ALTITUDE AND COMMON MEDICAL CONDITIONS - Medicine for Mountaineering and Other Wilderness Activities - page 372

hypoxia. Shunting would be expected to contribute to altitude illness, including high-alti-
tude pulmonary edema, as well as to dyspnea, although these individuals tend to have a
lower hypoxic ventilatory response as a result of their chronic hypoxia. An interesting re-
lated question is whether defects resulting in reduced pulmonary blood flow, such as tetro-
logy of Fallot, might be protective for HAPE.
Whetherindividualswithpersistentpulmonaryhypertensionaftercorrectivesurgeryfor
septal defects may have problems at high altitude is unknown. When patent foramen ovale
(a type of atrial septal defect) was noticed in persons with HAPE, it raised the suspicion
that shunting and hypoxemia may have contributed to the illness, but further investigation
disclosed others with patent foramen ovale who did not develop HAPE.
THE EFFECT OF ALTITUDE ON PULMONARY VASCULAR DISORDERS
In addition to congenital cardiac defects, any illness resulting in pulmonary hypertension
(increased blood pressure in the lungs, which normally is much lower than the pressure in
the rest of the body) may be a relative contraindication to high-altitude exposure. Hypox-
ic pulmonary vasoconstriction would probably exaggerate pulmonary hypertension. Given
the prominent role of pulmonary hypertension in the pathophysiology of HAPE, any such
illness may predispose to that disorder. Conditions for which this caution would apply in-
clude unilateral absent pulmonary artery and restrictive lung diseases, both of which have
been associated with HAPE.
Persons with primary pulmonary hypertension (PPH) would be expected to be more
symptomatic—to be more short of breath, to have more frequent fainting episodes, and to
be weaker on exertion. However, some individuals with this disorder are able to tolerate
high altitude. Hypoxic gas breathing can be used to identify an individual's response to
hypoxia.
Persons with PPH who must travel to high altitude may benefit from calcium channel
blockers, isoproterenol, or low-flow oxygen. These individuals must also be aware of a
probable increased susceptibility to HAPE. A lowland woman with pulmonary hyperten-
sionastheresultoftakingfenfluraminedevelopedtwoepisodesofHAPE:thefirstat7600
feet (2300 m) and subsequently at only 6100 feet (1850 m), although she skied up to 7750
feet (2350 m).
Other conditions that may produce pulmonary hypertension include bronchopulmonary
dysplasia, recurrent pulmonary emboli, and mitral stenosis. Whether pulmonary hyperten-
sion is primary or secondary to some other disorder, individuals with this condition should
be aware of the hazards of high altitude, including right heart failure and HAPE. Pulmon-
ary hypertension is at least a moderate contraindication to ascent to altitude.
THE EFFECT OF ALTITUDE ON HEMATOLOGIC PROBLEMS