HBOT: Is it just a bunch of hot air?
November 9th, 2007
Hyperbaric Oxygen Therapy (HBOT) is arguably the hottest new fad in the “alternative” autism therapy world. Parents all over the US are stuffing their autistic children into zip-up “soft chambers” to experience this latest “cure”.
But what are they actually doing for (to) their children?
One hypothesis, expounded by a number of practitioners who administer HBOT to autistic children (and for a variety of other ailments), is that they are increasing oxygen delivery to the brain, and that this increase in oxygen delivery - even though it only lasts for the hour or so of the HBOT treatment, somehow (mysteriously) changes something about the brain (much hand waving at this point).
Without addressing how increasing the oxygen delivery to the brain for an hour or so might help with autism, let’s look at the claim for increased oxygen delivery.
Oxygen delivery to the brain depends largely on two factors: brain blood flow and blood oxygen content. The literature on cerebral blood flow response to HBOT is mixed, so that isn’t too helpful. Of note, none of the “studies” looking at HBOT in autism measured cerebral blood flow. And, it should be noted, the studies of HBOT that showed changes in cerebral blood flow were done at pressures of 4 and 5 atmospheres (atm) - about 60 psi. The typical “soft chamber” used in HBOT for autism can only go up to a pitiful 1.3 atmospheres pressure (only 4 psi above ambient air pressure).
How about blood oxygen content? Well, there is reason to believe that HBOT can increase blood oxygen content. In fact, just look at the graph below (fig.1), which shows the amount of oxygen in the blood (milliliters of oxygen per liter of blood) while breathing air at various pressures.
[Click on the thumbnail to enlarge. Use the "back" button on your browser to return]
The reason that the curve isn’t linear is because of hemoglobin. Hemoglobin carries the grand majority of the oxygen in the blood of most (if not all) mammals. We can’t live without it because not enough oxygen will dissolve in our blood plasma to keep us alive. In fact, one of the real uses of HBOT is to treat people who - for one reason or another - are having problems with their hemoglobin (e.g. carbon monoxide poisoning).
However, if you have functional hemoglobin, raising the pressure doesn’t do much to increase the blood oxygen content, not until you get beyond the pressures most (real) hyperbaric chambers can reach (most have a maximum of 6 atm).
And what about the zip-up “soft chambers” that folks are using for autism? They can’t hold more that 1.3 atm (at sea level). They are pressurized to only 4 psi above atmospheric pressure - less than the pressure inside a party balloon.
OK, so simply exposing your child to air at elevated pressures doesn’t have much impact. How about raising the oxygen concentration?
Figure 2 shows the effect of increasing the oxygen concentration at the pressure relevant to most HBOT used for autism.
Figure 2.
As you can see, the differences are minuscule - about 5% difference in blood oxygen content between breathing air at sea level and breathing 50% oxygen in a typical “soft chamber”. Now, it maybe that this is enough to reverse autism, but it doesn’t seem very likely. After all, you the same effect without the hyperbaric chamber.
Figure 3 shows what happens to blood oxygen content (at sea level pressure) breathing various concentrations of oxygen.
Figure 3.
To get to the same level as breathing air in a “soft chamber” only requires breathing 50% oxygen at sea level. To get to the same level as breathing 50% oxygen in a “soft chamber”, you only need 65% oxygen at sea level.
So, it looks as though the “benefits” of HBOT are not due to increasing the oxygen content of the blood. And the jury is still out on what HBOT does to the blood flow, although it should be noted that the studies showing any changes were done at much higher pressures.
But there isgood news: ”soft chamber” HBOT therapy is not capable of reaching pressures high enough to cause oxygen toxicity (that takes 1.6 atmospheres, even with 100% oxygen). Although, if people are concerned about “oxidative stress” in autism, adding more oxygen to the mix seems like a poor way to address that concern.
Dr. Rossignol, a key HBOT for autism promoter, has acknowledged that the increase in oxygen delivery is minimal and speculates that the effect he sees might be due to direct pressure effects. In my next post, I’ll “do the numbers” on that hypothesis.
