Altitude sickness is a physiological reaction to the lower oxygen amount available at high altitudes due to the lower air pressure. The body will respond in various ways to the relative low content of oxygen. Some are in normal, some become ill. The illness causes a health hazard. It can result in death, if he or she ignores it or leaves it untreated.
The further people move away from the sea level up into higher altitudes, the lower the air pressure is. The body has two main problems with high altitudes and the corresponding lower air pressure.
＊Due to the lower air pressure at the high altitudes, the body intakes less oxygen per lungful. It adjusts to the lower oxygen content by making more red blood cells to carry oxygen efficiently. However, this process takes more than a week, and in the meanwhile travelers may get ill.
＊The lower the air pressure is, the faster water evaporates. It can lead to dehydration. The physiological changes caused by dehydration are quite complex and dramatic.It causes the body difficulties on maintaining a good oxygen supply and keeping related problems under control. The difficulties are directly related to both the very altitude and the recent changes of altitude.
The above are two major factors that cause altitude sickness.
Travelers must be aware that the risk is higher ascending further away from sea level. They also must be alert to the duration of ascending. The shorter the duration is, the higher the risk is. Conversely, the single most important factor that reduces or eliminates all forms of altitude sickness is descending towards sea level.
There are four major reasons why altitude sickness is dangerous. Firstly, it attacks people in a rapid progression. Secondly, it can result in death. Thirdly, sufferers are usually in quite a distance from medical help and are not able to evacuate swiftly. The last but not the least, the sufferers are over-reliant on their health, because they have done a lot of physical activity in dangerous environment.
How high is the high altitude?
A minority of people, about 20 percent of people, may have some symptoms of altitude sickness, when they ascend to around 2,500 meters(8,000 feet) above sea level, and sleep there. However, most of people can acclimatize to 3,000 meters(10,000 feet) with relative ease. Perhaps, symptoms occur to them after the first night.
It is much more difficult to acclimatize the elevation of 3,000-5,000 meters(10,000-16,000 feet). When people reach this altitude, it is absolutely necessary for them to ascend slowly and return to a lower altitude to sleep after hiking around a higher altitude during the day. More than 50% of people will become ill, if they ascend rapidly from sea level to 3,500 meters(11,000 feet) without acclimatization, and nobody can feel well, if they rapidly ascend to 5,000 meters(16,000 feet). It is thought to be impossible to permanently acclimatize the altitudes above 5,500 meters(18,000 feet). It is possible to spend several weeks sleeping as high as 6,000 meters(20,000 feet) once acclimatized, but gradual deterioration of physiological well-being still occurs. Regions above 7,500 meters(25,000 feet) are referred to as the Death Zone. While people remain at such high altitudes, their bodies will deteriorate noticeably. Some major systems of the body will shut down. Even the professional climbers could only remain there for two or three days. Death rates caused by altitude sickness are estimated at 4% of all people, if they venture such high altitudes over 7,000 meters(23,000 feet). People who live in a high plateau gain a definite leg up on ascending to higher elevations. Their habitation is significantly above the sea level, but it could not make them immune to altitude problems. It only helps to push the threshold higher for the onset of altitude sickness. Most of healthy people who live at elevations of 1,500---2,500 meters(5,000---8,000 feet), an elevation range containing quite a few major cities, may suffer a little from the troubles caused by altitude sickness, when they travel to altitudes of 3,000 meters(10,000 feet) or a little bit higher. But if they go higher to 5,000 meters(16,000 feet) above the sea level, they will be also at risk of altitude problems.
Risk Factors
Altitude sickness tends to affect men more than women, particularly men between the age of 16 and 25. It is necessary to be aware that someone is young and healthy enough, even they never suffered altitude sickness in the past, it does not mean that they can immune it on the future climbs. On the other hand, bad health is a risk factor, especially cardiac and respiratory problems. It takes a hard enough time even for healthy heart and lung to get oxygen to the tissues at the high altitude. People should consider that the physical problems naturally make exertion difficult, and at high altitude the exertion would be much harder. In addition, scuba diving increases compression sickness. If someone has recently gone diving, and not yet fully gotten rid of nitrogen in his body, he should not ascend to a high altitude.
