In Water Recompression

[Akimbo]

I've personally never seen a DCS case go to 165 feet, though some facilities use deeper tables and swear by them.

That makes sense after so much time has passed. I have seen several cases where we had to drop to 165' to get relief, but they were when treatment started within minutes. They were also from 300'+ bounce dives (less than 1 hour bottom time). Treatment that starts hours after most of the diluent has left the body doesn't benefit as much from more pressure since there are so few remaining bubbles to compress or drive back into solution.

 

[Kevrumbo]

Not that it would increase the likelihood of this happening, but you could get away without the 6 ATA. A chamber that goes to 60 fsw and has O2 would handle 99.9% of DCS cases. That opens up the option of some lighter flexible recompression chambers.

Best regards,
DDM

I've personally never seen a DCS case go to 165 feet, though some facilities use deeper tables and swear by them. The one time it happened at Duke (before my time) is still legendary there. The old protocol for gas embolism used to involve a 165 foot spike and the option is still there if the diver can be placed in the chamber immediately or doesn't respond to initial treatment at 60 feet.

This isn't a product endorsement, but the Hyperlite 1 chamber is one example of a flexible recompression chamber that would take up a lot less space than the DDC in the picture that Akimbo posted (though the old hard hat diver in me loves it). It's still very pricey and so probably isn't a realistic option for any but the most well-funded (or well-connected) dive expeditions. It also does require additional training and experience.

Best regards,
DDM

A large steel 6ATA Recompression Chamber gives the Hyperbaric Physician the immediate option to treat an emergency AGE dive casualty. Large enough and room for multiple occupancy of the Patient along with a Tender and an EMT/Paramedic to perform CPR on the Patient in a worst case full cardiorespiratory arrest condition (the Chamber Crew's worst nightmare is the full arrest near drowning AGE scenario). An auxiliary transfer lock allows pressurizing the Physician to ambient treatment levels in order to examine the Patient in the main treatment lock and provide additional Advanced Cardiac Life Support (ACLS) as needed; and then decompress back in the auxiliary transfer lock, returning the Physician to surface pressure in order to further conduct the medical treatment NOT under the influence of Nitrogen Narcosis.

@RayfromTX , @Akimbo , @Duke Dive Medicine, @thin_air -->We actually had this onboard 6ATA multiplace double lock chamber capability on stand-by during our liveaboard 2013 Bikini Atoll Expedition with Dr. Simon Mitchell as the attending Hyperbaric Physician. To keep this chamber available for my dive teammates as well as preventing an early end to the expedition itinerary on the eighth of nine diving days, I elected to perform O2 IWR Therapy for a type I DCS pain only Right Arm & Shoulder, with later surface O2 breathing and Dr. Mitchell providing adjuvant IV Therapy (Plasmalyte w/ Ibuprofen drip).

 

[Kevrumbo]

CO2 as a major risk factor complicit in Oxygen Toxicity Seizures; and how it may apply to O2 IWR maximum recommended depth of 9 msw/30 fsw (ppO2 of 1.9 bar).

@Dr Simon Mitchell's findings were:

A good estimate of CO2 levels in the body (and therefore a good indication of whether CO2 is being retained) is provided by measuring the CO2 in the expired breath at the end of exhalation. This is referred to as the ‘end tidal CO2 measurement’. Unfortunately, no one has perfected a means of obtaining this measurement in immersed divers on actual real-world dives. However, on a recent trip to Bikini Atoll we went second best by measuring the end tidal CO2 in rebreather divers completing decompression immediately upon surfacing after direct ascent from the final decompression stop. We did this following 34 dives completed by 18 divers, and we repeated each diver’s measurement at rest on the boat later for comparison. The surfacing divers had an average end tidal CO2 of 36.8mmHg (normal is 35–45) and the measurements after rest on the surface averaged 36.9mmHg. Thus we concluded that there was no general tendency to retain CO2 during decompression.

