In Water Recompression

TEKDiveUSA

TEKDiveUSA

Member
What are your thoughts on in water recompression? At TEKDiveUSA.2018 David Doolette will be presenting the process and evidence behind a committee of diving medicine experts who recently revised guidelines for the prehospital management of decompression illness. This committee reached a cautious, qualified endorsement of in-water recompression in some circumstances. Is this a topic you are following?
daviddoolette2018-1024x621-jpg.442473


Full description of the presentation here- In-water recompression: expert diving medicine committee opinion - TEKDiveUSA
 
IMHO, the fundamental problem with in-water recompression is that the more the diver needs it, the less he's able to do it.

At one end of the spectrum, we have someone who's got some pain in the arm, or maybe some skin mottling, after a one hour dive. No problem going back in the water, but is it useful?

At the other, we have a diver who can't stand by himself, keeps vomiting (or trying to), is already dehydrated and possibly cold, has a CNS above 100% (and a max ppO2 above 1.5 to boot)... Would it be useful? Sure thing. Is it likely to end with a better outcome than staying on the surface on O2? Well, no.

In between, obviously, there's a big gray area. And within that gray area, there's some circumstances where there is no other option. Since it will happen, I think it's great that knowledgeable people have come up with guidelines about what to do and when. And I'd be delighted to listen to this.

But I'd be cautious about people focussing on this over basic simple steps like: Who's bringing the O2 kit, and how much of it do we want? Where the nearest chamber? How do we get there?

Cheers,

Matthieu
 
I'm in Florida teaching a CCR Cave course this week and diver (not from our team) got bent and called DAN for a referral to the nearest chamber. They were unable to refer him to a chamber within the state of Florida that was accepting divers for recompression. It is a scary situation. The only reason I bring this up is that it is not just far flung reaches of the globe where access to a chamber can be difficult. I for one am excited to see the industry taking steps to educate divers on various options including in water recompression.
 
emmbee said:
IMHO, the fundamental problem with in-water recompression is that the more the diver needs it, the less he's able to do it.


At the other, we have a diver who can't stand by himself, keeps vomiting (or trying to), is already dehydrated and possibly cold, has a CNS above 100% (and a max ppO2 above 1.5 to boot)... Would it be useful? Sure thing. Is it likely to end with a better outcome than staying on the surface on O2? Well, no.


Cheers,

Matthieu
Click to expand...

Do you not recall a paper I shared with you about an observational study on IWR amongst Hawaii fishermen from about 1985-86 and its extreme efficacy in particular on type II bends. Taken from page 4:

upload_2018-1-21_12-10-23.png

Link to paper http://nsgl.gso.uri.edu/hawau/hawaut86001.pdf

Their method was to go as deep as necessary on air to mechanically re-compress the bubble immediately and then start the ascent.

Granted its only an observational paper but that's all your going to get as I cant see too many divers volunteering to get a type II bend to see if IWR works.

Cathal
 

Attachments

  • upload_2018-1-21_12-8-51.png
    upload_2018-1-21_12-8-51.png
    205.5 KB · Views: 4
I certainly do recall you talking about it :)

There's a couple of things that needs to be pointed out about this:
- there's a massive survivorship bias. They only looked at active divers. It goes without saying that those who couldn't take this kind of punishment got out of the business. Or got dead. So all this says it that "it works for those for who it works - at least for a while". Which, well, yes, that's good to know, but that's not quite the same as "it works".
- it's very anecdotal. In particular the story of the guy who did IWR and was fine while his buddy died on the way to the chamber is a strong narrative that suggests IWR is better than waiting for the chamber. You know as well as I do that divers getting bent regularly have buddies who did the exact same dive and are perfectly fine. DCS is inherently probabilistic. You can't derive meaning from one anecdote.
- the conditions are very different from what people on this forum do. Some are pointed out. Warm, clear water. They also do many short dives. In between they get some rest. They get a nice air break. They get food. They get water. We don't. The paper doesn't talk about dive times, but I wouldn't be surprised if you spent more time in the water in one dive than they did in a day. Obviously going back in after their first dive of the day (which is what they intended to do anyway), or any for what matters, is a much more reasonable proposition than it would be for you after your one dive (that you ran as if you would not go back in).

In any case, I certainly did not say that IWR did not work. There's little question that it does. If you consider the pressure alone, you do the same thing using water depth as they do in a chamber which compressed gas, and that works, so there. The problem is "everything else" that makes it safe to do in a chamber, and not safe at all in the water.
The question then always was when, under what circumstances, is it a reasonable thing to do, and what to do exactly. Until recently the answers were never and don't do it at all. And that's fine, but clearly there are cases where it would in fact be the right thing to do. So, like I said, I think it's great that the right people came up with more flexible guidelines and procedures, and I'd love to hear this talk. I'd just be cautious about people taking IWR as an general alternative to surface O2 and possibly a trip to the chamber.

Cheers,

Matthieu
 
Last edited:
Randy Thornton said:
I'm in Florida teaching a CCR Cave course this week and diver (not from our team) got bent and called DAN for a referral to the nearest chamber. They were unable to refer him to a chamber within the state of Florida that was accepting divers for recompression. It is a scary situation. The only reason I bring this up is that it is not just far flung reaches of the globe where access to a chamber can be difficult. I for one am excited to see the industry taking steps to educate divers on various options including in water recompression.
Click to expand...

