Multiple Lightning Strikes. (Photo contributor: Lawrence B. Stack, MD.)
High-altitude pulmonary edema (HAPE) is a form of noncardiogenic pulmonary edema, generally beginning within the first 2 to 4 days after ascent above 2500 m (8200 ft). Early symptoms are fatigue, weakness, dyspnea on exertion, and decreased exercise performance. Symptoms of AMS, such as headache, anorexia, and lassitude, may also be present, but HAPE may develop without AMS. The first symptoms usually include persistent dry cough and dyspnea followed by tachycardia, tachypnea, and cyanosis at rest. Patients suffering from HAPE often experience sudden onset of symptoms upon awakening after the 2nd night at altitude. Eventually the victim develops dyspnea at rest and orthopnea with audible crackles in the chest. Pink frothy sputum is a grave sign. Patients may experience concurrent mental status changes and ataxia due to hypoxemia or associated high-altitude cerebral edema.
High-Altitude Pulmonary Edema. Chest x-ray in patient with HAPE. Note normal heart size with bilateral “patchy” pulmonary infiltrates. (Photo contributor: Peter Hackett, MD.)
“Gamow Bag.” Portable hyperbaric chamber (Gamow bag). A HAPE patient is being treated at 4300 m at Pheriche, Nepal. Due to orthopnea, the patient was unable to tolerate lying flat, so the bag was propped up (head elevated) immediately after inflation. (Photo contributor: Ken Zafren, MD.)
Management and Disposition
Mild cases (oxygen saturation in the 90s on low-flow oxygen) at moderate altitudes (below 3500 m [11,500 ft]) may be treated at altitude with bed rest and oxygen. If supplemental oxygen and a reliable person are available, the patient may be discharged with oxygen therapy and bed rest at home or in lodgings. Patients with more severe cases should descend immediately with as little exertion as possible. These patients may require admission to a hospital at a lower altitude and, in extreme cases, intubation and mechanical ventilation. Nifedipine, which lowers pulmonary artery pressure, is of benefit but is not a substitute for descent. Some experts use phosphodiesterase-5 inhibitors such as sildenafil or tadalafil instead of nifedipine. Hyperbaric therapy, especially with a portable hyperbaric chamber (Gamow bag), has an efficacy equal to that of supplemental oxygen and is mainly helpful in prehospital settings where oxygen availability is limited.