Tech Diving Mag - issue 25

[Red Sea Shadow]

The new issue of #Tech_Diving_Mag is available for download at Tech Diving Mag | Free online technical diving magazine

Contents:
* Arterial Bubble Model
* Suggested Protocol for Emergency In-water Recompression
* Did Haldane Really Use His "2:1"?
* Living the Dream?
* Diving Ras Atantur

 

[kensuf]

So.. I'd like to suggest that the article on IWR be taken with a grain of salt and read with a critical eye. I was kind of shocked by the suggestions in it because the idea of breathing a PO2 of 2.8 while in the water is highly unconventional.

Most IWR schedules have no oxygen delivery below 30'. There's a reason for this: there's a correlation between a higher risk of CNS OxTox while being submerged, and the risks of OxTox are very real with PO2's that high.

Close to 20 years ago I took a Type 2 hit and won the prize of spending a night in the chamber. Although I was in a dry metal tube, I toxed during two of the on-oxygen portions (at 60'). I believe that if I had been in the water when I toxed, instead of being in a nice dry chamber, it would have been difficult for me to survive.

Wikipedia has a couple of different protocols for IWR. None of them advocate breathing O2 below 30'. I would urge anyone that is thinking about adding IWR to their arsenal of emergency protocols to do a thorough reading of other IWR protocols before just settling on any particular one as an article of faith.

 

[kensuf]

BTW, otherwise, nice mag. Thanks for publishing.

 

[Red Sea Shadow]

Currently looking for new, well-illustrated articles for the next issue. If you have something to contribute drop me a line. Quality photos (with or without articles) are most welcome.

 

[Kevrumbo]

So.. I'd like to suggest that the article on IWR be taken with a grain of salt and read with a critical eye. I was kind of shocked by the suggestions in it because the idea of breathing a PO2 of 2.8 while in the water is highly unconventional.

Most IWR schedules have no oxygen delivery below 30'. There's a reason for this: there's a correlation between a higher risk of CNS OxTox while being submerged, and the risks of OxTox are very real with PO2's that high.

Close to 20 years ago I took a Type 2 hit and won the prize of spending a night in the chamber. Although I was in a dry metal tube, I toxed during two of the on-oxygen portions (at 60'). I believe that if I had been in the water when I toxed, instead of being in a nice dry chamber, it would have been difficult for me to survive.

Wikipedia has a couple of different protocols for IWR. None of them advocate breathing O2 below 30'. I would urge anyone that is thinking about adding IWR to their arsenal of emergency protocols to do a thorough reading of other IWR protocols before just settling on any particular one as an article of faith.

I had three separate type I DCS incidents experienced on Truk Lagoon Trips in Oct-Nov 2014 -all were upper Right arm/Shoulder classical acute "pulsing" symptoms with increasing pain within 90min time post-dive, and occurring within three to four days of starting Open Circuit Deep Air bottom mix dives with 50% & O2 deco (two tech deco dives per day with a 3 hour SIT). Possible contributing factors were dehydration, insufficient "acclimatization" to the tropical environment, and no prior "work-up" practice deco dives to sensitize the body'simmune/inflammatory response system to high FN2 saturation & resultant residual bubbles in slow tissues & venous blood vessels (first early AM deep dive with deco of that trip was SF Maru at 51m ave depth, 45min BT and over two-and-a-half hours runtime, after long trans-pacific flight from Los Angeles arriving late in the night before). Also rule-out neo-vascularization of Right Shoulder Joint/Upper Arm due to previous type I DCS injury (Bikini Atoll 2013).

All DCS type I Pain Symptoms at that time in Oct-Nov 2014 were resolved with In-Water-Recompression (IWR) sessions which were performed off the end of Truk Stop Hotel Pier. Lying prone & relaxed at 9m depth on a sandy bottom in 28 deg C water temp, the modified Australian Method IWR as taught by UTD was used -with either 30, 60 or 90min of elective prescribed O2 breathing therapy at 9m depth (10min O2:with 5min Air Break); and then slow 0.1m/min ascent to surface (same breathing 10minO2:with 5min Air Break). Went with 60 minutes O2 time at 9m (Air Breaks do not count or accrue credit into the O2 time at 9m; and on the slow 0.1m/min ascent you have to hold at depth during the 5min Air Break). The entire IWR treatment session took three-and-a-half hours and the CNS readout on the Petrel Dive Computer was maxed out at "999".

 

[Remy B.]

Kev, what was your Dive/Deco plan/Profile for the SF Maru ?, what Algorithm did you use and under what setting, and did you padded, if you don't mind to share.

 

[RyanT]

I was kind of shocked by the suggestions in it because the idea of breathing a PO2 of 2.8 while in the water is highly unconventional.

Yep, that raised a big red flag for me too.

 

[Kevrumbo]

Kev, what was your Dive/Deco plan/Profile for the SF Maru ?, what Algorithm did you use and under what setting, and did you padded, if you don't mind to share.

RD 1:2 on Deep Air, no initial extra O2 padding (only started adding O2 extended stops on subsequent dives, and later on all profiles during a return trip in Jan 2015). Type 1 DCS Symptoms after the third day of similar dive profiles on the deeper wrecks of the Fourth Fleet anchorage (SF Maru, Nagano Maru, Aikoku Maru etc):

Modified Australian IWR has a lesser ppO2 exposure of 2.0 at a shallower depth of 30'/9m, while still squeezing/off-gassing pathogenic DCS bubbles to at least 80% of their original size; while Bret Gilliam's Navy Table 6 modification in the article has ppO2 of 2.8 at 60'/18m and reducing bubble size to 70%. The risk of Oxygen toxicity is still there though in both IWR methods. . .

For those worried about Ox-Tox seizure potential in IWR might be feel somewhat better with this article (apologies & regards to @kensuf above):
End tidal CO2 in recreational rebreather divers on surfacing after decompression dives. - PubMed - NCBI

". . .We found no general tendency to CO2 retention during decompression. It is plausible that breaching oxygen exposure limits during resting decompression is less hazardous than equivalent breaches when exercising at deep depths. Mitchell SJ, Mesley P, Hannam JA. End tidal CO2 in recreational rebreather divers on surfacing after decompression dives."

 

[Remy B.]

If you got DCS 1, did you change your RD or you changed using GF or VPM ?

 

[RyanT]

Remy, no offense, but you're really not getting this. As others have said before, slow down, gain more experience, then find another instructor.