This result is reassuring. It does not, of course, exclude the possibility of oxygen toxicity after long exposures to a high PO2 when resting on decompression, but it does suggest that one of the principle risk factors (high CO2) is usually not present. Divers have to make their own choices about risk when it comes to the PO2 they inspire during decompression. Many technical divers breathe 100% oxygen from 6m (where the inspired PO2 would therefore be 1.6bar). There are very few documented seizures associated with this practice, which is perhaps not so surprising given our study’s findings. I personally prefer to go on 100% at my shallowest stop, which is usually 3–4.5m. The reduced inspired PO2 at these depths (PO2 = 1.3–1.45 bar) will inevitably further reduce the risk of oxygen toxicity.
Advanced Knowledge Series: Carbon Dioxide Retention | Dive Magazine

Goals of Oxygen Therapy in suspected DCS Syndrome case:
-Bubble Resolution through Denitrogenation (bubble contents almost pure nitrogen).
-Surround bubble with high oxygen environment
-Diffuse Nitrogen out of bubble into blood.
-Nitrogen transported to the lungs and exhaled.

Augmented with IWR for simple type I DCS only, goals are:
-Pain alleviation with Bubble size reduction.
-Best compromise oxygenation of hypoxic tissues and reduction of tissue edema with regard to Oxygen Toxicity risk factors at no deeper than 9msw/30fsw (1.9ATA).

Bubble size Reduction:
-Best compromise treatment at 1.9ATA on Oxygen, with theoretical reduction at 80% of Original Pathological Bubble Diameter (or 20% decrease in occluding size).

For reference, standard chamber HBOT at 2.8ATA: bubble size reduction is at 70% (or 30% decrease in occluding size). And at 6ATA breathing Nitrox50 or Heliox 50/50 (ppO2 is 3.0 bar max) for AGE: critical bubble size reduction at 55% (or vital 45% decrease in stroke-causing occluding size).

 

[Kevrumbo]

TABLE 1

527 IN-WATER RECOMPRESSIONS IN HAWAII

Complete resolution of symptoms: 462

Residual symptoms but no further treatment sought
as symptoms disappeared within a few days: 51

Residual symptoms needing further treatment: 14

Divers made worse by in-water recompression: 0

Total: 527

Compiled from:
Farm FP Jr, Hayashi EM and Beckman EL. Diving and decompression sickness treatment practices among Hawaii’s diving fishermen. Sea Grant Technical Paper UNIHI-SEAGRANT-TP-86-01. Honolulu, Hawaii: University of Hawaii Sea Grant College Program, 1986

Comment from Pyle and Youngblood (1997) on Table 1 quote above:

. . .From the cases described above, it should be evident that IWR has almost certainly been of benefit to some DCS victims in certain circumstances. If the selection of cases seems biased towards "successful" attempts at IWR, it is only a reflection of the numbers of actual cases on record (Table 1). . .
In-water Recompression as an Emergency Field Treatment of Decompression Illness

------------

I would like to have more discussion on this apparent disagreement that has been unacknowledged so far:

. . . There is also literature to suggest that delays in treatment are not as harmful as was once believed. A couple of examples are linked below:

Risk factors and clinical outcome in military divers with neurological decompression sickness: influence of time to recompression. - PubMed - NCBI
How delay to recompression influences treatment and outcome in recreational divers with mild to moderate neurological decompression sickness in a r... - PubMed - NCBI

Rebuttal to the links above:

The major factor in determining whether IWR should be implemented is the distance and time to the nearest recompression facility. In 1963, Rivera studied more than 900 cases of DCI in USN divers, found that 91.4% of the cases treated within fifteen minutes were successful, whereas the success rate when treatment was delayed 12-24 hours was 85.7%.(22) A similar study on DCI cases among sport (recreational) divers showed similar results. Of 394 examined cases, 56% of divers with mild DCI symptoms achieved complete relief when treated within 6 hours, whereas only 30% were completely relieved when treatment was delayed 24 hours or more.(23) The same study found that 39% of divers with severe symptoms were relieved when treated within 6 hours, whereas only 26% were relieved when treatment was delayed 24 hours or more. In reviewing these numbers, Moon stressed that delay of treatment for DCI should be minimised, but also noted that response to delayed treatment is not entirely unacceptable.(24) Knight recommends that IWR should be considered when the nearest recompression facility is more than 6 hours away.(17). . .

