Unilateral high-altitude pulmonary edema (HAPE): A case report and discussion of pathophysiology

High-altitude pulmonary edema (HAPE), a potentially life-threatening altitu de adaptation disorder, is considered to be caused by an exaggerated increa se in pulmonary blood pressure and a non-cardiogenic rise in pulmonary vasc ular permeability subsequent to alveolar hypoxia. A 40-year-old male mounta ineer was affected by an advanced stage of HAPE at high altitude (Monte Ros a plateau, 4000 m). The symptoms abated immediately after the patient desce nded from the altitude. However, six hours after the symptoms had resolved, radiographic signs of pulmonary edema, confined to the right lung, were se en. This rarely described unilateral radiological pattern of HAPE resolved completely within two days. We suggest that aspiration events of nasal secr etion, the right sleeping position at night and an elevated right diaphragm reduced the patient's compensatory hyperventilation capacity of the right lung. The resulting increased alveolar hypoxia in the right lung was respon sible for unilateral edema. The pathophysiological mechanism underlying uni lateral HAPE is discussed.