Algorithms, Conservative Factors, Altitude, Planned Deco - Questions

[CandiveOz]

Guys, I think we all agree that workload increases the risk of DCS.
Uwatec and Shearwater agree that workload increases the risk of DCS. Uwatec, uses breathing rate, heart rate and temperature to estimate workload, while Shearwater relies on the common sense of the diver to adjust his GFhi. Based on this agreement, I think it unwise for a diver to ignore an increase workload during the dive because it "it doesn't fit the model or plan." I have emphasised breathing rate and heart rate because they represent, not one, but two problems the diver faces once he successfully deals with the high workload event and leaves the bottom; remaining gas supply and increased decompression obligation. The first cannot be ignored, the second should not be ignored.

 

[CandiveOz]

I took an average of their arrival and departure NDLs at their given depths and then averaged those results. The %'s are versus the NDL in the top row, as are the differences in minutes.

Hi Jay, I think we are on the same track. I simply added the numbers where you averaged them which is essentially adding the numbers (like me) and then dividing by the number of events. But I am a little confused. What NDL in the top row are you referring to? I must be missing something.​

 

[sigxbill]

we do know the Buhlmann formula and developers are just changing two variables within the same formula; GFlow/GFhi.

GF is NOT part of Buhlmann. GF is an anecdotal overlay that modifies the ascent profile of the algorithm. One could do this to any algorithm to modify how the ascent looks, and make it look the way they want.

 

[CandiveOz]

Have a read of Are You Dive Fit? - Divernet

Wow Ken, what an article. Thanks for sharing. I hate to say this, but this is a hard reality divers do not want to face. I don't know about your club but the average age of ours is growing older. Unlike BSAC, we don't train divers although some members are/have been instructors. So we don't have that natural supply of new divers. Dive shops in Sydney are finding it tough, more are closing than opening. If they implemented these benchmarks it would devastate the clubs, shops; the industry in general. I don't think we can use BMI because some will cry "fat shaming." To determine VO2 max properly is difficult and potentially dangerous because its necessary to push the body to its physical limit during the test. A VO2 max of 45 would probably knock out most of our club member base. Is the benchmark too high? Not really but the general population of divers would probably struggle with a VO2 max of 45. Likewise, a middle aged recreational men's football club who play on weekends would struggle with a VO2 max of 45.

Some members in my club don't do shore dives because humping the gear to the site and getting in and out of the water is too difficult. They would rather roll off the side of the club boat and be picked up. I get it, but I would hate to test the effectiveness of the buddy system. Its nice to think that your buddy can save you, but in reality, maybe the best he can do is drag you back to shore so they have a body to bury. Am I a pessimist or a realist? In reality being underwater is a dangerous place; not because of sharks but because water can kill you in about a minute. But experience counts for something; its our saving grace. Experiance keeps us calm rather than panic. It allows us to think things through to resolve minor issues before they escalate. Experience teaches us that no matter how fit we are, we cannot fight the current; so just relax and go with the flow (the skipper will pick us up). Personally, I would rather dive with an experienced old beer belly BSAC Brit than a just qualified physically fit PADI in Pampers.

 

[CandiveOz]

In my OP I asked Shearwood users what's in store for the future; what will they create so to make their Terics obsolete. Shearwood may incorporate heart rate monitoring but use a different approach to Scupapro/Uwatec.

Ooops, I want to correct this before Stuartv reprimands me. I meant Shearwater; not Shearwood.

 

[kelemvor]

And your grand kids will laugh at you for breathing open circuit just like we smile at people today who play vinyl records & 8 track tapes.

Just wanted to point out that "young adults" say 18-30 year olds tend to laugh at people who still use CD's. They've probably never even seen a cassette let alone records or 8-tracks. It won't be long before we've got adults walking around who have never even seen a CD.

 

[scubadada]

Guys, I think we all agree that workload increases the risk of DCS.
Uwatec and Shearwater agree that workload increases the risk of DCS. Uwatec, uses breathing rate, heart rate and temperature to estimate workload, while Shearwater relies on the common sense of the diver to adjust his GFhi. Based on this agreement, I think it unwise for a diver to ignore an increase workload during the dive because it "it doesn't fit the model or plan." I have emphasised breathing rate and heart rate because they represent, not one, but two problems the diver faces once he successfully deals with the high workload event and leaves the bottom; remaining gas supply and increased decompression obligation. The first cannot be ignored, the second should not be ignored.

At what workload, above the usual range of your dives, do any adjustments need be made to the deco algorithm you have chosen to dive with? Do these adjustments apply to no stop dives, deco dives, or both? For deco dives, does the adjustment vary by duration and/or depth of deco or gases used? Is any adjustment made based on the intensity and duration of the increased workload? Do adjustments apply equally to all deco algorithms on the wide spectrum from conservative to liberal? And then, of course, there is the variable of temperature/skin temperature. This could be act independently, or it could play into the workload adjustment, how?

Who knows how heart rate, breathing rate, and skin temperature affect the Scubapro Buhlmann ZH-L16C ADT deco algorithm, singly, or in combination. There appears to be little to no specific information available. On top of the relatively conservative native algorithm, there's also the microbubble levels and the profile dependent intermediate stops. With all these adjustments increasing conservativeness, I would imagine it is pretty safe.

The Shearwater adjustment of the GF hi is under the control of the diver, who decides when to make it and the magnitude of the change. Nobody pretends this is hard science. The surfacing GF and the slope of the ascent line will simply be more conservative than initially chosen.

 

[KenGordon]

It would be nice if there was information available from Scubapro, but people could take the same approach as you did moving from DSAT to ZHL, try it for a while and see how it goes. If you don’t it you can always just follow your regular computer. After all, how do you choose a GF number if not by comparison to other (hopefully successful) dives?

 

[scubadada]

It would be nice if there was information available from Scubapro, but people could take the same approach as you did moving from DSAT to ZHL, try it for a while and see how it goes. If you don’t it you can always just follow your regular computer. After all, how do you choose a GF number if not by comparison to other (hopefully successful) dives?

Right on. I have 1600 successful dives with DSAT. I know how to track DSAT to Buhlmann ZH-L16C with GF. I would have no problem switching over.

 

[dmaziuk]

Just wanted to point out that "young adults" say 18-30 year olds tend to laugh at people who still use CD's. They've probably never even seen a cassette let alone records or 8-tracks. It won't be long before we've got adults walking around who have never even seen a CD.

Cool kids and HiFilytics have always been a minority so it's easy enough to meet an adult who's never seen either. Case in point: all cool kids play vinyl. And if you want lossless audio and are not satisfied with iTunes' selection, CDs are pretty much it. Or you can rip your vinyl into FLACs to play from hard drive.