Altitude Illness

Ascending to high altitudes (> 21,000 ft) reduces the supply of oxygen needed to power the body.  The incidence and severity of altitude illness caused by hypoxic conditions is determined by the rate of ascent, altitude attained (especially sleeping altitude), length of exposure, level of exertion, lack of rest, level of hydration, and diet (high fat and protein intake increases risk). Additionally, there appears to be an inherent constitutional abnormality in some people that renders them physiological susceptible to altitude.

Acute Mountain Sickness (AMS)

Acute Mountain Sickness (AMS) is a group of symptoms that begin 6-72 hours after arrival at high altitude.

• Headaches due to the expanded blood volume needed to maintain oxygen diffusion to the brain.
• Malaise, an uneasy feeling characterized by drowsiness and lassitude.
• Loss of appetite, nausea, and vomiting result when perfusion of the gastrointestinal tract decreases as blood is shunted to vital organs.
• Peripheral edema causes fluid retention in the face and hands.
• Disturbed sleep manifested in Cheyne-Stokes respiration where the rate and depth of breathing increase slowly and then cease for 5-50 seconds further decreasing the oxygen level of the blood.
• Cyanosis, a bluish appearance in fingernail beds, mucous membranes, and around the mouth resulting from low blood oxygen saturation.

High Altitude Pulmonary Edema (HAPE)

High Altitude Pulmonary Edema (HAPE), a condition seen most often in young males, is caused by fluid accumulation in lungs which reduces the alveoli's ability to exchange oxygen and carbon dioxide with ambient air.  Symptoms begin 24-96 hours after arrival.

Symptoms of AMS Dry cough or shortness of breath during activity that changes to a wet cough producing blood-tinged spitum Rales (the sound of fluid in the lungs) Increased heart rate (> 110/min) and respiratory rate      (> 30/min) Patient experiences fatigue or becomes ataxic, lethargic, or unconsious

.  Fluid accumulation in the chest cavity of a patient with  high altitude pulmonary edema

Treatment: Administer oxygen and descend at least 2,000-3,000 feet until symptoms abate.

High Altitude Cerebral Edema (HACE)

High Altitude Cerebral Edema (HACE) occurs when damage to the brain tissue causes swelling within the cranium resulting in rising intercranial pressure.  Symptoms include:

• Signs of acute mountain sickness
• Change in level of consciousness
• Ataxia
• Severe lassitude
• Headache
• Nausea and vomiting
• Vision disturbances
• Paralysis
• Seizures
• Hallucinations

Thrombophlebitis

Thrombophlebitis is the increased tendency for blood to thrombose (clot) in arteries and vains possibly caused by dehydration, increased red blood cell volume, and immobility during bad weather.  It most often occurs within deep veins of the calf muscle.  If the clot breaks lose, an embolism blockage of the circulatory system in the lungs may result.

Acclimatization

courtesy of Dr. J. Bindon, University of Alabama

The best way to acclimatize to extreme altitudes is to climb high and sleep low.  By establishing camps at low altitudes and making day trips up the mountain, climbers can reduce their exposure to hypobaria.  Eating a high carbohydrate diet  reduces metabolic oxygen requirements though some fat and protein are still needed to meet the body’s nutritional needs.  Finally, drinking copious amounts of fluid will ensure maximum hydration and metabolic efficiency and conserve the scarce oxygen available at extreme altitudes.