Until then….
Prometheus
Filed under: Autism Practitioners, Autism Science, Autism Treatments
November 10th, 2007 at 12:09 pm
The MIND Institute is sarting a HBOT study (I believe with a hard chamber) and they invited my son to participate, but I declined. I’d rather wait for the results of their research. My son and I do have hemoglobin problems - we have Thalassemia minor - but that scares me even more to take him to the oxygen chamber.
November 10th, 2007 at 12:49 pm
It has come to my attention that the cheaper way for achieving 1.2-1.4 atm in one’s body is to inhale deeply, purse one’s lips to seal tightly, and attempt to blow thus inflating one’s cheeks and achieving DAN! pressures. One thing is for sure, your teeth and tongue won’t have autism anymore. And if you keep it up for a really long time, the world will have a reprieve from science-free and inane comments for a minute or so (until consciousness is regained).
Additionally, if one was to chug some coke and then swallow a few whole mentos in short order, the pressure buildup in one’s stomach would ensure that parts of the enteric nervous system would no longer be autistic. It’s the gut-brain connection.
Alternatively, one could do the coke-mentos bit Best-JB Handley style and go at it from the other end. Butt that’s another story.
November 10th, 2007 at 2:29 pm
I wonder whether any insurers are reimbursing this nonsense. I would guess not, but who knows.
November 13th, 2007 at 4:27 am
I can’t believe the UC Davis IRB approved the HBOT study (yes I can).
Hendren was running the B12 study because oxidative stress causes autism, then he was going to run the HBOT study because oxidative stress is good for autism.
They were trying to figure out if it was ethical to put kids in a hard chamber with no additional oxygen (just room air) as the control for the kids in the hard chamber with oxygen last I heard.
November 13th, 2007 at 12:09 pm
Dear isles:
RE: insurance coverage: I suspect that an insurer would conclude that this is “experimental” and deny coverage for that reason. See Dr. Barrett’s article at http://www.chirobase.org/19Insurance/ash.html for a general discussion. There are a lot of dubious treatments out there. See articles at http://www.srmhp.org/0101/autism.html and http://chealth.canoe.ca/columns.asp?columnistid=3&articleid=2858&relation_id=0
Unfortunately, Dr. Barrett has become a victim of his own success in trying to fight quackery. 7 years of constant lit around the country takes its toll, emotionally and financially. In addition to the websites he and others maintain in the Anti-Quackery Ring, I’d check the website of (the late) Dr. Saul Green, Ph.D. Unfortunately he died about 6 months ago, but there’s still much relevant, timely info in his columns.
My rule of thumb is that if your insurer won’t provide coverage, that’s a major red flag. You can always ask the insurer for the reason for a denial of coverage, and see if the person proposing the “treatment” has real evidence to rebut the insurer’s reason. In every state insurers are subject to laws which can impose penalties and attorney’s fees for wrongful denials of coverages, so insurers (& their trade associations) tend to be fairly thorough in this area.
“Dr. Rossignol, a key HBOT for autism promoter, has acknowledged that the increase in oxygen delivery is minimal and speculates that the effect he sees might be due to direct pressure effects.”
At least that’s not a wholly implausible idea — Dr. Temple Grandin wrote about the calming effects of deep pressure long ago. But, she never claimed it was treating her autism, only that it helped with her anxiety symptoms.
As I recall, 1.3 atmospheres of pressure is about the same as being about 12 feet down in water. I’d speculate that any money one might spend on HBOT would be better spent on family scuba lessons — assuming that an ASD child can understand, follow and handle the safety precautions, time spent together in supervised shallow dives might have more lasting benefits.
November 13th, 2007 at 1:45 pm
Totally off point, but of interest.
[site deleted at commenter's request - it appears to be a come-on site]
Dear Prometheus:
The above is the link to a site that supposedly rates Blog Readability Level. Your site rates “High School.”
