C02 building up while racing underwater to figure out working SAC?

[spectrum]

even nearing a CO2 hit.
I then kept my reg on a light purge and just breathed deep breaths, trying to get my breathing back to a normal pace. Purging the reg kept me from having to activate the cracking pressure, which at that point seemed like an awful lot.

It sounds like that would also flush the 2nd stage dead volume between breaths. This would let you avoid the dead volume rebreathing of the stale second stage case contents.

 

[g1138]

Thanks!...
I don't think I was hyperventilating~

Whether you were or weren't you don't have to hyperventilate to take a CO2 hit. Hyperventilating can be a contributing factor to a CO2 hit which was the reason I mentioned it in that second example. I was trapped in a static position but still felt as winded as when I was drilling the sci dive trainees.

Like TSandM said, anything rapid and shallow in your breathing isn't going to remove CO2 at an effective rate.

It sounds like that would also flush the 2nd stage dead volume between breaths. This would let you avoid the dead volume rebreathing of the stale second stage case contents.

Good point; that too.

 

[danvolker]

If you are trying for a maximum "working pace" as described, one breathing technique to improve exchange and efficiency of the lungs, is to create a double inhale, then double exhale....like some time trialers do on a bike race....get a rythm going for the breathing, like a dance step....in---in---out--out...in--in---out--out..... You pull in a half breath with the first in, then fill volume of lungs with 2nd in...same in exhale....

Begin at just slightly fast pace, and gradually increase till you feel like you are at your maximum sustain aerobic pace. Keep the "beats" in the breathing rythm in your mind, and use your kick turnover rate with the timing of this.

It should terminate the problem with fast/shallow breathing, and should help you to match your pace and breathing rate with workoad.

Try it and see.

 

[ianr33]

Another scary thing about over exertion and CO2 buildup is how long it takes to recover from it,especially at depth.

I learned that on a cave dive (JB) when the flow was high. After 30 minutes of swimming /pulling hard I was breathing very heavily,so I turned the dive and drifted out with the current. On the surface it would have taken only a minute or 2 to recover,but, ten minutes later I was still gasping for breath,even with zero exertion. Fortunately I understood what was happening,so it was just a case of waiting, but it was an interesting experience.

Exertion at depth is bad. Exertion really deep,on air, is very,very bad.

 

[Soakedlontra]

As you know, Betty ... I do that exercise in my AOW class. But I'm curious ... why 27 feet? Granted, you can calculate your SAC rate at any depth by dividing actual consumption by ATAs at that depth ... but the math is much easier if you go a few feet deeper and do it at 33 fsw.

Next time, as soon as you feel the onset, signal your buddy to slow down a little bit ... and concentrate on modulating your breathing to a slower, deeper pattern. If the feeling persists more than a few seconds, discontinue the exercise, relax, and get your breathing back under control ... you don't want to push it to the point of a feeling of "I can't get enough air" ... that imposes a powerful urge to bolt to the surface.

... Bob (Grateful Diver)

Why 27 feet? Because, I guess, we did not know any better. I looked up at my notes but somehow I did not remember that it would have been better keeping the depth at 33 ft! It did accord to Sam but only after we were back home and he was resting in bed!

Well we did goofed up a bit because Sam kept swimming at 27 feet and was above me and I for some weird reasons was swimming deeper below him then after a while I was more concerned about my breathing than the depth. I figure we could have planned this exercise a bit better while on the surface.

---------- Post added January 27th, 2013 at 10:39 AM ----------

It sounds like that would also flush the 2nd stage dead volume between breaths. This would let you avoid the dead volume rebreathing of the stale second stage case contents.

Sorry about my ignorance but ? (what the hell are you talking about?)

 

[g1138]

It sounds like that would also flush the 2nd stage dead volume between breaths. This would let you avoid the dead volume rebreathing of the stale second stage case contents.

Sorry about my ignorance but ? (what the hell are you talking about?)

