Altitude-related illness.

There are a number of conditions which can be grouped together as ARI. Many represent potentially fatal pathophysiological states that are rapidly reversible if identified and treated properly. Physiological alterations that result from the hypobaric hypoxia of altitude include cerebral vasodilatation, altered ventilatory patterns, pulmonary vasoconstriction, decreased cardiac output, and altered fluid and electrolyte balance. The various altitude-related illnesses represent a spectrum of conditions with overlapping presentations. The symptoms of AMS and HACE represent a continuum of disease that appears to be related to alterations in cerebrovascular autoregulation. High-altitude retinal hemorrhage may be related to similar vascular events in the retinal circulation. Although the etiology of HAPE remains unclear, it is likely that alterations of pulmonary vascular tone and flow play an important roles in its production. Knowledge regarding ARI is important in planning prophylaxis and instituting therapy. Gradual ascent and acclimatization are the mainstays of prophylaxis. Pharmacological prophylaxis is available for those who are prone to severe AMS. Prompt recognition, descent, and administration of oxygen constitute the major therapies for severe ARI. The ability to perform these three tasks can rapidly reverse a potentially fatal illness.