Effects of Altitude
High altitude causes some physiological effects on all people. The following effects are not the symptoms of illness, although they are signs of the increased difficulty that the body has got.
Hyperventilation
Due to the lower air pressure, people naturally breathe faster to compensate for the lower oxygen intake per lungful, although probably they will not notice it. It is a similar effect with air travel.
Altitude Diuresis
Increased urine is a response to hypoxia. The increase of bicarbonate makes it possible to increase breathing. It is the reason why people urinate a lot at high altitudes. If they are not urinating much more than they usually do, they must have been actually dehydrated.
Periodic Breathing
When people travel to high altitudes, their bodies’ respiratory controlling mechanism would become in disorder for the following reasons, the disruption to oxygen intake, carbon dioxide level in blood, chemistry changes in body and hyperventilation. While they are awake, they are able to breathe, but when they fall asleep, it is common for them to have interrupted breathing. They would be holding their breathing for up to 15 seconds, and then breathing rapidly when they start to breathe again. It is normal response to the high altitude, and happens to everyone.
Altitude Illnesses
Even though, the above effects of altitude are less dangerous, but the high altitude makes people susceptible to the following actual illnesses. Some are very dangerous!!! When it occurs, people should take it seriously, and take sensible steps to avoid the deadly strike caused by those illnesses.
Dehydration
A dehydration headache is the result of the following symptoms at high altitudes, the loss of appetite, the precursor to nausea. People need to increase their fluid intake, when they travel to high plateaus. Unfortunately, people often mistake the dehydration headache for AMS headache and vice versa. If a headache improves after drinking a liter of water, it is usually considered as the dehydration headache. Otherwise, it must be an AMS effect. Pulse rate comparing is another method to recognize the dehydration headache. The pulse rate usually goes up 20%, when someone stands up after lying down for 5 minutes. It could be recognized as the dehydration headache. They need more water intake.
AMS
The most common unhealthy response to high altitudes is Acute Mountain Sickness(AMS). It is a collection of signs that the body has been becoming ill and not yet successfully adapted the high altitude.
People should assume that any illness they get is AMS, when they travel to high plateaus. That is the most safe way for their travel. People usually fail to descend as soon as they should for the following bad assumptions. People assume that it is just a sign of weakness having AMS, that their fitness level does not mean they may have AMS. Sometimes they mistake their symptoms for the flu or some other illness. AMS happens to healthy strong people. Even if it does not turn out that people are indeed sick with AMS, descending to a lower altitude makes their body easier to heal anyway. It is necessary for people to assume AMS at the beginning when they have the following symptoms of AMS, headache, dizziness, fatigue, nausea or vomiting, loss of appetite, confusion, walking difficulty or gait ataxia, feeling extremely ill and rattling breath. Particularly the last three are signs that people are becoming quite ill. It is very dangerous to wait for the onset of these symptoms which can help people to acknowledge that they have had AMS. The last three symptoms are fairly reliable indicators of HACE or HAPE.
People usually become confused and can not realize how ill they are, if they have AMS. Members should keep an eye on each other for the signs of AMS and if he or she is getting worse. The loss of appetite is a reliable sign to tell if someone has AMS, because anyone should be very hungry for a good meal in the evening after walking and climbing for a whole day. If someone has got AMS, he or she would better not ascend further. If someone has HAPE, he or she must descend immediately. Their life depend on it.
HACE(High Altitude Cerebral Edema)
HACE is short for high altitude cerebral edema. As the end-stage of AMS, when people have HACE, their brains swell, and stop working properly. Conversely, AMS is considered to be the mild form of HACE.
HACE can be tested by a number of signs, like confusion, fatigue, unusual behaviour and gait ataxia. Gait ataxia is the most reliable one to test if someone has got HACE. People can test it by walking heel to toe along a straight line on the ground. Healthy people can pass the test easily. But anyone who has HACE may has difficulty on balancing while they take the test. It is just the most reliable sign of HACE.
HACE is the leading cause of death, it is extremely serious. People can not have a few hours to help someone who is suffering from HACE. It is most important treatment to descend immediately for HACE. The sufferers who are experiencing HACE symptoms need a significant help. Dexamethasone is a drug that can be used to relieve symptoms, but it is just a temporary treatment to give more time for descent.
