Friday, June 4, 2010

Hyperbaric Oxygen: What Is The Correct Dose?

Ask four experts and you'll get five opinions, as the old joke goes. We were so looking forward to Thursday afternoon's UHMS plenary session but came away even more completely baffled about how your average hyperbaric physician decides what pressure, duration, and number of treatments to prescribe. To say there is wide variation in practice would be a gross understatement.

Only the Navy, the Air Force, and the Divers Alert Network, it seems, stick to some sort of standard dosing tables. Even these standards share a dubious pedigree, which speaker Paul Sheffield traced back to (1) the arbitrary selection of the 90-minute sessions used to treat gas gangrene in 1961 and (2) the strange translation from 45 feet of seawater or FSW to 2.36 atmospheres absolute or ATA. Well, that explains that, anyway.

Practice is one thing. A lack of guidance on dosing also hamstrings the responsible clinical investigator. Dr Neil Hampson, of Virginia Mason Medical Center in Seattle, recounted his quest for "the Holy Grail of HBO2 dosing" when powering his ongoing randomized, controlled trial for carbon monoxide poisoning. He ended the session by suggesting that some measure of cumulative dose, such as ATA-hours, might prove more meaningful than individual doses or numbers of treatments. We seriously doubt it. And we're little comforted by Dr Hampson's claim that "HBOT works, but we still don't know the right dose." Only the right dose works, or are we wrong?

Oxygen is a drug. Pressure is strong medicine. Yet dose ranging studies and so much other basic science has been left undone, for so many decades, we sometimes wonder how hyperbaric physicians expect to gain the respect of the broader medical community.

By holding plenary sessions like this one, is the answer, and sharing a healthy, truthful accounting of the state of affairs. Now to act on the lack of information. Then the applause, applause.

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