In Water Recompression

[Kevrumbo]

. . .Those types of places are few and far between though and you can only get so much funding to keep a site like that open. In NC we are lucky because the odds of Duke shutting down that complex are pretty small, same for the one in Catalina all due to the research funding they're doing.. . .

No @tbone1004 , the Catalina Chamber other than weekly training runs is primarily on 24/7 stand-by only for the emergency treatment of Dive Casualties. FYI, this is how the model works (and what Shands/UF and the local North Florida Diving Community should have implemented back in 2011 to keep their Chamber operational): How the Chamber is Funded > USC Catalina Hyperbaric Chamber > USC Dana and David Dornsife College of Letters, Arts and Sciences

. . .IWR thankfully is outside of that and pretty goes along the lines of "go to 30ft on O2, if symptoms resolve, then run the IWR procedure" for that and pray. If symptoms don't resolve, then go 10-30ft deeper depending on your beliefs and repeat, then go deeper and repear until symptoms resolve then follow procedure and pray.

The key about IWR for me is that timing seems to be everything. If you are capable of getting back in the water, then you get immediate treatment and theoretically immediate relief of symptoms with a great rate of success. If I came up and got a hit at the quarry where we do training, which is just under an hour from Duke's chambers, which operate 24/7 for diving emergencies, I would STILL do IWR first because even with that proximity to Duke, it will be at least 2 hours until you get recompressed

@Dr Simon Mitchell wrote a very informative rebuttal post on the hazards of going beyond ppO2 1.9 ATA (that is 30ft/9m on an elective Oxygen IWR Therapy Table):

Hello,

This has just been pointed out to me. I want to add one important perspective to this discussion. First, however, can I be clear that I support the concept of in-water recompression of properly selected DCS victims by properly prepared groups of divers.

The perspective that I wish to add is that 2.8 ATA of oxygen underwater is an unacceptably dangerous dose, even for relatively short periods. You should NOT be conducting a USN Table 5 underwater.

Many decisions about therapy involve balancing risk vs benefit. There is good reason to consider the risk of what is being recommended here to be very high. I could raise various references to the literature, but the most important and revealing data come from an era when the sort of experiments required to answer the relevant questions could still be done. I refer to Donald’s seminal work in the UK during the second world war. The key findings relating to this discussion were reported by Vann and Hamilton in the DAN Technical Diving Workshop Proceedings which can be downloaded here:

Technical Diving Conference Proceedings.

If you look at figure 12 of their paper on page 48 you will immediately appreciate why the advice to recompress sick divers to 60′ on pure oxygen is dangerous. The survival curve in 12(d) for exposure to 50′ of oxygen (LESS than is being recommended here) when immersed at REST shows that 50% of divers will exhibit symptoms of oxygen toxicity in LESS time than the exposure being recommended here. It should be noted also that Donald’s subjects were not being recompressed after a prior oxygen exposure (which might be substantial – eg in a technical diver with DCS), or in a physiologically compromised state. These factors without doubt will further increase risk.

In his work Donald concluded that “diving on pure oxygen below 25′ is a hazardous gamble”.

Figure 15 (page 53) in the Vann and Hamilton paper is also revealing. It is based on US Navy data from working dives, and shows iso-risk curves for seizures at different inspired PO2s (on the vertical axis). It is clear that at 2.8 ATA there is virtually NO time before the risk exceeds 8% (the rightmost curve). I accept that divers undergoing in-water recompression should be resting, but this can never be guaranteed. In truth, activity during an in-water recompression in realistic conditions is likely to lie somewhere between work and rest.

