I would like to have more discussion on this apparent disagreement that has been unacknowledged so far:
My thoughts on the matter:
- There isn't much hard data that I can find on divers getting recompressed within ~5min of symptom onset (i hope DDM can confirm or deny this). Early recompression is within 90min in some studies.
- There seems to be anecdotal data of early recompression working (such as 100days-a-year's post).
- Current literature in other medical field puts a strong emphasis on earlier reperfusion improving outcomes (specifically in stroke and MI patients, where a symptom onset to treatment time of 60-90min is targeted)
- It will be difficult to power a study enough that one can find small changes in outcomes for the patient population we are looking out
- We know that Sur-D works, so recompression prior to symptom onset is very effective
- It would be quite strange if the function of (time to recompression from symptom onset) to (clinical outcome) was discontinuous, we know that when (TTR from symptom onset) is negative, the outcomes are good, and we know that when (TTR from symptom onset) goes towards infinity (no treatment), outcomes are worse
First citation
"Fifty-nine divers with DCS treated in less than 6 hours from onset of symptoms to hyperbaric recompression were included retrospectively."
"There was a relationship between a longer delay to treatment and incomplete recovery"
Second citation
"The medical histories of 28 divers treated at a hyperbaric facility in the Maldive Islands in the Indian Ocean were evaluated."
"Divers presenting later than 17 hours after surfacing (the median time to treatment after surfacing for the whole group) were likely to have more intense symptoms on VASS (median 100%) than those who presented earlier for treatment (median 30%, P = 0.02)."
I don't feel these quotes do justice to the data stated in the articles
- from the first article: "TTR did not appear to influence the final outcome when univariate analysis was applied with a cut-off of 90 min.... ... we noted a relationship between TTR and incomplete recovery (P = 0.03), but the increase risk appeared negligible with an adjusted OR of only 1.01..."
- for the second article, that statement speaks only to severity on presentation, not outcome from their outcome "Neither more HBOT nor a worse outcome of DCS could be related to delay to treatment longer than 17 hours."
Hi thin_air,
Our (DDM's) opinion on in-water recompression is that it may be a reasonable part of an emergency plan when it is administered by an appropriately trained, experienced, and equipped team. Certainly there are times when it's appropriate, as there are times when administering 100% O2 on the surface and observing is appropriate. It's up to that team to weigh the risks and the benefits of recompressing in the water on the spot vs transporting to a recompression facility, and at the risk of sounding elitist, not every dive team is qualified to do that. Sometimes they don't know what they don't know.
Part of what I'd consider the irony of in-water recompression is that the injured divers who could most benefit from recompression, i.e. those with the most severe symptoms and are most in need of immediate recompression, are also the ones who are most likely to be harmed by it. It's hard to establish solid go/no-go criteria since there is so much individual variability. It's worthwhile to look at established references like the US Navy Diving Manual: "In divers with severe Type II symptoms, or symptoms of arterial gas embolism (e.g., unconsciousness, paralysis, vertigo, respiratory distress (chokes), shock, etc.), the risk of increased harm to the diver from in-water recompression probably outweighs any anticipated benefit." (p 17-16)
Having a plan and a bunch of switched on dudes (and dudettes)to execute that plan is generally better than the alternatives. I think part of the disconnect in many of these conversations is the failure to differentiate patient populations, something like this:
- minor type 1/2 that resolves upon reaching depth
- minor type 1/2 that doesn't resolve upon reaching depth
- major type 1/2 that resolves upon reaching depth
- major type 1/2 that doesn't resolve upon reaching depth
For minor type 1 (and possibly 2) hits, we probably aren't having a huge effect on morbidity with IWR vs surface O2.
For major hits that resolve at depth, the risk to the patient is probably less then those that don't resolve, as they're "normal" at depth.
For the major hits that don't resolve upon reaching depth, the question (as i have it in my mind) becomes what is the risk of keeping them at depth longer with their symptoms and the associated risks vs how quickly can we surface them again and provide surface care to manage their symptoms (and reduce their in water time with severe symptoms that increase the risk of a poor outcome).
I don't know who's doing what with respect to IWR in the tech-rec diving community. I'd love to find out. When I see posts like some of the previous ones here, though, I get concerned about it being misapplied, with possibly serious consequences. A good example is the post above about divers returning to diving hours after IWR for DCS involving paralysis. That's incredibly dangerous and the unfortunate consequence of getting away with it is that the behavior is reinforced and perpetuated. Again, classic normalization of deviance. Of course people are going to do what they will, and in the grand scheme of things I believe you're right about the pendulum swinging to and fro. All my colleagues and I can do is provide information based on what we know to be best practice at present.
I do appreciate the effort that you and your colleagues put forth in helping educate those who don't do hyperbarics on a daily basis, it certainly helps move the field along and helps us make better decisions.
As for what happens out in the real world, I suspect there is a non-trivial amount of divers who return for a reped (as Akimbo calls it) or IWR. For example, I do staged deco dives from shore, and have on multiple locations started walking out of the water (with doubles +/- 1 or 2 stage/deco bottles), gotten thigh deep in water and turned right back around because something doesn't feel "right", and did a short dive on O2 or 50% in the 3-6m range, then come back to exit in 20min and all is well.
Where does this fall on the spectrum, I don't know, but it's been working alright for me so far (although now i just pad my 6m stops significantly and use a more conservative GF). It would seem the spectrum goes something along the lines of padding stops, a reped (getting back in to do more deco with no symptoms), the grey area of getting back in with subclinical DCI symptoms, getting back in for IWR with minor symptoms and lastly trying to treat major symptoms with IWR.
This is gross oversimplification, but if it can help push people to the left of that spectrum (that is to say, towards padding stops) then a small victory can be achieved.
There will always be those who will use tools at their disposal inappropriately. If you don't understand what you are doing and why, this may very well be you. If the only exposure someone has to IWR and DCI treatment is this thread (or even all conversations on this forum) then they aren't in the strongest position to do IWR. I would hate for that to blunt the conversation.