A while back on Autism Street, I questioned the claim by DAN! doctor, Dan Rossignol, that children he wrote about in an article that appeared in the pay-to-publish, not peer-reviewed journal Medical Hypotheses, were treated with “mild hyperbarics” at 1.3 ATA.
In hyperbaric medicine, the term “1.3 ATA” has the very specific scientific meaning of “1.3 Atmospheres Absolute”, and it is a likely overstatement (due to rounding) of the actual treatment pressure in that particular study. Put simply, “atmospheres absolute” refers to the total pressure, and includes that actual pressure of the atmosphere. It’s also an absolute pressure that is apparently beyond the physical capabilities of the equipment that was used (a Vitaeris 320), unless the chamber were located well below sea-level, or housed inside another, larger, and pressurized hyperbaric chamber. I suggested that he publish an erratum. He was kind enough to reply to my e-mail, in which he responded, in part with:
HBOT measurements are typically reported to 2 significant figures, i.e. 1.3, 1.5, 2.0, 2.4, 3.0 ATA, etc… Therefore, this properly rounds to 1.3 ATA (we did not report the pressure to 3 significant figures as would be the case with 1.30 ATA).
As it turns out, this may not be entirely true. I responded with the following:
At least two of the papers cited in your references (Collet et al., and Montgomery et al.) show treatment pressures of 1.75 atmospheres. There might even be more. Would those have been acceptable to be published at 1.8? Do you think a real peer-reviewed journal would be requiring that you publish an erratum? I think so, but I could be wrong. In many of the “typical” numbers you list, reporting to 2 significant figures does not change the accuracy anyway (2.0 ATA is stated instead of 2.00 ATA, 3.0 ATA instead of 3.00 ATA, etc.).
Dr. Rossignol, to my knowledge, did not publish an erratum. He did not comment on the apparent overstatement of treatment pressure further. So it would appear that he intends to stick with his assertion that,
HBOT measurements are typically reported to 2 significant figures, i.e. 1.3, 1.5, 2.0, 2.4, 3.0 ATA, etc…
That’s fine, we can work with that, but remember it. It’s going to be very important in a minute.
I later wrote a little more about the physics of so-called “mild hyperbarics” again, and included a notation of a new study that Dr. Rossignol, appeared to be working on.
There’s another “hyperbaric therapy as a treatment for autism” study underway. It appears to be headed up by Dr. Rossignol, and has three clinical locations supervised by Doctors Liz Mumper (Virginia), Cindy Schneider (Arizona) and Jeff Bradstreet (Florida) – none of which appear (according to a search at ABMS) to have board certification in Developmental-Behavioral Pediatrics, Child Neurology, Neurodevelopmental Disabilities or Undersea & Hyperbaric Medicine.
Well, it looks as though that study has wrapped up. Is there a forthcoming publication that will claim that the children in the study were treated with “mild hyperbarics” at 1.3 ATA? Will it be published in a journal like Medical Hypotheses, JAPandS, or Medical Veritas? If it’s headed for a respectable peer-reviewed medical journal, and the treatment pressure is claimed to be 1.3 ATA, there might be a problem.
You see, in the real world, a Vitaeris 320, is probably not a hyperbaric chamber that can produce a full 1.3 Atmospheres Absolute – even at sea-level. Its non-rigid construction means that it’s directly influenced by the ambient atmospheric pressure. To calculate the absolute pressure inside the chamber at any given time doesn’t require anything more than knowing the current actual atmospheric pressure outside the chamber, and the slight pressure added by the compressor that inflates it. Although it does vary slightly, at sea-level the average atmospheric pressure is about 14.696 PSI. According to the manufacturer’s spec sheet, the chamber introduces an operating pressure of 4 PSI, which would yield a total pressure of about 18.696 PSI – 1.27 ATA. Don’t forget, that’s at sea-level!
The study mentioned above, lists the following clinical trial locations:
Are all of those cities at sea-level? No.
Will this matter? Absolutely.
