Latest ScubaLabs reg test - huh?

[tbone1004]

What I want to know is how much variation is there among production regulators. If we take 100 regulators is each one going to give the same result? Will the be within 5% of each other? 10%? more? I would have to think that the regulators submitted for the review would be either special built or specially selected before being sent.

A related issue is how accurate is the testing method? If I test the same regulator 100 times will it give the same results each time?

some first stages take a bit of time to settle down and truly stabilize. With unbalanced regs especially that will create a lot of variation in the first few hundred breaths and then it should really be retuned.
The individual variation will be there depending on how well they were set up and matched prior to going in for testing, again especially important with unbalanced regulators.

The main issue with this test is that by scoring them on a scale of 1-5 instead of giving the numbers, you have no idea where in that range they fell. The Deep6 was a 3 on their more intense tests and the Apeks MTX-4 was a 4. You don't know if the MTX was a 1.55 and the Deep6 was a 1.56. The Apeks scored 4-3-4-3 and the Deep6 was 5-3-3-0. Both could have been right on the edge of being on the next number up or down which would put them more closely aligned. It's a very skewed way to purchase a reg in my opinion

 

[KenGordon]

@stuartv no pressure gradient in air so orientation doesn't matter. There is a LOT of venturi effect that happens in the exhaust diaphragm on exhale if it is in the right orientation, and obviously everyone is aware of the venturi on the inhale side if they've ever experienced a freeflow that stopped when the mouthpiece went down.

As to the AI question.
I have not used AI to map my breathing though am curious to do so at some point. The reasoning behind it being unlikely that you would be able to maintain that amount of breathing rate for any extended time unless you regularly do sprint type exercises is that you are in what is considered hyperventilation territory. Even those that do that regularly are rarely able to maintain it for over 1 minute without passing out.

Per CARB who did a big study, a male jogging at 12min/miles will breathe just under 60lpm or about 2cfm. While that is obviously not terribly fast and is certainly something that most people can maintain if you do any cardio work, it is unlikely you'll ever have to do something like that unless you are running away from something.
Walking a 24min mile is about .9cfm fwiw
So let's map to see if 3cfm is reasonable to attain for a while.
Total vital capacity of someone your size who marched brass instruments could be up to about 6 liters or .2cf. This is over twice what the ANSTI machine uses because to get that amount of air, you have to suck in as much as you can, and then forcefully exhale as much as you can. You have to repeat that 15x/minute to hit 3cfm. If you attempt this, do it on the couch because if you force yourself to maintain it for a full minute, you are liable to pass out. If you do it for 3 minutes, I'll be amazed. I have seen people that can do this, but when they did it, they were about to go to BUDS so were training for it.

A more realistic number is about about 3l/breath which is similar to the breath you would take while playing trombone and running around a football field. It is as much as you can reasonably inhale without trying very hard. To do that at 3cfm, you have to take those size breaths 29x/minute. In for 1s, out for 1s. If you do that, you are likely to pass out as well. This would be more analogous to running a 5k or something. Again, not impossible, but the odds that someone has a reason to maintain that underwater for any length of time is unlikely

The USN fwiw defines 2cfm as equivalent to running a 7.5min mile and is under "Heavy Work" and only specs up to 3.5cfm as "Severe Work". Hyperventilating causes O2 levels to drop in the body as it is trying to expel CO2 which is why you pass out. The USN says that their fit divers can maintain a SAC rate of 2.6cfm for about 2 minutes but any more than that is high risk. Anything over 2cfm is considered "extreme conditions" and is to be avoided if at all possible. They spec that anything over 1.4cfm means that the diver needs to slow down. If they are in hard hats the tenders will know their breathing rates and tell them to calm down. Now, this was taken primarily from a hardhat standpoint, but breathing is breathing, so if the USN says that their guys in good shape *which is a complete level if crazy in shape* can do 2.6cfm for 1-2 minutes if they have to, I find it hard that us mere mortals could maintain 20% more than that for 50% longer. If I had AI and I saw that on the graph, I'd definitely know what happened that caused a spike equivalent to what probably feels like trying to catch your breath after sprinting a mile.


Reference for CARB paper
Research Note: # 94-11 How Much Air Do We Breathe?
Good discussion in the KM manual on breathing rates. Obviously scheduled around hard hats, but same principals apply
http://www.kirbymorgan.com/sites/default/files/pdf/manuals/km77/KM77_Complete.pdf

Some very big logical jumps here trying to compare running with diving. Also you seem to think that you need to be fit to keep up high ventilation rates. Is if not the case that unfit people are limited by the efficiency of ventilation and perfusion? As hard and fast as they breath they can't turn that o2 into actual work. So for the same output they will actually be breathing harder than a fit navy diver.

Anyhow, I looked back over a couple of years worth of OC dives (in DM5, from a Suunto, including dives with three mixes and plenty of deco to best offend the sensibilities of SB posters) - it looks to my eye that my peak consumption is usually between 50 and 80% higher than my average consumption. In other words an average 20l/minute dive will hit 30 to 36l/minute briefly now and again through the dive (not counting the descent/ascent where suit and wing will make a big difference).

So I would say I absolutely need headroom of 100% vs whole dive RMV and probable a bit more.

So the question is not 'how does it feel?' but 'when in a big panic does it keep up?'

 

[scubadada]

Some very big logical jumps here trying to compare running with diving. Also you seem to think that you need to be fit to keep up high ventilation rates. Is if not the case that unfit people are limited by the efficiency of ventilation and perfusion? As hard and fast as they breath they can't turn that o2 into actual work. So for the same output they will actually be breathing harder than a fit navy diver.

