In Water Recompression

[Akimbo]

How much deeper, and what's an acceptable nitrox mix?

Perhaps the bigger question is how big a diluent load in the faster tissues does it take before deeper than 20' matters in terms of bubble formation sufficient to cause symptoms?

(background for other readers)
It is very rare that DCS symptoms are perceived by divers while still in the water; even on commercial deep HeO2 bounce diving tables. This was true even in the days when bells were commonly used for commercial bounce dives -- where divers were less distracted and decompression could easily be switched to treatment.

We also know that time to treatment is a critical factor in the onset of DCS symptoms. There is a very broad gray area between "prophylactic decompression" and DCS treatment; in the water or in a chamber. These days, the difference between proprietary commercial Sur-D (Surface Decompression using Oxygen) tables and a Treatment Table 5 or 6 are hard to tell apart. In fact, I can't remember a case where a diver perceived DCS symptoms during the <5 minute surface interval before getting back in the chamber for Sur-D, which would be a severe case of omitted decompression without the chamber portion of the table.

 

[Duke Dive Medicine]

IWR will always have 2 camps. From the spearfishing community and talking to people at tournament weigh ins, no one formally reports doing IWR. But it's well talked about among spearos. I'd guess from those spearo's who took a hit, IWR was used 5 - 10 times more than going to a chamber, it's that wide spread.

Great information, thanks!

Best regards,
DDM

 

[rjack321]

I have done IWR a couple times myself. And sent people back down for more deco a few times. When someone is on the boat ladder, still fully kitted up, and you ask, "how was the dive?" and the answer is "great but my arm hurts" sending them back down is the best option. Yes they could be having an MI, you are still hours (by boat) away from any kind of EMS. Doing an extra 30 mins of supervised deco (I hesitate to call this IWR since their feet never even got dry) addresses the horse in the room, but perhaps not the zebra.

 

[Duke Dive Medicine]

When someone is on the boat ladder, still fully kitted up, and you ask, "how was the dive?" and the answer is "great but my arm hurts" sending them back down is the best option. Yes they could be having an MI, you are still hours (by boat) away from any kind of EMS. Doing an extra 30 mins of supervised deco (I hesitate to call this IWR since their feet never even got dry) addresses the horse in the room, but perhaps not the zebra.

No sir, with all due respect, it is not the best option, not by a long shot. You hit the nail on the head yourself by saying that it could be an MI (or a mechanical injury, or a blood clot, or an infection, or lots of other things). It IS IWR, however you want to label it, and as soon as you send somebody down with the goal of treating a medical condition, you've assumed responsibility for whatever happens to that individual. MI in a diver is not a zebra. If your diver WAS having an MI and died of it in the water after you send him back down without properly evaluating him, you would be in a legally and morally indefensible position.

Best regards,
DDM

 

[rjack321]

This is probably the number 1 IWR recompression situation, happening every day. Cause there is a whole lot of diving happening further than 12 hrs from a chamber. Another top treatment choice is a crapload of ibuprofen, water, and surface O2. I need many fingers and toes to count the number of slightly bent divers self medicating (in one fashion or another).

And just how is another divers choice to redescend and do more deco my responsibly? I'm just a buddy here. We are a day away from the chamber (or worse they have no insurance) "I'd do more deco, I'll get in with you" is not a medical order here.

ps it wasn't even the left arm

 

[Duke Dive Medicine]

This is probably the number 1 IWR recompression situation, happening every day. Cause there is a whole lot of diving happening further than 12 hrs from a chamber. Another top treatment choice is a crapload of ibuprofen, water, and surface O2. I need many fingers and toes to count the number of slightly bent divers self medicating (in one fashion or another).

And just how is another divers choice to redescend and do more deco my responsibly? I'm just a buddy here. We are a day away from the chamber (or worse they have no insurance) "I'd do more deco, I'll get in with you" is not a medical order here.

Sorry, I don't know you and your title says "captain". Going by that and by the way you phrased your post, i.e. "send them back down", you sound as if you're in a position of some authority on a dive boat. If it's happening every day the way you describe it, then IWR is being dangerously misused. You're calling it IWR in the first paragraph here and "do more deco" in the second paragraph. You can't have it both ways. The scenario you described, i.e. surfacing with arm pain, still wet, then going back down to "do more deco", is a medical treatment designed to alleviate something that you diagnosed on the fly, without even an attempt at ruling out other causes. Further, a diver who has actual DCS pain immediately on surfacing is in a bad way from a decompression standpoint and could deteriorate. What you're describing is a classic case of "drift", or normalization of deviance. You're doing something medically inappropriate and potentially dangerous without consequence, which reinforces the behavior. That's fine, until it's not.

Best regards,
DDM

p.s. MI pain can present in either arm, not just the left. That's a common misconception, and further reinforces my point.

 

[thin_air]

Thanks tbone. That's where I would respectfully disagree - it's not essentially going back for more decompression, because you're getting in the water breathing O2 with the intention of treating a medical issue. While your symptoms were minor, seemed to resolve at depth on O2, and you suffered no ill effects, it's still a medical treatment.

Best regards,
DDM

Hi DDM,
I preface this by stating that i'm a clinican, but not in hyperbarics or environmental medicine.
In the case of more deco vs treating DCI: where do we draw the line, and does drawing the line really matter (I will ignore "professional relationships" for the purposes of this conversation, boat crew to divers, instructors to divers ect.). We have people treating themselves every day for a wide variety of illnesses and ailments with a pretty good success rate. The parent who treat their young for a cold/URTI with rest and proper nourishment, the athlete who does some physiotherapy type exercises when they tweak a muscle, the folks who take a glass of milk for their heartburn after supper; where do we draw the line on these for medical treatment vs doing what makes me feel better?

