Altitude Sickness :
Acute mountain sickness is better prevented than treated.
Peter Hackett, M.D.
Altitude sickness is an environment-related condition that can affect anyone who ascends too rapidly too high elevations without acclimatizing properly. High elevations are usually considered to be above 10,000 feet (3000m). In rare cases serious complications, including death, have occurred as low as 8000 feet (2500m). The most common problem at altitude is acute mountain sickness (AMS). Headache, lack of energy, and shortness of breath while walking or exercising are typical of the symptoms experienced, though the severity and onset vary with each individual. They do not necessarily occur together, nor do they appear at any specific elevation. In extreme situations, the symptoms of AMS may be the preliminary stages of the most serious and potentially deadly altitude-related illnesses, high altitude pulmonary edema (HAPE) and high altitude cerebral edema (HACE). Making a correct diagnosis, and making correct decisions to prevent further complications, are often a matter of following your instincts and using common sense.
The most effective way to prevent altitude-related problems is to give your body sufficient time to adjust to your new environment. Gradual acclimatization is important because the amount of atmospheric oxygen available for breathing at high elevations is considerably less than it is at sea level. At 10,000 feet (3000 m) the partial pressure of oxygen is 30 percent lower than at sea level; at 18,000 feet (5,500 m) it's 50 percent lower. With less oxygen in the air, the ability to perform tasks, even easy chores such as getting dressed, may be exhausting until the body adjusts. The lack of oxygen might also be responsible for triggering the symptoms of AMS.
In popular Himalayan trekking regions such as Nepal, trekkers are encouraged to ascend to high elevations at a slow rate that allows everyone in the party to acclimatize properly. In Tibet, gradual acclimatization is difficult due to the extreme elevation of the entire country; flying into Lhasa means landing at an elevation of around 12,000 feet (3660 m), while driving to Tibet from Nepal involves crossing Thang La (17,060 ft, 5200 m), followed by a night in Dingri or Shegar at about 14,000 feet (4270 m).
For most people the physical adjustment to higher elevations can happen rather quickly, requiring as little as a night of rest at the new elevation. If you fly into Tibet, the ideal situation is to spend 3 or 4 days in Lhasa before setting off on a trek. The first day should be treated as a rest day, though a half day of sightseeing at the Jokhang or strolling the Barkor market is fine. During the next few days be more active and try to spend at least a few hours every day going for walks, preferably into the hills. Dayhikes will help you warm up for your trek and the exercise seems to help the body adapt to the altitude. If your time is limited, a minimum of 2 nights should be spent in Lhasa before starting a trek that ascends above 14,000 feet (4270 m) on the first day.
If you are driving into Tibet from Nepal, consider spending a night acclimatizing in Nyelam before crossing Thang La. The stopover can make a big difference as to how you adapt to the higher elevations over the next few days.
Once a trek begins, the rule of thumb is not to ascend at a rate of over 1300 feet (400 m) per day. For every 3000 feet (1000 m) of ascent, plan on taking one entire rest/acclimatization day. If you're feeling well, use these days to explore nearby valleys or climb onto a ridge for panoramic views; it's better to stay active than laze around camp.
Some people just don't acclimatize well at high elevations, regardless of the precautions taken and how slowly they ascend. One medication that has been found useful for preventing the symptoms of AMS is acetazolamide a few hours before the flight to Lhasa, or the morning you depart from the Nepal-Tibet border. The usual dosage is one 250 mg tablet, 2 times a day, though some people prefer to take only half a tablet each time. (The smaller dosage is still effective but helps reduce the need to urinate frequently.) Do not take acetazolamide if you are allergic to sulfa drugs. It has no known harmful side effects and can be taken for several days, even weeks, though some people experience an unpleasant tingling feeling in the fingers, toes, or lips. Be sure to drink plenty of fluids to prevent dehydration while using this drug.
Maintaining an adequate fluid intake at high elevations may also be helpful in preventing altitude sickness. Most people need between 2 to 5 quarts (liters) of liquid per day to remain properly hydrated in Tibet's dry mountain climate. The color and volume of your urine is generally a good clue: drink enough to keep it clear and abundant.
Acute Mountain Sickness :
AMS is the general term for a number of high altitude--related symptoms. The severity of these symptoms and the rate of their onset depend on factors such as how fast a person ascends at high elevation, the maximum elevation reached, and the susceptibility of each individual. Most people who ascend to elevations between 11,000 to 20,000 feet (3,350 to 6100 m) will experience one or more of the following mild symptoms of typical AMS: headache, lack energy, lack of appetite, nausea, vomiting, shortness of breath while exercising, difficulty sleeping at night, light-headedness, peripheral edema (swelling of the hands, feet or face), Cheyne-Stokes breathing (a condition of unusual respiration patterns), or feelings similar to those accompanying a case of the flu. Any of these symptoms can appear on its own and be unrelated to an increase in elevation. If more than one symptom is present, the likelihood of having AMS is increased. A headache is one of the most common symptoms of AMS, though other factors such as overexertion, dehydration, and prolonged exposure to the intense mountain sunlight may also be the cause. Headaches of this type will usually go away after resting, having a cup of hot soup or tea, or taking aspirin or acetominophen. An AMS headache does not go away so easily and may linger on despite medication. Waking in the morning with a headache is also a sign of not acclimatizing properly, especially if the headache does not go away after you have moved about or taken aspirin. A severe or progressively worsening headache, particularly if accompanied by vomiting, lassitude, or ataxia (loss of balance), could well be the first sign of HACE.
