In-Water Recompression, Revisited

[Dr Simon Mitchell]

Not really, I am asking the question "what to do when it doesn't work", just like the treatment decision matrix does with Table 5 in a chamber.

I apologise. It seemed to me you were advocating an answer as much as asking a question. Complete whatever protocol you are on eg at 9m, surface, and immediately be in touch with a diving medicine authority. If your symptoms / signs are significant and not completely resolved (or if this cannot be established with certainty), then be evacuated to the nearest hyperbaric chamber for definitive recompression.

I don't think that 13.3x at 60' will go away.

Agreed. It is likely to be the standard approach to chamber recompression for a long time to come.

Simon M

 

[cerich]

Hello cerich,

IWR on air was considered in our review. I have already broken the publishing rules by pasting a segment of it earlier, and I can`t reproduce any more. Suffice to say there is limited evidence to suggest that air is not as effective as oxygen for IWR and Akimbo has provided some mechanistic discussion above. There are stories of it having appeared to work, but also some disasters too.

Simon M

My point regards air was actually along the lines of what Akimbo talked about regards mechanics..
First, I think it's important to consider when IWR is being considered. For some expeditions it's "part of the plan" and they will have stuff life a ffm and gas planned and available. That may fall inside their risk acceptable. Others, if budget allows may go flexdec. Most seem to go with a prayer however and a irrational faith that between DAN and the local whoever will come thru.
There are times when IWR even when planned out and prepared for won't be an option. The "patient" is simply going to be too afflicted. (A very recent Doria death springs to mind, from reports I have heard iwr or even a chamber on site would likely have not made much of a outcome difference)
I wonder if taking advantage of a deep drop on air followed by the more shallow high PPO2 I as per the study may have some benefits ..in consideration of the mechanical stuff that Akimbo mused about.

 

[Kay Dee]

Given that our biggest fear, death, is inescapable.............

Well, first, I can definately see your not from ISIS, nor suport their ideology!

Second, we, the collective we that is, should really learn not to 'fear' death, after all as you yourself infer, it is going to happen to every single one of us, and besides, it is just a continuation of life, albeit in a different realm. Of couse, believe or agree with that or not, that is of course everyones choice.

Nevertheless, as the (rather) late great Jim Morrison sang (and I can see you should be old enough to remember him) " Nobody gets outta here alive". So if I may be so flippant, we all should at some stage in life come to terms with that 'drop of wisdom' so to speak.

 

[Akimbo]

I wonder if taking advantage of a deep drop on air followed by the more shallow high PPO2 I as per the study may have some benefits ..in consideration of the mechanical stuff that Akimbo mused about...

Just for background, decompression chambers were used in the US and Europe for treatment long before Oxygen was introduced. Treatment was also "not very formalized" to put it diplomatically. Rules of thumb like returning the diver to the max depth of the dive and doubling ascent times were used... all on air. I have seen primitive single lock chambers that were riveted, had 2-3" diameter glass viewports, no medical/utility locks, gasketed doors, and... wait for it: lead piping. Yikes. The ASME (American Society of Mechanical Engineers) stamp was 1921. There are photos of others from the late 1800s.

As near as I can tell, Oxygen came into play in the 1930s at NEDU to accelerate decompression, at water stops and in the chamber for Sur-D (Surface Decompression). Using it for treatment didn't show up outside of hyperbaric labs until the 1950s. Sur-D-O2 was adopted relatively quickly as offshore oil stated to move into deeper and colder water. Early US Navy Sur-D tables only returned the diver to 40' but industry started developing tables by the 1960s that started looking more like Table 5 & 6... 60' on O2 but faster ascents. I got to see proprietary Sur-D-O2 tables from major US and European companies in the 1970s and they were all very similar, with the French tables being generally more aggressive using higher ppO2.

High ppO2 is much simpler on pure Oxygen, both logistically and physiologically, but treatment mixes and automatic mix-makers were widely available on bounce and saturation diving systems by the mid-1970s. They are still rare outside of sat systems, even on all but the most sophisticated HBOT (HyperBaric Oxygen Treatment) facilities.

In the end, it is functionally pretty simple. Max ppO2 plus adequate compression = DCS treatment. Staying as close to the edge of OxTox as possible = the optimum (most rapid) treatment.

Aside from developing IWR tables on pure Oxygen, I think that the expedition divers are missing an important bet. Taking advantage of those automatic Mix-Makers on their backs known as eCCRs for treatment needs development work. There will come a time when rebreathers come with "IWR treatment modes" including the ability to monitor the diver for OxTox onset.

Ultimately, they will also come with the ability to detect microbubble formation instead of using algorithms to determine decompression, effectively eliminating the need for treatment. Now if we can just find computing and sensor functionality that doesn’t self-destruct with a drop of salt water. Interesting times.

 

[Duke Dive Medicine]

So forgive me for re-intruding but........... re the above Akimbo, with all due respect it seems you do little if any true expeditionary diving.

I know he can speak for himself, but that is incorrect. He was doing expeditionary diving when I was a little kid watching Diver Dan on TV.

Best regards,
DDM

 

[Kay Dee]

I know he can speak for himself, but that is incorrect. He was doing expeditionary diving when I was a little kid watching Diver Dan on TV.

Best regards,
DDM

Pardon me, and with all due respect, but his statement of not diving, or choosing not to dive, further than an hour from a chamber seems to leave little room for expeditionary diving IMO. (No offense meant to Akimbo.) I guess it may hinge though on what you / one refers to as 'expeditionary' diving I suppose.

And yes, it doesn't surprise me you used to watch Diver Dan. If I may be so rude to ask, what is your definition of 'expeditionary diving'? Not watching Diver Dan I assume?

