Chapter 2

the blood cause a systemic vasodilatation, or expansion of blood vessels. This increased vascular size
stretches the vessel walls causing leakage of the fluid portions of the blood into the interstitial spaces,
which leads to cerebral edema or HACE. Unless treated, HACE will continue to progress due to the
decreased atmospheric pressure of oxygen. Further ascent will hasten the progression of HACE and could
possibly cause death.
2-125. While the body has an overall systemic vasodilatation, the lungs initially experience pulmonary
vasoconstriction. This constricting of the vessels in the lungs causes increased workload on the right
ventricle, the chamber of the heart that receives de-oxygenated blood from the right atrium, and pushes the
blood to the lungs to re-oxygenate. As the right ventricle works harder to force blood to the lungs, its
overall output is decreased. This in turn decreases the overall pulmonary perfusion (the pushing of blood
through the lungs, in this case). Decreased pulmonary perfusion causes decreased cellular respiration―the
transfer of oxygen from the alveoli to the red blood cells. The body then experiences increased carbon
dioxide levels due to the decreased oxygen levels, which now causes pulmonary vasodilatation. Just as in
HACE, this expanding of the vascular structure causes leakage into interstitial space resulting in pulmonary
edema or HAPE. As the edema or fluid in the lungs increases, the capability to pass oxygen to the red
blood cells decreases. This creates a vicious cycle that can quickly become fatal if left untreated.

HIGH-ALTITUDE PULMONARY EDEMA
2-126. HAPE is a swelling and filling of the lungs with fluid, caused by rapid ascent. It occurs at high
altitudes and limits the oxygen supply to the body.
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HAPE occurs under conditions of low oxygen pressure, is encountered at high elevations (over
8,000 feet), and can occur in healthy Soldiers. HAPE may be considered a form of, or
manifestation of, AMS since it occurs during the period of susceptibility to this disorder.
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HAPE can cause death. Incidence and severity increase with altitude. Except for acclimatization
to altitude, no known factors indicate resistance or immunity. Few cases have been reported after
10 days at high altitudes. For Soldiers who remain at the same altitude, the incidence of HAPE is
less frequent than that of AMS. No common indicator dictates how a Soldier will react from one
exposure to another.
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Symptoms of AMS can mask early pulmonary difficulties.

CONTRIBUTING FACTORS
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A history of HAPE.
A rapid or abrupt transition to high altitudes.
Strenuous physical exertion.
Exposure to cold.
Anxiety.

SYMPTOMS
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2-24

Progressive dry coughing with frothy white or pink sputum (this is usually a later sign) and then
coughing up of blood.
Cyanosis—a blue color to the face, hands, and feet.
An increased ill feeling, labored breathing, dizziness, fainting, repeated clearing of the throat,
and development of a cough.
Respiratory difficulty, which may be sudden, accompanied by choking and rapid deterioration.
Progressive shortness of breath, rapid heartbeat (pulse 120 to 160), and coughing (out of contrast
to others who arrived at the same time to that altitude).
Crackling, cellophane-like noises (rales) in the lungs caused by fluid buildup (a stethoscope is
usually needed to hear them).
Unconsciousness, if left untreated. Bubbles form in the nose and mouth, and death results.

TC 3-97.61

26 July 2012