Regulator breathes much harder when inverted

[Onewolf]

While conducting a test of running out of air in the swimming pool last week, I noticed that both my primary reg (Atomic B1) and secondary air (Atomic SS1) were much harder to breath when I was laying on my back versus any other position. I was curious if this is normal and what causes this regulator behavior?

Thanks.

Doug

 

[fjpatrum]

I definitely haven't noticed that on the few dives I've done with mine. I roll around all the time to look up at the sky, find other divers, whatever, and I've never noticed any difference in breathing.

 

[captndale]

When you are on your back the diaphragm of your regulator may be several inches higher than your lungs. This results in an increase in differential pressure. What this means is that you are trying to breath air that is at a significantly lower pressure than your lungs. i. e. You have to suck harder.

 

[Onewolf]

...snip.... You have to suck harder.

She said knowingly.

 

[Akimbo]

Normally (face-down horizontal) the diaphragm that activates the demand lever is about the same level as your lungs. When the diaphragm is 4" higher, you effectively add 4" of water pressure to the cracking pressure or inhalation resistance.

In the diaphragm-up position, the inhalation resistance will be ¾-1" higher than your exhaust valve, thus slightly less than inhalation pressure. Exhalation resistance decreases compared to face-down horizontal since the water pressure is acting to deflate your lungs. All this has nothing to do with brand, quality, or regulator design.

Nothing has changed in the regulator. For example, in the standing position the inhalation phase of the respiratory work load is higher than face-down horizontal. Head down, the exhalation cycle increases while the inhalation decreases.

Edit: Sorry captndale, your post was up before my cache was updated.

 

[Akimbo]

I was thinking about your post. It occurred to me that many dive classes don’t teach this stuff anymore, at least not in enough detail that you can relate to. So, forgive me of this is redundant.

Every diver using the imperial system knows that one atmosphere of pressure equals about 33' of sea water or 14.7 PSI. This comes from the fact that an average cubic foot of sea water weighs 64.1 Lbs.

Imagine a container that measures 12" x 12" x 12" or 1 Ft³. When you fill it with sea water, the weight will increase 64.1 Lbs; thus exert 64.1 Lbs per square foot or .445 pounds per square inch (PSI) on the bottom of the container — 64.1 Lbs divided by the area of the bottom or 144 Inch² = .445 PSI. Therefore a 1" x 1" x 12" tall column of sea water will weigh .445 Lbs. Therefore, a 1" tall column of water will exert 0.037 PSI (.445/12).

Regulator performance can be a little mystifying if you confuse the cracking pressure your regulator is adjusted to on the technician's bench and inhalation/exhalation resistance in the water. It can be even more perplexing when you factor in the respiratory work load. The respiratory work load is basically the work of breathing. People rarely ever discuss that what a relaxed diver senses first is a change in pressure that occurs in their mouth, felt in their lips and cheeks. Without going too deep into those factors, just keep them in mind as you think about what you are feeling.

An ideal, but currently impractical, solution would be for a differential pressure sensor to be imbedded in the center mass of your lungs and used to control your regulator. It would produce the lowest possible respiratory work when your mouth (and nose) are horizontally in line with the center mass of your lungs. It would also produce the lowest respiratory work load possible in other less advantageous positions.

The original double hose regulators developed by Cousteau/Gagnon were even more position sensitive than the single hose regulators in use today since the diaphragm is even farther from your mouth. Does any of this help you understand what is happening or is it just confusing?

 

[FlyingRhino]

I also wondered if the position of the regulator made a difference. I am just recently certified and while sharing air with my buddy he spun around on me so I rotated the regulator 180 so I could keep it in my mouth. I couldn't suck hard enough to get anything out of it. I wasn't sure if this was normal or not. Needless to say I learned very quickly to choose your buddy wisely.

 

[LeadTurn_SD]

I also wondered if the position of the regulator made a difference. I am just recently certified and while sharing air with my buddy he spun around on me so I rotated the regulator 180 so I could keep it in my mouth. I couldn't suck hard enough to get anything out of it. I wasn't sure if this was normal or not. Needless to say I learned very quickly to choose your buddy wisely.

Even on your back, you should still be able to breath the reg (although it will feel significantly harder).

If you inverted the regulator (if I understand your description, you turned the reg upside down) you should still be able to breath from it, but you'd possibly get "wet" breathing (exhaust valve is now higher than diaphragm and mouthpiece) and more bubble interference with the exhaust "T" upside down.... if you really couldn't get any air out of it, it needs to be checked out and possibly adjusted.

A properly-functioning 2nd stage should deliver air in any possible position.... just harder (and maybe wetter) in some positions.

Best wishes.

 

[Nemrod]

Simple physics:

ALL regulators behave as described above.

N

 

[LeadTurn_SD]

Thanks Nem, this is a case where a picture really is worth 1,000 words.