ACUTE MOUNTAIN SICKNESS

ETYMOLOGY, PATHOLOGY, AND PATHOPHYSIOLOGY

 

High-altitude illness is due to a decrease in oxygen at high altitude.

 

Atmospheric pressure decrease as altitude increases but the percentage of oxygen in the air remains constant; as a result, the partial pressure of oxygen decreases with altitude and is at 5500m (18000 feet) is about ½ of that at the sea level.

 

High-altitude illness is seen in people in people who have recently arrived at high altitude or have just gained altitude, and may start any time from few hours to a few days after ascending. High altitude is arbitrarily defined as altitudes higher than 3.000 m (10.000 ft). people with heart and hung decreases may have difficulty at lower altitudes and, rarely, a healthy, a healthy person will develop altitude illness at as low as 2500 m (8.200 ft).

 

 

 

ACCLIMATISATION

A person exposed to altitude gradually develops an integrated series of responses that restore tissues oxygenation toward normal. The higher the altitude the more time full acclimatization takes. Above 55oo m deterioration is more rapid and there are no permanent residents. Major features off acclimatization include moderate hyperventilation, increased number of red blood cells enlarged capillaries. After many generations at altitude different populations have acquired slightly different strategies of acclimatization.

 

Remember when you GO High Mountain

CLIMB HIGH – SLEEP LOW

 

HOW IS SUSCEPTIBLE?

 Anyone proceeding to high altitude risks developing altitude illness. Some individuals are inherently more susceptible, others are rather resistant. Younger persons (children) are more risk than older ones, only partly because they generally walk faster. Differences in mode of ascent ( i. e. flying, driving or climbing to altitude), rate of ascent, overexertion, cold exposure, and dehydration may be predisposing factors.

 

SOME PREVENTIVE RECOMMENDATIONS:

Altitude illness is better to prevent than treat. Simple preventive measures can be very effective:

 

GRANTED ASCENT

 If taken passively to altitude ( e. g. by airplane), do not exert yourself or move higher for the first 24 hours. Ones above 3000m should not ascent faster than 300 m a day. While you are acclimatizing, it is best to go a little higher than the sleeping altitude- carry higher and sleep low. Take an acclimatization night for every 1000 m gained, starting at 3000m or so. This means sleeping at the same altitude for two consecutive nights.

 

AVOIDANCE OF OVEREXERTION

Bed rest is less beneficial than mild exercise. Packs should be lighter than at a lower altitude. The rest-step should be used when going up steep hills.

A climbing party should be placed at the rate of its slowest member. Even those with considerable altitude, experience are advised to follow all these recommendations to derive the maximum benefit of acclimation.

 

DRINKING ENOUGH FLUIDS

Drink enough fluids to maintain clear and copious urine. Water loss is greatly increased by over-breathing the dry air at high altitudes. So drink much more fluids than usual, but additional salt should be avoided. Alcohol seems to worsen high altitude illness.

 

LIGHT DIET OF CARBOHYDRATES

A light diet, high in easily digestible carbohydrates improves altitude tolerance and is recommended for the first few days.

 

FORCED DEEP BREATHING

Forced deep breathing is also beneficial.

No taking sleeping pills

Do not take sleeping pills (barbiturates, opiates) at altitude.

 

MEDICATIONS

There are no medications which we recommend routinely for the prevention of acute mountain sickness. Medication for this propose may be harmful, both because of side effects, and giving one a false sense of security. Acetazolamide (Diamox) has been found to have a considerable prophylactic effect against AMS (Acute Mountain sickness) but the physician should provide a prescription

 

CLASSIFICATION:

The spectrum of illnesses (or maladaptation) observed at high altitude include acute mountain sickness (AMS), high altitude pulmonary edema (HAPE) and high altitude cerebral edema (HACE or CE). There are other altitude-related problems such as retinal hemorrhages (bleeding spots in the back of the eye).

 

AMS (Acute Mountain sickness) is a complex of symptom (Boxes). These symptoms usually appear together, with variation among individuals. For the purpose of this discussion, AMS is divided into three categories: mild-moderate and severe. Pulmonary and cerebral edema is included in the serve category of AMS.

 

MILD AMS

Most persons with mild AMS are able to continue their ascent. The symptoms will usually disappear spontaneously in 24 to 28 hours. Mild AMS should be taken as a warning that one needs more time to acclimatize. It is best to stop and spend an extra day or night acclimatizing.

 

This will prevent progression to moderate AMS. People less tolerant of the symptoms usually need to descend only 200 to 300 m for relief and can then often re-ascent the next day.

 

MODERATE AMS:

It means the progression of symptoms to the point where one feels quite uncomfortable. The headache may be served ( only partially relieved by aspirin). There is often lassitude, weakness, loss of appetite perhaps with nausea, and difficulty with coordination. ( It is easy to test- heel to heel walking test, Romberg test).

 

There is the stage at which AMS must be recognized and dealt with correctly! Practically all cases of severe AMS are preceded by the moderate form, Persons with moderate AMS must stop ascending. If there is no improvement after a few hours (or overnight) then descent is necessary. The earlier may be necessary for recovery. Otherwise, 300 to 600 m (1000-2000 ft) is usually adequate. If descent is done early enough, renascent after recovery in two or three days is often possible.

 

If for some reason, the descent is impossible, oxygen if available should be given

 

SERVE AMS:

This is essentially the presence of fulminate pulmonary edema and/or cerebral edema. This category obviously overlaps with moderate AMS.

 

Signs of HACE are persistent vomiting, severe, persistent headache, gross fatigue, or extreme lassitude, delirium, confusion and coma, loss of coordination, staggering.

Signs of H.A.P.E. are: marked shortness of breath with only slight exertion, rapid breathing after resting ( 25 or more per minute ), bubby, we breathing, severe cough, coughing of pinkish sputum, rapid heart rate after resting ( 110 or more beats per minute), blueness of face and lips, and low urine output ( less than 500 ml).

 

The only treatment is Descent! Descent! Descent!

 

Do not wait for a doctor, a helicopter or rescue party, do not wait for the morning. A strong, healthy person should accompany the victim, avoiding exertion as much as possible. Oxygen, if available, may be given but it is not as effective as the descent. Often descent for 600-800 m will have miraculous results.

 

The best way to determine that illness (symptoms) at altitude is altitude illness is to go down a few hundred meters and see if you get better.

 

The drugs for AMS after is developed are DIAMOX (for severe headache), COMPAZINE (for nausea) and if symptoms are moderate or severe, OXYGEN, DEXAMETHASON (for cerebral edema), FUROSEMIDE, and NIPEDPINE (by H.A.P.E.). Medications can be given only by a physician.

 

The clearest symptoms of altitude illness to watch for in yourself are breathlessness at rest, resting pulse over 110 per minute, loss of appetite, and unusual fatigue while walking. The clearest ones to watch for in others are skipping fatigue while walking, antisocial behavior, being the last person to arrive at the destination. If you have Oxygen with mask and regulator or Portable altitude Chamber (Gamow Bag) you should give it to the victim.