Hyperbaric Oxygen therapy (HBOT) has risen in recent years as an “alternative” therapy for many conditions, autism included. The logic behind HBOT is rather fuzzy . For example, there was some discussion of using HBOT to reduce oxidative stress a few years back. How increasing oxygen in the body would decrease oxidative stress was not clear. Some other discussions focused on oxygen perfusion . Basically, some studies have shown that some areas of the brain may be getting less oxygen in autistics than in non-autistics. The idea was that increasing the oxygen to those areas might result in some improvement in some measure or another.
This begs the question: are there areas of higher perfusion (hyperperfusion) in the brains of autistics? Seems an important question to pose when proposing increasing perfusion. But one can not find the term “hyperperfusion” in this review promoting HBOT and autism , for example. But the answer is, yes, people have measured hyperperfusion in autistic’s brains:
In specific, they found
Using the simplistic logic of HBOT/autism promotors, one then is left with the question of whether could HBOT make seizure activity worse? I wouldn’t put too much weight on this question other than to point out that it isn’t 100% clear that there can be no downside to HBOT. The logic “there is hypoperfusion therefore HBOT should benefit” isn’t strong; the idea that “there are areas of hyperperfusion, therefore HBOT could have a downside” is also not strong. There are three other studies mentioning hyperperfusion and autism. And, I was interested to see that there are 350 hits for a search of hyperperfusion and epilepsy in pubmed. Compare this to 30 hits for autism and hypoperfusion.
Back to HBOT. There isn’t much science for HBOT, to be frank. Most of the momentum, at least in publications, is from one source: Dan Rossignol. An early paper: Hyperbaric oxygen therapy may improve symptoms in autistic children. by Dr. Rossignol was published in Medical Hypotheses–a pseudo medical journal. I believe Dr. Rossignol’s clinic in Florida provides HBOT.
While there have been articles like the above and some small open label study reports, true randomized trials have been lacking. A recent review Hyperbaric oxygen therapy for treatment of children with autism: a systematic review of randomized trials reported
Also worth noting is that HBOT is currently rated as “non-accepted” by the European Committee for Hyperbaric Medicine . An indication that there was not good evidence either way at the time they prepared their statement.
Two recent studies (the one which is the focus of this article and another) have used a more randomized/blind methodology and one has looked at biomarkers considered important in HBOT and autism (cytokines). The results have not been encouraging.
First the more biomarker based study. This group studied autistic children given HBOT and looked at cytokine levels ( Brief report: Hyperbaric oxygen therapy (HBOT) in children with autism spectrum disorder: a clinical trial .) Per that study,
So, if there is a benefit from HBOT, it isn’t due to changes in cytokines. Which HBOT doesn’t seem to affect.
Another somewhat recent study attempted a clinical trial as well
Finally, a study out in the past couple of months again attempts a randomized controlled study: “ Hyperbaric oxygen in the treatment of childhood autism: a randomised controlled trial. ” The study is out of Thailand. One factor of note is the attempt to do a real control using a “sham” air group. Obviously HBOT studies are complicated in that study subjects can easily detect the changes in pressure. Of note, HBOT in this case is 100% oxygen:
While some reports have used 100% oxygen at 1.5ATA, many have used either air or enriched air and sometimes lower pressure (1.3ATA). I.e. this study involves higher oxygen exposure than in many studies. Air is about 21% oxygen . So, a 1.5 atmospheres of pure oxygen is about 7.5 times the oxygen partial pressure in air. Many reports in early studies were about 1.3 ATA air or slightly enriched air. 1.3 ATA (atmospheres absolute) at 25% O2 is about 32% oxygen. For divers, these levels of oxygen are comparable to Nitrox or enriched air. One can get a higher oxygen level from a mask at 1 atmosphere. Which has been a critique of HBOT from the start. Early anecdotal reports from HBOT practitioners claimed that oxygen delivered by mask was not effective. Only high pressures gave whatever results were claimed. Which is counter intuitive to the simple explanations of how HBOT should work.
But, with both high pressure and pure O2, the Thailand study should provide clarity in these questions. Which begs the question, what are those results? The full paper is online and the abstract is below.
Repeat for emphasis: “Children with autism who received 20 sessions of either HBOT or a sham air exposure had significant improvements in overall behaviour but there were no significant differences in improvement between groups”
Reports from parents and clinicians did not agree and the authors conclude “no overall clinically significant benefit from HBOT could be shown”.
HBOT is not cheap. A single “dive” can cost in the neighborhood of $100. Parents have purchased portable chambers which run in the $10-20k range (depending on model and whether new). And have modified these to provide O2 enriched air, outside the manufacturer’s specifications. There is a resale value in these chambers so far, so the net cost is not going to be as high. But, all told, there is substantial outlay of funds and time in HBOT. The science pro is shaky at best. And now there are two negative controlled trials.
These results will likely do little to dampen the enthusiasm for HBOT. All studies of HBOT and autism in clinicaltrials.gov are completed , so future data may not be forthcoming.