Altitude sickness

Altitude sickness is the body's reaction to air with low oxygen content at high altitudes, caused by lower air pressure. It varies how the body reacts to this - some reactions are normal while others are signs of illness. The medical reactions are serious and can, if you do not end up in medical care, lead to death.

Background

The higher up from the sea surface you get, the lower the air pressure. The body has three main problems with high altitudes and the accompanying lower air pressure:

Air contains a lower amount of oxygen per unit. The body compensates for this by immediately increasing the work of breathing and the production of red blood cells in order to improve oxygen uptake. However, the process is slowed down by the body not allowing the displacement of the acidity in the blood that results from increased ventilation. To make increased ventilation possible, the kidneys therefore begin to secrete bicarbonate after two to three days of reduced oxygen content in the blood.

Red blood cells are constantly being produced, but it takes more than a week to form them. It is therefore impossible to get a true increase in red blood cells during the first week (see also the section on high-altitude diuresis).
Breathing is more inefficient in a supine position. This means that the lowest oxygen levels in the blood will occur at night, which means both that these are the ones that stimulate the most adaptation, and that this is when you run a greater risk of becoming ill.

The changes that the body undergoes at high altitudes are complex and can be quite dramatic. Some reactions are normal while others are signs of illness. The body's way of managing the oxygen supply and related problems is directly dependent on how high you are and on recent height changes. These are the main causes of altitude sickness.

For that reason, this article talks a lot about the changes in height, either on the way up or down. Getting higher and higher up from the sea surface is risky and you have to be vigilant about the body's reactions. In the same way, it is precisely the descent that constitutes the best help for people with moderate to severe altitude sickness.

Altitude sickness is very dangerous due to four causes:

it has a rapid course, it is deadly
the victim is usually far from medical expertise and thus difficult to evacuate to hospital
many of those affected trust their physique and fitness because they often stay and train in dangerous environments

How high is high?

A minority, about 20%, show some symptoms of altitude sickness if they stay and sleep in places 2,500 meters above sea level or higher. Many ski resorts and cities are so high and sometimes you hear, although it is rare, that people die of altitude sickness in ski resorts. However, most have no problem with altitudes up to 3,000 meters, although they may show some symptoms after the first night.

It is much more difficult to acclimatize to altitudes of 3,000-5,000 meters and it is absolutely necessary to go down to a lower altitude to sleep if you moved at a higher altitude during the day. Over 50% develop AMS (see below) if they reach up to 3,500 m.ö.h. from sea level without acclimatizing. Every will develop AMS if they go all the way up to 5,000 m.ö.h.

The highest permanent settlements in the Andes and Himalayas are just over 5,000 meters. There are also a few workplaces at or over 5,000 meters, such as the high-altitude observatory in Chajnantor, but there are oxygen generators running around the clock to prevent altitude sickness. The same technology is used on the train to Lhasa, maximum altitude 5,076 meters.

It is considered impossible to acclimatize to and stay permanently at altitudes above 5,500 m.ö.h. It is possible to stay for several weeks at an altitude of 6,000 meters once you get used to it, but your health will still gradually deteriorate.

Areas over 7,500 m.ö.h. mentioned as death zone. You quickly get worse if you stay at such a high altitude, several of the body's most important systems will stop working and climbers will only stay there for two to three days. The death toll for those who rise so high is 4%.

If you live in an area that is high enough (at least 1,500 meters) above sea level, you certainly have an advantage when you go even higher up, but it does not give immunity to altitude sickness. It just pushes the boundaries of what you can handle. Most healthy people who live at altitudes around 2,500 meters, an altitude where a number of larger cities are located, have little or no problems climbing to altitudes around 3,000 meters or even slightly higher, but they will also have problems with altitude. around 5,000 meters.

Risk factors

The absolute most important risk factor is not the height itself, but how fast you get there. Current safety rules tell you not to rise more than 300-500 meters per night camp above 3,000 meters, and to put in an extra night for every thousand meters . Walking / traveling higher during the day is not a risk factor, but on the contrary a basic rule for improving acclimatization: "climb high, sleep low" is the maximum for climbers.