Some comparisions (Disclaimer: done by someone else, I haven’t checked them myself):
Elementary school: Drudge Report
Junior high: Daily Kos, Instapundit, Weather Channel
High school: Dan Drezner, Andrew Sullivan, Transterrestrial Musings, AP, UPI
College undergrad: Stevenbainbridge.com, Michelle Malkin, Samizdata
College postgrad: - Accuracy in Media, LGF
Genius: Rush Limbaugh, Agence France Presse, Ananova, Granma Int’l (English translation)
I have Zero idea on how the rating is done. But, I think it means that someone having an average understanding of English should be able to follow your presentations. That, I believe, is a good thing.
November 13th, 2007 at 1:54 pm
Dear Prometheus:
You may want to delete my last posting. I checked a little more — and there are reasons to think the link is to a site that may link to “come-on” type sites. That can be a problem even with finding info on what are usually trust-worthy sites. Can’t be fully certain of info from the internet from any source.
I apologize for violating one of my basic rules — always cross-check any info found on any website, even good ones.
November 15th, 2007 at 12:19 pm
Several years ago, HBOT was touted for treating multiple sclerosis and cerebral palsy. Studies (one at McGoll) showed no benefit over room air. One of the regular posters to the CP newsgroup managed to force Georgia to pay for HBOT, but, as far as I know, no one else pays for HBOT unless it is clearly indicated (gangrene, etc.).
November 28th, 2007 at 6:45 pm
You say “However, if you have functional hemoglobin, raising the pressure doesn’t do much to increase the blood oxygen content, not until you get beyond the pressures most (real) hyperbaric chambers can reach (most have a maximum of 6 atm).
You are incorrect in this statement. When Oxygen is delivered in a pressurized environment (greater that 1ATA) the molecules enter the plasma of the blood and raise the pO2 by between 20 to 30 times (1.5ATA) what hemoglobin can carry. This is well known science … in fact the effect of pressure on nitrogen will cause nitrogen to enter the bloodstream in great quantities. if the pressure is released to quickly (coming to the surface too quickly) the nitrogen will come out of solution in the blood and form bubbles… this is commonly known as the “bends” and is treated with recompression and slow decompression. I have read many blogs like this and am continually amazed by the misunderstanding of HBO2 therapies…. Insurance compensates for non healing wound therapy… it is on the list of indications endorsed by the UHMS. How do you think HBOT works in this case? Duh, by raising the level of oxygen in the blood, spinal fluid body tissue and brain… the increased oxygen speeds the healing. Check your science before you mislead innocent people with ranting and smart talk… think and research before you publish…
You also say ” “Dr. Rossignol, a key HBOT for autism promoter, has acknowledged that the increase in oxygen delivery is minimal and speculates that the effect he sees might be due to direct pressure effects.”
I ask you what is the whole context of this statement and what is his exact quote?
November 28th, 2007 at 7:17 pm
Mac,
Take a look at the graphs. Since the amount of oxygen carried on hemoglobin peaks at about 1 atmosphere, any rise above that point is due to the increased amount of oxygen dissolved in the blood plasma.
However, it is wildly inaccurate to say that the increase is “30 times” or anything even close to that by 1.5 atmospheres pressure. The graphs show that increased pressure does increase the oxygen dissolved in the plasma, but the hemoglobin carries so much more oxygen that the increase is trivial until extremely high pressures are reached.
Breathing air, it takes a pressure of 43 atmospheres (about 630 psi) for dissolved oxygen in the blood to equal the amount of oxygen carried on hemoglobin at sea level pressure
Breathing 100% oxygen (very dangerous at elevated pressure), it still takes 9 atmospheres (about 130 psi) to bring dissolved oxygen up to the amount of oxygen carried on hemoglobin, breathing air, at sea level pressure.
You dan’t have to take my word for it - the calculations are in most physiology texts.
As for Dr. Rossignol’s comment, that was in an exchange of comments on the “Autism Street” ‘blog, if I recall. You can look for it there. His acknowledgement of reality is really quite irrelevant to the discussion, but I thought it only fair to mention that he is aware of the problem, as well.
