Background: Although there are several cases reporting the efficacy of mild hyperbaric oxygen therapy in the treatment of Mountain Sickness, no series larger than a few patients have been published thus far.

Study Design: 50 patents with AMS were randomized to receive either hyperbaric oxygen therapy (Group A: 90 min at 1.3 ATA, while breathing oxygen by mask at 8L/min, 23 patients), or 8L/min oxygen by mask for 90 min (Group B, 27 patients). Mean age was 46.7+29.2 years. A detailed medical history and a comprehensive physical exam were performed in every patient. Lake Louise scores were obtained immediately before and after each treatment, 24 and 48 hours later. Telephone follow up was performed weekly for up to one month.

Results: In both Groups pulse oximetry improved comparably. Twenty-three patients completed hyperbaric therapy without incidents. Two patients in Group A could not equilibrate tympanic pressure and were crossed over to Group B. Initial Lake Louise scores varied from 9 to 20, mean 17+3. After 90 min of hyperbaric oxygen therapy, average scores were 3+2; all but one patient had resolution of symptoms, and could move to higher altitudes the same day without return of symptoms. Although Group B improved considerably, none obtained complete resolution of symptoms. Their Lake Louise went to 11+2; all Group B patients required home oxygen for substantial parts of their day and all night for an average of 3 days (2-5 days).

Conclusions: Mild hyperbaric oxygen therapy is safe and more rapidly effective than oxygen by mask in the treatment of Acute Mountain Sickness.