Breathing technique

[Perryed]

I have no real idea what my SAC rate is. My main concern when I`m underwater is to maximize my bottom time. I do this by staying relatively shallow and have had many 1 1/2 to 2 hour dives. I try to just relax and breathe slowly. I`ve never had to worry about running out of air when on a boat dive. You have everything very much under control, so enjoy all the bottom time you can get!

 

[Angelo Farina]

I purposely breathe more deeply underwater. I fill my lungs from bottom to top and exhale slowly from top to bottom with a pause at each interval. Consciously breathing in this fashion quickly became habitual. This “technique” improved my air consumption, but you have to find what works best for you.

This is how I was trained, back in the seventies, mostly using the ARO (oxygen rebreather), but also with air scuba.
There are three factors to evaluate for optimizing breathing:
1) proper gas exchange (eliminating CO2, mostly, as Oxygen is already too abundant)
2) reducing the effort for breathing
3) reducing SAC
The order of importance is as above, 1) is of utmost importance, reducing SAC is quite less important.
In the fifties-sixties, here in Italy, it was much more common to use oxygen rebreathers than air cylinders, hence learning the proper breathing technique, for avoiding CO2 accumulation, was absolutely important.
Breathing normally is absolutely NOT effective for avoiding CO2 retention, as normal breathing is very short, the vented volume for each breath ranges between 0.5 liters to 1 liter maximum. Considering the dead spaces in your pulmonary system and inside the regulator, it means that up to half of the vented volume never reaches your lungs. So you make a lot of effort (and consume a lot of air) obtaining bad gas exchange.
It is much better to employ always almost entirely your vital capacity, which can be as large as 6 liters (it is 5.2 liters for me). Of course, the number of complete ventilations per minutes must be reduced. At the end you will vent less liters per minute, but almost 90% of it will reach your lungs, giving you much better capability of eliminating CO2. This is the most important thing for tech and deep diving.
Let's go to the second point.
If you look at the chart of pressure-volume of a modern regulator, you will see that for initiating the inspiration you need to provide some depression (around 0.7-1 inch of water), but then the venturi effect reduces this to almost zero, or in some regs, with a lot of venturi effect, it even goes to positive pressure "inflating" your lungs. At the end of the inspiration, you again need to exert some positive pressure for closing the inlet valve and opening the exhaust valve, then again the venturi effect reduces the effort during the expiration.
This means that every cycle you get two strong peaks of negative and positive pressure that you have to provide with your muscles, followed by a phase in which the reg is less demanding. So if the cycles are very long and a few each minute, you spend much less time exerting these larger pressures, and you make much less respiratory effort. Instead if your breathing is "normal", you make a lot of short cycles per minute, and the regulator never goes in the low-effort state, as you immediately invert the flow.
And finally, reducing the SAC. After having already got a fully controlled breathing, employing always the whole vital capacity, and with very slow rate, then for improving SAC the final trick is to add some short inspiratory pause.
This is what many instructors advise against, as they fear the risk of pulmonary embolism if the diver goes up without exhaling. This is a serious risk, so only divers with enough skills and experience for being 100% safe against this can risk experimenting with the inspiratory pause. One could think that interrupting breathing could work against requisite 1), causing CO2 retention. In reality, a proper inspiratory pause does not only improves SAC, but also helps eliminating CO2. This is because the rate of gas exchange in your lung is proportional to two factors, the pressure difference between CO2 in the blood and in the gas mixture trapped in the lungs, and the surface of contact between blood and gas.
Such a surface is maximised when the lungs are completely full, hence, for a certain period, this overcompensates the fact that, while time is passing, the pressure difference reduces. Of course there is an optimal duration of the inspiratory pause, which is inversely proportional to the CO2 production (hence to the muscular effort being done).
In some type of diving, for example in a pass at Maldives, the diver is completely steady, looking at fish (sharks, eagles, manta rays) passing above him through the pass. The water is warm (usually no suit is needed), the effort is minimal, and the inspiratory pause can be up to 10s. When swimming, particularly if attempting to swim fast with short, hard fins, and using inefficient kicking (for example bicycle or frog kicking) the muscular effort is high, and the inspiratory pause cannot be longer than 1s.
I would say that in average conditions a pause around 4-5 s should be OK, but each one has to evaluate this according to his metabolism, muscular activity and kicking capability. Forcing it too long causes CO2 retention, which is something really bad. Remember, learning a proper controlled breathing method is mainly aimed exactly to avoid CO2 retention! A pause of proper length eliminates more CO2 than without any pause, as your lungs are fully extended, exchanging gas at maximum rate, during such a pause. But beyond a certain duration this is not true anymore, and is better to start exhaling, for expelling the CO2 which is now trapped inside the gas mixture in your lungs.
As you cannot swallow a CO2 meter for checking what is happening inside your lungs, you have to learn how to adapt yourself the length of inspiratory pause.

