By Jim Melwert

PHILADELPHIA (CBS) — Twenty-year-old Susanna DeForest, from Collegeville, died on August 17th while hiking with friends in Colorado.

While an official cause of death has not been determined, her mother posted on Facebook that her daughter died from “acute altitude sickness”.

Acute altitude sickness is generally seen above 8,000 feet, according to Doctor Ben Usatch of Lankenau Hospital, especially while hiking or climbing when your body needs more oxygen.

“And you’re breathing at an increasing rate, yet you’re not able to get in enough of the oxygen because there’s just less oxygen carried in the air. And that’s when the symptoms start,” Dr. Usatch said.

He says mild symptoms are similar to a hangover: headache and nausea. But it can be deadly if lungs begin to fill with fluid or the brain begins to swell.

“The only cure for mountain sickness, unless you happen to be carrying a hyperbaric chamber behind you like they do at Mount Everest, is to descend,” said Usatch.

Susanna DeForest was hiking with friends to Conundrum Hot Springs near Aspen. The trail elevation is listed as about 8700 feet to more than 11,000.

Her friends went for help, but rescue crews were unable to get to her in time.