High altitude

High altitudes can pose special challenges to people who are unacclimatized to them. This is because the density of air gets dramatically lower with increasing higher altitudes. As a result, the concentration of oxygen in air decreases as altitude becomes greater. Since oxygen is needed for survival of the human species, the body must adapt to changes in altitude, or cease to function.

Oxygen Saturation

Oxygen saturation in hemoglobin affects our ability to use the vital gas. After the body reaches around 7000 feet above sea level, the saturation of oxyhemoglobin begins to plummet. At approximately 60% saturation, most people lose consciousness.

Altitude acclimatization, the physiological adaptions to altitude, can have immediate and long term effects.

Immediate Effects

• Hyperventilation
• Fluid loss (due to a decreased thirst drive)
• Increase in heart rate (HR)
• Slightly lowered stroke volume

Long Term Effects

• Lower lactate production (because reduced glucose break down decreases the amount of lactate formed).
• Alkaline loss
• Decrease in plasma volume
• Increased Hemocrit
• Increase in RBC mass
• Higher concentration of capillaries in striated muscle tissue
• Increase in myoglobin
• Increase in mitochondria
• Increase in aerobic enzyme concentration
• Decrease in 2,3 DPG

Altitude-Related Illnesses:

Acute Mountain Sickness (AMS):

Occurs frequently in people adjusting to altitudes of ~10,000 feet or more. Symptoms include:

• Headache
• Dizziness
• Nausea
• Vomiting
• Visual impairments
• Insomnia
• Weakness

Diets high in carbohydrates tend to 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):

Occurs in ~2% of those who are adjusting to altitudes of ~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
• Rales

Descent to lower altitudes alleviates the symptoms of HAPE.

High-Altitude Cerebral Edema (HACE):

A life threatening condition that can lead to coma or death. It occurs in about 1% of people adjusting to altitudes above 9,000 feet. Symptoms include:

• Headache
• Fatigue
• Visual impairment
• Bladder dysfunction
• Bowl dysfunction
• Loss of coordination
• Paralysis on one side of the body
• Confusion
• Slowed reflex response

Descent to lower altitudes may save those afflicted with HACE.

Altitudes and Athletic Performance

In the athletic arena, it is thought that acclimatization to high altitudes enhances performance compared to training at sea level. However, these assumptions have not been backed with any significant evidence. Contrary to these beliefs, studies have shown that athletes may not be able to train with as much intensity at high altitudes compared to sea level.

Yet, for those determined to adjust to high altitudes, without being at high altitudes, inventors have cranked out state-of-the-art altitude acclimatization devices. Chambers that reduce barometric pressure, hydrobaric chambers with increased nitrogen concentration (which reduces oxygen), and tents that supply a limited amount of oxygen are used by athletes to acclimatize to high altitudes.

Finally, it is important to realize that to benefit from altitude acclimitization, one must stay in that altitude for a long period of time. Any benefits of altitude acclimatization are lost quickly by those who only dwell in high altitudes, or simulated circumstances, for a short amount of time.