All that said, I did usually never teach all this to my students, and I just ask them to breath continuously, simply more slowly than when on the ground. This is much more safe for the instructor... And when teaching in a resort, all the training and certification must be accomplished in a few days and in just 4-5 dives. So there is really no time enough for learning proper breathing. It takes several months, perhaps years...

 

[Celt]

I don’t know my SAC but more importantly I couldn’t care less. If you relax and enjoy your diving breathing comes natural. If I need more air I use more air.

 

[giovyledzep]

This is how I was trained, back in the seventies, mostly using the ARO (oxygen rebreather), but also with air scuba.
There are three factors to evaluate for optimizing breathing:
1) proper gas exchange (eliminating CO2, mostly, as Oxygen is already too abundant)
2) reducing the effort for breathing
3) reducing SAC
The order of importance is as above, 1) is of utmost importance, reducing SAC is quite less important.
In the fifties-sixties, here in Italy, it was much more common to use oxygen rebreathers than air cylinders, hence learning the proper breathing technique, for avoiding CO2 accumulation, was absolutely important.
Breathing normally is absolutely NOT effective for avoiding CO2 retention, as normal breathing is very short, the vented volume for each breath ranges between 0.5 liters to 1 liter maximum. Considering the dead spaces in your pulmonary system and inside the regulator, it means that up to half of the vented volume never reaches your lungs. So you make a lot of effort (and consume a lot of air) obtaining bad gas exchange.
It is much better to employ always almost entirely your vital capacity, which can be as large as 6 liters (it is 5.2 liters for me). Of course, the number of complete ventilations per minutes must be reduced. At the end you will vent less liters per minute, but almost 90% of it will reach your lungs, giving you much better capability of eliminating CO2. This is the most important thing for tech and deep diving.
Let's go to the second point.
If you look at the chart of pressure-volume of a modern regulator, you will see that for initiating the inspiration you need to provide some depression (around 0.7-1 inch of water), but then the venturi effect reduces this to almost zero, or in some regs, with a lot of venturi effect, it even goes to positive pressure "inflating" your lungs. At the end of the inspiration, you again need to exert some positive pressure for closing the inlet valve and opening the exhaust valve, then again the venturi effect reduces the effort during the expiration.
This means that every cycle you get two strong peaks of negative and positive pressure that you have to provide with your muscles, followed by a phase in which the reg is less demanding. So if the cycles are very long and a few each minute, you spend much less time exerting these larger pressures, and you make much less respiratory effort. Instead if your breathing is "normal", you make a lot of short cycles per minute, and the regulator never goes in the low-effort state, as you immediately invert the flow.
And finally, reducing the SAC. After having already got a fully controlled breathing, employing always the whole vital capacity, and with very slow rate, then for improving SAC the final trick is to add some short inspiratory pause.
This is what many instructors advise against, as they fear the risk of pulmonary embolism if the diver goes up without exhaling. This is a serious risk, so only divers with enough skills and experience for being 100% safe against this can risk experimenting with the inspiratory pause. One could think that interrupting breathing could work against requisite 1), causing CO2 retention. In reality, a proper inspiratory pause does not only improves SAC, but also helps eliminating CO2. This is because the rate of gas exchange in your lung is proportional to two factors, the pressure difference between CO2 in the blood and in the gas mixture trapped in the lungs, and the surface of contact between blood and gas.
Such a surface is maximised when the lungs are completely full, hence, for a certain period, this overcompensates the fact that, while time is passing, the pressure difference reduces. Of course there is an optimal duration of the inspiratory pause, which is inversely proportional to the CO2 production (hence to the muscular effort being done).
In some type of diving, for example in a pass at Maldives, the diver is completely steady, looking at fish (sharks, eagles, manta rays) passing above him through the pass. The water is warm (usually no suit is needed), the effort is minimal, and the inspiratory pause can be up to 10s. When swimming, particularly if attempting to swim fast with short, hard fins, and using inefficient kicking (for example bicycle or frog kicking) the muscular effort is high, and the inspiratory pause cannot be longer than 1s.
I would say that in average conditions a pause around 4-5 s should be OK, but each one has to evaluate this according to his metabolism, muscular activity and kicking capability. Forcing it too long causes CO2 retention, which is something really bad. Remember, learning a proper controlled breathing method is mainly aimed exactly to avoid CO2 retention! A pause of proper length eliminates more CO2 than without any pause, as your lungs are fully extended, exchanging gas at maximum rate, during such a pause. But beyond a certain duration this is not true anymore, and is better to start exhaling, for expelling the CO2 which is now trapped inside the gas mixture in your lungs.
As you cannot swallow a CO2 meter for checking what is happening inside your lungs, you have to learn how to adapt yourself the length of inspiratory pause.

All that said, I did usually never teach all this to my students, and I just ask them to breath continuously, simply more slowly than when on the ground. This is much more safe for the instructor... And when teaching in a resort, all the training and certification must be accomplished in a few days and in just 4-5 dives. So there is really no time enough for learning proper breathing. It takes several months, perhaps years...