And how much 'expeditionary' diving do you yourself do (outside of a chamber that is, and again no offense meant, as that does appear to be you 'profession' as it were, no?).

PS. Just to be clear, I do not include Akimbo's commercial / navy diving experience in what I refer to here as expeditionary diving (although I SINCERELY admire and respect his knowledge and experience in those endeavors).

 

[Akimbo]

Second, we, the collective we that is, should really learn not to 'fear' death...

Interesting observation and I concur. That is a characteristic of every saturation diver and ex-combat swimmer I have worked with. You really have to "come to terms" with death to do the work and not go nuts. IMHO, that is a major factor that makes people panic resistant. OOA rarely kills divers; panic kills them because it makes them stupid/irrational.

I suppose that some people just aren't wired that way, which is an indication that maybe they are better-suited to pastimes that don't require self-rescue skills.

 

[Akimbo]

... It seemed to me you were advocating an answer as much as asking a question...

Nope, definitely what I would do and the evolution of how I would deal with worsening situations. Now for another pet-peeve:

How are you addressing convulsion management beyond just saying use an FFM? From personal experience, I submit that recreational FFM training is not nearly enough for IWR. The biggest risk isn't convulsion; it is barfing in the mask and not knowing how to deal with it. I have never personally seen or worked with diving supervisors that had a diver convulse them. However, almost everyone has pulled divers off BIBS masks for an air break due to nausea (a common OxTox symptom). Some have barfed in the chamber... but some may have been from excessive libations onshore.

The supers noticed excessive belching, twitching, etcetera about half the time. It isn't knowable how many of these less violent symptoms would have been followed by convulsion but almost certainly more than zero. Commercial and military divers have been taught how to barf in a hat or mask. To the best of my knowledge, recreational divers are not.

Think about it, you are on a FFM, probably dehydrated due to ultra-dry O2, and hanging-off with a small swell. You are in a stress-inducing situation or wouldn't be doing IWR. I contend that you are more likely to barf than if you were breathing O2 on deck.

The diver has to made acutely aware of all OxTox symptoms because their in-water tender can't see many of them like they could in a chamber. They also need a Jon-line so they can float effortlessly and MUST be trained to breathe very deeply and slowly to manage CO2, which is worse in a FFM and is believed to exacerbate OxTox.

Sorry if I'm covering old territory for you but like you indicated, lots of divers are reading this.

 

[Duke Dive Medicine]

Pardon me, and with all due respect, but his statement of not diving, or choosing not to dive, further than an hour from a chamber seems to leave little room for expeditionary diving IMO. (No offense meant to Akimbo.) I guess it may hinge though on what you / one refers to as 'expeditionary' diving I suppose.

And yes, it doesn't surprise me you used to watch Diver Dan. If I may be so rude to ask, what is your definition of 'expeditionary diving'? Not watching Diver Dan I assume?

And how much 'expeditionary' diving do you yourself do (outside of a chamber that is, and again no offense meant, as that does appear to be you 'profession' as it were, no?).

PS. Just to be clear, I do not include Akimbo's commercial / navy diving experience in what I refer to here as expeditionary diving (although I SINCERELY admire and respect his knowledge and experience in those endeavors).

LOL you obviously know him and if you do then you know what he's done, much of which falls into my own definition of expeditionary but perhaps not yours. My bio is on the website but for the record I'm a retired Navy salvage and EOD diver (inspired largely by Diver Dan and JYC) who got into health care as a second career. Much of what we're trained in and what we did was expeditionary. I've also participated in what you'd probably consider expeditionary dives with some film crews in remote locations. I don't dive in any medium any more because my ears are broken. Cheers back at ya

Best regards,
DDM

 

[Duke Dive Medicine]

Nope, definitely what I would do and the evolution of how I would deal with worsening situations. Now for another pet-peeve:

How are you addressing convulsion management beyond just saying use an FFM? From personal experience, I submit that recreational FFM training is not nearly enough for IWR. The biggest risk isn't convulsion; it is barfing in the mask and not knowing how to deal with it. I have never personally seen or worked with diving supervisors that had a diver convulse them. However, almost everyone has pulled divers off BIBS masks for an air break due to nausea (a common OxTox symptom). Some have barfed in the chamber... but some may have been from excessive libations onshore.

The supers noticed excessive belching, twitching, etcetera about half the time. It isn't knowable how many of these less violent symptoms would have been followed by convulsion but almost certainly more than zero. Commercial and military divers have been taught how to barf in a hat or mask. To the best of my knowledge, recreational divers are not.

Think about it, you are on a FFM, probably dehydrated due to ultra-dry O2, and hanging-off with a small swell. You are in a stress-inducing situation or wouldn't be doing IWR. I contend that you are more likely to barf than if you were breathing O2 on deck.

The diver has to made acutely aware of all OxTox symptoms because their in-water tender can't see many of them like they could in a chamber. They also need a Jon-line so they can float effortlessly and MUST be trained to breathe very deeply and slowly to manage CO2, which is worse in a FFM and is believed to exacerbate OxTox.

Sorry if I'm covering old territory for you but like you indicated, lots of divers are reading this.

I know that's to Simon but FWIW I've only seen a couple of people throw up from O2 toxicity during my career. I've seen lots of convulsions, though at IWR depths on established tables both are highly unlikely. I do think you raise an excellent point about FFM training, though personally as both a military and commercial diver, nobody ever taught me how to throw up in any type of breathing apparatus and I'm not sure how you'd simulate that (cue the peanut gallery).

Best regards,
DDM

<edit> I take it back. In Mk 16 school they mentioned that it was possible to vomit into the breathing loop. We didn't practice though