Easier to breath = higher SAC rate ?

[dumpsterDiver]

If you've ever used a crappy reg, it trains you to take slower more relaxed breaths, When you first switch to a reg that tends to blast air at you as soon as you bigin the inhale, then this promotes a faster inhalation and I think a higher SAC.

Taken to the extreme, a really poor reg would induce stress and cause and elevate SAC , but for a typical relaxed dive, I've seen first hand evidence of regulator induced conservation.

 

[Rhone Man]

+1 for lower SAC. I have a high performance reg and several low performance regs, and my computer measures SAC on each dive. Higher resistance creates higher WOB, which leads to greater gas consumption.

 

[ajduplessis]

I just bought a Mk25/A700 and did my first dive with it last WE. Now this was not the ideal dive to compare breathing and consumption (quite rough sea), but I was wondering if an easier to breathe kit would actually lead to higher SAC rate ?

My first reaction would be no... as higher SAC rate means more volume of air inhaled while easier to breath is not the same concept.
My second reaction is, well if easier, you can definitely get more air out easily !
and my third reaction is to get back to the first one !

What are your thoughts on this ?

When I will have a few more decent dives on this reg, I will be able to compare the SAC rates for real, but in the mean time, it does not hurt to make our brains work out ;o)

This is not the best experiment, but your could learn a couple of things about yourself and your equipment .......

Try adjusting the flow valve on your A700 from very sensitive (easy flow), and then to the least sensitive setting (could also fiddle with the pre-dive switch to add breathing effort). Do a couple of dives at the same depth on each setting, record your SAC and compare the information. Also make some metal notes on each dive about what you feel and experience. If you have an Air Integrated dive compueter with the option to download the data to your PC, even better. You could find some interesting stats and habits during these dives.

I would recommend doing the dives at a shallow depth, as the MK25/A700 combo you have works better and better the deeper you dive.

My feelings are that the easier you breath, the lower your SAC will be. If you decide to try this, please post your findings. Enjoy your diving!!

 

[DA Aquamaster]

If you've ever used a crappy reg, it trains you to take slower more relaxed breaths, When you first switch to a reg that tends to blast air at you as soon as you bigin the inhale, then this promotes a faster inhalation and I think a higher SAC.

Taken to the extreme, a really poor reg would induce stress and cause and elevate SAC , but for a typical relaxed dive, I've seen first hand evidence of regulator induced conservation.

Harder to breathe regs tend to lead to elevated CO2 levels and elevated CO2 levels increase the urge to breathe. So a harder breathing reg has to cause an increase in CO2 levels that negatively impact your SAC rate. Alternatively the diver could compensate for the elevated CO2 levels and keep the SAC low by resisting the greater urge to breathe - in effect tolerating the higher CO2 levels. However this will, as an often unnoticed consequence, cause the diver to experience the increased narcosis that occurs with elevated CO2 levels.

Specifically, "it trains you to take slower more relaxed breaths" means "it trains you to tolerate higher CO2 levels."

 

[HenrikBP]

Could venturi effect be an additional factor affecting air consumption? If the venturi effect - as opposed to cracking pressure - force feeds air, then maybe that would increase SAC?

Henrik

 

[dumpsterDiver]

Harder to breathe regs tend to lead to elevated CO2 levels and elevated CO2 levels increase the urge to breathe. So a harder breathing reg has to cause an increase in CO2 levels that negatively impact your SAC rate. Alternatively the diver could compensate for the elevated CO2 levels and keep the SAC low by resisting the greater urge to breathe - in effect tolerating the higher CO2 levels. However this will, as an often unnoticed consequence, cause the diver to experience the increased narcosis that occurs with elevated CO2 levels.

Specifically, "it trains you to take slower more relaxed breaths" means "it trains you to tolerate higher CO2 levels."

Obviuosly higher CO2 levels are bad and a well tuned reg that functions optimally is good. The high performance capability of a regulator is only needed infrequently and this is during high levels of exertion.

I personally noticed that with a really old and crappy reg, it helped promote the slow and rather deep breathing cycle that is most effcient. I saw evidence myself, when i first started using a high performance regulator that sac increased somewhat.

 

[idocsteve]

I have an older Beuchat reg and it's got that lever on it that allows you to adjust how easy it is to breathe from the reg. I was advised, and I have always found it most comfortable, to set the reg at "maximum ease of breathabity" that also avoids free flow on the surface.

If it's set to breathe hard I feel that I have to really work to pull breaths and I have little doubt the extra effort is going to drive up my SAC rate.

 

[LeadTurn_SD]

Easier to breath = higher SAC rate ?:

No, for most folks, easier to breath = lower SAC rate. The easier and more "natural" breathing feels, the more you'll relax, and your SAC should drop.

Best wishes.

 

[H2O 70]

I'm inclined to disagree with folks here.

I use Apeks regs and I can adjust their resistance to cracking.

In the beginning I used to have this thing set to provide the lowest resistance which made it real easy to breath. I could suck on that thing till I felt like I was going to pass out. No shortage of air. However I always felt like I was getting too much. It felt like there was a micro second when I would stop inhaling and it continued to provide air.

My SAC was crappy. Still is to be honest with you.

One day I turned the knob so that it increased the cracking resistance. What I found was it took a few moments to get used to. I felt like I actually had to inhale. In the end though when I stopped inhaling, it stopped delivering.

My SAC improved by .1cuft/min. Blew my mind.

I can open it up all the way and decrease my SAC by .1cuft/min.

Maybe a reg tech can chime in here, but there is something to adjusting the resistance and SAC.

 

[Diver0001]

The extra work of carrying the penny is about 1 joule. Not big work. It has been described as one hundredth of the energy a person can receive by drinking a drop of beer.

Makes a guy feel like an olympic weight lifter when you put it like that.... LOL

My first thought was what a couple of the others said.

Easier breathing = more comfort = less effort = lower SAC.

I have no basis for this other than intuition.

R..