excessive) of fluids
gentle exercise only for the first 2 hours
eat a light but high calorie diet
avoid alcohol.
Acetazolamide (Diamox)
Acetazolamide (Diamox) can prevent symptoms of AMS by increasing the rate at which the body acclimatizes. It may be considered in those susceptible to AMS or where a rapid ascent is unavoidable. It can be prescribed by your GP or Travel Advisor if felt appropriate for you.
It should not be used as an alternative to a slow ascent.
The dose is 125mg Acetazolamide (Diamox) twice daily:
consider trial at sea level for two days before a visit to high altitude
commence 2- 3 days before ascent
discontinue 2-3 days after reaching highest sleeping altitude, or once descent has begun.
symptoms of AMS may still develop when on Acetazolamide (Diamox) and must not be ignored
if are allergic to sulphonamide antibiotics you may also be allergic to acetazolamide (Diamox) and it may therefore be inadvisable to take this drug.
Common side effects:
increased urine output (it is a diuretic); tingling in fingers/toes, facial flushing and altered taste, especially of carbonated drinks.
dizziness, vomiting, drowsiness, confusion and rashes.
A range of other medicines and products (Coca tea in South America) have been suggested to be of benefit in preventing AMS. As yet there is not enough evidence to support the use of any of these substances.
HACE and HAPE
If AMS is ignored and ascent continues then there is a real risk that either or both of the two serious forms of altitude sickness will occur: High Altitude Cerebral Oedema (HACE) and High Altitude Pulmonary Oedema (HAPE).
HACE is due to swelling of the brain occurs in approximately 1% of people who ascend to 3000m. Symptoms include:
severe headache
unsteadiness or inability to walk in a straight line heel to toe
vomiting
drowsiness
becoming confused or irrational.
HAPE is caused by fluid gathering in the lungs and is the most common cause of death from altitude sickness. Symptoms include:
breathlessness – this is progressive and will occur at rest
marked fatigue
fast pulse
bluish discolouration of the skin (cyanosis).
Both conditions are medical emergencies and can be rapidly fatal; descent must be carried out immediately.
The person suffering from these conditions should be carried down to lower altitude; added exertion would worsen their condition. If descent is problematic, air evacuation by helicopter (if available) may be required.
Further Information
Read more: Acclimatization and Altitude Sickness - How To Prepare and What You Need To Know
Altitude.org
This website is produced by UK doctors and aims to provide information about high altitude and its effect on the body. It includes several useful interactive altitude calculators and detailed tutorials about altitude sickness and also allows individuals who may have had HAPE to register on a HAPE database
Medex.org
This website provides support for those carrying out medical expeditions. The Travel at High Altitude booklet is an excellent resource for those planning a trip at altitude and for carrying with them
View the Travel at High Altitude Booklet Information for Doctors/Climbers/Trekkers.
British Mountaineering Council
British Mountaineering Council website is very comprehensive and informative with additional records on all aspects of health whilst mountaineering.
Resources
Download the High Altitude Mountain Pack List
Download the Kilimanjaro Pack List
Download the Lake Louise Symptom Score for AMS
Disclaimer: This information has been developed for educational purposes only. It is not a substitute for professional medical advice. Should you have questions or concerns about any topic described here, please consult your healthcare professional.
