High Altitude Military Parachuting - Health Risks

Health Risks

This type of parachuting technique can be dangerous. At high altitudes of the Earth's atmosphere (greater than 22,000 feet ), the partial pressure of oxygen (required for human respiration) is low. Lack of pressure can lead to hypoxia. Also, rapid ascent in the jump aircraft without all nitrogen flushed from the bloodstream can lead to decompression sickness (also known as caisson disease or "the bends").

A typical HALO exercise will require a pre-breathing period (30–45 minutes) prior to jump where the jumper breathes 100% oxygen in order to flush nitrogen from their bloodstream. Also, a HALO jumper will employ an oxygen bottle during the jump. Danger can come from medical conditions affecting the jumper. For example, cigarette smoking, alcohol and drug use (including histamine antagonists, sedatives, and analgesics), anemia, carbon monoxide, fatigue and anxiety can all lead to a jumper being more susceptible to hypoxia. In addition, problems with the oxygen bottle and during the changeover from the pre-breather to the oxygen bottle can result in the return of nitrogen to the jumper's bloodstream and, therefore, an increased likelihood of decompression sickness. Theoretically, a single breath of atmospheric air may elevate the jumpers arterial nitrogen level to dangerous levels. A jumper suffering from hypoxia may lose consciousness and therefore be unable to open his parachute. A jumper suffering from decompression sickness may die or become permanently disabled from nitrogen bubbles in the bloodstream, which causes inflammation of joints.

Another risk is from the low ambient temperatures prevalent at higher altitudes. At an altitude of 35,000 feet, the jumper faces temperatures of –45 °C (–50 °F), and can experience frostbite. However, HALO jumpers generally wear polypropylene knit undergarments and other warm clothing to prevent this.