Wow, thanks for the great info!
So the inspiratory pause would be placed between inhaling and exhaling. What about after the exhale? Can there be a pause there too or would that be counterproductive to the O2 request from the body?

Also, as I understand, the longer the breathing cycle the better, but is there a point where too long becomes a problem (as with the inspiratory pause) or not? I can easily make a single cycle last for a minute or even more (I have some freediving training, plus I used to sing, so am familiar with diaphragm and deep breathing), but would that impact CO2 retention?

Finally what about inhale-to-exhale ratio? Should the exhale be as long as the inhale, should it be longer, or it doesn't matter?

Do you agree with the points made by The Iceni (4th reply) here? Breathing question>

Thank you very much

 

[TMHeimer]

I don’t know my SAC but more importantly I couldn’t care less. If you relax and enjoy your diving breathing comes natural. If I need more air I use more air.

Same. I think I figured out my SAC years ago but have no idea what it was.

 

[Angelo Farina]

giovyledzep, I try answering the better I can.
1) Expiratory pause: this was very important breathing the ARO, to give time to the scrubber to fix the CO2 inside the bladder.
But this is not the case when using an OC system, there is almost no gas exchange when your lungs are empty, so better not to do any expiratory pause.
Regarding the flow rate; remember that the primary goal is to remove CO2 from your blood, not to reduce SAC. Hence there is some minimum flow rate, if you go slower, the CO2 is not removed quickly enough. As for the inspiratory pause, the duration of a complete cycle should be inversely proportional to muscular effort.
Final point, the duty cycle: the standard approach is to inhale and exhale at the same speed. But remembering the primary goal, you can see that two modifications are advantageois.
The first one is to stay more time with lungs expanded (so their exchange surface is larger) hence slow down when lungs are almost full, and going fast exhaling and inspiring when they are empty.
The second is to expire faster and to inhale slower.
Combining the two concepts, lets divide the whole cycle in 4 parts: inspiration beginning and end, expiration beginning and end.
A sensible shaping of flow rate, in arbitrary units, could be as follows:
inspiration begin: 3 (moderately fast)
inspiration end: 1 (slow)
expiration begin: 2 (moderately slow)
expiration end: 4 (fastesy)
Usually speeding up the end of the expiration allows to better empty completely your lungs, eliminating all the CO2 trapped.
If you look at this strategy you can see the similitude to some hyperventilation techniques used by deep free divers for preparing before the dive.

 

[Soloist]

So the inspiratory pause would be placed between inhaling and exhaling. What about after the exhale? Can there be a pause there too or would that be counterproductive to the O2 request from the body?

Also, as I understand, the longer the breathing cycle the better, but is there a point where too long becomes a problem (as with the inspiratory pause) or not? I can easily make a single cycle last for a minute or even more (I have some freediving training, plus I used to sing, so am familiar with diaphragm and deep breathing), but would that impact CO2 retention?

You may be overthinking it just a bit. As your diving progresses chances are your task loading will increase dramatically. When I’m lobster hunting or spearing the last thing I’m concentrating on is my breathing. Just get in the habit of breathing deeply and efficiently.

 

[noserider]

If you want to learn how to breathe better / properly take up Yoga for a few months, it will revolutionise the way you breathe and allow you to fully utilise more of your lungs thus increasing oxygen intake and expelling more CO2 and will aid calmness. Not sure what it will do your gas consumption under water but as your breathing is more efficient intuitively I would say it should help lower consumption

 

[Nemrod]

"Breathing normally" is not good advice though I know that is what the abc agencies now teach. Most people pant, shallow, quick breaths almost to the point of hyperventilation. SCUBA diving you will find that taking long, slow, controlled breaths to near full volume, followed by a moment of hesitation and then an equally long or longer and controlled exhalations. You do not need to squeeze your chest to get the last little bit out on an exhalation, lol!

Everyone one tells you to just relax and breath normally, phooey. Good breathing technique will help you to relax, not the other way around. Get horizontal in the water, get trimmed out and weighted and STOP arm swimming and STOP kicking all the time. Learn to be STILL! The not holding your breath admonition has been taken largely out of context. If you are not changing position in the water, you will not suffer an embolism. Breath holding has other complications as in passing out, nobody means for you to hold your breath for any length of time but it is normal to have hesitations between breaths and if that hesitation is some seconds long, it is okay.

You want a low SAC rate, get your body weight to the BMI charts, get yourself physically fit.

N

 

[Angelo Farina]

"Breathing normally" is not good advice though I know that is what the abc agencies now teach. Most people pant, shallow, quick breaths almost to the point of hyperventilation.

I agree almost entirely to what you wrote, except one point where it is advisable to correct you.
What untrained divers risk, keeping a short breathing cycle, is not hyperventilation: it is dyspnea, which actually is the opposite.
During hyperventilation, the CO2 content of your blood falls too low, as you are venting too much. During dyspnea, the CO2 accumulates in your blood, as you are breathing inefficiently, and the CO2 stimulates the short breath.
Disambiguation is given here:
https://www.webmd.com/lung/breathing-problems#1