Acute pulmonary edema is an uncommon but serious and sometimes fatal complication of rapid exposure to altitudes above 9000 leet. Hypoxia is considered the primary etiologic agent. Many earlier fatal cases were erroneously diagnosed as pneumonia Young, unacclimatized persons and acclimatized residents who have sojourned at lower altitudes for a few day or weeks appear most susceptible. Recurrences are common in those who have experienced an attack Rapid ascent and heavy physical exertion increase susceptibility.
Autopsy findings have included wet lungs congested with serosanguineous edema fluid. Brnnchioiar and alveolar edema with hyaline membranes, resembling those seen in hyaline membrane disease of the newborn, over the internal walls of alveoli, alveolar sacs, and alveolar ducts have been characteristic findings. Dilatation of preterminal arterioles and thrombosis of septal capillaries and of small and medium-sized pulmonary arteries have also boen observed The exact pathogenic mechanism is conjectural A comparative increase in capillary pressure is thought to Ik- responsible for the alveolar edema.
In a few cases pulmonary artery pressure has been elevated and electrocardiograms have suggested acute right ventricular overloading. The hyaline membrane formation, not a characteristic finding in death caused by simple hypoxia, has not been explained, but a deficient pulmonary fibrinolysis system has been postulated.
When Pulmonary Edema Symptoms Occurs?
Symptoms usually appear fi to 36 hours after exposure to altitude and may he preceded by acute mountain sickness. Exertional dyspnea, weakness, malaise, and a persistent, dry. irritating cough are the charactenstic initial symptoms Later, noisy respiration, rales, cyanosis, orthopnea, and hemoptysis develop. Unless continuous oxygen therapy is carried out or the patient descends to u lower altitude, these symptoms progress, and death occurs. (Irudual acclimatization and avoidance of undue physicu! exertion during the early period of exposure to altitude are important preventive measures.