Acute mountain sickness

Altitude sickness, also known as acute mountain sickness (AMS) or altitude illness is a pathological condition that is caused by lack of adaptation to high altitudes. It commonly occurs above 2,500 metres (approximately 8,000 feet). If untreated, the condition can result in death. more...

Another, rarer, type of altitude sickness caused by prolonged exposure to high altitude is chronic mountain sickness, also known as Monge's disease.

Introduction

Different people have different susceptibilities to altitude sickness. For some otherwise healthy people symptoms can begin to appear at around 1,500 meters (5,000 feet) above sea level. This is the altitude of Mexico City (2,240m.-7,349ft.) and Denver, Colorado (1,609m.-5,280ft). Diets high in carbohydrates may make people suffering AMS feel better. The carbohydrates seem to liberate more energy and oxygen compared to their lipid counterparts. High-altitude pulmonary edema (HAPE) and cerebral edema are the most ominous of these symptoms, while acute mountain sickness, retinal hemorrhages, and peripheral edema are the milder forms of the disease. The rate of ascent, the altitude attained, the amount of physical activity at high altitude, and individual susceptibility are contributing factors to the incidence and severity of high-altitude illness.

Signs and symptoms

Headache is a primary symptom used to diagnose altitude sickness. A headache occurring at an altitude above 8000 feet, combined with any one of the following symptoms, indicates probable altitude sickness.

• Anorexia (loss of appetite), nausea, or vomiting
• Fatigue or weakness
• Dizziness or light-headedness
• Insomnia
• Cheyne-Stokes respiration

The early symptoms of altitude sickness include drowsiness, general malaise, and weakness, especially during physical exertion. More severe symptoms are headache, insomnia, persistent rapid pulse, nausea and sometimes vomiting, especially in children. Extreme symptoms include confusion, psychosis, hallucination, symptoms resulting from pulmonary edema (fluid in the lungs) such as persistent coughing, and finally seizures, coma and death.

Severe cases

The most serious symptoms of altitude sickness are due to edema (fluid accumulation in the tissues of the body). At very high altitude, humans can get either high-altitude pulmonary edema (HAPE), or high altitude cerebral edema (HACE). These syndromes are potentially fatal. The physiological cause of altitude-induced edema is not conclusively established. For those suffering HAPE or HACE, dexamethasone may provide temporary relief from symptoms in order to keep descending under their own power.

HAPE occurs in ~2% of those who are adjusting to altitudes of ~3000 m (10,000 feet) or more. It can be life threatening. Symptoms include fatigue, dyspnea, headache, nausea, dry cough without phlegm, pulmonary edema, fluid retention in kidneys, and rales. Descent to lower altitudes alleviates the symptoms of HAPE.

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