Yeah, I heard a similar story here just a couple of months ago. Rapid ascent, hospital emergencies, doctors googling up DCS, public chamber unavailable due to a technical issue preventing staffing, private chamber unavailable due to insurance issues.

The thing is, none of this is new. All of it happened before. And it will happen again. So it should be considered before the incident happens. It certainly shouldn't be a surprise. And if it is a surprise, it's hard to see how they'd be ready for IWR.

Having said that, I entirely agree that it's great that the industry recognises this and is moving forwards.

Cheers,

Matthieu
 
emmbee said:
I certainly do recall you talking about it :)

There's a couple of things that needs to be pointed out about this:
- there's a massive selection bias. They only looked at active divers. It goes without saying that those who couldn't take this kind of punishment got out of the business. So all this says it that "it works for those for who it works". Which, well, yes, that's good to know, but that's not quite the same as "it works".
- it's very anecdotal. In particular the story of the guy who did IWR and was fine while his buddy died on the way to the chamber is a strong narrative that suggests IWR is better than waiting for the chamber. You know as well as I do that divers getting bent regularly have buddies who did the exact same dive and are perfectly fine. DCS is inherently probabilistic. You can't derive meaning from one anecdote.
- the conditions are very different from what people on this forum do. Some are pointed out. Warm, clear water. They also do many short dives. In between they get some rest. They get a nice air break. They get food. They get water. We don't. The paper doesn't talk about dive times, but I wouldn't be surprised if you spent more time in the water in one dive than they did in a day. Obviously going back in after their first dive of the day (which is what they intended to do anyway), or any for what matters, is a much more reasonable proposition than it would be for you after your one dive (that you ran if you would not go back in).

In any case, I certainly did not say that IWR did not work. There's little question that it does. If you consider the pressure alone, you do the same thing using water depth as they do in a chamber which compressed gas, and that works, so there. The problem is "everything else" that makes it safe to do in a chamber, and not safe at all in the water.
The question then always was when, under what circumstances, is it a reasonable thing to do, and what to do exactly. Until recently the answers were never and don't do it at all. And that's fine, but clearly there are cases where it would in fact be the right thing to do. So, like I said, I think it's great that the right people came up with more flexible guidelines and procedures, and I'd love to hear this talk. I'd just be cautious about people taking IWR as an general alternative to surface O2 and possibly a trip to the chamber.

Cheers,

Matthieu
Click to expand...

As we are not looking to make Training Agency statements on this topic on a public forum I cannot see the downside of a symptomatic diver at depth who is conscious, accompanied by their buddy, can maintain a safe breathing loop, has good buoyancy control is warm and attached to a shot line staying on elevated levels of O2 for as long as they can manage physiologically i.e. until they get cold. Especially with the increasing use of heated undergarments, a diver that adds an additional 60-90 mins on top of his planned run-time at elevated levels of O2 in the event of being symptomatic can only add to the chances of experiencing a successful outcome.

Cathal
 
emmbee said:
IMHO, the fundamental problem with in-water recompression is that the more the diver needs it, the less he's able to do it.

At one end of the spectrum, we have someone who's got some pain in the arm, or maybe some skin mottling, after a one hour dive. No problem going back in the water, but is it useful?

At the other, we have a diver who can't stand by himself, keeps vomiting (or trying to), is already dehydrated and possibly cold, has a CNS above 100% (and a max ppO2 above 1.5 to boot)... Would it be useful? Sure thing. Is it likely to end with a better outcome than staying on the surface on O2? Well, no.

In between, obviously, there's a big gray area. And within that gray area, there's some circumstances where there is no other option. Since it will happen, I think it's great that knowledgeable people have come up with guidelines about what to do and when. And I'd be delighted to listen to this.

But I'd be cautious about people focussing on this over basic simple steps like: Who's bringing the O2 kit, and how much of it do we want? Where the nearest chamber? How do we get there?

Cheers,

Matthieu
Click to expand...


Hello Matthieu, as someone who has seen IWR work first hand using the diver's CCR, I can't imagine not trying it unless the diver's condition is such that they could not maintain consciousness, or water conditions were too cold or rough. I would certainly want to use it were I symptomatic. Citing a theoretical CNS clock percentage as a reason for caution is alarmist given that many if not most CCR divers exceed 100% CNS regularly, and that CNS calculations are an entirely theoretical model, and a very conservative one at that. One way to mitigate the IWR tox risk would be to have a dedicated FFM on an O2 CCR. If I were running a tech boat I would have one charged up and ready to go.

In all but the most ideal circumstances, like having a chamber on the vessel, there will be a delay in treatment, which means a higher probability of sustaining permanent damage from DCS. I'm glad to see an attempt to formalize the procedure. We all acknowledge the dangers of CCR diving, so I don't really understand such emphasis on caution regarding something with the potential to completely reverse the symptoms of DCS. The emphasis should be on making IWR procedures maximally safe so people are less afraid to try it when it's the best option... -Andy
 
You must log in or register to reply here.
Back
Top