The only way to get an idea of whether you will develop altitude sickness or not and if so, how much is through previous experience. If you have previously climbed to a high altitude without problems, it is perhaps less likely that you will have problems with it in the future. If, on the other hand, you have been affected by heights, you must make proper changes in your behavior, ie. travel slower upwards in the first place.

Good physical condition is not necessarily a good factor, nor is physical strength or good health. Age is not a factor in itself either, statistically so those who are more than fifty years have something lower frequency of altitude sickness, even with the same activity. You can react strongly to heights even if you are fit, young and healthy. The young, healthy and well-trained can come across an unpleasant surprise. If you know that you are in shape, you can easily be led to believe that you can handle heights well, which is far from always true. If you have no previous experience of high altitudes, it is best to assume that you can happen to perform altitude sickness just like everyone else.

Poor health, on the other hand, is of course a risk factor, especially if you have heart or lung problems. Healthy lungs and hearts must work hard to supply the body with oxygen at high altitudes. If you get problems from hard physical exertion, you should think before you go up - it gets much worse the higher up you are.

Impact and symptoms

Heights affect all people physiologically. These effects are not in themselves disease symptoms, but they are signs of the body's increased difficulty in getting enough oxygen.

Hyperventilation

To compensate for the decreasing air pressure, you will automatically breathe faster. It is possible that you do not notice this - something similar happens when you fly.

Height diuresis

Lack of oxygen leads the body to stimulate increased respiratory work by increasing the excretion of bicarbonate from the kidneys: lower pH provides a strong respiratory stimulation. This means that you urinate significantly more at high altitudes. This also results in an increased concentration of red blood cells in the blood, as the volume of fluid has decreased. If this does not happen, but you urinate less than normal, this may be a sign of dehydration, something that must be compensated with more drink.

Respiratory arrest

Due to the body's altered altered oxygen and carbon dioxide levels in the blood, as well as hyperventilation, the body's normal respiratory regulation is disturbed. As long as you are awake, you remember to breathe, but when you sleep, it happens that you hold your breath for up to 15 seconds to compensate for disturbances in the blood's acidity, and then start breathing quickly when it has been restored. This can be very worrying if you wake up realizing that you were not breathing or were out of breath, or if you notice that someone else has stopped breathing. However, this is one normal physical reaction of, above all, insufficiently acclimatized. Acclimatization helps, even acidifying medication.

Just as the body can suffer from less dangerous physiological problems, high altitude also makes it more susceptible to other diseases, several of them very dangerous. Even if you can not avoid all the effects at high altitude, you should prepare well for real diseases and, if it does occur, take it seriously and act accordingly.

Fluid balance

You need to increase your fluid intake at high altitudes. A decreased appetite, the precursor to nausea, can further lead to headaches caused by dehydration. Unfortunately, it is common to confuse dehydration with AMS (see below) and vice versa. If the headache does not go away after drinking about a liter of fluid, it should be seen as a symptom of AMS. Headaches due to dehydration can also be detected if you compare heart rate: if your heart rate goes up more than 20% when you stand up after lying down for five minutes, you need more fluid. Extreme water intake, with water-clear urine, can cause hyponatremia, a life-threatening condition.

Acute altitude sickness (AMS)

Acute altitude sickness,Acute mountain sickness (AMS), is the most serious condition at high altitude: there are several different signs that the body is getting worse and has not yet adapted to the higher altitude.

To be completely safe, you should therefore Always assume that a condition may be a sign of AMS. The most common reason why people generally do not go down to lower altitudes when they really should do so is due to poor judgment. In many cases, you think that AMS is just a sign of weakness, that your condition makes it impossible for you to suffer from AMS or think that the reason you feel bad is that you have a cold or the like. Therefore, always assume that it can be AMS: like seasickness, it can affect everyone, regardless of whether you are healthy and strong or not. If it turns out that the nausea is due to something else, it is at least best to go down to a lower height because it makes the body easier to handle the situation.

