|The evidence for the therapy discussed on this page is anecdotal,|
and hasn't been published in a scientific journal.
Hyperbaric oxygen therapy (HBOT) is the medical use of oxygen at a higher than atmospheric pressure. The therapy involves sitting in a pressurized chamber and breathing in 75% oxygen for an hour. The treatment is given every day for several weeks, or on a schedule, such as every other day.
Proponents of hyperbaric oxygen therapy claim that an increase in oxygen consumption can be helpful for a wide variety of conditions, including autism, arthritis, diabetes, Alzheimer's, lyme disease, acne, asthma, HIV/AIDS, migraines, and frequent air travel.  These uses are not approved by the U.S. Food and Drug Administration.
In the case of autism, the theory is that HBOT increases the blood flow in the brain, which stimulates areas in the brain that have previously been idle. This stimulation, according to HBOT proponents, helps autistic people to develop the areas of their brains that have been functioning improperly. 
Critics point out that the case for using HBOT to treat autistic people is based on anecdotal evidence -- personal, first-hand accounts from parents -- rather than scientific research using double-blind experiments.
In an April 2007 article in The Baltimore Sun, Dr. Tina Iyama, professor of pediatrics at the University of Wisconsin-Madison, explained,
"I understand that what all parents want is to be able to look back and say they did everything they possibly could to help their child. That's why they are trying all these experimental new treatments. But... there is absolutely no reason to think that improving oxygen levels in a child with autism will be helpful."
Dr. Gary W. Goldstein, president and CEO of the Kennedy Krieger Institute in Baltimore, agreed:
"There is no evidence in any brain problem that a hyperbaric chamber helps. Here there is no scientific rationale, and there's actually a school of thought developing that... breathing in too much oxygen can actually damage brain tissue." 
One study showed that children receiving the treatment did improve—but so did the children who didn't receive the treatment. This suggests that HBOT is a waste of time and money.
Dangers and Deaths
The FDA does not recommend HBOT for treating non-critical conditions.
"Patients receiving HBOT are at risk of suffering an injury that can be mild (such as sinus pain, ear pressure, painful joints) or serious (such as paralysis, air embolism). Since hyperbaric chambers are oxygen rich environments, there is also a risk of fire."
- Hyperbaric Therapy Center
- "Hyperbaric Oxygen Therapy Shows Promising results for Autism", Reimer Hyperbaric of Canada.
- "Oxygen therapy for kids with autism debated", Kirsten Scharnberg, The Baltimore Sun. April 27, 2007.
- Hyperbaric oxygen in the treatment of childhood autism: a randomised controlled trial.
- FDA.gov: Hyperbaric Oxygen Therapy: Don't Be Misled
- Forbes: FDA Warns Consumers About Common Off-Label Autism Therapy
- Forbes: The 5 Scariest Autism 'Treatments'