If you will be visiting mountain areas you should be prepared to recognise and respond to the symptoms of altitude illness which are caused by the lower level of oxygen available at high elevations. Although the human body can adjust to changes in altitude, the process (called acclimatisation) takes time. Acclimatisation is not completely understood, although there is some evidence that suggests genetic factors might play a part in an individual’s response to altitude.
Each person has his or her own “acclimatisation line.” Below it you probably won’t experience altitude illness, but going above it causes symptoms to begin. For most people, this line initially lies somewhere near 2,700 meters, but it can be adjusted by following preventive techniques.
The simplest way to avoid or reduce the symptoms of altitude illness is to ascend slowly to give your body time to become accustomed to changes in oxygen concentration. It’s also important to increase your fluid intake to counteract symptoms of dehydration induced by dry mountain air and increased respiratory rate.
Spending the night at or just below one’s acclimatisation line gives the body time to adjust. If you begin to feel symptoms of altitude illness, you are probably near your acclimatisation line. Once you reach your acclimatisation line, or an altitude of 3,000 meters, it is best to keep your total daily altitude gain under 300 meters. You can exceed 300 meters of altitude during the day’s climb, but you should descend to sleep at an altitude that is no more than 300 meters above the previous night’s altitude. Ascending during the day and descending partway to sleep will help you acclimatise more efficiently. Your acclimatisation line adjusts, and most people can continue climbing the next day. This is the source of the maxim “climb high, sleep low“.
Symptoms of altitude illness occur during ascent, not descent. If a group tries to push past the limits of its individual climbers, there is a good chance that those who are most susceptible will experience symptoms of altitude illness. If you or a member of your party becomes ill during ascent, you should always assume the problem is due to altitude illness and act accordingly.
Keep a log of the altitude at which your trip begins, the amount gained each day, and the altitude at which you sleep each night. If you become ill, this information will be very important.
Avoid using alcohol or any unnecessary medications since their effects may be increased at high altitudes. Sleeping pills, tranquilisers, and narcotic-based pain relievers, in particular, can cause serious problems at high altitudes because they can decrease breathing rate. Consult with your health care provider about any medications you plan to bring with you.
Three Types of Illnesses
Acute mountain sickness (AMS) typically appears at altitudes above 2,400 meters, though illness can begin at elevations as low as 1,500 meters in some individuals.
Symptoms usually appear within a few hours of ascent, and may include one or many of the following:
- muscle aches
- loss of appetite
- nausea or vomiting
- swelling of the face, hands, and feet
If you experience mild AMS symptoms, limit your activity level and remain at the same altitude for a day or two before resuming the climb. Aspirin or ibuprofen can be used for headache. If symptoms become worse during a day of rest, it is very important to descend until you begin to improve.
Additional drugs and oxygen treatment may be necessary, depending on the severity of the illness.
Consult your health care provider or travel medicine specialist for specific recommendations about prevention and treatment.
High Altitude Cerebral Edema (HACE) can be thought of as a worsening of AMS symptoms, with the addition of changes in consciousness and/or a loss of coordination as intracranial pressure increases. Persons affected may hallucinate, appear confused, and begin to stumble or stagger. They can have severe headaches and incapacitating fatigue. This is a dangerous form of altitude illness, and it can lead to coma and death.
High Altitude Pulmonary Edema (HAPE) is a buildup of fluid in the lungs that can occur along with HACE or as a separate illness. Like HACE, it is a medical emergency. Those affected will be breathless and very tired when walking and have a sense of fullness or pressure in the chest. Eventually victims will be short of breath even while resting. At this point the illness can rapidly progress to death. Victims must be guided back down and receive drug and oxygen treatment as soon as their illness is recognised as HAPE. They should be kept warm and assisted as much as possible, since exertion will make their condition worse.
Danger signs include severe headache, extreme fatigue, or breathlessness (especially while resting), and any neurological problems such as stumbling, confusion, poor judgment, or changes in consciousness.
It is crucial to descend until symptoms begin to diminish if these signs are present.
There is a good chance that those who have had altitude illness once will have it again at high elevations. If you have had altitude problems previously or if you are planning to go to extremely high altitudes, consult your health care provider to discuss your options for prevention and treatment of illness. If you have a pre-existing health problem (e.g., heart or lung problems, sickle cell trait or sickle cell disease, or other blood disorder), it is especially important to consult your health care provider. Cardiac or pulmonary evaluation or other types of screening might be needed before travel. Persons with sickle cell trait or sickle cell disease should be aware that even moderate altitudes -such as those encountered in airplane travel-can trigger a sickle cell crisis, and these persons should avoid high altitudes. People with low red blood cell counts could have difficulty adjusting to high altitude, since their oxygen-carrying capacity would already be low. People with too many red blood cells (a condition called polycythemia) could be at risk for blood clots at altitude. Your health care provider can advise you on prevention and treatment options if you have these or other pre-existing conditions, and can advise when you should avoid travel to high altitude.
Pregnant women should not trek at high altitude because of the isolation from medical care that would be needed in the event of early labor or complications of pregnancy and because of the rapid drop-off in oxygenation above 12,000 ft or so. There is no data available concerning the risks of altitude on the fetus.
There is very little data available on the effect of high altitude on young children. Anecdotal opinion is that very young children might be more susceptible to altitude illness than adults. When contemplating taking young children to high altitude, be aware that pre-verbal children will not be able to tell you how they are feeling and should be observed closely for signs that may seem vague, such as increased sleepiness, decreased appetite, or irritability. Children who can report on their symptoms are easier to monitor. (In addition to altitude, small children may have increased problems with cold weather and may be at risk for infectious diseases in a remote area if one is trekking in a developing country).
The decision to take a child to high altitude in a remote area should not be taken lightly, but can be done safely if the trip is oriented around the child and you are willing to descend readily if you are uncertain as to how your child is doing. There have been no altitude-related deaths among children in more than 30 years of trekking in Nepal.