In principle, you can say that if you have just climbed to a higher altitude and sheep headache or any other abnormal symptom then you have suffered from AMS. Other signs of AMS may vary, but may for example consist of:

fatigue
dizziness
decreased appetite
nausea or vomiting
confusion
difficulty moving (ataxia)
difficulty breathing
a general feeling of being really sick

In particular, the last three symptoms are a sign that you are quickly getting sick of it. You should never wait for these symptoms before deciding to have AMS, but they are quite clear signs that you have HACE or HAPE (see below).

It is important to keep an eye on each other and be aware of the symptoms of AMS, if you suffer from it or if you get worse quickly. Very sick people can become confused and have difficulty determining how sick they really are. Decreased or lost appetite is a very clear sign: those who have climbed or walked for a whole day should be really hungry in the evening.

If you have AMS or symptoms of AMS, do not climb higher. Instead, seriously consider returning downhill.

If you experience symptoms of HACE or HAPE, go down immediately. It is a directly life-threatening condition.

Cerebral hepatic edema (HACE)

Cerebral altitude edema. high altitude cerebral edema (HACE) is the last stage at AMS. Similarly, AMS can be seen as a mild form of HACE. When you suffer from HACE, the brain swells and does not function properly.

The symptoms of HACE are many, especially various mental signs such as fatigue, dizziness and irrational behavior. The most obvious is ataxia, ie difficulty moving. If you want to do a test on this, you can try to walk along an imaginary straight line and put your feet immediately after each other, much as if you were walking on a rope. Those who are healthy can do this without major problems, but those who show signs of HACE will not be able to keep their balance.

HACE is very serious and it may only be a matter of a few hours to help someone with HACE.

High altitude pulmonary edema (HAPE)

High altitude pulmonary edema, high altitude pulmonary edema (HAPE), is another very serious ailment. It sometimes appears with AMS or HACE, but sometimes does not. This is believed to have various causes. When you suffer from HAPE, your lungs fill with fluid. Signs of HAPE may include fatigue, shortness of breath (unless it is due to something else - take a break and see if the shortness of breath comes with it), cough (especially mucus cough and possibly with blood traces), runny or heavy breathing, chest pain or blue lips, fingers or other extremities. Sometimes fever can occur. HAPE usually occurs at night.

HAPE is a very serious condition and should, like HACE, be treated as an emergency.

DCS

Pressure disease, decompression sickness (DCS), also known as caisson disease, is a severe disease when small bubbles of nitrogen form in the blood and thus complicate the blood supply in the body. Symptoms may include tingling in body parts, itching, rash, confusion and fainting. DCS occurs during very rapid changes in air pressure (in practice a change in altitude), for example if an aircraft where you are suddenly loses cabin pressure. However, a rapid rise in altitude, for example with an airplane, usually does not cause any problems. An exception may be if you have recently dived, after which you should avoid staying at a higher altitude than the level where the diving took place for 12-24 hours.

Prevention

Gradual acclimatization

Acclimatization is the process where the body gradually gets used to higher altitudes and air with lower oxygen content by stopping at regular intervals and staying at the various altitudes on the way up. The most important thing here is that you gradually increase the "sleep height", ie the height where you spend the night. If you are hiking or climbing, a common strategy is to spend a day (initially part of a day) at a higher level but return a bit to sleep. This also works for those who practice winter sports at high-altitude ski resorts - feel free to stay at high altitude during the day, but sleep in the valley at night.

Fluid balance

Adequate fluid intake is important, especially to be able to rule out dehydration as a cause of headaches. Drink enough to be able to maintain good urine production, with a thin yellow color. Increase fluid intake if your urine starts to get a stronger color, and try a single dose of up to a liter of water for headaches to make sure you are not dehydrated. Do not try to get in you dramatically increased amounts of fluid, it increases the load on the heart and kidneys and can in the worst case cause disturbances in salt and electrolyte balance.