NEDU Study

[victorzamora]

View attachment 400544

Ross: You're claiming that VPM would safely get you out of the water 90minutes faster than the tested solutions, right? Under those exact high-intensity workloads in that temperature environment?

Honest question: Under those EXACT bottom-time conditions, would you dive VPM-B on any conservatism setting 0-5?

 

[scubadada]

Ross: You're claiming that VPM would safely get you out of the water 90minutes faster than the tested solutions, right? Under those exact high-intensity workloads in that temperature environment?

Honest question: Under those EXACT bottom-time conditions, would you dive VPM-B on any conservatism setting 0-5?

Hi @victorzamora

I've been wondering about the NEDU profile and more common decompression strategies also. The workload can't be replicated but the water temperature is just a little warmer than Caribbean summer. The DCS rates of 1.6 and 5.1% in the NEDU study would certainly give me pause. Out of curiosity, I ran the NEDU profile on MultiDeco. It turns out that Buhlmann ZH-L16C 50/80 and VPM+2 have nearly identical total run times/deco times. However, they have very different profiles regarding the distribution between deep and shallow stops:

Buhlmann:

VPM:

 

[rossh]

Ross: You're claiming that VPM would safely get you out of the water 90minutes faster than the tested solutions, right? Under those exact high-intensity workloads in that temperature environment?

Honest question: Under those EXACT bottom-time conditions, would you dive VPM-B on any conservatism setting 0-5?

Everything, all models, published military tables, DCIEM, lastest USN.... get you out between 90 and 120 mins RT. The nedu test went on for an extra 1 and 1/2 to 2 hours, to make them cold.

 

[victorzamora]

Everything, all models, published military tables, DCIEM, lastest USN.... get you out between 90 and 120 mins RT. The nedu test went on for an extra 1 and 1/2 to 2 hours, to make them cold.

Ross, that didn't answer my question: Would you personally and repeatedly dive those exact dives under those exact circumstances (temp, workload, gases, etc) with VPM-B+2 (for example) and feel safe?

 

[fsardone]

Everything, all models, published military tables, DCIEM, lastest USN.... get you out between 90 and 120 mins RT. The nedu test went on for an extra 1 and 1/2 to 2 hours, to make them cold.

Ross,
are you saying that in same temp a shorter deco profile gives you less pDCS than a longer one?

Thanks

 

[victorzamora]

Hi @victorzamora

I've been wondering about the NEDU profile and more common decompression strategies also. The workload can't be replicated but the water temperature is just a little warmer than Caribbean summer. The DCS rates of 1.6 and 5.1% in the NEDU study would certainly give me pause. Out of curiosity, I ran the NEDU profile on MultiDeco. It turns out that Buhlmann ZH-L16C 50/80 and VPM+2 have nearly identical total run times/deco times. However, they have very different profiles regarding the distribution between deep and shallow stops:

Craig, I understand that you can't replicate the workload in Multideco...and that's honestly the entirety of my point. Under the workload and temperature conditions of the NEDU test, these "excessively long and conservative" (paraphrasing Ross's position on those profiles in the past) were bending divers at an unacceptably high rate of occurrence.

If he truly believes these ascent curves are too long, then he should (to be consistent) willing to do those exact dives with VPM-B and 90min less deco. I, personally, wouldn't cut 90 minutes of deco off of a dive that was already bending 1.6-5% of divers.

Edit to add: Thanks, mod, for fixing the formatting. I hadn't caught that.

 

[rossh]

Ross, that didn't answer my question: Would you personally and repeatedly dive those exact dives under those exact circumstances (temp, workload, gases, etc) with VPM-B+2 (for example) and feel safe?

In my bad old air days, I have dived the DCIEM tables, precisely and exactly to specs, on both sides of this nedu profile.... 160/30 and 180/25.

15 years ago, I made many personal test dives on VPM at 165ft (a rock I would sit on), perfectly timed, perfect ascents. All done for my own experience and satisfaction. I'm still here

So yes... I would dive any of those models, with its base settings, or with one notch of conservatism.

*****

Same conditions? You mean naked and riding a bicycle, and then sitting perfectly still for 3 hours in the shade, getting deliberately chilled? No that's asking for trouble... and they got it.

Getting cold ruins every plan, and no amount of extra deco can fix it. Simply put, staying longer makes the problem worse.

.

 

[victorzamora]

In my bad old air days, I have dived the DCIEM tables, precisely and exactly to specs, on both sides of this nedu profile.... 160/30 and 180/25.

15 years ago, I made many personal test dives on VPM at 165ft (a rock I would sit on), perfectly timed, perfect ascents. All done for my own experience and satisfaction. I'm still here

So yes... I would dive any of those models, with its base settings, or with one notch of conservatism.

*****

Same conditions? You mean naked and riding a bicycle, and then sitting perfectly still for 3 hours in the shade? No that's asking for trouble... and they got it.

If that's true, what makes you think that you'd be safe with 90min LESS deco? I mean that sincerely, despite it sounding argumentative. I'm trying to learn, but I personally don't see a reason to think that such a drastic reduction of deco could be done safely under those exact conditions.

Those stretched out and exaggerated profiles seem to have been extremely long and stretched out/exaggerated to compensate for the high workload. I understand those are conditions not normally seen in the Rec world (as in non-commercial, non-military, ie: most of us)....but those are likely conditions valid to them. I think that might explain why they look so goofy relative to "standard rec" algorithms such as VPM and ZHL.

 

[UWSojourner]

Same conditions? You mean naked and riding a bicycle, and then sitting perfectly still for 3 hours in the shade, getting deliberately chilled? No that's asking for trouble... and they got it.

Getting cold ruins every plan, and no amount of extra deco can fix it. Simply put, staying longer makes the problem worse.

.

Yes, they did get the DCS they were looking for. That was the point of the test. But they got roughly 3x the DCS using the deep stop profile (A2). That is the point.

The deep stop profile resulted in a higher DCS rate for the exact same dive under the exact same conditions.

 

[fsardone]

In my bad old air days, I have dived the DCIEM tables, precisely and exactly to specs, on both sides of this nedu profile.... 160/30 and 180/25.

15 years ago, I made many personal test dives on VPM at 165ft (a rock I would sit on), perfectly timed, perfect ascents. All done for my own experience and satisfaction. I'm still here

So yes... I would dive any of those models, with its base settings, or with one notch of conservatism.

*****

Same conditions? You mean naked and riding a bicycle, and then sitting perfectly still for 3 hours in the shade? No that's asking for trouble... and they got it.

.

Ross,
the point is both groups the shallower ones and the deeper ones did the same: a lot of work deep (facilitated on gassing) and still during deco (impeded off gassing). Why the shallower got bent less than the deeper according to you?

Your experience is anecdotal and therefore remains a good story to tell whilst drinking a beer ...

Cheers

Fabio