How to Avoid High-Altitude Illnesses

Altitude training involves spending several weeks at a higher altitude (preferably over 2000 m or 8000 ft above sea level) to adapt the body physiologically. At elevations greater than 1200 m or 3950 ft, there is a decrease in atmospheric pressure which reduces the partial pressure of oxygen in inspired air. This causes decreased arterial oxygen levels and leads to increased ventilation and cardiac output, along with an elevation in heart rate. Performance will decrease for individuals that have not acclimatized to the change in pressure and are consequently exposed to a risk of high-altitude illnesses.

Acclimatization

Acclimatization is the process of adapting to the decrease in oxygen concentration at a specific altitude. With acclimatization, there will be an increase in heart rate, blood pressure, bicarbonate excretion, respiratory frequency and volume along with a reduction in plasma volume. To compensate for the decreased arterial oxygen levels, erythropoietin (EPO), a hormone in the body, will trigger more red blood cell production to aid in oxygen delivery to the muscles. Training at high altitudes allow athletes to produce additional red blood cells that will provide a greater cardiovascular effect on performance at competitions held at lower elevations.


Acclimatization requires an altitude exposure of more than 1 week. Staged ascents promote gradual and partial acclimatization when an individual resides at a moderate elevation before ascending to a higher elevation to reduce the adverse consequences of rapid ascent. The first stage of ascending should be greater than 3 days at a moderate altitude. Remaining at a moderate altitude for 3 to 7 days will reduce the symptoms and risk of altitude sickness. However, a time period of 6 to 12 days will improve athletic performance.

High-Altitude Illnesses

High-altitude illnesses can occur at elevations above 2500 m. Mild altitude illness can occur between 2000 and 2500 m.

Acute mountain sickness ( is commonly experienced by individuals 6 to 12 hours after ascending to elevations above 2500 m with the prevalence and severity increasing with higher altitudes. Symptoms include: headaches, nausea, dizziness, and sleep disturbance. Some risk factors may be a lack of previous acclimatization, history of migraines, age of 46 and above, or being a female. Symptoms typically resolve within 1 to 2 days with rest or with non-steroidal anti-inflammatory drugs (NSAIDs) such as aspirin. If symptoms become severe, descend immediately or use supplemental oxygen.


High-altitude cerebral edema (HACE) is a more severe form of altitude illness. Symptoms include: truncal ataxia (loss of body control), decreased consciousness, mild fever, and coma. If a headache is poorly responding to NSAIDs, then this is an indication of acute mountain sickness progressing to (HACE).

High-altitude pulmonary edema (HAPE) presents with a loss of stamina, dyspnea, dry cough, cyanosis (bluish skin), or pink, frothy sputum (phlegm). The risk of HAPE increases with increased altitude and faster ascents. HAPE occurs when fluid accumulates in the lungs due to rapid altitude ascent or ascent accompanied by strenuous exercise. Untreated HAPE may result in death approximately 50% of the time.

PREVENTION & TREATMENT

Prevention of high-altitude illnesses involve acclimatization before exposure, slow ascent, and appropriate pharmaceuticals for the corresponding illness. For mild AMS, take a rest day or descend 500 to 1000 m if there is no improvement in symptoms. For severe AMS, descend immediately and use supplemental oxygen at 2 to 4 L per minute. A hyperbaric may also be used for severe AMS. AMS may be treated with NSAIDs or acetazolamine. For severe AMS, use an appropriate dosage of dexamethasone.


Descend immediately if symptoms of HACE or HAPE are experienced. Use supplemental oxygen at 2 to 4 L per minute or a hyperbaric bag. Consider dexamethasone for HACE and nifedipine for HAPE. Consult a physician for more information on which drugs to use.

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