Acute mountain sickness (AMS): Acute mountain sickness (AMS)
is the effect on the body of being in a high altitude environment.
AMS is common at high altitudes, that is above 8,000 feet (2,440
meters). Three-quarters of people have mild symptoms of AMS over
10,000 feet (3,048 meters). The occurrence of AMS depends on the
altitude, the rate of ascent, and individual susceptibility.
Mild AMS: Many people experience mild AMS during the
acclimatization process (the first 1 to 3 days at a given altitude).
Symptoms usually start 12-24 hours after arrival at altitude and
include headache, dizziness, fatigue, shortness of breath, loss of
appetite, nausea, disturbed sleep, and a general feeling of malaise.
These symptoms tend to be worse at night when respiratory drive is
decreased.
Mild AMS does not usually interfere with normal activity and
symptoms generally subside within 2-4 days as the body acclimatizes.
As long as symptoms are mild, and only a nuisance, ascent can
continue at a moderate rate. When hiking, it is essential to
communicate any symptoms of illness immediately to others on your
trip. AMS is considered to be a neurological problem caused by
changes in the central nervous system. It is basically a mild form of
high altitude cerebral edema.
Mild AMS is usually treated with pain medications for headache and
a drug called DIAMOX which allows one to breathe faster and so
metabolize more oxygen, thereby minimizing the symptoms caused by
poor oxygenation. This is especially helpful at night when
respiratory drive is decreased. Since it takes a while for DIAMOX to
have an effect, it is advisable to start taking it 24 hours before
going to altitude and continue it for at least 5 days at higher
altitude.
Moderate AMS: Moderate AMS includes severe headache (not
relieved by medication), nausea, vomiting, increasing weakness and
fatigue, shortness of breath, and decreased coordination. Normal
activity is difficult. At this stage, only advanced medications or
descent can reverse the problem. Descending even a few hundred feet
(70-100 meters) may help. Definite improvement is usually seen in
descents of 1,000-2,000 feet (305-610 meters). Twenty-four hours at
the lower altitude usually results in significant improvement. The
person should remain at lower altitude until symptoms have subsided
(up to 3 days). At that point, the person has become acclimatized to
that altitude and can begin ascending again.
The best test for moderate AMS is to have the person "walk a
straight line" heel to toe. Just like a sobriety test, a person with
AMS will be unable to walk a straight line. This is a clear
indication that immediate descent is required. It is important to get
the person to descend before the AMS reaches the point where they
cannot walk on their own.
Severe AMS: Severe AMS presents as an increase in the
severity of the symptoms, including greater shortness of breath at
rest, inability to walk, decreasing mental status, and fluid buildup
in the lungs. Severe AMS requires immediate descent to lower
altitudes: 2,000 - 4,000 feet (610-1,220 meters).
The only cure for AMS is acclimatization or descent. (Based in
part on the Princeton University Outdoor Action "Guide to High
Altitude: Acclimatization and Illnesses" by Rick Curtis).
is the effect on the body of being in a high altitude environment.
AMS is common at high altitudes, that is above 8,000 feet (2,440
meters). Three-quarters of people have mild symptoms of AMS over
10,000 feet (3,048 meters). The occurrence of AMS depends on the
altitude, the rate of ascent, and individual susceptibility.
Mild AMS: Many people experience mild AMS during the
acclimatization process (the first 1 to 3 days at a given altitude).
Symptoms usually start 12-24 hours after arrival at altitude and
include headache, dizziness, fatigue, shortness of breath, loss of
appetite, nausea, disturbed sleep, and a general feeling of malaise.
These symptoms tend to be worse at night when respiratory drive is
decreased.
Mild AMS does not usually interfere with normal activity and
symptoms generally subside within 2-4 days as the body acclimatizes.
As long as symptoms are mild, and only a nuisance, ascent can
continue at a moderate rate. When hiking, it is essential to
communicate any symptoms of illness immediately to others on your
trip. AMS is considered to be a neurological problem caused by
changes in the central nervous system. It is basically a mild form of
high altitude cerebral edema.
Mild AMS is usually treated with pain medications for headache and
a drug called DIAMOX which allows one to breathe faster and so
metabolize more oxygen, thereby minimizing the symptoms caused by
poor oxygenation. This is especially helpful at night when
respiratory drive is decreased. Since it takes a while for DIAMOX to
have an effect, it is advisable to start taking it 24 hours before
going to altitude and continue it for at least 5 days at higher
altitude.
Moderate AMS: Moderate AMS includes severe headache (not
relieved by medication), nausea, vomiting, increasing weakness and
fatigue, shortness of breath, and decreased coordination. Normal
activity is difficult. At this stage, only advanced medications or
descent can reverse the problem. Descending even a few hundred feet
(70-100 meters) may help. Definite improvement is usually seen in
descents of 1,000-2,000 feet (305-610 meters). Twenty-four hours at
the lower altitude usually results in significant improvement. The
person should remain at lower altitude until symptoms have subsided
(up to 3 days). At that point, the person has become acclimatized to
that altitude and can begin ascending again.
The best test for moderate AMS is to have the person "walk a
straight line" heel to toe. Just like a sobriety test, a person with
AMS will be unable to walk a straight line. This is a clear
indication that immediate descent is required. It is important to get
the person to descend before the AMS reaches the point where they
cannot walk on their own.
Severe AMS: Severe AMS presents as an increase in the
severity of the symptoms, including greater shortness of breath at
rest, inability to walk, decreasing mental status, and fluid buildup
in the lungs. Severe AMS requires immediate descent to lower
altitudes: 2,000 - 4,000 feet (610-1,220 meters).
The only cure for AMS is acclimatization or descent. (Based in
part on the Princeton University Outdoor Action "Guide to High
Altitude: Acclimatization and Illnesses" by Rick Curtis).
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