SAC rate has been uncharacteristically high?

[WantSomeScuba?]

This feels like a stupid question, but I have been perplexed...

My SAC is normally right around .7 cf/m. I can get it lower if I'm consciously trying, and if I'm working, it may be higher, but for the last two weeks, it has been stupid high for me, like consistently 1.1-1.3. For contrast, when I took Fundies, it was around .8 cf/m, and I was getting my ass handed to me the whole time. Even at the pool last night, it was high, and I wasn't doing anything I haven't done a million times.

I have no idea what's up. I leak checked my regs--nothing. The only thing I'm doing different is that I've been at work more and not exercising as much, but I feel like there's no way that accounts for the jump.

Any body have any ideas outside of the normal tips for improving air consumption? Or is that the answer here, and I'm over-thinking it?

 

[wetb4igetinthewater]

This feels like a stupid question, but I have been perplexed...

My SAC is normally right around .7 cf/m. I can get it lower if I'm consciously trying, and if I'm working, it may be higher, but for the last two weeks, it has been stupid high for me, like consistently 1.1-1.3. For contrast, when I took Fundies, it was around .8 cf/m, and I was getting my ass handed to me the whole time. Even at the pool last night, it was high, and I wasn't doing anything I haven't done a million times.

I have no idea what's up. I leak checked my regs--nothing. The only thing I'm doing different is that I've been at work more and not exercising as much, but I feel like there's no way that accounts for the jump.

Any body have any ideas outside of the normal tips for improving air consumption? Or is that the answer here, and I'm over-thinking it?

What method do you use for determining your SAC rate?

 

[WantSomeScuba?]

What method do you use for determining your SAC rate?

Gas consumed/(exposure time x average ATA).

 

[gobuyastick]

I use this- DiveNerd - SAC Rate / RMV Calculator, Imperial Units plug in your info and see if you get anything different

 

[Bob DBF]

One thing about SAC/RMV, is that it depends on when you take the readings and what you are doing.

I record the tank pressure after I set up but before I get in the water, then after I'm out of the water removing gear. In cold water I lose a little, and also any final air checks or BC fill. I've been doing it this way a long time and I believe it gives a better idea of how long the tank will last when planning before a dive.

As for what you are doing, my ridiculous example is that I get a lousy SAC when I'm filling lift bags. More seriously, anytime air is added to the BC, a free flow, purging a reg, and so on your SAC will go up.

The changing of your personal routine may have more to do with it than you give credit. Stress will make a difference, stressing over the change won't help. You may be overthinking the problem, but, if you can, separate the problem solving for this issue from the diving.


Good Luck

Bob

 

[northernone]

Three thoughts :
Perhaps your math is misleading you?
Could what you are doing trying to lower your SAC is stressing you and increasing it instead recently?
Any new medications or illness that might be changing your metabolism?

My mental state has the most significant impact on my breathing.

All that said, a 30-40% change isn't significant in my world. Does make me curious though.

Keep us posted
Cameron

 

[yle]

Possibly just a miscalculation. It's instinctive to think that you're least likely to make a mistake with a simple calculation, like the one you show above, but my experience (dealing with a lot of people making a lot of calculations) has been just the opposite: the simpler the calculation, the more likely a simple mistake.

If you want to post some of your basic data (average depth, time, start and end pressure), we can at least check your calc and possibly rule that out.

 

[scubadada]

Hi @WantSomeScuba?

That does seem like a significant increase in your RMV. Have you made any changes that may have affected your calculations but have not been taken into account, such as a change in cylinder size or operating pressure? Otherwise, I assume you are making your calculations like you have done for some time.

I have all my RMVs for the last 7 years/900 dives, calculated in my AI computer download software. The range is amazingly narrow, despite seemingly significant changes in effort and thermal comfort. In general, my highest RMVs are about 20% above my average. The numbers you gave are an increase closer to 60-85%. You did not mention any extraordinary circumstances to help explain the increase.

It wouldn't hurt to contact the DAN routine medical information line, 919-684-2948, to discuss your concern. Have you noticed any changes in other activities, particularly exercise or exertion tolerance? If yes, you might consider seeing your physician for a check.

Best of luck, Craig

 

[Michael Guerrero]

Assuming you're doing your math consistently and correctly, I'd look to the job. As was said in post 2 or 3, more time at work assumes more stress from work/life issues. Less exercise, for how long exactly, leads to being more easily winded during a dive. Do you think about work or stress during your dive? Do you find yourself distracted by things other than the dive?

Just some ideas.

 

[blac86]

Has the temperature of water changed? Has your rig changed? Have changed fins? Added hunting tools or a camera?​