Prometheus
November 28th, 2007 at 7:32 pm
Mac,
After re-reading your comment, I thought that it would be interesting to have you explain how raising the total pressure by 50% (e.g.from 1 atm to 1.5 atm) you could increase the partial pressure of oxygen by 30 times.
Additionally, to answer your “Duh!” - insurance covers HBOT treatment of non-healing surface wounds. The exposure to atmospheric oxygen at high pressures can help them to heal and it is hoped that the native circulation will be adequate to provide oxygen and other nutrients to the tissues once they have healed.
Mac, perhaps you should check your science before you mislead innocent people with ranting and smart talk - think and research before you comment.
Prometheus
December 19th, 2007 at 8:31 am
It is a hypothesis. An apple, an idea, a hypothesis, a fact.
February 7th, 2008 at 9:27 am
Photon,
Get a grip. There is a third group to consider. People with a biology background who are even more skeptical than you.
I am crying foul constantly at the epidemiological crap claiming no connection between thimerosal/mmr and autism.
Methodological shell games, all of them.
I wish I had saved the reference. A British medical group reported out on their findings some 7 or 8 years ago on a subset of ticksheet data lookiing at autistic children. There was a group in that subset which cried out for closer examination, but the authors obviously and intentionally dismissed it. To me, it was blatant. These sorts of games go on all the time.
Moreover, I notice that “your side” tends not to engage the main arguments. The data on Japan, for example, is very compelling, but your side always has an excuse for not taking a closer look at an obvious pattern.
Similarly, the lack of autism in Amish children has been dismissed with the most specious of arguments: Amish are genetically different from everyone else. With all the population genetics work done to date, it should be self evident how silly that claim is. Yet it is taken as sufficient by the powers that be at the CDC and the FDA to avoid doing a real study.
That, plus the suddenly strange behavior of the CDC in the middle of the New Jersey cluster study simply illustrates that the government is being incredibly dishonest about this whole matter. A prudent and responsible agency would function in a completely different manner - not throwing up barriers everywhere.
So, this biologist smells a rat.
Moreover, the people on your side don’t have any problem with simply smearing us with false statements like “anti-vaccination” and calling us ignorant. Bad form.
As for HBOT, we have used it for about a year. Your particular take on oxygenation of blood in a mildly high pressure environment is only partially compelling. More is involved than regarding blood as “passive” solvent into which you pump more gas. There are other proteins besides hemoglobin that absorb oxygen. Moreover, there is a host of unanswered questions about various shifts induced in blood physiology by merely having higher amounts of nitrogen and oxygen in the blood.
Blood is only about 8% denser than water. Also, coincidentally, the solubility of oxygen in water is around 8%. That qualifies as low solubility. Pressure obviously increases that. The equation is not handy, but pv = nRT lives on!!! Add to that the oxygen capacity of human serum albumin, a multi-facted protein indeed which binds to all sorts of things. Anyway, you get the point.
Most importantly though, we have seen significant, not profound, improvements in our son as a result of HBOT. Certainly, enough so to keep doing it. The effect is generalized, so finding the right measures to capture the phenomenon would be tricky. “Finding” the wrong measures for a study that wants to demonstrate NO statistical significance would be much easier to do.
It has been a difficult lesson in life to realize both lawyers and scientists can be adept at making sure they don’t ask the right questions.
February 7th, 2008 at 2:12 pm
Cort,
You make a lot of accusations but hold back on presenting your supporting data. You even seem to be holding back enough information for anyone to even clearly identify the “issues” you are addressing. You also seem to have a good deal of misinformation.
For example:
“There was a group in that subset which cried out for closer examination, but the authors obviously and intentionally dismissed it.”
I understand that you’ve lost the reference, but could you at least explain why you feel that this subgroup “cried out for closer examination”? Or at least tell us what distinguished the subgroup?
“The data on Japan, for example, is very compelling, but your side always has an excuse for not taking a closer look at an obvious pattern.”