HAPE(High Altitude Pulmonary Edema)
HAPE is short for high altitude pulmonary edema. As another extremely sever altitude illness, it often occurs in conjunction with HACE or AMS. But sometimes it attacks people due to different causes. If a person has HAPE, his or her lung fills with fluid. Symptoms of HAPE include breathlessness, extreme fatigue, a cough, a fever, rattling or gurgling breath, very fast breath, very fast pulse rate, chest congestion, and blue extremities. The breathlessness is different from the interrupted breathing which could be recovered in 30 seconds upon waking. The cough usually is wet with blood in the sputum. The fever commonly sets in at night.
HAPE is an altitude illness as serious as HACE. Both should be treated as a critical emergency. Rapid descent is the most important. As a drug of choice for HAPE treatment, Nifedipine could only provide temporary relief.
Cheyne-Stokes Breathing
Above 3,000 meters(10,000 feet), some people may experience a periodic breathing during sleep. It is known as Cheyne-Stokes Respiration. The pattern begins with a few shallow breaths. Then a deep sighing respiration increases and rapidly falls off. Respiration may entirely cease for a few seconds. Afterwards, it begins again with shallow breaths. Climbers usually become restless and awake with a sudden feeling of suffocation, when breathing stops. It disturbs sleeping pattern and exhausts climbers.
Acetazolamide is a helpful drug in relieving periodic breathing. This type of breathing is considered normal at high altitudes. It is a sign of serious disorder, if it occurs first during a illness other than altitude illnesses, or after an injury particularly a head injury.
DCS(Decompression Sickness)
DCS is short for decompression sickness, also known as bends or caisson disease. It is a serious illness that blood supply to parts of body is blocked by the bubbles of nitrogen formed in the blood. Symptoms are persistent tingling or joint pain, itching rashes, fatigue, confusion and collapse. DSC is caused by extremely sudden changes in air pressure, such as loss of air pressure in a cabin of plane. Even a fast ascent to relatively extreme high altitude does not normally cause DSC, except for those who have recently being scuba diving. They should avoid to ascend to high altitudes within minimum 12 hour to maximum 24 hours depending on their diving activity.
Prevention
Keep Hydrated
It is necessary to drink adequately, around one liter extra of water. But it does not help to protect against AMS pushing large volumes of water. It can cause the same symptoms as severe as AMS due to electrolyte imbalance, like headache, nausea, vomiting and so on.
Acclimatize to Altitude Gradually
Acclimatization is a process that humans’ body adapts the lower oxygen level during ascending slowly to high altitudes. Climbers should ascend gradually, and spend some time for their body to adapt at each stop of ascent. Particularly, they should increase their sleeping elevation slowly. The sleeping elevation refers to the altitude climbers spend nighttime. It is a typical strategy for climbers to spend a day or initially a part of day at a high altitude and return to a lower altitude to sleep. It also works for people doing winter sports at high altitudes. For instance, people ski at the top of resorts, and sleep at the bottom.
Some recommended maximum increases of sleeping elevation are listed below:
＊ascend less than 2,400 meters(8,000 feet) for the first night
＊limit the increase of sleeping elevation at going up by 300 meters(1,000 feet) per night after reaching 3000 meters(10,000 feet) above the sea level.
＊spend a second night at the same altitude after having ascended every 1,000 meters(3,000 feet)
The above recommendations help most people to stop from proceeding to AMS. During acclimatization, it is helpful to adequately intake non-alcoholic drinks.
Avoid Rapid Ascent
Rapid ascent is the opposite of acclimatization. Climbers should avoid to gain altitude faster than recommended above. For instance, it is distinctly unwise to fly from sea level to Lhasa, Tibet, where is 3,700 meter(12,000 feet) above sea level. If someone plans to travel around Tibet, they would better spend several days at an intermediate altitude, and not go to some inhabited areas where are over 5,000 meters(16,000 feet) above the sea level until they have been thoroughly acclimated in Lhasa.
