Overbreathing my regulator

[Hatul]

I am more and more convinced that the reason for this has to do with the relative depth of the mouthpiece and the diaphragm, and to a certain extent the relative depth of the exhaust valve and the diaphragm. The former is very easy to demonstrate with a double hose reg, in which you can easily change the relative depth of the mouthpiece and diaphragm simply by moving the mouthpiece around. The latter is a result of case fault geometry; somewhat simplified, the exhaust valve acts as a limiting factor on how much pressure can be present in the 2nd stage case; when it is deeper than the diaphragm, the pressure in the case is somewhat higher, which I believe is a contributor to the increase in cracking pressure.

I've experimented quite a bit with my D series 2nd stages; those have a coaxial diaphragm/exhaust valve arrangement in which there is never significant difference in depth between the two. Those regs are far less sensitive to position changes in breathing resistance than conventional 2nd stages.

But, I think that the strongest contributing factor is the relative depth of the mouthpiece exit point and the diaphragm. Another easy demonstration of this is a freeflowing 2nd stage can be stopped simply by turning it mouthpiece down. The effect is dramatic, and of course, there are no lungs involved in that one.

If you experience a little difference in breathing resistance between vertical heads up and vertical head down, it's because the mouthpiece is not inline with the center of the diaphragm, and so with head down it's a little deeper. On my conventional 2nd stages (G250/109) there is almost no difference. I attribute that to the slight increase in mouthpiece depth being offset by the slightly shallower exhaust valve lowering the pressure limit in the 2nd stage.

If that's the case then those regs with a small distance between the mouthpiece and diaphragm would breathe best upside down? And also with shallower exhaust valve. Also a side diaphragm should breathe almost the same upright or upside down.

 

[Trimix2dive]

Exactly.

Now on the surface, it is in most cases a bit easier to breath with the regulator out of your mouth. No matter how finely-tuned the regulator, you still have to overcome the resistance of the 2nd stage spring, which while slight is still present; and you have to overcome the slight resistance of the exhaust valve to exhale. If you are breathing hard, this will lead to a feeling of not getting enough air, since you hard having to work slightly harder to get it.

Also, many (most) regulators will breath "easier" underwater than on the surface, at least in a normal horizontal swimming position. A regulator set to "crack" at 1.5"/H2O pressure on the surface may crack at .5" (or less?) due to the 2nd stage case geometry and the effect of water pressure on the 2nd stage diaphragm once you assume a normal swimming postion underwater. So inhalation effort underwater is generally less than on the surface.

Underwater, as Walter said, all modern regulators will supply more than enough air for two hard breathing divers at recreational depths.

Best wishes.

I read the first page and the last page up to this. I will fall in line with these two. Physics is hard to argue against. Overbreathing a regulator is theoretically very difficult unless you are the jolly green giant, or something equivalent.

Slow Deep Relaxed Breathing - relax even when the surface swim sucks.

 

[halocline]

If that's the case then those regs with a small distance between the mouthpiece and diaphragm would breathe best upside down? And also with shallower exhaust valve. Also a side diaphragm should breathe almost the same upright or upside down.

I'm not sure what you mean by upside down (head down vertical or face up horizontal) but, in general, regs with less distance between the mouthpiece and diaphragm should be less sensitive to position changes.

Side diaphragm regs should breathe easiest on your side with the diaphragm side down. No difference between head down vertical and head up vertical. Is that what you're asking?

 

[Hatul]

I'm not sure what you mean by upside down (head down vertical or face up horizontal) but, in general, regs with less distance between the mouthpiece and diaphragm should be less sensitive to position changes.

Side diaphragm regs should breathe easiest on your side with the diaphragm side down. No difference between head down vertical and head up vertical. Is that what you're asking?

Yes by upside down I meant face up.

 

[Zung]

... concentrate on breathing slowly and deeply. This will purge carbon dioxide from your lungs and do away with the feeling you can't get enough air.

Just a small detail: *exhale* slowly and deeply to expell the CO2; inhale whatever it takes to refill. This kinda works better in the mind. With a little practice, it comes automatically.

I never experienced out-breathing with my current setup (SP MK20/G250) or my previous one (AL Supra/XL); and yes, top side with surge, I'd rather breath air through the reg than water through my mouth.