Which data and how is it compelling? The only data out of Japan that I’m aware of are the fact that changing from the MMR to single vaccines didn’t change the trajectory of autism prevalence (although it did appear to contribute to a measles outbreak). Although there isn’t as much data out of Japan as there is, say from the US or UK, it appears that they are experiencing the same rise in autism prevalence as the US and UK.
Maybe you could be clearer.
“Similarly, the lack of autism in Amish children has been dismissed with the most specious of arguments: Amish are genetically different from everyone else. With all the population genetics work done to date, it should be self evident how silly that claim is.”
Cort, are you a real biologist, or do you just play one on TV? Or maybe you didn’t take the population genetics course.
The Amish are a genetically isolated population - there have been hundreds of papers documenting that fact. They have a much higher incidence of several genetic disorders, which should be proof to any real biologist that they are not a good population to study, since they are genetically different from the general population.
Any results from studying the Amish would not be generalizable to the population at large. That’s why the NIH and CDC are resisting calls to study them for autism, not some sort of tinfoil-hat conspiracy.
You would also be reluctant to use the Amish as a study population to research autism in the community, if you really knew anything about population genetics.
“That, plus the suddenly strange behavior of the CDC in the middle of the New Jersey cluster study simply illustrates that the government is being incredibly dishonest about this whole matter.”
Can you be more specific? And can you back up your claims?
“There are other proteins besides hemoglobin that absorb oxygen. Moreover, there is a host of unanswered questions about various shifts induced in blood physiology by merely having higher amounts of nitrogen and oxygen in the blood.”
I believe that my point was the the amount of additional oxygen (and, it turns out, nitrogen) in the blood under “mild” HBOT is trivial. As for other proteins that “absorb [sic]” oxygen, they do exist, but none (apart from myoglobin, which shouldn’t be in the blood) come anywhere close to hemoglobin’s ability to carry oxygen.
And your point was….?
“Blood is only about 8% denser than water. Also, coincidentally, the solubility of oxygen in water is around 8%. That qualifies as low solubility.”
I’m not sure what your point about the density of blood was - I’m hoping that you do. As it turns out, the solubility of oxygen in water (at 20 deg C) is a hair over 9 milligrams per liter, which works out to 0.0009%. I agree, that is “low solubility” [8% would be 80 grams per liter - nearly 10,000 times more]
The solubility of oxygen in water goes down as temperature increases and as salinity (dissolved salts) increase. So, the solubility of oxygen in plasma is around 6 milligrams per liter, or about 0.0006%.
You might want to check the source of your data.
“Pressure obviously increases that. The equation is not handy, but pv = nRT lives on!!! Add to that the oxygen capacity of human serum albumin, a multi-facted protein indeed which binds to all sorts of things. Anyway, you get the point.”
Actually, I don’t get your point. The Ideal Gas Law (pv=nRT) is the relationship between pressure and volume, which really doesn’t apply. I think what you’re looking for is Henry’s Law (p = kc).
At the highest reported pressure for “mild” HBOT - 1.5 atm - the solubility of oxygen in plasma goes up to 9.6 milligrams per liter. That would be 0.00096%. While that is a significant increase, the amount of additional oxygen (and nitrogen) is trivial.
Albumin, while it does bind an amazing number of things, doesn’t bind oxygen all that much. Maybe you’re thinking of heme-albumin, one of the possible synthetic blood substitutes.
“It has been a difficult lesson in life to realize both lawyers and scientists can be adept at making sure they don’t ask the right questions.”
The difficult lesson that I’ve had to learn is that people are more willing to believe a pleasant fantasy than an unpleasant fact.
Prometheus
February 15th, 2008 at 8:40 pm
A few days ago my pediatrician showed me a mailing from our local DAN person, Dr. Mary Megson, which gave the rundown and prices for her latest offering, HBOT. It’s $650 an hour for the initial consultation and $450 an hour for the chamber. If one Googles her website, one can see that she includes dyslexia and ADHD as autism spectrum issues.
Gosh, that’s interesting.