Breathing

[John C. Ratliff]

I'm trying to improve my air consumption. I'm always the air hog and the dive ends because of me. I usually do breathe from my diaphragm and I try to slow things down as much as I can, but I was reading recently some tips and ran across this aritcle on scubadiving.com which says:

• Pause after inhaling. Use your diaphragm to hold air in your lungs a few extra seconds while keeping your throat open. This allows even more time for gas exchange. Your breathing pattern should be: Exhale, inhale, pause. Exhale, inhale, pause.
  Note: Every time we describe this breathing pattern, someone writes us, "Isn't this skip breathing?" It's not. Skip breathing involves holding your breath by closing your epiglottis (like when you grunt) and holding it for much longer. Closing your throat creates a closed air space that is vulnerable to embolism if you ascend. Keeping your throat open avoids that risk. Besides, skip breathing doesn't work. Holding your breath too long means retaining too much carbon dioxide, triggering the urge to breathe sooner than necessary and resulting in rapid shallow breathing. The net result: You use more air by skip breathing, not less.

The most important thing I was taught was that I should *never* hold my breath, but this is basically telling me that I should "pause" for a few seconds (three?) before exhaling, which seems to me to basically be holding my breath. This would certainly slow down my breathing, because I was trying to keep a constant circular flow going, and just try and slow down the exhale and inhale parts by doing it as slowly as I could.

Do other people do this? Is this why I'm always dragging people back to the surface when they still have twice the air left as I do? Do you have other tips?

I've read a lot here, but I'm not sure how much to believe. This U.S. Navy Diving Manual drawing (Figure 1-24, Lung Volume, from the March 1970 edition on page 1.3.4) shows how many people breathe. If a diver simply uses his or her tidal volume, the respirations are much more frequent and pass less air (average about half a liter). But we have a lot more vital capacity than that, up to 4-5 liters (mine is 6+ liters, as measured by spirometry on a respirator physical for work). In diving, we want to increase the breathing depth to include both some of our inspiratory reserve volume, anhd our expiratory reserve volume, as is shown in the center of the diagram for the "work" phase of breathing. This increases the efficiency of breathing, decreases the possibility of CO2 buildup, and actually decreases air consumption as the air breathed is more efficiently used. You can read more in the current U.S. Navy Diving Manual at this link:
http://www.navsea.navy.mil/Portals/103/Documents/SUPSALV/Diving/US DIVING MANUAL_REV7.pdf?ver=2017-01-11-102354-393

Here is what this latest version of the manual states about air consumption:

3-4.8 Oxygen Consumption. A diver’s oxygen consumption is an important factor when determining how long breathing gas will last, the ventilation rates required to maintain proper helmet oxygen level, and the length of time a canister will absorb carbon dioxide. Oxygen consumption is a measure of energy expenditure and is closely linked to the respiratory processes of ventilation and carbon dioxide production.

Oxygen consumption is measured in liters per minute (l/min) at Standard Temperature (0°C, 32°F) and Pressure (14.7 psia, 1 ata), Dry Gas (STPD). These rates ofoxygen consumption are not depth dependent. This means that a fully charged MK 16 oxygen bottle containing 360 standard liters (3.96 scf) of usable gas will last 225 minutes at an oxygen consumption rate of 1.6 liters per minute at any depth, provided no gas leaks from the rig.

Minute ventilation, or respiratory minute volume (RMV), is measured at BTPS (body temperature 37°C/98.6°F, ambient barometric pressure, saturated with water vapor at body temperature) and varies depending on a person’s activity level, as shown in Figure 36. Surface RMV can be approximated by multiplying the oxygen consumption rate by 25. Although this 25:1 ratio decreases with increasing gas density and high inhaled oxygen concentrations, it is a good ruleofthumb approximation for computing how long the breathing gas will last.