In general, the best approach is to consider any symptom observed at high elevations to be altitude-related until it can be proven otherwise. Mild to moderate AMS symptoms are typically self-limiting and improve on their own after a day, or can be treated by stopping an ascent. Acetazolamide may be helpful for relieving AMS symptoms, though it is important to realize that is is not a cure for AMS. Acetazolamide can also be useful for stopping altitude-related insomnia and irregular breathing. Aspirin or acetominophen can be taken along with acetazolamide to relieve altitude headaches. Pain medications with codeine should be avoided because they can suppress the respiratory system. By depressing the body's blood oxygen levels. The same is true for sleeping pills, barbituates, sedatives, and alcoholic drinks. Administering oxygen (some rooms at the Lhasa Holiday Inn have oxygen outlets near the beds) is sometimes helpful at a flow of 2 liters per minute, though oxygen is not necessarily curative and the problems could return once it is discontinued.
If symptoms do not improve or become worse despite treatment, a more severe stage of AMS is indicated and further action is necessary to prevent deadly complications such as HAPE or HACE. Although several drugs are known to temporarily relieve these symptoms, the most guaranteed means for alleviating AMS is to DESCEND TO A LOWER ELEVATION.
Often a descent of 1000 to 3000 feet (600 to 900m), or to the elevation where the person last felt well, is all that is needed for rapid improvement. After a few days of rest, it may be possible to resume the trek and continue beyond the highest elevation previously gained if care is taken to acclimatize during the re-ascent.
Descending to a lower elevation is not always practical in Tibet; with serious cases of AMS the only choice may be evacuation by plane to the lower elevations of Kathmandu or to Chengdu in China's Szechuan province. Vehicle evacuation to Nepal may be the quickest alternative from the Everest region, though this involves crossing Thang La to reach the border.
Some people refuse to accept that they could have an altitude-related problem, or refuse to admit it to others in their group for fear of upsetting everyone's trekking plans. This is especially true with people who have had previous experience at high altitudes, but ascending to high elevations without complications in the past does not mean altitude problems cannot occur the next time.
Sometimes problems such as diarrhea or a cold-can tip the balance, causing symptoms of AMS to manifest. There are cases of mountaineers who successfully climbed Mount Everest, yet died later of severe mountain sickness while climbing a lower mountain. The majority of AMS deaths seem to occur when people deny their situation.
High Altitude Pulmonary Edema ( HAPE )
HAPE and HACE are considered the most dangerous forms of altitude sickness. Anyone suspected of suffering from their symptoms should be watched carefully; both illnesses can worsen overnight, becoming life-threatening in as little as 8 to 12 hours after being recognized. In many cases HAPE and HACE occur together.
HAPE occurs when the alveoli, or air spaces, that comprise most of the lung tissue become flooded with fluids. One of the first symptons is a dry, persistent cough that is present during exercise as well as at rest. Coughs caused by the dry air are common in Tibet, but a persistent cough that is not associated with a cold or a chest infection is a warning sign of HAPE. Other important symptoms are excessive shortness of breath and a long recovery time after exercise. Most people will experience some shortness of breath after being active at high elevations, but unusual labored breathing compared to others in the group could be due to HAPE. In HAPE's more advanced stages breathlessness occurs even after resting 15 to 20 minutes. The cough becomes wet and eventually produces frothy sputum (phlegm) that may have a pinkish color or be streaked with blood. Sometimes a gurgling sound can be heard in the chest. At this point death could be only hours away. Once HAPE has been diagnosed or is highly suspected, it is imperative that the affected person descend immediately to a lower elevation, even if it's late at night. If the person cannot walk unassisted, he or she should be carried in a litter or ride on a horse or yak. If oxygen is available, an initial flow of 4 to 6 liters per minutes should be used for 15 minutes, followed by 2 liters per minute. Oxygen is sometimes helpful for mild cases of pulmonary edema, but it is usually not curative without descending to a lower elevation. Recovery after descent can be rapid. There is no completely effective drug regime for treating HAPE once the symptoms are present.
High Altitude Cerebral Edema ( HACE )
HACE occurs when the brain cells fill with abnormal quantities of fluid, preventing the brain from functioning normally. The symptoms of HACE are basically the same as a moderate case of AMS, but are much more severe and unresponsive to treatment. It is important to differentiate between the two; the condition of someone with HACE can deteriorate rapidly, causing him or her to go into a coma or possibly resulting in death. Important signals to watch for are ataxia (lack of muscular coordination or balance), a severe headache, and vomiting. A headache caused by AMS can lead to vomiting and/or ataxia. These are good signs and must be treated as a preliminary stage of HACE. Lassitude (unusually intense, persistent weariness or marked indifference to everyday events such as eating or personal hygiene), mental confusion, and unusual behavior may also be present.
Ataxia is probably the best indication that a person has HACE. If someone staggers into camp at the end of the day looking quite ill, an easy test for ataxia is to have him or her walk slowly for 10 to 15 feet (3 to 5m), heel to toe, along a line drawn on the ground (heavy hiking or climbing boots should first be removed). A normal person should not have any difficulty passing this test; someone with mild ataxia will sway and be off-balance but can complete the test. Suspect HACE if the person steps off the line, staggers, or falls down. However, if a person has no other signs of AMS the lack of coordination or balance might be due to hypothermia or exhaustion. If the ataxia has not improved after he or she had warmed up with a hot drink and had a rest, preparations should be made to go immediately to a lower elevation. Ataxia may worsen quickly, forcing the victim to be carried in a litter. Oxygen should be administered at a flow of 4 to 6 liters per minute if available. Dexamethasone -a 10 mg injection initially, then 6 mg every six hours for no more than 3 or 4 days - is helpful when descent is impossible, or can be used in conjunction with descent to allow the victim to assist with the rescue efforts. This powerful anti-inflammatory steroid should only be administered by a doctor.
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