IN-WATER RECOMPRESSION AS AN EMERGENCY FIELD TREATMENT OF DECOMPRESSION ILLNESS

 

[thin_air]

BTW, Reped is short for REPEtitive Dive... Repet sounds like replacing your dog. I think I picked it up from the Brits in the 1970s.

thanks, always good to add new words to the vocabulary

@RayfromTX , @Akimbo , @Duke Dive Medicine, @thin_air -->We actually had this onboard 6ATA multiplace double lock chamber capability on stand-by during our liveaboard 2013 Bikini Atoll Expedition with Dr. Simon Mitchell as the attending Hyperbaric Physician. To keep this chamber available for my dive teammates as well as preventing an early end to the expedition itinerary on the eighth of nine diving days, I elected to perform O2 IWR Therapy for a type I DCS pain only Right Arm & Shoulder, with later surface O2 breathing and Dr. Mitchell providing adjuvant IV Therapy (Plasmalyte w/ Ibuprofen drip).

Having a chamber, along with one of the top physicians in the field onsite certainly expands one's options, unfortunately that isn't realistic for most of us. I think the interest in IWR is driven by those who don't have easy access to these resources (physical and intellectual). What can the layperson/average dive team do to provide the best outcome with the resources typically available to them when DCI crops up.

 

[Akimbo]

thanks, always good to add new words to the vocabulary

I was ASSuming that it was a common phrase, my bad.

 

[100days-a-year]

I thought reped was a foot transplant....

 

[Kevrumbo]

. . .
Having a chamber, along with one of the top physicians in the field onsite certainly expands one's options, unfortunately that isn't realistic for most of us. I think the interest in IWR is driven by those who don't have easy access to these resources (physical and intellectual). What can the layperson/average dive team do to provide the best outcome with the resources typically available to them when DCI crops up.

For the traveling tropical tech diver overseas, you need at minimum a dive operation that can at least supply 100% O2 and Air in separate Aluminum 11L cylinders (you may have to bring your own FFM); and a shallow lagoon or clear boat-dock space with a firm sandy bottom at 9msw/30fsw to lie prone on.

There are two versions of "modified" Australian O2 IWR Therapy:
(I)
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 breathe 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. . .

(II)
(R. Walker in Carl Edmonds' Diving and Subaquatic Medicine)
Descend to 9m
Breathe O2 for 30-90min depending on symptoms, take an airbreak every 25min

Ascend to 8m at 1 m every 12min
Ascend to 7m at 1 m every 12min
Ascend to 6m at 1 m every 12
Ascend to 5m at 1 m every 12
Ascend to 4m at 1 m every 12
Ascend to 3m at 1 m every 12
Ascend to 2m at 1 m every 12
Ascend to 1m at 1 m every 12
Ascend to surface , breathe O2 for 1hr then 1 hour off for a further 12 hrs, intermingled with fluids.

Notes:
Run time of 138-208 min depending on time at 9m + the additional 6hrs on surface of oxygen

If no full face mask available then
do not exceed 6m on O2, to get a PO2 of 1.6 for 30 min
Then ascend to 5m in 12 minutes and remain at 5m for 30-60min

Ascend to 3m in 15minutes and resume above schedule.

 

[100days-a-year]

I've personally never heard of IWR runtimes longer than 30 to 45 minutes locally.AFAIK complete resolution and return to diving has always been the goal and it has so far been accomplished with shorter dives.Not that longer ones are a bad idea for safety's sake.

I look forward to DDM's questionnare. I will see if I can either get the local guys to respond or at least relay their experience to me.

Agree no tech op should ever venture far without enough 02 unless operating nearshore and close to a chamber.

 

[Kevrumbo]

I've personally never heard of IWR runtimes longer than 30 to 45 minutes locally.AFAIK complete resolution and return to diving has always been the goal and it has so far been accomplished with shorter dives.Not that longer ones are a bad idea for safety's sake.

I look forward to DDM's questionnare. I will see if I can either get the local guys to respond or at least relay their experience to me.

Agree no tech op should ever venture far without enough 02 unless operating nearshore and close to a chamber.

An O2 IWR Therapy -if it cannot be as deep as an USN TT6 in order to mitigate CNS oxygen toxicity risks- then it should be long enough in total treatment time to have some reasonable expectation of efficacy similar to a standard TT6 in resolving type I DCS symptoms.