Re-Evaluating My GF

[Graeme Fraser]

Who else checked out this thread thinking GF= Girlfriend?

Hang on..... Just working out the optimum girlfriend lo and girlfriend hi settings now. Back in a few minutes.

 

[Graeme Fraser]

Hang on..... Just working out the optimum girlfriend lo and girlfriend hi settings now. Back in a few minutes.

Oh dear. Results appear random, completely unpredictable and often dangerous.

For a safer outcome I've decided to go back to checking my O2 cylinder for leaks. Now where did I leave those matches?

 

[Miyaru]

Oh dear. Results appear random, completely unpredictable and often dangerous.

For a safer outcome I've decided to go back to checking my O2 cylinder for leaks. Now where did I leave those matches?

Sounds like a Graeme Fraser high

 

[Neilwood]

Oh dear. Results appear random, completely unpredictable and often dangerous.

For a safer outcome I've decided to go back to checking my O2 cylinder for leaks. Now where did I leave those matches?

Definitely safer - in fact adding dynamite to the O2 & matches combo might still be safer than the GirlFriend lo/ Girlfriend hi experiments.

 

[J-Vo]

, the changes you’re talking about are very minor on a dive like this.

Get rid of the air. Replace with trimix.
Consider your thermal protection.
Consider your hydration.
Consider your post dive exertion.
Consider your exertion level on the dive.

You are correct that all those factors need to be taken into account.

I wouldn't consider an algorithm that gets me out of the water 40 minutes earlier on a dive that bent a statistically significant number of Navy divers as a marginal difference. I'm also looking for my algorithm to work for more extreme exposures. Switching GFs for every dive just doesn't sit well with me.

No deep air for me. Those are just comparisons to the NEDU study witch was 170 for 30 on air. The dive I was bent on was planned 200' for 30. Actual was more like 190 for 28. I was on 19/35. Surface altitude was about 4600'. O2 and 50% for deco.

 

[J-Vo]

Which study is that? Can you provide a link to it?

And consider your pre dive exertion!
___________________

I'm interested in why you chose 50/80.
A recommended starting point would be 30/70, now also the factory default for SW. But then again, that is a starting point. Personal experience leads to other GFs.

The study is not yet available to the public and I have only seen a synopses of the results:Fraedrich D. Validation of algorithms used in commercial off-the-shelf dive computers. Diving and Hyperbaric Medicine. 2018 December 24;48(4):252–258. (Updated thanks to @boulderjohn )

As for pre-dive exertion, it is typically quite low for us as we have plenty of time to lazily prepare for our dives at this location.

50/80 was mentioned in some of the deep stop threads by experts in the field as their personal choice. As such that was my starting point. 30/70 is too deep as far as I am concerned.

 

[victorzamora]

This is way more aggressive then the NEDU deep stop profile.

Given that the NEDU profile was bending the Navy divers I feel much less bewildered by my bend in September. I was also working on the bottom (with my shoulders) and cold during deco, so no surprise.

So, where do I go from here? On top of moving my GF High lower, I'm considering significantly raising my GF Low. I may even go to something like 70/70.

So, hold up a second. You stated something that wasn't entirely accurate.

One thing that's commonly missed when discussing the NEDU profiles is the high workload and cold temps on the NEDU dive. They did this explicitly to increase the amount of Deco Stress they saw in the study. You cannot directly take ascent profiles from the study and compare them to your diving unless you had similar workload and thermal problems.

If your diving involves that much thermal stress and that high of a workload, you should either chill out and get more exposure protection OR add a lot of deco.

Asking which GFs are optimal is a good question, and I'm of the belief that there's no one right answer. If one GF profile makes you feel better, chances are that's better for you.

AJ asked the right questions, though. What was your hydration level? Post-dive exertion? Any weird exertion during the dive? Thermal protection? A buddy got bent (left shoulder) and we believe it was from awkwardly holding his light ahead of him during the dive. Could something similar have happened to you? "Unpredictable" hits can and do happen.​

 

[PfcAJ]

You are correct that all those factors need to be taken into account.

I wouldn't consider an algorithm that gets me out of the water 40 minutes earlier on a dive that bent a statistically significant number of Navy divers as a marginal difference. I'm also looking for my algorithm to work for more extreme exposures. Switching GFs for every dive just doesn't sit well with me.

No deep air for me. Those are just comparisons to the NEDU study witch was 170 for 30 on air. The dive I was bent on was planned 200' for 30. Actual was more like 190 for 28. I was on 19/35. Surface altitude was about 4600'. O2 and 50% for deco.

Youre getting out of the water earlier because of deco gases. There were no deco gases in the NEDU study youre talking about.

 

[J-Vo]

So, hold up a second. You stated something that wasn't entirely accurate.

One thing that's commonly missed when discussing the NEDU profiles is the high workload and cold temps on the NEDU dive. They did this explicitly to increase the amount of Deco Stress they saw in the study. You cannot directly take ascent profiles from the study and compare them to your diving unless you had similar workload and thermal problems.

If your diving involves that much thermal stress and that high of a workload, you should either chill out and get more exposure protection OR add a lot of deco.

Asking which GFs are optimal is a good question, and I'm of the belief that there's no one right answer. If one GF profile makes you feel better, chances are that's better for you.

AJ asked the right questions, though. What was your hydration level? Post-dive exertion? Any weird exertion during the dive? Thermal protection? A buddy got bent (left shoulder) and we believe it was from awkwardly holding his light ahead of him during the dive. Could something similar have happened to you? "Unpredictable" hits can and do happen.​

AJ's questions are all valid and I have reviewed at them all. As with any dive accident, it's usually a combination of all the factors and we should make an effort to control all the variables we can.

One thing I refute is the "high workload" from the NEDU study. Those guys where spinning ~135 Watts if memory serves me well. As a former professional cyclist I can firmly say that would be simulating a light flutter kick for a Navy diver. So, more of a standard dive simulation than "high workload".

For my dive we where attempting to bag lift a small boulder to move it. I was doing a fair amount of pulling and jerking with my arms. I did get chilled on the O2 stops as well, witch was unexpected as I am typically fine with the thermal protection I was wearing but it does happen in 55F. Hydration was good, and post dive work load is not a factor when you are feeling it before you surface.

Another thing to note is that our O2 stops are always swimming at this location. For bigger dives we will swim on our 30' stop as well. So we are working on deco. In this instance we happened to be at the exit pretty much exactly when our PDCs cleared. On ascent a felt pressure that became painful at the surface. We communicated and decided to go back to 20'. Since all symptoms abated at 20' we continued our swimming deco until we ran out of O2. My buddy assisted with gear on surfacing while I sat down with more O2.

Personally I would rather pick a GF that's going to work for all my diving than change to more aggressive profiles because I'm more "comfortable" with a dive. There are a hole lot of people over in the beginner forum that would not consider 200' for 30 a "light" dive. Although, I have been known to slip down that slope as well.

 

[J-Vo]

Youre getting out of the water earlier because of deco gases. There were no deco gases in the NEDU study youre talking about.

Look at my post, I compared GF 50/80 with air deco to the NEDU profile.

Same first stop depth with 40 minutes less deco.