Unlike oxygen consumption, the amount of gas a diver inhales is depth dependent. At the surface, a diver swimming at 0.5 knot inhales 20 l/min of gas. A SCUBA cylinder containing 71.2 standard cubic feet (scf) of air (approximately 2,000 standard liters) lasts approximately 100 minutes. At 33 fsw, the diver still inhales 20 l/min at BTPS, but the gas is twice as dense; thus, the inhalation would be approximately 40 standard l/min and the cylinder would last only half as long, or 50 minutes. At three atmospheres, the same cylinder would last only onethird as long as at the surface.

Carbon dioxide production depends only on the level of exertion and can be assumed to be independent of depth. Carbon dioxide production and RQ are usedto compute ventilation rates for chambers and free-flow diving helmets. Thesefactors may also be used to determine whether the oxygen supply or the duration of the CO2 absorbent will limit a diver’s time in a closed or semiclosed system.

I would not fixate on improving air consumption, but rather try to relax and enjoy diving. I used to dive our jump tanks (twin 42s) with other PJs diving twin 72s, and I would stay about twenty feet above them and have about the same time in the water.

'Hope this helps.

SeaRat

 

[twistypencil]

some things that I feel should have been asked or said.
4) how is your physical condition?
5) get rid of excess lead and anything that can cause drag that you don’t need for the dive.

This. Trying to enforce some artificial breathing rate is dangerous and silly. Your body needs what it needs, and to deny it is asking for trouble.

Others have mentioned the skills you need to develop... good trim, relaxing, proper weighting etc. But I have found over years and years is that those who have really high consumption rates tend to be "larger" people. Define "larger" any way you want... tall, wide, thick. If any of these are you, and you have the ability to change it (I guess that's the "thick" part) then do what you can.

And get fit, if you aren't.

But if you're simply a large person, embrace it! One of my occasional buddies is simply huge. He's 6'7'' and must weight 350 pounds. He's not obese, he simply large. He was burning through air at an alarming rate. His solution was to start to dive side mount. SM can generally be accomplished anyway assuming you have the backplate, wing and regulators. I can't see any charter operator or resort preventing you from diving this way.

My physical condition is good, I am a tall person, nearly 6'4", but I'm not overweight (185lbs).

I think I can shed some weight, and hope to try that this week. I'll also work on making slow and deliberate movements, and frog kicking!

 

[Stoo]

So it'll come in time... I haven't read back through the entire thread, but based on your bio, if you truly fall into the 25-49 dives, you're but a wee guppy. Relax and work on trim etc.

And honestly, some people just use more air. It's not the end of the world and a lot can be dealt with by using larger tanks.

 

[TONY CHANEY]

In diving, we want to increase the breathing depth to include both some of our inspiratory reserve volume, anhd our expiratory reserve volume, as is shown in the center of the diagram for the "work" phase of breathing. This increases the efficiency of breathing, decreases the possibility of CO2 buildup, and actually decreases air consumption as the air breathed is more efficiently used.

I had to read and read this again and again. Why? Because it is suggesting a change to normal breathing patterns. So I'll try to explain my problem with this theory. The only way that you can get a larger breath is to allow for a longer time to inspire more volume. This longer inspiratory time will decrease the expiratory time. Normal I:E ratio is around !:2. Inspiratory limb is for oxygen and expiratory limb is for getting rid of CO2. So, I just want to say, to be careful with prolonging the inspiratory time and shorting the expiratory time. CO2 will build up. We only use an inverse I:E ratio for very special patients.
This is just a small example without getting too deep: Ventilation I:E ratio

The second part of your post is referring to a rebreather.

Loved the picture of diving mini doubles in Okinawa. I got certified there and my oldest daughter (15) is getting her cert. even as we speak. I was there 84-88 and then 1999-2003. I also have two mated yellow 45's steel I was going to sell but I might just double them up. PJ's are simply the best of the best, and this is coming from a retired Marine.

 

[TMHeimer]

There are many views/tips on breathing. Obviously, the faster you swim or move around, the more air you use. And body/lung size, lung capacity, 02 needed for tissues--all factors of course. My thought was always breathe slowly and regularly--somewhat "deeply" if you will, but not consciously "breathing deep". Just get in a normal breathing pattern and that's that.