Based on the best evidence we have I conclude that the advice given in this blog should be modified in respect of the recommended oxygen dose. 2.8 ATA has been chosen for dry recompressions as a compromise between bubble compression and risk of oxygen toxicity in the dry chamber environment. To advocate the same dose in the immersed diving environment where the risk of oxygen toxicity is proven to be markedly higher ignores the logic of the original compromise, and the benefit is unclear. It is likely (though obviously not proven) that much of the benefit of recompression can be achieved at a lower dose of oxygen that is safer in the immersed environment. The US Navy recommend 1.9 ATA and IANTD adopted 1.6 ATA for their in-water recompression course out of concern for oxygen toxicity. I serve on both the UHMS Adjunctive Treatments Committee and the Diving Committee, and can state with confidence that none of my colleagues on these committees would support the administration of a Table 5 to an immersed diver.

Simon Mitchell

[From blog Bret Gilliam’s Navy Table 5 modification for IWR]

For Type 1 DCS only:

The modified Australian IWR Method as taught by UTD has either 30, 60 or 90min choice of prescribed O2 breathing therapy at 9m/30ft depth (10min O2:with a 5min Air Break); and then a very slow 0.1 meter-per-minute (0.3 feet-per-minute) ascent to surface breathing 10min on O2 with 5min Air Break.

So choosing 60 minutes of O2 time at 9m for example, you breath 10min on Oxygen, and then take a 5min break on Air for a total bottom time of 90 minutes (Air Breaks add to the total bottom time and do not count or accrue credit into the O2 time at 9m), and on the slow 0.1mpm O2 breathing ascent you have to hold at depth after every 1 meter of ascent for the 5min Air Break, before starting again the 0.1mpm O2 breathing ascent –a total time to surface of 135 minutes. So the total treatment time would be 90min bottom plus 135min ascent equals 225 minutes. Can be done with an AL80/11L cylinder of Oxygen and another of Air on Open Circuit. . .

Modified Australian IWR has a lesser ppO2 exposure of 1.9 to 2.0 at a longer time & shallower depth of 30′/9m, while still theoretically reducing pathogenic DCS bubbles to at least 80% of their original size; while Bret Gilliam’s Navy Table 5 modification in the article above has ppO2 of 2.8 at a shorter time but deeper and riskier 60′/18m depth, and reducing bubble size to 70%.

 

[tbone1004]

@Kevrumbo deeper than 30ft is on nitrox. Thought I wrote that, but may have been accidentally deleted during edit

good to know about Catalina, I thought they were still doing research there but may have been thinking of another chamber

 

[lv2dive]

I'd knock on some variant of wood my friend!!!! That's triple dog daring the gods

i occasionally dive deeper than 30' yea. but i'm a race horse and nigh unbendable

 

[LiteHedded]

I'd knock on some variant of wood my friend!!!! That's triple dog daring the gods

when i finally get bent everyone is going to point and laugh

 

[PfcAJ]

when i finally get bent everyone is going to point and laugh

Patiently waiting.

The day will come.

 

[LiteHedded]

Patiently waiting.

The day will come.

 

[lv2dive]

Omg that is hysterical... my original response was "you better knock on some variant of wood my friend, that's just asking for the gods to point AND laugh!"

when i finally get bent everyone is going to point and laugh

 

[PfcAJ]

View attachment 442787

I will be so smug.

 

[Kevrumbo]

when i finally get bent everyone is going to point and laugh

Patiently waiting.

The day will come.

Even assuming you successfully complete a prescribed deco profile:

Hopefully it's usually going to be only an "unexpected/unexplained" type I DCS at worst, a slow-tissue limb or joint pain, and that may be treated & resolved by elective O2 IWR Therapy if necessary and worth the risk.

There's also the rare and potentially very serious Pulmonary Chokes w/ ARDS complication type DCS.

But there shouldn't ever be a catastrophic type II or AGE unless you totally 'effd-up' . . . (Or else you have a gaping PFO or other atrial septal defect, or gross venous-arterial shunt you don't know about). Better find an emergency 6ATA Chamber quick for these cases.

 

[Johnoly]

I will be so smug.

Allow me to 'pile on'.

Is this a good time to discuss advanced Yoga Poses underwater during IWR to facilitate & improve moving the stuck bubbles?
I've clipped my SMB to my butt ring to help hold the "Dog Down Pose" at 60 feet !