 

[scubafanatic]

well, I can't say I've ever experienced the 'overbreathe' event, and from time to time I've really given my regs a workout, but the regs just laugh it off, sayin' 'is that all you want, wake me up when you REALLY need some real air !' ......but my main regs are Apeks XTX 200 (2) and Atomic M1 and T2's......but even my 'old' Mares and 'cheap' Aqualung Titan LX's have been fine too.

 

[Luis H]

The lungs/reg relative position is not the cause of increased breathing resistance. This is very common misconception that's repeated over and over. This is very easy to prove; on a dive with a conventional 2nd stage try breathing vertically head up and then vertically head down; you'll find that it's about the same, even though those two positions represent the most extreme difference in lung/reg depth.

Then try positioning horizontal facing down and horizontal facing up, these are far lower pressure differentials between lungs and reg, yet they present by far the most dramatic differences in breathing resistance.

I am more and more convinced that the reason for this has to do with the relative depth of the mouthpiece and the diaphragm, and to a certain extent the relative depth of the exhaust valve and the diaphragm. The former is very easy to demonstrate with a double hose reg, in which you can easily change the relative depth of the mouthpiece and diaphragm simply by moving the mouthpiece around. The latter is a result of case fault geometry; somewhat simplified, the exhaust valve acts as a limiting factor on how much pressure can be present in the 2nd stage case; when it is deeper than the diaphragm, the pressure in the case is somewhat higher, which I believe is a contributor to the increase in cracking pressure.

I've experimented quite a bit with my D series 2nd stages; those have a coaxial diaphragm/exhaust valve arrangement in which there is never significant difference in depth between the two. Those regs are far less sensitive to position changes in breathing resistance than conventional 2nd stages.

But, I think that the strongest contributing factor is the relative depth of the mouthpiece exit point and the diaphragm. Another easy demonstration of this is a freeflowing 2nd stage can be stopped simply by turning it mouthpiece down. The effect is dramatic, and of course, there are no lungs involved in that one.

If you experience a little difference in breathing resistance between vertical heads up and vertical head down, it's because the mouthpiece is not inline with the center of the diaphragm, and so with head down it's a little deeper. On my conventional 2nd stages (G250/109) there is almost no difference. I attribute that to the slight increase in mouthpiece depth being offset by the slightly shallower exhaust valve lowering the pressure limit in the 2nd stage.

You are only talking about sensation. What we feel is often very misleading.

It is true that we do not have pressure sensation in our lungs, but that doesn’t mean there is no pressure differential. There is a pressure difference in the water column whether you feel it or not.

This is like some people don’t feel the cold like others do. That doesn’t mean that they are not loosing heat. Heat will always flow from hot to cold… it doesn’t matter whether you feel it or not.

A lot of people don’t feel cold on their heads and therefore don’t wear a hat in the winter (me included). You still loose a lot more heat from your head than from any other area of the skin. And when you put on a hat you tend to feel warmer all over, not just your head.

Sensations are not always a good indicator of what it is actually happening. You probably did a bunch of experiments in junior high that showed how easily it is to fool all of your senses… I know I did.

Just because you do not feel the work that your lungs are doing (actually the muscles surrounding the lungs) it doesn’t mean they are not doing any work.

You will also feel tired at the end of a cold day even if you never actually felt cold… your body is doing work to keep you warm and you never felt it.


The other regulator performance issue (as a function of position and water column)… we have talked about that in many other threads.

 

[halocline]

Luis, as much as I respect you, I'm not convinced. It is so easy to demonstrate that air flows out of a mouthpiece with ease dependent on the relative depth with the diaphragm, and I cannot concede that when there is clearly increased effort in inhalation, that it's somehow not really there simply because my sensations are misleading.

I don't think the cold analogy is a good one. It's very easy for us to sense hot and cold. You're talking about gradual loss of body heat and the body's ability to maintain its core temperature. These are very different issues.

I am not talking about the diaphragm's orientation with regards to the surface; I'm talking about the relative depths of the exit point of the gas from the regulator to the diaphragm. This also explains why there is such a larger position dependence of doublehose regs. If the issue were truly a matter of lungs/diaphragm depth relationship, then single hose and double regs would act very similarly with position change, as the diaphragm/lung depth differential is similar in both types of regulators; in fact, with double hose regs, the cans are closer to lung depth, meaning there should be less change in inhalation resistance with position changes.

What is different between double hose and single hose regs is the difference between mouthpiece (exit point for the gas) depth and diaphragm depth. With dh regs the depth difference is far greater in position changes, and this is reflected in dh regs' sensitivity to position change.