Should the athlete who tweaks a muscle and starts adding some specific range of motion and strength and stability exercises really consider this medical treatment, or just a change to their training due to how they feel? How about the parent taking care of their kid, no different from the basics of nursing care, or the milk after supper to settle the stomach? Each of these cases could be something sinister, but probabilistically speaking, it's a horse, not a zebra. Should the layperson be scared into thinking about rhabdomyosarcoma, meningitis or peptic ulcer disease?

I don't think the cases tbone describes are any different from any of the above situations. He recognized something wasn't optimal in how he was feeling and modified an activity he was already doing/had already done in order to try to feel better.
Furthermore, he has (from what i glean from his posts) a better-than-layperson understanding of what he is doing and the safety, risk and efficacy thereof.

We, the medical community, have already over medicalized (not sure if that's a real word...) much of life/health related things that people do everyday. In many cases this hasn't had much benefit, and in some cases has proven to be harmful (how many kids are overmedicated with psych meds? does an overweight but generally healthy 30yo really need to see their PCP before starting an exercise program, or does it scare them?).
I'm lucky enough to practice in a jurisdiction that is much less litigious than then US so perhaps this biases me in some way, but I'm hesitant to take something which can in one setting be construed as medical treatment and in another as something non medical and look at it through the lens of medical treatment in all settings - even if the goal is to get people feeling better.

 

[Duke Dive Medicine]

Hi thin_air,

That's an excellent and thought-provoking post. I try to be acutely conscious of over-medicalizing - if that isn't a real word it should be. The last thing I or any medical professional I know wants to do is act as if we own the keys to the medical world and mere mortals shouldn't be dabbling in it. Full disclosure, I know tbone personally and we've had a lot of offline discussion about this so I know he's not as casual about IWR as he sounds in his posts. He's perfectly capable of treating a minor case of DCS in the water and he knows to call for help when he needs it. I also know that a lot of other people could read this thread so I take pains to make my posts applicable to the general diving public, not just the people involved in the thread at the moment.

I like your comparison of athletic injuries to diving injuries. In my mind, DCS is a sports injury. I used to run with Mike, the biomechanical engineer at the Duke hyperbaric center. He's faster than a scared rabbit and the only time I could catch him was on the downhill parts of the run. He'd tell me to be careful running full-speed down hills otherwise I'd hurt myself, but I couldn't stand the sight of the bottoms of his shoes so I did it anyway. I ended up tearing a meniscus and having to have surgery. Nobody ever gave me grief about it, all I got was well-wishes even though I'd taken risks with my body, pushed it too hard and gotten hurt. Divers being divers, that isn't always the case with DCS, but I think it should be.

To me, the difference between putting some Tiger Balm on a sore muscle and doing in-water recompression is the potential gravity of misdiagnosis and the higher risk of the treatment. Of course that risk is a continuum, and a simple case of type I joint pain seems (and may be) straightforward to treat, but diagnosing it isn't always as simple as it appears. There are a lot of misconceptions, some of which have been demonstrated previously in the thread. You and another poster both mentioned zebras - for the non-medical folks who may not have heard the saying, there is a well-worn piece of medical wisdom that says you don't look for zebras in a herd of horses. Before looking, though, one first has to be able to identify both horses and zebras and any other equids that may be around.

Thanks again for the dialogue.

Best regards,
DDM

 

[Kevrumbo]

the saying, there is a well-worn piece of medical wisdom that says you don't look for horses in a herd of zebras.

No @Duke Dive Medicine , the aphorism as it applies to medical differential diagnoses is "When you hear hoofbeats, think horses -NOT zebras. . ."
(Zebra (medicine) - Wikipedia )

For an example, if a diver comes up to the surface face down and unresponsive -it's probably indicative of an AGE with near drowning, and NOT a "Carotid Artery Dissection."

If a tech diver comes up after an hour of a relaxed Oxygen Decompression and an unremarkable completed profile, and complains later of only sharp shoulder pain -it's probably an instance of an "unexpected" type I simple DCS slow tissue pathology, and NOT an impending sign of Myocardial Infarction. . .

 

[Duke Dive Medicine]

No @Duke Dive Medicine , the aphorism as it applies to medical differential diagnoses is "When you hear hoofbeats, think horses -NOT zebras. . ."
(Zebra (medicine) - Wikipedia )

For an example, if a diver comes up to the surface face down and unresponsive -it's probably indicative of an AGE with near drowning, and NOT a "Carotid Artery Dissection."

If a tech diver comes up after an hour of a relaxed Oxygen Decompression and an unremarkable completed profile, and complains later of only sharp shoulder pain -it's probably an instance of an "unexpected" type I simple DCS slow tissue pathology, and NOT an impending sign of Myocardial Infarction. . .

Whoops. I got the zebra analogy bassackwards. Thanks. The edited version is how I heard it. You may have heard it differently.

And no, a face down unconscious diver on the surface is not "probably" anything. You spent enough time at the Catalina chamber to get a little bit of knowledge and I'm not going to argue with you about this, but there's another saying that's applicable to medical diagnosis and lots of other things: don't jump to conclusions. And another saying from Clint Eastwood as Dirty Harry: a man's gotta know his limitations.

Re the second case, granted, but that's not what was discussed in the thread.

Best regards,
DDM