Anyhow, I looked back over a couple of years worth of OC dives (in DM5, from a Suunto, including dives with three mixes and plenty of deco to best offend the sensibilities of SB posters) - it looks to my eye that my peak consumption is usually between 50 and 80% higher than my average consumption. In other words an average 20l/minute dive will hit 30 to 36l/minute briefly now and again through the dive (not counting the descent/ascent where suit and wing will make a big difference).

So I would say I absolutely need headroom of 100% vs whole dive RMV and probable a bit more.

So the question is not 'how does it feel?' but 'when in a big panic does it keep up?'

Thanks Ken,

My experience is very similar. I use 100%, twice my usual RMV for contingency purposes, pony for solo diving...

 

[tbone1004]

@KenGordon the point there was to look at what some studies found for breathing rates as well as what the USN considers "extreme".
I usually plan for at least 2x my normal sac rate *jumps from .45 or so to 1.0* when I do contingency planning as I am aware that that is a reasonably conservative average number.
The concept of hyperventilating and how that negatively impacts the body is something that I am somewhat familiar as a musician.
As a general rule, with obvious exceptions
If you take an olympic runner and have them play flute or tuba *two very high volume instruments* they will not be able to play for very long without getting lightheaded as their lungs are optimized to convert O2 very quickly and if they are forced to play a passage as long as a professional musician can play, they will likely pass out from lack of O2.
That same musician has had their lungs optimized in a different way to allow them to play those passages and if you have them sprint at the olympic level, odds are they will start hyperventilating at the end to try to expel CO2 and because their lungs can't convert the O2 as fast, they will get hypoxic and pass out *why you feel light headed when you hyperventilate*.

So, the reason I say that it is unlikely that a person can maintain that level of breathing without passing out is because hyperventilation causes the body to go hypoxic, and unless someone is in very good shape and has trained for that higher breathing rate, it is unlikely they will be able to maintain that breathing rate for any length of time due to the hypoxia.

Planning for hypercapnia on a ccr? 3.0cfm for easy numbers in the US or somewhere between 80-90lpm over there if you want easy numbers. I think that's reasonable for maybe 3 minutes? Basically an al80 just disappears instantly before you can really start making forward or upward progress. In terms of planning for that SAC rate for any length of time above that? I tend to side with the USN where they say that their super fit guys can maintain a 2.0cfm sac rate for about 2 minutes when working

 

[Akimbo]

@KenGordon the point there was to look at what some studies found for breathing rates as well as what the USN considers "extreme".
I usually plan for at least 2x my normal sac rate *jumps from .45 or so to 1.0* when I do contingency planning as I am aware that that is a reasonably conservative average number...

Just as a point of reference, we typically used a 1.5 CFM RMV for gas planning for working commercial and military surface-supplied divers (on demand, not free-flow). We typically averaged a little lower but it was a decent high-average. Of course these divers have more dead air space to ventilate, working harder, don't worry about running out of gas, and aren't paying for it.

 

[KenGordon]

If you take an olympic runner and have them play flute or tuba *two very high volume instruments* they will not be able to play for very long without getting lightheaded as their lungs are optimized to convert O2 very quickly and if they are forced to play a passage as long as a professional musician can play, they will likely pass out from lack of O2.

You have done this experiment?

You think a fit person will pass out first when forced to breath hard? Do you force feed the tuba and flute players with pies and keep them in a dark room as training?

Breathing is regulated by the co2. The large, unfit diver will have plenty of o2 as they are breathing at high pressure. They will have more co2 than a smaller fitter person. So they will have more urge to breath and actual need to breath. How fit navy divers perform is not going to be more breathing than unfit large divers.

Going back to the paper you quoted. An average adult male was breathing about 60l/minute doing 5 mph running. So how about the worst case older, heavier diver? And then add some headroom for the short term peaks.

I think that the machine simulated rates are easily justified.

I also think that compared to the past almost all regulators are perfectly fine, breathing wise. The real questions are - can I get it serviced? If I let my twinset blow over in the wind, how much will I cry about it? Is it cosmetically too offensive to allow in the house? (I looking at Apeks here)

 

[tbone1004]

@KenGordon those athletes can't hold their breath for long enough because they generate CO2 too quickly from more efficient transfer in the lungs. I think Harvard did a study on it about 20 years ago I'll try to find it.

The paper I quoted reported the average across a huge variety of people up to 77yrs old. It wasn't just 30yr old, relatively healthy non-smokers. It was a WIDE cross section.

I don't think the machine rates are out of the realm of reality under extreme circumstances, but the SAC rates that Stuart quoted are.

Point still stands that regardless of how fit you are, hyperventilating leads to hypoxia and will cause you to pass out. The more fit you are, the slower the hypoxia will onset so you can deal with it for longer than a non-fit person.

 

[crofrog]

I have the computer-recorded-via-AI gas consumption data from pretty much every dive I have ever done. My highest RMV over the course of a whole dive was 1.36cu-ft/min, on a 20 minute dive with a max depth of 45'. Looking at the dive's data, I can see a stretch early in the dive with a sustained RMV over 3.0 for around 3 minutes, with a peak of 3.6 cu-ft/min. That was just me. The dive was just over 1 year ago and my notes tell me where I was and who I was with, but I don't really remember the dive specifically. It was just practice in the local quarry.

I know this is bumping an old thread, but this is really easy to create when you go from hot tanks to cold water...

These were on double 133s that were sitting in the sun on a 93-degree day and then dropping into 53-degree water, between adding air to the wing and drysuit, breathing, and the tanks cooling off it was a 3.86cuft decrease. The grey dots are actually the pressure increaseing when going back above the thermocline.