Lead reviewer Michael Bennett of Prince of Wales Hospital in Sydney examined studies that evaluated normobaric oxygen therapy and hyperbaric oxygen therapy. Normobaric therapy consists of patients inhaling pure oxygen at normal room pressure, and hyperbaric therapy involves patients breathing oxygen at higher pressure in a specially designed chamber.

Five studies compared hyperbaric versus placebo therapy for migraine; two compared hyperbaric versus sham therapy for cluster headache; and two investigated the use of normobaric therapy for cluster headache.

The review, published in The Cochrane Library, said three studies reported the number of patients who had significant relief from their migraines within 40 to 45 minutes of hyperbaric therapy.

For cluster headaches, two studies involving 69 patients found a significantly greater proportion of patients had relief of their headaches after 15 minutes of normobaric compared to placebo therapy.