He means the air space that isn't exchanged with fresh air. When you exhale into the regulator, some of that exhaled air stays in the second stage and doesn't get replaced. So you rebreath that "dead air" on your next inhale.
There's still enough O2 in that air to function on, however there is an increased amount of CO2 as well. It might have been mentioned in your lectures that CO2 is what triggers us to breath, so rebreathing that doesn't help the problem.
The same concept of dead air/volume occurs with a snorkel and even the same thing with your lungs. You never actually exhale all the air in your lungs, otherwise your lungs would collapse.

 

[Soakedlontra]

He means the air space that isn't exchanged with fresh air. When you exhale into the regulator, some of that exhaled air stays in the second stage and doesn't get replaced. So you rebreath that "dead air" on your next inhale.
There's still enough O2 in that air to function on, however there is an increased amount of CO2 as well. It might have been mentioned in your lectures that CO2 is what triggers us to breath, so rebreathing that doesn't help the problem.
The same concept of dead air/volume occurs with a snorkel and even the same thing with your lungs. You never actually exhale all the air in your lungs, otherwise your lungs would collapse.

Thanks! Yes that is one of the few things that I remember CO2 triggers breathing... Yes you are supposed to learn all of that in the class but the problem is if you don't keep what you have learned up to speed it easy to get complacent and just keep diving without having completely and fully understood and retained all of that information.

Today I am in Port Townsend and I am planning to move as slow as a sea slug! :blinking: Sam is no there so I will have to dive with a new buddy :shocked2:!

 

[Soakedlontra]

Yesterday my buddy and I tried again to figure out our working SAC. This time we did not swim in the water column keeping a depth of 33 ft but found a bunch of tires at 33 ft at Langley Tire Reef, leaned over it in a horizontal position and then kicked at a steady pace for 5 minutes with our hands on one tire. It was like being on an underwater treadmill. Those 5 minutes were endless! Once again my buddy was fine while I began to struggle and I had to slow way down my kicking rhythm. There was nothing to be worried about, the depth was shallow, it was a familiar site, there was no current etc.etc.

I am baffled by the way my body reacted. As far as I can guess the reason may be:

1) my regulator is not working properly or its ability to deliver a large amount of air under those circumstance is limited (it's a Mares Abyss);

2) my metabolism is out of whack (sadly I have to admit that I have started to show some signs of pre-menopause...My buddy does not have to worry about this...Darn!)

3) my circulatory system is out of whack

or

4) my respiratory system is out of whack

Considering my family health history I pressed on and managed to make an appointment with my PA (physician assistant), who, unfortunately, is not a scuba diver. Wish me good luck!

 

[danvolker]

Yesterday my buddy and I tried again to figure out our working SAC. This time we did not swim in the water column keeping a depth of 33 ft but found a bunch of tires at 33 ft at Langley Tire Reef, leaned over it in a horizontal position and then kicked at a steady pace for 5 minutes with our hands on one tire. It was like being on an underwater treadmill. Those 5 minutes were endless! Once again my buddy was fine while I began to struggle and I had to slow way down my kicking rhythm. There was nothing to be worried about, the depth was shallow, it was a familiar site, there was no current etc.etc.

I am baffled by the way my body reacted. As far as I can guess the reason may be:

1) my regulator is not working properly or its ability to deliver a large amount of air under those circumstance is limited (it's a Mares Abyss);

2) my metabolism is out of whack (sadly I have to admit that I have started to show some signs of pre-menopause...My buddy does not have to worry about this...Darn!)

3) my circulatory system is out of whack

or

4) my respiratory system is out of whack

Considering my family health history I pressed on and managed to make an appointment with my PA (physician assistant), who, unfortunately, is not a scuba diver. Wish me good luck!

Have you been doing interval training on a bicycle, or swimming fast laps with fins and snorkel? In other words, what have you been doing that would have caused the adaptations to aerobic training that are required for a heavy workoad on scuba, to feel easy?

I can assure you, get to the point of being able to do 25 mile rides on a bike, at an average pace of 20 mph ( around a beginning Cat 5 cyclist level), and the fast pace at the underwater tire, or at 40 feet, should be a non-issue.

Walking or yogo, or TV, will not prepare anybody for what you would like to accomplish

 

[TSandM]

For once, I'm absolutely with Dan. I suspect Sam is just fitter than you are.