Air consumption vs regulator ease of breathing

[Green Frog]

I guess my attitude is that the less you need to concentrate on your breathing, the better your air consumption will be… if you are relaxed, you won’t be sucking down air frantically. I had my old Conshelf XIV serviced right before my trip to Nassau in June and even though I hadn’t dived in four years until a couple of pool sessions right before my trip… my air consumption (or should I say conservation?) was the best ever. The difference? Even though I had a slight difficulty with an oversized BCD (I’ve lost 50#) I was as relaxed as I ever remember being. Calm = good air consumption!
Now, as for the original question, as long as your reg is adjusted sufficiently well that you don’t need to actively fight with it, your air consumption will be OK. If you notice it because you have to work to breathe, air consumption will be worse (ie more).

 

[Fishdip]

Just had my regulator serviced and it breathes amazingly easy. (On the tank at home---I haven't had it in the water yet.) It has always been an easy breather, but this tech adjusted it to a fine degree. I have always used very little air, especially for a big guy. I'm usually the last one back on the boat. Wondering if anyone has experienced or has any info on this: Could an exceptionally easy breathing regulator actually make a diver more likely to use MORE air (gas) than just a good regulator? Is a slight bit of breathing resistance a good thing? Maybe a crazy question. Any ideas or experience on this????

So what you might find is at depth its going to free flow a little and or not close as fast and you 100% will use more air if its doing that my rec rig has so you can adjust the air so it feels like its breathing for you and I have found as I go deeper I have to turn it down or that will happen.

 

[Fishdip]

You say this but my biggest improvement was by adding an AI transmitter and trying to find a breathing pattern, while watching my live SAC rate. This happened after I had decent buoyancy and finning.

this 10000 % I love playing the Sac game in the dark at 100 feet.

 

[John C. Ratliff]

Anecdotally, yes, yes, and yes. This is exactly what Dacor attempted to achieve with their Dial-A-Breath double hose regulator back in the 1960s. The idea was to make divers "conserve" their air by increasing breathing resistance. Was it a good idea? The regulator's nickname was Dial-A-Death. YMMV.
View attachment 801477

Actually, the Dacor R-3 Dial-A-Breath regulator was one of the first to have any Venturi effect. The setting was such that there could be blow-by from the regulator through the mouthpiece and into the exhaust, bypassing the diver. By working the vane in front of the intake horn the diver could tune it so as to have ease of breathing without blow-by. Also, the U.S. Navy divers who evaluated this regulators didn’t like easy breathing regulators, and wanted it to breathe harder rather than too easy, thinking they were ”conserving air.” The competitor at that time was the DA Aqualung regulator from U.S. Divers Company, and it had no Venturi at all as the air was routed against the case on the far side of the intake horn. So at that time, divers were not accustomed to an easy breathing regulator.

SeaRat

 

[John C. Ratliff]

If anything concentrate more on exhaling properly, your reg gives you more dead space, and then you get more co2 out of your system.

When I dive usually everything slows and relaxes, and it's a nice breathing rhythm, with nice deep exahles,

With modern regulator second stages, I don’t think this is correct. The regulators use an injector system with Venturi that virtually ensures that you get air directly out of the LP line, and not exhaled air. This used to be a problem with full-face mask scuba units, as that could lead to more CO2, but not normal second stages. It is also a potential problem with the newer snorkel masks, which are full-face units.

SeaRat

 

[BoltSnap]

I believe the best way to increase your SAC rate is to use your muscles as little as possible.

You mean the best way to "improve or decrease" your SAC rate?

 

[John C. Ratliff]

By definition, the WOB is work. Work requires power, and power oxygen, so a lower WOB equals lower gas consumption. Not complicated. QED.

But while I prefer an easy-breathing reg for a number of reasons, I have never seen the WOB quantified as a percentage of the gas consumption total, either at rest or at different levels of activity. So I don't know to what extent a lower WOB helps reduce gas consumption. I'd love to see measurements someday...but they could be significant, or a just rounding error, despite how much a low WOB has been touted by reg manufacturers.

Anybody got data?

I think the U.S. Navy Experimental Diving Unit has data on this. I’ll check.

SeaRat

PS, Well, now that I’ve checked, I’m going to throw a different wrinkle into this discussion. It turns out that higher negative breathing in scuba divers because of body position, and the function of the regulator, can significantly contribute to a condition known as interstitial pulmonary edema, a potentially life-threatening conditidon. Here’s the 2018 study abstract‘s key points:
[/quote]

Key points​

• The exercise-induced increase in tidal volume during immersion elevates right heart preload, triggering a right to left ventricular imbalance and lung congestion.
• Exercising with negative pressure breathing further increases the inspiratory work of breathing, right ventricle loading, right to left heart imbalance, and rate of interstitial lung water accumulation.
• Positive pressure breathing decreases cardiovascular changes and pulmonary edema during immersion with exercise.
• Plasma levels of atrial natriuretic peptide increase with inspiratory work and correlates with lung comet scores.
• An altered right to left heart imbalance provokes the development of immersion pulmonary edema when inspiratory work is high, e.g., during swimming at high intensity level or SCUBA diving with negative pressure breathing setting.[/quote]

The Key Roles of Negative Pressure Breathing and Exercise in the Development of Interstitial Pulmonary Edema in Professional Male SCUBA Divers - Sports Medicine - Open

Background Immersion pulmonary edema is potentially a catastrophic condition; however, the pathophysiological mechanisms are ill-defined. This study assessed the individual and combined effects of exertion and negative pressure breathing on the cardiovascular system during the development of...

sportsmedicine-open.springeropen.com

This is a very different “take” on harder breathing regulators, which may affect our perceptions on regulator performance.

 

[John C. Ratliff]

I guess my attitude is that the less you need to concentrate on your breathing, the better your air consumption will be… if you are relaxed, you won’t be sucking down air frantically. I had my old Conshelf XIV serviced right before my trip to Nassau in June and even though I hadn’t dived in four years until a couple of pool sessions right before my trip… my air consumption (or should I say conservation?) was the best ever. The difference? Even though I had a slight difficulty with an oversized BCD (I’ve lost 50#) I was as relaxed as I ever remember being. Calm = good air consumption!
Now, as for the original question, as long as your reg is adjusted sufficiently well that you don’t need to actively fight with it, your air consumption will be OK. If you notice it because you have to work to breathe, air consumption will be worse (ie more).

Congratulations on the weight loss. That will not only have an effect on your diving, but you’ll be diving a lot longer in life.

SeaRat

 

[Bazzathemammoth]

I turn down/off the venturi nob on my SP G260. The Venturi would give me the sensation of the regulator inflating my lungs for me at the end of the inhalation cycle. Without it, my breathing cycle feels much more natural.

I do the same. I found that it felt really weird when I first got my regs and my SAC went up significantly. I've got my mk25evo/g260 setup they way I like it now, and wouldn't change a thing.

I stopped caring about my SAC a while ago. It has gone up since then, but I don't mind. I don't think about breathing now which gives me more headspace to enjoy the dive. 15l/min average is good enough imo. I could get it down to 12/13 if I really tried.

 

[Guille G]

I’m a simple guy. Easier breathing: good. Harder breathing: bad.

Current or position pushing your easy breathing reg into constant flow? That’s what the adjustment knob is there for.