OP
In-Water Recompression, Revisited
- Thread starter Duke Dive Medicine
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Kay Dee
Contributor
To clarify, I'm not an MD, I'm a nurse. Best fishes to you as well
Best regards,
DDM
My sincere apologies, I did not mean to insult you by referring to you as an MD!
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I totally agree, but there appears to be some blow-back on requiring FFMs, let alone surface supplied. Like I said, it isn't complicated but neither is a FFM.
Directed to all readers:
There are issues like keeping the ppO2 in the monoplace chamber below about 0.7 at 60'. It takes a fair amount of monitoring and ventilation, even with overboard dump BIBS masks. Larger metal DLCs have so much more volume that a little O2 leakage past the mask takes much longer to "contaminate" the atmosphere. You need to keep the Oxygen level down for air breaks, in case of convulsion, and fire safety... especially in a fabric chamber. A pressure hull failure of a fabric pressure vessel filled with pure Oxygen at 2.8 ATA goes way beyond the poor diver inside. It could easily take out the boat or aircraft and everyone onboard.
HBOT monoplace chambers do run a pure Oxygen atmosphere, typically around 2 ATA, but they can just surface the chamber during a convulsion (which is a much lower probability than at 2.8 ATA) and rarely treat DCS. It is also much easier to control fire risk issues in a clinical environment than on a rolling deck in a diver emergency. There is more to it than just closing the door and opening the valve, but any motivated diver could learn it.
Just to expand the discussion, there are pretty inexpensive fabric chambers rated for <5 PSI that are useful for transporting DCS injuries by air, especially in unpressurized aircraft. They are on the order of one-tenth of the price of a well-equipped 2.8 ATA version.
Not many people invest in monoplace chambers for DCS because there are a lot of limitations. Limited IWR with relatively little preparation mostly using already available gear is a good thing. Investing big bucks leads to expectations in contingency planning like treating a buddy-pair, omitted decompression, Type 2/CNS hits, dealing with simultaneous physical injuries, and treating unconscious patients. All of that is possible in a DLC (Double Lock Chamber).
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well stated.
To your last paragraph, the use of IWR in remote locales is feasible in certain circumstances, and a good idea. there seems to be an extrapolation occurring among some proponents that planning IWR for technical diving expeditions is a prudent step. IMHO, given the profiles and types of true tech expeditions among the punters (non mil/commercial) and the widespread use of ccr in such, the likelihood of IWR being an actual appropriate course of action for the most likely types of problems, is very, very slim. Sorta like using a 40 for bailout at 300fsw in a 3 person team and convincing yourself that team bailout will work. The gods of luck have to be riding on your shoulder that day..
OP
OP
With an overboard BIBS dump and a good seal the O2 percentage could be minimized. It would be interesting to hear the manufacturer's recommendation re control of the O2 percentage in the chamber atmosphere in a Flexidec. There's not much on their website. Of course you'd have to screen for flammables including polyester fabrics. Also, the procedure for seizures in a monoplace chamber is to hold the depth constant until the seizure stops to minimize the risk for pulmonary barotrauma if the seizure involves a closed glottis. A grand-mal seizure is typically self-limiting when the patient becomes hypoxemic; the chamber can be depressurized after it stops. In status epilepticus there may be no choice, and the operator would ascend extremely slowly, but that's relatively rare.
Best regards,
DDM
We're singing from the same book.
I should have made it BOLD. I have always defended IWR when other options sucked more.
No offense but that sounds like something I would write. Normally I would recommend seeking professional help when that happens!
Seriously, I agree. One of the reasons I finally decided to jump into this thread was to expand perspectives. I think any IWR procedure is a huge improvement over just a few years ago, but I'm also concerned that IWR-lite will create a false sense of security. Bad things rarely join the party solo.
(more for all readers)
For sure, they are way-better than inboard dumps. Most chambers I have seen used overboard dump BIBS since the late 1970s. We often had an O2 monitor and found that there was a lot of variation on how fast the "contamination" climbed, even with the same diver on different runs. It is hardly noticeable on a large ID chamber like 6'/1800mm-plus compared to a typical 54" ID DLC used in the field. A torpedo chamber with and inexperienced BIBS user is anyone's guess how fast it may or may not climb. Dump BIBS also have a lot more exhalation backpressure at 30' than 60'.
For those who have no clue what we're talking about, some BIBS (Built-In Breathing System) masks only have a demand regulator, very much like a Scuba second stage, mounted to an oral-nasal mask. Exhaling dumps a lot of Oxygen in the chamber... often called "contamination" for short. They aren't as available anymore but are still around, and are way less than half the price.
Overboard dump BIBS also have a demand exhaust regulator so exhalations are directed out of the chamber. Most chambers depend on the pressure in the chamber to drive the gas out so the exhaust back-pressure increases at shallow depths. More leaks past the oral-nasal mask seal when that happens.
Another factor that causes mask leakage is the supply and exhaust hoses are stiff enough to skew the mask when the head moves and the patient or attendant isn't on top of it. Factors like beards, yawning, trying to eat or drink, sneezing, and non-average face geometry can also make leakage variable.
Masks for emergency and treatment mixes used beyond pure O2 depths use a negative-biased back-pressure regulator to keep the exhaust pressure within the demand valve's limits... similar to what first stages do on Scuba regulators. Here's one of the better models: Amron International 450M BIBS Mask
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Kay Dee
Contributor
Man, pardon my french but that is a load of crap. How many IWR cases have you seen / taken part in?
I need more than two hands to count the ones I have seen over the years, and they ALL worked, some using the most basic of kit, (and surprise surprise, none to 2.8ata!). Some chose for a follow up chamber ride when back ashore, just to be safe, but most kept on diving, some the next day, some with a day off, and a couple who choose to not continue diving on that expedtion (but not because of any residual symptoms, they just thought it prudent to not do so).
However no expedition I was ever on - and mark my words I have been on a lot - that had a DCS incident that was treated with IWR was ever aborted because of said incedent (with the wholehearted consent of the treated diver of course).
And luck has nothing to do with IWR if just a few people involved have the knowledge of what they are doing.
And if one is a so called tech diver or ccr diver doing the dives you allude to, and are doing so in any local that one might refer to as a remote area, and are not at least mentally prepared for IWR, but are just relying on the CG or a helo ride to get em out trouble, well they certainly are rolling the dice big time!
And I'd hardly refer to expedtionary divers as 'punters' by the way.
Anyway, with all due respect, what you just said seems that you are very very out of touch with 'remote' expedtionary diving, very out of touch!
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A few, certainly not not more than I would need two hands to count. Possibly better planning? While sometimes bends happen, among truly experienced divers doing push type diving they have normally gotten pretty in touch with how they react to various schedules. But whatever YMMV. Some folks go on expeditions with "leaders" that have may as well hand out red shirts to the paying customers that go along, so many have been hurt or killed, but as long as the leader is a great marketer... people beam down.
You seem to think I am anti IWR, I am anti "IWR is the plan and we'll be fine" it's naive and simplistic to expeditions (then again I have seen many expeditions done in such a manner, and as the world has it, many turn out just fine, thus there is "normalization of deviance" and so forth.
Your third last paragraph just either shows a comprehension issue with regards to my earlier statements or an attempt to put words in my mouth. Either merit no response.
To your offense at my using punters. Ego much?
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