UTD Decompression profile study results published

[Dr Simon Mitchell]

Hello,

The UTD decompression profile project results were published in Diving and Hyperbaric Medicine this month.

Spisni E et al. A comparative evaluation of two decompression procedures for technical diving using inflammatory responses: compartmental versus ratio deco. DHM 2017;47(1):9-16.

This study attracted a lot of discussion after Andrew Georgitsis posted a video on You Tube that strongly (but incorrectly as it turns out) assumed an advantage for ratio decompression in this investigation:


The authors compared a ratio deco and GF30:85 approach to decompression from a 50m 25 min trimix dive with nitrox 50 and oxygen decompression. There were 51 dives (28 ratio deco and 23 GF deco) and the end points were venous bubbles and assays of inflammatory markers suggestive of vascular injury.

Despite having a longer decompression the ratio deco profile was associated with greater production of inflammatory markers after the dive. The ratio deco profile produced grade 3 or 4 bubbles in 4/28 (14.3%) divers and the GF profile produced grade 3 or 4 bubbles in 2/23 (8.7%) divers. The differences in inflammatory marker production were statistically significant, but the difference in the proportion of divers producing high bubble grades was not.

The ratio decompression profile puts greater emphasis on deep stops in comparison to the GF profile, and the results constitute further evidence that the "love affair" we had with deep stops in the early 2000s has resulted in over-emphasis of the strategy by some algorithms. For clarity, and to avoid misinterpretation, the study does not establish GF 30:85 as optimal decompression. It simply indicates an advantage for that algorithm over one which places more emphasis on deep stops.

Simon M

 

[Capt Jim Wyatt]

Thanks Simon!!

 

[wedivebc]

Thank you for that Dr Mitchell.

 

[Kevrumbo]

Hello,

The UTD decompression profile project results were published in Diving and Hyperbaric Medicine this month.

Spisni E et al. A comparative evaluation of two decompression procedures for technical diving using inflammatory responses: compartmental versus ratio deco. DHM 2017;47(1):9-16.

This study attracted a lot of discussion after Andrew Georgitsis posted a video on You Tube that strongly (but incorrectly as it turns out) assumed an advantage for ratio decompression in this investigation:


The authors compared a ratio deco and GF30:85 approach to decompression from a 50m 25 min trimix dive with nitrox 50 and oxygen decompression. There were 51 dives (28 ratio deco and 23 GF deco) and the end points were venous bubbles and assays of inflammatory markers suggestive of vascular injury.

Despite having a longer decompression the ratio deco profile was associated with greater production of inflammatory markers after the dive. The ratio deco profile produced grade 3 or 4 bubbles in 4/28 (14.3%) divers and the GF profile produced grade 3 or 4 bubbles in 2/23 (8.7%) divers. The differences in inflammatory marker production were statistically significant, but the difference in the proportion of divers producing high bubble grades was not.

The ratio decompression profile puts greater emphasis on deep stops in comparison to the GF profile, and the results constitute further evidence that the "love affair" we had with deep stops in the early 2000s has resulted in over-emphasis of the strategy by some algorithms. For clarity, and to avoid misinterpretation, the study does not establish GF 30:85 as optimal decompression. It simply indicates an advantage for that algorithm over one which places more emphasis on deep stops.

Simon M

Well . . .UTD's Study at least was a better and preferred clinical & ethical paradigm in having divers with indicating "inflammatory markers" in the blood & urine lab work along with echocardiogram bubble grade scores, rather than the experimental design of eliciting overt and patently acute DCS symptoms suffered by the Navy Diver subjects in the NEDU Deep Stops Study.

Still would really like to know in addition to classical gas-tissue kinetics, how the variable of the Immuno/Inflammatory System figures in, and looking for various definitive "biomarkers" of its reactionary complement activation encompassing the full range of sub-clinical stress to acute signs & symptoms of DCS. And even if we do finally find these bloodstream biomarkers, the technology to monitor them in vivo (i.e. Realtime during a dive like today's technology of rudimentary biometric monitoring of heart & breathing rate for example) doesn't exist yet.

How definitive or correlative these markers are for DCI together with bubble grade scores for other deep stop/bubble models like VPM should be the next comparative experimental study...

 

[mmadiver]

Thanks for posting Simon. Another useful data point in the deep stops saga.

Any insights into AG's response to the study? UTD making any changes to their ratio deco?

AG's comments at the end of the video made me laugh a little "It's bad enough they're diving 30:85, guess they drew the short straws."

 

[lv2dive]

it's been a long week/weekend, I do apologize if I missed this, but I was wondering if there was a link to the study or the summary of it?

More importantly: as always, many thanks to you (and your colleagues) not only for doing the work, but for utilizing various forms of communication including social media, to help keep the rest of us mere mortals up-to-date on the latest decompression data/science. You really go above and beyond in helping educate the dive community, and it is greatly appreciated.

Regards, Kate

Hello,

The UTD decompression profile project results were published in Diving and Hyperbaric Medicine this month.

Spisni E et al. A comparative evaluation of two decompression procedures for technical diving using inflammatory responses: compartmental versus ratio deco. DHM 2017;47(1):9-16.

This study attracted a lot of discussion after Andrew Georgitsis posted a video on You Tube that strongly (but incorrectly as it turns out) assumed an advantage for ratio decompression in this investigation:


The authors compared a ratio deco and GF30:85 approach to decompression from a 50m 25 min trimix dive with nitrox 50 and oxygen decompression. There were 51 dives (28 ratio deco and 23 GF deco) and the end points were venous bubbles and assays of inflammatory markers suggestive of vascular injury.

Despite having a longer decompression the ratio deco profile was associated with greater production of inflammatory markers after the dive. The ratio deco profile produced grade 3 or 4 bubbles in 4/28 (14.3%) divers and the GF profile produced grade 3 or 4 bubbles in 2/23 (8.7%) divers. The differences in inflammatory marker production were statistically significant, but the difference in the proportion of divers producing high bubble grades was not.

The ratio decompression profile puts greater emphasis on deep stops in comparison to the GF profile, and the results constitute further evidence that the "love affair" we had with deep stops in the early 2000s has resulted in over-emphasis of the strategy by some algorithms. For clarity, and to avoid misinterpretation, the study does not establish GF 30:85 as optimal decompression. It simply indicates an advantage for that algorithm over one which places more emphasis on deep stops.

Simon M

 

[Michael Guerrero]

Advil anyone?

 

[nadwidny]

30/80? AG has gotten conservative. I suppose old age does that. It doesn't seem that long ago I was running 20/90s. And the really bold ones were doing 20/110's.

 

[rossh]

Interesting...

The CDM / ZHL GF 30/85 profile shown in the test report, and VPM-B+2, for this dive are virtually identical.

This is another success story for real models and proper gas tracking (ZHL, VPM-B). i.e. follow the basic gas kinetic rules - one cannot argue with the physics. I have always thought RD to be a problem... it ignores the basics at its peril..

Please.....To avoid a giant argument, please do not try to associate the RD with VPM-B, or tar VPM-B with this test.... In this example and test, the VPM-B +2 profile is a virtual copy of the CDM GF profile shown, and this CDM ascent approach was concluded to be the better one. Ergo, VPM-B+2 would have been the better approach too.

.

 

[victorzamora]

If I remember right, AG added arbitrary deep stops to the 30/85 profile. Is there going to be a public release of the write-up of the test methods, curves, and results? Or is it staying behind the steep paywall?