It’s a simple fact of physics that as elevation increases, atmospheric pressure decreases. Although there are several influencing variables involved, this is probably most easily understood in layman’s terms by knowing that weight of the column of air above you gets smaller as your altitude increases (as you ascend, the column above you is shorter and simply weighs less – exerting less pressure).
So what does this mean for this study? It means that if the study used Vitaeris 320 chambers, and reports that children were treated with 1.3 Atmospheres Absolute, it should raise more than a few eyebrows.
Firstly, if the study does not report actual atmospheric data for pressure at the study locations during treatment, it will be incomplete. Remember, for a non-rigid chamber, treatment pressure is measured by adding the actual ambient pressure to the pressure added by the compressor used to inflate the chamber. There is no way to measure the actual treatment pressure without knowing the actual ambient atmospheric pressure at the time of treatment.
Side note: It could be tempting for one to read a weather report from the National Weather Service in the U.S. and simply think that the pressure reported is the actual ambient atmospheric pressure at the study location (station pressure). Unfortunately, that’s not how it usually works. The National Weather Service typically reports “altimeter pressure” and “sea-level pressure”. See section 11.6, Table 11-2 from the Federal Meteorological Handbook No. 1. These adjusted pressures (corrected for elevation and temperature) are done to make pressure systems on weather maps more meaningful (and not simply reflective of the topography), and to allow aircraft pilots to adjust their instruments to the current conditions. With an altimeter calibrated to what the pressure “would be” at sea-level, instruments can accurately reflect the actual altitude of the plane. This is important if you intend to land on a runway that is always 1135 ft. above sea-level.
Secondly, if the study does not claim to have “measured” the treatment pressure, but instead asserts that it is 1.3 ATA, it will be difficult for any publication to substantiate the claim that the treatment pressure was uniformly (or even approximately) 1.3 Atmospheres Absolute at all study locations, due to the varying elevations of the study locations.
Let’s use Phoenix, Arizona (one of the study locations) as an example. The elevation of Phoenix, Arizona is approximately 1135 ft. above sea-level. This means that the ambient atmospheric pressure is about 14.10 PSI simply due to the elevation. 14.10 PSI plus an added 4 PSI gives us a total of 18.10 PSI – 1.232 ATA! Using Dr. Rossignol’s statement,
“HBOT measurements are typically reported to 2 significant figures, i.e. 1.3, 1.5, 2.0, 2.4, 3.0 ATA, etc…”
1.232 ATA in Dr. Rossignol’s words, “properly rounds to” 1.2 ATA!
Will the study report this? Or will it claim a very unlikely (if not impossible) treatment pressure of 1.3 Atmospheres Absolute? Following Dr. Rossignol’s apparent rounding preferences, we’re talking about a potential overstatement of the pressure added by the hyperbaric chamber of 50% for Phoenix alone. The Lynchburg, Virgina study location will quite likely present similar problems (elevation 938 ft. above sea-level) for Rossignol’s work. Is Dr. Rossignol, really concerned about the accuracy of the science in his work? We might just find out soon enough.
For anyone interested, here’s a table of estimated total pressure provided by a Vitaeris 320 at selected U.S. cities. Keep in mind that these estimates reflect the manufacturer’s specification of 4 PSI of operating pressure, and the expected atmospheric pressure due to elevation alone, and do not account for the slight variations in the weather. (Elevations retrieved from Airnav.com).
It’s no surprise that parents of autistic children who “believe” that “mild hyperbarics” will somehow provide benefit for autism itself, would seek insurance reimbursement. In fact, some may interpret a statement by Dr. Rossignol to express such a view:
One of the reasons we wanted to study the 1.3 ATA chambers is because this is something that is available at home. We hope that if it does work and is proven, we can begin to have insurance reimburse for hyperbaric and this is one of our goals, as well.
Besides the obvious problem that scientifically “proving” that treatment with “1.3 ATA” will be difficult with chambers that likely don’t provide 1.3 Atmospheres Absolute, what are insurance companies supposed to think? Would insurance companies like the idea of reimbursing for HBOT treatment at a specific pressure that really isn’t?