Most likely, rapid ascent over recommended above makes climbers to get AMS and it makes the process to serious illness faster. When the symptoms occur, people could only have a short time to descend. Climbers must be wary of rapid ascent, particularly any sudden ascent to over 3,000 meters(10,000 feet).
Oxygen Equipment
It is necessary to prepare oxygen equipment. Some climbers died of altitude illness, because they were not acclimatized to low oxygen level at high altitudes. But if they prepared oxygen equipment, they would survive. But the oxygen equipment is only used in emergencies, because it takes time for the body to get acclimatized to the low oxygen level, and if they use the oxygen equipment at the very beginning when the altitude effects occur, the body may not acclimatize any longer.
Restrain from Smoking and Drinking Alcohol
Climbers must be wary that smoking and alcohol intake may cause the body unable to acclimatize to high altitudes. It is necessary climbers to restrain from smoking and drinking alcohol.
Avoid a Cold
If a climber gets a cold and AMS at the same time, it means that his life is in danger.
Treatment
As soon as the symptoms appear, the first priority for climbers is recovering. They must not ascend any further until the symptoms have disappeared. The process of acclimatization usually takes up to 48 hours. If the symptoms become even worse, climbers must descend immediately. Sometimes immediate descent could make the onset of symptoms disappear much faster, probably within hours.
If someone is getting sicker or his body is showing signs of HACE or HAPE, he must descend to a lower altitude as quickly as possible. If it is during nighttime, and if it is possible, do not wait for morning. They should descend as far as they could, at least to the altitude at which they spent the night without AMS symptoms appeared. Seeking a hospital care is needed, if it is possible.
People frequently become confused and exhausted whey they are affected by HAPE or HACE. They need a help for descent. Partners should try their best to help them to get descended.
Hyperbaric bags are a kind of equipment available to treat people with HAPE or HACE at high altitudes. The sufferer can lie in the bags which provide a higher pressure atmosphere. Likewise, because the shortage of oxygen intake is the main cause of HAPE or HACE, breathing oxygen from tanks may slow the onset of these illnesses, and provide some temporary relief of symptoms. Even the treatments mentioned above can buy some time for the sufferer when it is too dangerous to descend immediately, descent to a lower altitude is still not substituted.
DCS sufferers need a hospital care. Descent to even sea level is not sufficient for them to alleviate DCS symptoms. They should be treated in a recompression chamber. Like the treatment for HAPE or HACE, breathing oxygen provides some temporary relief of symptoms and allows time enough for rescue.
Acetazolamide
Acetazolamide is a drug which can stimulate breathing. It is sold as Diamox. originally designed as a treatment for glaucoma. The drug has a side effect of increasing breathing rate and depth, which has been proven to be helpful for climbers. It helps climbers to improve periodic breathing, acclimatize high altitude and recover from AMS more fast. Acetazolamide has some other side effects, like a mild to moderate diuretic effect. For this reason, an adequate intake of fluid is very important. The drug is used for people who once suffered from AMS, people who are suffering from AMS without the attempt to descend, people who have to be on a forced ascent. The forced ascent refers to any sudden ascent to high altitudes, for example, taking a flight to Lhasa from the sea level. It is also taken by many climbers as a prophylaxis. But the drug is not absolutely a preventative measure, particularly in the case of forced ascent. It is necessary to get a prescription and consult its proper dosages from a doctor.
Other Drugs
Some other drugs are also used for climbers, like Sameterol(serevent), Temazepam(Temaze), Dexamethasone and Nifedipine. Some of these drugs are made into capsules and sold in China. Gaoyuankang, for instance, contains dexamethasone. It is also purported that some herbal preparations help to prevent or treat altitude illnesses, such as Ginkgo Biloba and a combination capsule called Gaoyuanning sold in China, as well as coca leaves found in south America. But the effectiveness of these preparations still remain unproven and all of these drugs have significant side effects, especially dexamethasone, a potent steroid medication. It is necessary for tourists to consult their doctors prior to obtaining these medications. Foreign tourist should procure any necessary medications in their homeland, and must note what are the ingredients contained in the medications.
This article just offers readers some basic information about altitude sickness. It can never be a substitute for official medical advice.
