There are three primary levels of altitude sickness:
- High-altitude pulmonary edema
(HAPE) is the next severe form and can be very dangerous or even life-threatening; it is a buildup of fluid in the lungs.
- High-altitude cerebral edema (HACE) is the most severe and life-threatening form of altitude sickness; it happens when there is fluid in the brain.
Additionally, the military also identifies the potential for altitude-induced peripheral edema (HIPE), a more common and mild condition resulting in swelling of the face and hands, and high-altitude retinal hemorrhage (HARH), patchy bleeding from the retinal blood vessels at high altitude.
Some of the most common effects of altitude exposure on the human body include:
- headache
- nausea and vomiting
- fatigue
- difficulty sleeping
- dizziness
- difficulty breathing on exertion
- edema (where body tissues contain an excessive amount of tissue fluid)
More pronounced effects include:
- coughing
- difficulty breathing, noisy breathing or wheezing, gurgling in the airway
- impaired mental status such as confusion, vivid hallucinations or disorientation
- a swaying upper body, especially when walking
- poor wound healing
- apnea (a temporary pause in breathing during sleep)
- vision difficulties - dark adaptation is significantly reduced, at as low as 2,438 m
Treatment of altitude illness even if mild typically involves descending (e.g., 500 m) for recovery and additional acclimation. Under no circumstance should a person attempt higher altitudes when experiencing symptoms of altitude illness – even if mild this will often lead to more severe effects.
Specific military treatment regimens for various types of altitude illness are in TBMED 505 Chapter 6.
IMPACTS ON MILITARY UNITS
The effects of altitude illness along with other environmental exposures and individuals risk factors can have the following impacts on personnel:
Reduced physical performance: Soldiers cannot maintain the same physical performance at altitude as they can at sea level, regardless of their fitness level. Countermeasures include ensuring acclimatization, adjusting work rates and load carriage, planning frequent rests during work and exercise, and planning and performing physical training programs at altitude.
Dehydration: Dehydration is a very common condition in Soldiers at altitude. Causes include perspiration/sweating, vomiting, increased breathing, and diminished thirst sensation. Dehydration decreases physical performance, increases symptoms of altitude illness, and may increase risk of developing cold injuries.
Nutrition deficits: Poor nutrition can severely impact military operations and contribute to illness or injury, decreased performance and poor morale. At high elevations, dulled taste sensations (making food undesirable), nausea, or lack of energy can decrease the motivation to prepare or eat meals. Poor eating habits may also lead to constipation, aggravation of hemorrhoids, and undesired weight loss.
Psychological effects: Altitude exposure may result in changes to mood and personality and include decreased perception, memory, judgment, and attention, especially at extreme altitudes over 3,048 m. Some effects occur early and are temporary while others may persist even after acclimatization.
Increased Risk/Severity of Environmental Threats:
- Cold injuries: Frequent winds in mountain areas cause extremely low windchill. Because altitude exposures can result in poor judgment and decision-making, more cold injuries should be anticipated. Countermeasures for cold injuries include command emphasis on maintaining nutrition, drinking plenty of fluids, and dressing in multiple, loose layers. More information on cold injury prevention.
- Injuries caused by sunlight: Solar radiation injuries caused by sunlight are likely at altitude due to increased ultraviolet (UV) radiation and reflection of light from snow and rock surfaces. Solar radiation injuries can be severe and occur with much shorter exposure at higher altitudes. Injuries caused by sunlight include:
- Sunburn may be more likely to occur on partly cloudy or overcast days especially since personnel may be less likely to take appropriate precautions. Use sunblock (at least 30 SPF) to help prevent instances of sunburn.
- Snow blindness occurs when UV light is absorbed by the external parts of the eyes, such as the eyelids and cornea. There is no warning, aside from brightness, that sunburn-like eye damage is occurring. Damage can occur in just a few hours. Sunglasses or goggles with UV protection will prevent snow blindness. Sunglasses with side protectors are recommended.
- Terrain injuries: Altitude terrain dangers include avalanches and falls. The potential for being struck by lightning is also increased at higher altitudes, especially in areas above the tree line. Take shelter in solid-roofed structures or vehicles, stay low, and avoid tall structures or large metal objects.
- Carbon monoxide (CO) poisoning: Caused by using stoves, combustion heaters, and engines in enclosed, poorly ventilated spaces. Cigarette smoking is another source of CO. To prevent CO poisoning, do not sleep in vehicles with engines running, cook inside tents, or sleep in tents without adequate ventilation while using combustion heaters or stoves. Seek fresh air immediately if CO poisoning is suspected.
- Non-battle injuries: Altitude and cold can impair judgment and physical performance while maneuvering in rugged terrain. Heavy clothing worn for protection against the cold and specialized equipment can also restrict movement. Non-battle injuries can be prevented by carefully observing safety procedures.
- Infectious diseases: At moderate to high altitudes, insect-borne disease (from mosquitoes, ticks and flies) is common in most regions. In some areas, malaria-bearing mosquitoes range as high as 1800 m. Diseases transmitted person-to-person may be increased in cold climates since personnel are more likely to gather close to keep warm.
