Pyle/Microbubble Stops (shortcut)

[lowviz]

I'm confused... What does your dive computer dying have to do with your deco gas becoming unusable?

I sometimes do light (< 15 min) deco on backgas, same gas in the not-to-be-used buddy bottle.

I think he is saying you cant track oxygen exposure and deco obligation if you are only using a DC (now dead)., but I might be wrong.

The whole issue revolves around a point that I didn't bring up as is mostly just for my own entertainment and peace of mind.

Peace of mind:
I want to be able to properly terminate my dive if my DC was taken away at any point in the dive. -should just need depth and an SPG reading to be able to do this.

Entertainment:
I practice this with my (working) DC to see just how closely I can estimate it. I can't always tell in advance if my DC will give me a minute at 30 feet, that changes the location of the first "classic" Pyle stop. However, my VR3 seems to be generating deep stops in a manner similar to what I tried to say in Post #1.

 

[waterpirate]

I do a simmilar thing and was calling it my version of ratio deco. What it really was= recognising re-occurring schedules generated by vplanner and having enough biological memory left to implement those re-occuring schedules, sans my dc or cut tables went missing. It also helped me to call BS on my buddies malfunctioning dc. Given the profile the info it provided was BS.
Eric

 

[rossh]

Oh crud, sorry.

Yes, ASCEND 60' to the first stop.

Yes, that works. Another simple way of doing this, that also agrees with your method, is:

bottom depth - 2 ATA.

More details here: Decompression myths and mistakes

Regards

 

[gurnie]

I was under the impression that DAN no longer recommends deep stops, if you are looking for something you can do in your head, look into UDT Ratio Decompression.

 

[boulderjohn]

I was under the impression that DAN no longer recommends deep stops, if you are looking for something you can do in your head, look into UDT Ratio Decompression.

Which is very much into deep stops.

 

[TSandM]

If you read the DAN Symposium on Technical Diving, there is a lot of dubiousness about very deep stops. There is, to my knowledge, no evidence at all to prove they are necessary or useful, and I have heard rumors that there is a study going on that may show that they result in a higher grade of bubbling.

2ATA off the bottom works for me.

 

[lowviz]

rossh,

Thanks for that link, I finally "get it". Particularly after reading: "All these simple "one variable" based rule systems will fail at some point" and "The x% rule was originally designed for use with 270 to 300ft dives at WKPP..."

So you pick a simplistic rule that remains valid within your type of diving while realizing that other rules better describe other people's diving.

My VR3 doesn't keep a constant 2 ATA for the first deep stop and "my simplistic rule" tracks it rather well within my dive limits.



-just found this: http://www.bishopmuseum.org/research/treks/palautz97/deepstops.html

 

[rossh]

If you read the DAN Symposium on Technical Diving, there is a lot of dubiousness about very deep stops. There is, to my knowledge, no evidence at all to prove they are necessary or useful, and I have heard rumors that there is a study going on that may show that they result in a higher grade of bubbling.

2ATA off the bottom works for me.

Hi Lynne,

From that same Symposium, those involved in bubble listening studies were NOT able to draw a correlation between sizes to injury. None of them were able to show any connections to DCS rates.

The basics are that all diving makes supersaturation, and all super saturation makes bubbles. Your body has a natural ability to tolerate some bubbling. That's what allows us all to dive, and to use the NDL time. Without this ability, no one can dive at all.

The Symposium was split on the deep stop argument - some testing showed it was benificial.

Regards

 

[lowviz]

rossh,

-been looking into your work, most impressive. OK, VPM is overly conservative at shallow depths and long times. Very cool, you should have a handle on this. –bet you’ve been wrenching on it for a while...

Found a well-behaved function (well behaved for the intent of extrapolation) that predicts “NOAA No-Deco Air” end of dive Group Letter. (NOAA Diving Manual pg III-1) Quickest way to check its utility is via Excel, shared below:

=(EXP((3.0343259 + (-15.355991/LN(DepthInFt))))*TimeInMinutes^0.72366692) In Excel, make a depth and time cell first, highlight “DepthInFt” and replace with the depth cell, similar treatment for “TimeInMinutes“… also have equations for SITgroup and RNTs but those don’t figure into this post…



I often do light deco, thus my intense interest. The function tells me that the (light) deco obligations, when fulfilled, do not alter the predicted end of dive Group Letter. This is interesting.

Where I’m going with this:

Each depth/time limits on the NOAA table should be a curve that corresponds to a single compartment’s M value(?). A family of these depth curves should describe a well-behaved surface. The resulting single equation that defines that surface would allow one to predict a deco obligation given just depth and time. (exactly as the surface equation above for Group Letter) A simple approximation to this function may exist that would allow one to predict a deco obligation while underwater. In other words, I don’t have to memorize tables, -can guesstimate that it is time to get out of Dodge. (as a quick check of my DC)

1) Would it be reasonable to say that each depth times out (i.e. 200 min for 40ft) at 6 TC’s for the controlling compartment on the NOAA table? If not, what’s your guess as to how to best proceed???

2) For the purpose of curve fitting, would it be reasonable for one to change the dive times at a given depth to % saturations (using half-times)?

3) Never overlook the obvious, is there a quick way to determine that you are staring deco in the face?

Thanks,

Dennis