Or, if in fact you are correct about the sensation of increased resistance being misleading, I would say that it's almost irrelevant, because the topic is about the increase in sensation of breathing difficulty.

 

[knowone]

Someone once said here that it's almost impossible overbreathe a regulator.

Yesterday I was swimming on my back in heavy swells breathing off my Oceanic Delta 2 piston and it was definitely hard to breathe and tiring breathing off that thing. It made a huge difference breathing without the reg and with the reg. I've noticed this before both when swimming hard on the surface and at depth. And yes the reg gets regular service.

So I'm sure I can overbreathe this reg. I wonder if you guys with the newer high end regs like the Atomics and Zeagle have the same issue?

Adam

It seems if you read enough spec, re read it, quote it, learn it, then it must be correct. It probably is. Exertion during calm diving is equated to climbing stairs. When doing the Empire State Building, one is afforded the luxury, if over exerted, of slowing down or stopping. Catching ones breath. In the aquatic world, when working, caught in a current, stuck in surge, chasing buddies, the shot of that elusive fish or kicking on your back to a site, that luxury is completely diminished. To varying degrees we are hot, water is cold. This has the effect of masking the level of our exertion. When YOU are over breathed, all regs will taste the same. Being situationally aware and thermally protected is good.

 

[Luis H]

Luis, as much as I respect you, I'm not convinced. It is so easy to demonstrate that air flows out of a mouthpiece with ease dependent on the relative depth with the diaphragm, and I cannot concede that when there is clearly increased effort in inhalation, that it's somehow not really there simply because my sensations are misleading.

I don't think the cold analogy is a good one. It's very easy for us to sense hot and cold. You're talking about gradual loss of body heat and the body's ability to maintain its core temperature. These are very different issues.

I am not talking about the diaphragm's orientation with regards to the surface; I'm talking about the relative depths of the exit point of the gas from the regulator to the diaphragm. This also explains why there is such a larger position dependence of doublehose regs. If the issue were truly a matter of lungs/diaphragm depth relationship, then single hose and double regs would act very similarly with position change, as the diaphragm/lung depth differential is similar in both types of regulators; in fact, with double hose regs, the cans are closer to lung depth, meaning there should be less change in inhalation resistance with position changes.

What is different between double hose and single hose regs is the difference between mouthpiece (exit point for the gas) depth and diaphragm depth. With dh regs the depth difference is far greater in position changes, and this is reflected in dh regs' sensitivity to position change.

Or, if in fact you are correct about the sensation of increased resistance being misleading, I would say that it's almost irrelevant, because the topic is about the increase in sensation of breathing difficulty.

Hi Matt

If you read my post again you may notice that I never mentioned regulator (except on the last sentence in reference to other discussions). Put the regulator aside for a moment… don’t think at all about the regulator.

Think about a snorkel on the surface, a nice diameter snorkel with very low resistance. Now you can be on the surface breathing through the snorkel while you are in a horizontal position or a vertical position.

In a horizontal position you will be floating on the very surface with you back partially out of the water. In a vertical position only your head is out of the water. In either position you can be floating with minimal exertion.

Can you feel any difference on the breathing resistance? I think most people will say no… I know I have never notice any difference. But, your lungs are deeper in the water column when you are in a vertical position.

In a vertical position, the pressure outside the lungs is a bit higher (maybe something like 12 inches of water column, close to 1/2 psi), but the pressure inside the lungs is that of the surface. That is just basic physics.

BTW, your last statement is an important statement, not about me being correct, but about the fact that human sensations and perceptions are very important.

There is a whole field on human engineering just dedicated to this fact. In my new job one of my responsibilities is human engineering… I have a lot to learn.



And BTW, humans do not actually feel temperature, we actually feel heat flow. We are a warm body and all we sense is the relative heat flowing in or out of our skin.

This is another involved subject, but just one quick example. Think about a bar of soap and a bar of aluminum. Both have been sitting in a room over night so they are at the exact same temperature. You pick them up the next day. Do they both feel like they are at the same temperature? Nope, aluminum conducts heat much better than soap so the bar feels colder.

Again human sensations are very easily tricked and designers have to deal with that… because after all, it is the human paying the bill and buying the product.



Added: I thought my analogy/ example was very good. The heat loss from your head in a cold environment is by no means “gradual loss of body heat”. It is very substantial heat loss, but we don’t tend to feel it (at least not directly), but we surely feel the effects.