Altitude Sickness occurs when the lungs do not absorb sufficient oxygen. The amount of absolute oxygen absorbed into the body decreases the higher you go. Although the amount of Oxygen in the air is similar at higher altitudes, the air pressure is lower which results in less oxygen being inhaled and absorbed. If the incline is too quick and fast, the body cannot adjust to the change in air pressure which results in Altitude sickness.
In the last few years, excursions to high altitude destinations have greatly increased.
Climbing the various Mountains such as Mount Everest or travelling the Inca Trail has increased in popularity. This is partly due to the increased accessibility of trail routes and guides.
Many people now conduct high altitude excursions due to its challenge or even for various causes in order to raise awareness and money.
It can be physically and mentally challenging to undertake these types of excursions. We at Prescription Doctor want you to be safe and advise undertaking thorough research alongside your physical training to ensure you are well equipped for these challenges.
From a medical perspective, we want you to be aware of the possibility of Altitude Sickness and how it can manifest. It is important to understand the symptoms of Altitude Sickness in order to implement measures to treat and prevent potentially life threatening complications.
Altitude Sickness occurs when the lungs do not absorb sufficient oxygen. The amount of absolute oxygen absorbed into the body decreases the higher you go. Although the amount of Oxygen in the air is similar at higher altitudes, the air pressure is lower which results in less oxygen being inhaled and absorbed. If the incline is too quick and fast, the body cannot adjust to the change in air pressure which results in Altitude sickness. Therefore it is important to climb steadily and to rest when necessary in order to acclimatise to the altitude. Everyone is different, your acclimatisation period may be quicker or slower than others, however it is of primary importance to manage the climb at your own pace to protect yourself from Altitude Sickness.
Altitude Sickness is an umbrella term often used to describe the various associated conditions.
AMS can occur especially after 3000m when the ascent is too quick or if you fly into areas of high altitude, without allowing your body to acclimatise. Predisposing Heart conditions can increase the risk, however there is a common misconception that Gender, age, physical fitness increase the risk.
Previous performance at altitude is a good indicator in determining the risk of AMS. It also allows you to understand the rate of incline your body can take thus allowing yourself to effectively prepare for the challenge.
The Lake Louise symptom guide is an effective tool to measure the severity of Altitude Sickness. The guide describes AMS as the presence of headache and at least one other symptom, as listed below, after ascent to altitudes above 2500m.
AMS can lead to the potentially life threatening HACE if left untreated and ascent is continued. The continued lack of Oxygen can lead to swelling of the brain, this is dangerous and can be fatal if untreated. It is difficult to diagnose as it often be confused with other conditions such as Migraines. Medical assistance must be sought if HACE is suspected and treated promptly.
It precedes AMS and is characterised by:
If any of the above symptoms occur, medical assistance must be sought immediately and moving to a lower altitude may be essential.
HAPE is a respiratory complication and can rarely occur in the absence of Acute Mountain Sickness. It is usually developed when AMS is ignored or left untreated. It is difficult to diagnose especially at high altitudes and medical assistance must be sought if HAPE is suspected.
HAPE occurs due to an increase of fluid in the lungs and is associated with the following symptoms of:
The risk of altitude sickness is increased for areas 1500m above sea level. The risk increases if altitude ascent is increased too quickly which does not enable the body to acclimatise to the increased level. HACE and HAPE rarely occurs at altitudes lower than 2500m but symptoms of AMS can occur. It can generally take two days for symptoms to manifest after ascent to levels greater than 3000m. It is essential that medical assistance is sought immediately because the complications can be life threatening.
High Altitude is divided into 3 subcategories as detailed below.
|High altitude||Very high altitude||Extreme altitude|
|Altitude level||1500m to 3500m||3500m to 5500m||Above 5500m|
|Cities and Sites with High Altitude||Bogota |
|Everest Base camp |
Peru Inca Trail
Bolivia – La Paz
It is best to ensure you understand and are able to implement preventative measures to reduce the risk of Altitude Sickness. Previous experience in high altitudes does help however, there is still a risk if your body cannot acclimatise itself.
The NHS and various travel health organisations suggest ascending gradually especially above 3000m and at a pace suited to your body. It can take up to two days for the body to acclimatise to the altitude increase. The general recommendations for safe ascent at any level of altitude are:
The additional recommendations for altitude levels above 3000m are below:
If AMS symptoms are severe and last for more than 24 hours, descend to a lower level
Treatment options are dependant on the severity of the symptoms experienced. The Lewis Lake score can be used to ascertain the severity of the symptoms. The steps below should be considered if any symptoms are present in order to prevent further complications.
The following measures can be taken if the symptoms are not severe:
A medication called Acetazolamide (Diamox) can be given to help reduce the risk of Altitude Sickness. It is effective and is commonly used as a prophylactic treatment for travel to high altitudes. Our Doctors can provide a prescription for Diamox after a quick and easy consultation.
Page last reviewed: June 2018
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