Altitude sickness is also known as acute mountain sickness. It happens when you travel up to a high altitude - above 2,500m - without giving your body time to acclimatise to the surroundings. It happens because the air pressure decreases the further you are from the sea level, meaning less oxygen is getting to your heart and lungs. Acute mountain sickness feels similar to a hangover.
There are three types of altitude sickness: Acute Mountain Sickness, High Altitude Pulmonary Oedema and High Altitude Cerebral Oedema. Acute mountain sickness is the first step. If left untreated, it can quickly escalate into the two more severe and potentially fatal forms of altitude sickness.
Altitude sickness happens when you ascend to a high altitude too quickly. Climbing quickly does not allow the body to adjust to the height and the lower air pressure, causing difficulty getting adequate oxygen to the heart and lungs. If you plan a trek or climb, it is essential to prepare ahead of time as altitude sickness can affect anyone, even if you are an experienced climber.
Altitude sickness can feel mild at first, but it can escalate to become life-threatening. It's essential to be prepared for it and know how to seek medical assistance if required. Even if you are physically fit and a regular climber, this doesn't mean it won't happen to you.
Altitude sickness occurs at heights of 2,500m or higher. You cannot get it in the UK as the tallest mountain (Ben Nevis) is 1,345m. popular locations include:
Altitude sickness can be avoided by ascending to high altitudes above 2,500m at a slow and steady pace. Avoid taking a flight that lands in high altitude areas, instead take 2-3 days to get used to higher altitudes before travelling above heights of 2,500m. Other preventative measures include:
If you experience any symptoms of altitude sickness, do not ignore them. Stop and rest, do not continue climbing for the next 24-48 hours. You can take painkillers for headaches, and you can also take anti-sickness medicine if you experience nausea or vomiting. Stay hydrated and let any companions know how you are feeling, even if your symptoms feel mild. If altitude sickness escalates, confusion and denial of symptoms are common. If you do not feel any better after 24 hours, you must descend to a lower altitude.
Intermittent Hypoxic Training (IHT) or taking Acetazolamide are two ways of helping your body acclimatise quickly to high altitudes. IHT is interval training where you alternatively breathe in air with low oxygen and regular air through a mask. This gets your body used to lower blood oxygen levels before you travel to a high altitude. Acetazolamide is a medication you can access from a travel clinic or GP to prepare for your trip. You can also request it from Dr Felix, one of our GPs can issue a prescription and our UK based pharmacy can ship Diamox (acetazolamide) directly to your door. However, these methods may not always be effective. Always stop and treat symptoms of altitude sickness if they occur.
Acetazolamide can help to both prevent and treat altitude sickness. If you experience symptoms or feel unwell, the most important thing to do is rest and descend if you do not improve. The medication can help if you are unable to descend quickly.
Intermittent Hypoxic Training (IHT) involves practising air intake with lower oxygen, alternating with normal air with a mask. The training increases your body's tolerance to lower oxygen levels in the blood. This is to help your body acclimatise to the low oxygen and low air pressure at high altitudes.
A GP or a travel clinic can prescribe Acetazolamide before you travel if it is deemed suitable for you, Dr Felix can also prescribe and deliver this to your home or office. You should start taking it 2-3 days before beginning to climb to a high altitude. Acetazolamide can help your body to acclimatise to high altitudes quicker. However, it may not always prevent altitude sickness. If you experience any symptoms, then do not ignore them, always stop and rest. If they do not disappear within 24 hours, then you should descend right away.
Dehydration can lead to altitude sickness. At high altitudes, the humidity is higher than it would be at ground level and combined with the physical exertion produced during climbing, this means you will be sweating more. As a result, you need to drink a lot more water than you usually would to stay hydrated. Dehydration leads to headaches, fatigue and nausea.
Altitude sickness usually begins as acute mountain sickness. The symptoms can be mild, resembling a hangover, and it's typical to experience headaches, nausea, tiredness, dizziness and vomiting. If you do not seek treatment early, it can quickly escalate into more severe altitude sickness; HACE or HAPE. High altitude cerebral oedema (HACE) is the brain’s swelling, and HAPE, high altitude pulmonary oedema, is when fluid gathers in the lungs. Both of these conditions can be fatal.
Altitude sickness and cabin pressure are not quite the same things. The symptoms can be similar, but the change in cabin pressure causes discomfort or popping in the ears. This is not altitude sickness. It is possible to experience mild symptoms such as headaches, nausea, vomiting and dizziness.
Altitude sickness is caused by ascending to a high altitude of over 2,500m too quickly. Skydiving is a fast descent, and you are not at high altitude for long enough to get altitude sickness.
Altitude sickness can occur during a skiing trip. This is usually triggered by travelling on a ski lift. Symptoms are typically mild, given that you are not staying at a high altitude for very long.
Altitude sickness can occur at 2,500m or above. However, if you are at high altitudes for a short period of time, you should not get altitude sickness. You need to be over 2,500m for about 3-6 hours to experience altitude sickness.
Altitude sickness can affect anyone. However, people with certain medical conditions are at greater risk. These include those with:
Drinking alcohol can increase your risk of experiencing altitude sickness as it causes dehydration. It may also mask the symptoms and warning signs, as altitude sickness symptoms resemble those of a hangover.
Pre-existing medical conditions do not necessarily make it more likely that you will experience altitude sickness. Still, they can exacerbate symptoms or make it harder for your body to cope with them. If you have any of the following conditions, seek advice from a doctor before travelling to high altitudes:
If you are on any medications, then seek advice from a doctor before travelling to high altitudes.
Altitude sickness can be very dangerous if you are pregnant. The blood’s lowered oxygen levels will affect the amount of oxygen in the placenta, meaning the baby is getting less oxygen than usual. Pregnant women are advised not to travel to altitudes higher than 2,500m.
The symptoms of altitude sickness may feel similar to a hangover. They include:
Symptoms usually worsen at night and can escalate into severe altitude sickness if you do not quickly seek medical attention.
Altitude sickness does not usually occur right away. The symptoms will appear between 4 to 36 hours of being at high altitude. The first signs include a headache, nausea, sickness, feeling dizzy and tired. If you have three or more of these symptoms, this is known as acute mountain sickness, which can escalate into more severe altitude sickness if left untreated.
Acute mountain sickness is the least severe type of altitude sickness and is caused by going too high too fast without giving your body a chance to adjust. The symptoms resemble a mild hangover and include:
High altitude cerebral oedema is a more severe type of altitude sickness which occurs when acute mountain sickness accelerates. It causes swelling in the brain and statistically affects 1% of people travelling to high altitudes. The symptoms include:
HACE can become fatal in a matter of hours. If any of these signs occur, descend from the high altitude immediately and seek medical help.
High altitude pulmonary oedema is the third type of altitude sickness. This happens due to fluid gathering in the lungs and poses a severe risk of death. Symptoms can come on quickly and include:
Of all the types of altitude sickness, HAPE is the most likely to be fatal. If any symptoms occur, then descent must happen immediately as this is a medical emergency.
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