Severe altitude sickness develops when reduced oxygen availability results in capillary leakage and generalized body-tissue swelling. The organs most seriously affected by this are the brain and lungs, producing the symptoms of the medical problem we call Acute Mountain Sickness (AMS). These two major components are called High Altitude Pulmonary Edema (HAPE) and High Altitude Cerebral Edema (HACE).

Assessment of AMS: In the early stages, symptoms are attributable to the chemical effects of having less oxygen per breath and the work the body has to do to make up for it. Later, more serious symptoms appear as edema develops throughout the body. Its effects are first noticed in the lungs and brain. Severe altitude sickness includes the effects of pulmonary fluid and increased intracranial pressure.

Mild AMS is characterized by mild headache, easily relieved by aspirin or ibuprofen, and slight nausea with little or no vomiting. The patient may experience slight dizziness, loss of appetite, and mild fatigue. There is usually some degree of insomnia and increased shortness of breath.

Moderate AMS produces severe headaches, not relieved by aspirin or ibuprofen, and persistent vomiting. The patient will complain of moderate fatigue.

Severe AMS (HAPE and HACE) is a life-threatening emergency. The patient will show changes in onsciousness and mental status. He may become ataxic (unable to walk straight) and severely fatigued and short of breath even at rest. The examiner may note a cough, possibly with gurgling respirations due to the accumulation of fluid in the lungs. The patient may appear cyanotic (blue or pale) and much weaker than others in the group.

The symptoms of severe AMS can be confused or mixed with those of other problems such as hypoglycemia (low blood sugar), dehydration, hypothermia, hyperthermia, and exercise exhaustion. All of these problems call cause a decrease in muscular performance and efficiency. All can cause changes in level of consciousness and mental status. Under most field conditions, the most practical approach is to include all five problems as possible causes until proven otherwise.

Treatment of AMS: This is where two days of prevention is worth 4000 feet of cure. The key is to recognize the mild form of Altitude Sickness and allow your body time to adapt.

Mild AMS is treated with mild pain relievers such as aspirin, ibuprofen, or Tylenol. The patient should avoid sedatives, such as alcohol or narcotic drugs, which can depress respiration. This is the time to rest at the present altitude or descend to a lower altitude until the body adapts. Diamox, available by prescription, is occasionally used to increase the rate of respiration by changing blood pH. Consult a physician about its use.

Moderate AMS is treated with pain medication, rest, and avoidance of sedatives. In addition, an immediate descent of 1000-2000 feet is recommended, if possible. The patient should be observed closely for increasing severity of symptoms. Be prepared for an emergency descent if symptoms worsen. Supplemental oxygen and steroids (by physician's prescription) may be helpful if available.

Severe AMS is treated using all the techniques covered under the mild and moderate forms, plus an immediate descent of 2000-4000 feet. Exertion should be minimized, but there should be no delay in descent.