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March 2017    Download the Entire Issue (PDF) Available to the Public Vol. 32, No. 3   RSS Feed for Undercurrent Issues
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Tweaking the Inwater Recompression Protocol

medical experts share concerns about safety

from the March, 2017 issue of Undercurrent   Subscribe Now

While divers writing to Undercurrent generally indicate that in case of bends symptoms, they would seriously consider underwater recompression in remote places, two medical men, a DAN physician and the clinical director of dive medicine at Duke University, find serious fault with the protocol presented by Bret Gilliam.

"Most DCS cases improve with therapeutic surface oxygen which avoids the risk of drowning."

Petar J. Denoble MD, of DAN (Diver's Alert Network) wrote that although most diving medicine experts recognize the value of IWR in selected cases and in special circumstances, most physicians specializing in diving medicine have serious caveats.

Denoble pointed out that some DCS cases progressively deteriorate regardless of treatment, which raises the specter of a diver in treatment becoming dangerously ill while underwater. To re-immerse him quickly, as Gilliam's protocol suggests, would mean no opportunity to ask him questions and evaluate him properly. However, if treatment began on the surface with 100 percent oxygen for one cycle of 20 minutes, most of these progressive cases could be identified.

He says that most mild cases will resolve regardless of a treatment delay, so IWR would be an additional risk. In fact, he says, most DCS cases improve with therapeutic surface oxygen, which avoids the risk of drowning.

Denoble issued this dire warning: "What is most dangerous with Bret Gilliam's protocol is that he recommends treatment at depth of 60 feet (18m), 2.8 ATA (bar) of oxygen, which carries a high risk of oxygen seizures, much higher in immersion than in a dry recompression chamber. The excessive pressure of oxygen in such conditions cannot be justified in any way."

Eric Hexdall, Clinical Director at Duke Dive Medicine, said that Gilliam's protocol greatly exceeded the generally accepted immersed oxygen exposure limit of 1.6 ATA (bar) absolute. Citing U.S. Navy tables 5 and 6, he confirms that while patients treated on these tables routinely breathe oxygen at 2.82 ATA in a hyperbaric chamber with no adverse effect, these patients are at rest, on the surface and dry.

"Not perfect... but an acceptable risk under the circumstances."

"Immersion and diving greatly increase the risk of CNS O2 toxicity due to CO2 retention and other mechanisms that are still under investigation. The risk of CNS O2 toxicity while breathing 100 percent O2 under water at 60 feet (18m) is much higher than at the same partial pressure of O2 in a chamber. Further, the protocol referenced in your article recommends that the diver use an open-circuit scuba regulator. Should a diver on this protocol suffer a seizure under water, he or she would almost certainly drown. All of the established protocols for IWR that I'm aware of recommend use of a full face mask and do not exceed 30 fsw (9m) on 100 percent oxygen."

He, too, adds the warning, "The in-water recompression protocol outlined in your article presents an unacceptably high risk for divers and should not be attempted. There is no controversy about this statement; rather, it is grounded in medical science and well-established best diving practice."

Hexdall offered that "IWR should only be undertaken by divers who are equipped, trained and experienced in doing so, and should be part of an overall well-considered emergency plan. There are safer, established protocols for IWR."

More information can be found at: http://rubicon-foundation.org/in-water-recompression and http://www.navsea.navy.mil/Home/SUPSALV/00C3-Diving/Diving-Publications

Bret Gilliam's Rebuttal

Gilliam replied, "I was surprised to read the response from Petar Denoble, especially since I had discussed this subject fully with both Bill Ziefle (President of DAN) and him in a telephone conference before I wrote the material. I also provided them with the protocol I was suggesting.

I believed Denoble essentially agreed with me on the practical need for IWR when evacuation was not an option. That included my suggestion that the easiest path to resolution was a Table 5 that only required a total of 40 minutes at a depth of 60fsw (18m), split with an air break. He expressed concern only about the potential controversy among clinicians who were not experienced with innovative treatments for DCS in the field. I agreed ... noting that controversies always arise, but the reality of options in a remote location mandated action, and some minimal risk was tolerable. I did not think he expressed any disagreement at the time."

Gilliam says he endorses the use of full-face masks as well as thoroughly assessing a diver to evaluate the symptoms prior to putting him back in the water, plus an initial surface breathing period of 100 per cent oxygen while on deck to see if symptoms resolve. Only if symptoms were not relieved was there a primary priority in getting the diver back under pressure in the ocean and on O2 within the hour. Gilliam says the risk of a CNS toxicity reaction for a diver at rest at 60 fsw (18m), whether in a cramped, confined, hot chamber or in the cool fluid weightless environment underwater, is extremely low ... around one or two percent.

"Not perfect ... but an acceptable risk under the circumstances. We've never had an incident, and it's been used by scores of people since the early 1970s."

It seems that the only real disagreement from clinicians like Denoble is based on an initial depth of 60fsw (18m) for two 20-minute periods on oxygen. Gilliam says he understands the concern of those medical professionals who are used to working in a hospital hyperbaric facility.

"An informed decision, and a practical intellectual discussion of the risks and outcome, advances science and can save people who would otherwise face disaster. I do hope that the diving pros on the remotely located resorts and vessels will get the necessary gear and training and be ready should the time come."

- John Bantin

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