Deep Stops Increases DCS

[Dr. Lecter]

The reality for you nad's, you keep sticking your tongue on light poles this time of year up there in Edmonton, it will keep on getting stuck. . . (Lord Stanley's Cup says Hi from LA by-the-way!)

If I'm still alive & writing about what's been happening in my experience . . .then do as I say as lesson-learned and not as I did wrong in hindsight. . .

Kev, given your experiences with RD and type I symptoms, have you considered trying something different just to see how it works? I found VPM of any reasonable conservatism left me feeling less than super for similar/somewhat longer and deeper air or lean trimix dives - unless I hugely extended the shallow stops to compensate for the extra deep time. In the last year or so I have been very happy with GFs in the 50/80 or 60/80 range. Others I dive with have swung the needle even further, halving or zeroing out the HE % and moving to 80/85. So far, everyone seems happier than they were on the deeper-biased models, and while we're not pushing much past 100m or running more than several hours of deco, the dives aren't exactly forgiving of insufficient deco.

 

[Kevrumbo]

Kev, given your experiences with RD and type I symptoms, have you considered trying something different just to see how it works? I found VPM of any reasonable conservatism left me feeling less than super for similar/somewhat longer and deeper air or lean trimix dives - unless I hugely extended the shallow stops to compensate for the extra deep time. In the last year or so I have been very happy with GFs in the 50/80 or 60/80 range. Others I dive with have swung the needle even further, halving or zeroing out the HE % and moving to 80/85. So far, everyone seems happier than they were on the deeper-biased models, and while we're not pushing much past 100m or running more than several hours of deco, the dives aren't exactly forgiving of insufficient deco.

Once again, look at the Bottom Mix Gas used in the NEDU Study link (essentially Deep Air):

(Abstract, p.i). . .Divers wearing swimsuits and tshirts, breathing surface-supplied air via MK 20 UBA, and immersed in 86 °F water were compressed at 57 fsw/min to 170 fsw for a 30 minute bottom time during which they performed 130 watt cycle ergometer work. . . Results indicate that slower tissue gas washout or continued gas uptake offsets the benefits of reduced bubble growth at deep stops. . .

(Conclusion p.18) . . .The practical conclusion of this study is that controlling bubble formation in fast compartments with deep stops is unwarranted for air decompression dives.

This is the simple main practical point IMO/IME, that I've taken away from the study:

Of course you're going to have significant residual inert Nitrogen and potentially on-gas N2 at your deep stop & perhaps even possibly at intermediate deco stops on Eanx50 which may encroach on critical slow tissue M-values as well --if you were using a working bottom mix with a high fractional N2 content to begin with like Air. Plan accordingly, use a computer to track your inert tissue loading (i.g. Shearwater Petrel) and be prepared to extend your 6m depth 100% Oxygen deco profile along with a stand-by IWR contingency protocol.

For the past Oct-Nov 2014 Truk Trip, I still used Ratio Deco Method, but extended the O2 Deco Profile Times by another 20 to 30 minutes at 6m to better eliminate the residual N2 slow-tissue loading, since I was doing a lot of Air Bottom Mix over the course of nearly a month.

Near the end of the trip I was even more conservative (especially after three hits on my Right Arm/Shoulder successfully treated with IWR), coming up from long 6m/3m O2 deco stop profile times with 40 to 50% surfacing GF's showing on the Petrel Computer. . .

 

[Dr. Lecter]

I'm not talking about the NEUD study at this point - I'm talking about what you've found doesn't ing work all that well, and a possible avenue that might work better. But if you prefer the apocryphal Einstein quote, your doing the same thing over and over again while expecting different results is fine by me.

 

[Kevrumbo]

I'm not talking about the NEUD study at this point - I'm talking about what you've found doesn't ing work all that well, and a possible avenue that might work better. But if you prefer the apocryphal Einstein quote, your doing the same thing over and over again while expecting different results is fine by me.

No HANNIBAL!!! --C'mon!

The same thing -Rato Deco Method- that has been working well for the past five years, even with Deep Air --but now coming down with four type I Right Upper Arm/Shoulder episodes in the past year. . .!

Just have to extend my O2 6m stop profiles from now on, and I hope that's the answer.

 

[ajduplessis]

Use it, don’t use it.

You have taken 4 hits but still not considering changing you approach????? The fact that your deco profiles worked before does not mean it will continue to work especially as the years tick by. As a diver you need to evolve and learn from your and others experiences across the diving spectrum.

You have the right mindset, experience/knowledge, gear and practical knowhow with IWR to be in a position to find a different approach. My $0.02

 

[Dr. Lecter]

No HANNIBAL!!! --C'mon!

The same thing -Rato Deco Method- that has been working well for the past five years, even with Deep Air --but now coming down with four type I Right Upper Arm/Shoulder episodes in the past year. . .!

Just have to extend my O2 6m stop profiles from now on, and I hope that's the answer.

Yeah, staying in until I dropped to 70-60% GF surfacing worked for me too. Whatever you like, man. But sooner or later, odds are it won't just be some arm pain you fix by going back down until it feels alright.

 

[Kevrumbo]

ded December 17th, 2014 at 01:34 AM ----------

Use it, don’t use it.

You have taken 4 hits but still not considering changing you approach????? The fact that your deco profiles worked before does not mean it will continue to work especially as the years tick by. As a diver you need to evolve and learn from your and others experiences across the diving spectrum.

You have the right mindset, experience/knowledge, gear and practical knowhow with IWR to be in a position to find a different approach. My $0.02

If they were four separate incidents with serious Neuro type II DCS signs & symptoms, then I obviously was not spending enough time deep decompressing the fast tissues, or for some reason ascending like a rocket to the surface like a Trident SLBM. This is obviously not the case. . .

Look at the recent time frame: The fact that I had four Rt upper arm/shoulder hits -one in Bikini Atoll last year June- and three during this last Oct thru Nov Truk Trip that all happened within a week of Deep Air diving, and responded well to three IWR sessions (the other was a repetitive dive with a long O2 deco hang), means that I'm retaining a lot more residual slow-tissue N2 that's precipitating into acute type I symptoms after starting 30min to an hour into a nominal 3 hour SIT.

I'm just saying -The NEDU Study's conclusions & implications can be extrapolated to my case, even though there was no accelerated deco mixes & profiles utilizing 50% and O2 in its experimental design.

 

[ajduplessis]

Like I said. Use it, dont use it.

 

[LiteHedded]

anyone that thinks kevrumbo has ANY credibility when it comes to decompression is making a big mistake.
is ANYONE surprised that someone defending this UTD nonsense has been bent so often? it's silly to even bother debating him.

the guy who authored that NEDU study is a good friend and dive buddy, and he really dials back the deep stops. (as has GUE in their classes as a result of studies like this one)

 

[PfcAJ]

Kev, am I reading this right?

youre routinely getting bent doing your deep stops schedule. Your solution is to extend the oxygen (shallow) stop to compensate. But you're going to sit there and try and defend the deep stop schedule?

Am I having a stroke?