50 climbers who ascended denali developed pulmonary edema, and as high as 6% of climbers ascending rapidly in the alps . in climbers who had previously developed hape, re-attack rate was up to 60% with ascent to 4,559 metres (14,957 ft) in a 36-hour time period, though this risk was significantly reduced with slower ascent rates. it is believed that up to 50% of people suffer from subclinical hape with mild edema to the lungs but no clinical impairment. history hape was recognized by physicians dating back to the 19th century but was originally attributed to “high altitude pneumonia”. the first documented case of pulmonary edema, confirmed by autopsy, was probably that of dr jacottet who died in 1891 in the observatoire vallot below the summit of mont blanc. after participating in a rescue on the mountain, the doctor refused to return. instead, he spent further two nights at an altitude of 4,300 metres (14,100 ft) with obvious ams symptoms and died on the second night. this condition was subsequently noticed in otherwise healthy climbers who would die shortly after arriving at high altitudes. it was not until 1960 that charles houston, an internal medicine physician in aspen, published a case report of 4 individuals participating in high elevation activities that he had diagnosed with “edema of the lungs”. he described chest x-rays with edema and non-specific changes on ekg. even though these cases had been termed high altitude pneumonia in the past, houston indicated that these cases were “acute pulmonary edema without heart disease”.