Breathing question for boffins

[Charlie99]

Okay let me practice that throat open chest expansion movement!!!

Try this exercise: Cough. Note how your airway is closed just before you cough. That's the type of airway closure that you don't want to do while pausing.

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It may sound strange, but for a lot of people the secret to reducing their air consumption is to be weighted correctly and then properly using their BC to be neutral buoyant.

You should be able to just stop finning and stay at the same depth. Unfortunately, many new divers are both overweighted and then don't put enough air in their BC to offset that extra weight. They go around head up / feet down, maintaining their depth by finning.

The correct weight makes staying neutral easier. Staying neutral makes the dive less strenous. This reduces air consumption.

 

[DandyDon]

I have tried the skip breathing "technique" in the pool when I go swimming - one breath for two strokes. I am taking long strokes, not continuous, and normally inhale as I bring arms and legs forward for the stroke and then exhale as I exert energy. After a few strokes of skip breathing, I began to feel light headed so I decided that it wasn't a good idea.

From what I gather, if I don't worry about it and whatever air I use, I use and as long as I am aware of the SPG then the more I dive the more air efficient I will become due to practice, practice, practice.

Thanks for everyone's advice!!!

Okay let me practice that throat open chest expansion movement!!!

"Skip breathing" is normal when we're dry, but not good under pressure. And like Gary said, it's not lack of O2, but CO2 build-up that causes headaches and other problems.

 

[wedivebc]

I have tried the skip breathing "technique" in the pool when I go swimming - one breath for two strokes. I am taking long strokes, not continuous, and normally inhale as I bring arms and legs forward for the stroke and then exhale as I exert energy. After a few strokes of skip breathing, I began to feel light headed so I decided that it wasn't a good idea.

From what I gather, if I don't worry about it and whatever air I use, I use and as long as I am aware of the SPG then the more I dive the more air efficient I will become due to practice, practice, practice.

Thanks for everyone's advice!!!

Okay let me practice that throat open chest expansion movement!!!

DON'T DO IT! Skipp breathing is dangerous and at least will result in massive headaches from CO2 build-up. Others have posted that you try to slow down your movements NOT you breathing. One thing that works for me is to ensure that I completely exhale. It turns out that CO2 is what controls our breathing reflex and if you don't exhale all your air the brain will register the built up CO2 and make you breath faster. Forget about breathing rate, concentrate on full inhale/exhale cycles, do lots of diving and you'll be amazed at how quickly you go from HOOVER Vacuum to air god.

cheers,

 

[BlueDevil]

Quite a bit of good advice has been given. I particularly agree with the relax and take the dive very slowly strategies. However you also need to accept the fact that some people naturally use more than others, and it maybe that even if you can improve your air consumption a bit, it may still be higher than "average". The only solution to that is to use a bigger tank or maybe twin tanks. Also it is best to dive with a buddy who has similar air consumption to you, then no ones dive gets cut short by the other persons high air consumption. BUT, if you happen to be with a buddy who has low air consumption and still has plenty of air left when you are at a point where you have to surface...then tough luck! Your buddy just has to accept the fact that his dive is going to be a bit shorter than he would have liked - never put yourself in a position of being dangerously low on air simply because you were reluctant to tell your buddy you were geting low.

 

[Far_X]

I have just calculated my SAC for my recent dives and noticed that once I started using the dry suit which corresponded to diving in the NY waters, it has gone up. I had got it down to 1.77 before my night dive on Wednesday when it went back up to 2.2. Initial dives in NY were up to 3.3 which was much greater than when I was diving in FL in a wet suit!! I can see that it is improving and have noted that in moments of stress (losing buddy, strong current) the rate has gone up. I am still comparing myself with more experienced divers but as I can see that I am improving I am happy with that. I will take on board all the good advice offered here and hopefully I will see it come down further yet and join y'all who are in a zen like state under the waves!

 

[Charlie99]

I had got it down to 1.77 before my night dive on Wednesday when it went back up to 2.2. Initial dives in NY were up to 3.3 which was much greater than when I was diving in FL in a wet suit!! I can see that it is improving and have noted that in moments of stress (losing buddy, strong current) the rate has gone up.

Are you sure you are calculating correctly? 3.3 cubic feet per minute SAC (normalized back to 1ata surface level) sounds like panic or hyperventilating. Are you including depth in your calculations?

 

[Far_X]

Are you sure you are calculating correctly? 3.3 cubic feet per minute SAC (normalized back to 1ata surface level) sounds like panic or hyperventilating. Are you including depth in your calculations?

Looking back at those two dives for a 3.3 - I remember filling up my BC so I could do a surface swim back to the port of entry a couple of times. I had to dump my air to swim quickly with the current to the pier and then filled it back up again to swim back to the entry/exit point. Here are my figures: Air used - 2250 psi; depth - 10'; bottom time - 34 mins. I guess filling up the BC twice when it is empty for the dives may use up a bit but I doubt it used up a lot. I remember that dive because it was one of the dives where I felt relaxed for most of it - practicing my bouyancy and maintaing position for five minutes just watching a crab. Yeah, I am suprised it was so high on that dive.

 

[ShakaZulu]

"Boffins", haven't heard that word since I left South Africa, nice man.

 

[Far_X]

"Boffins", haven't heard that word since I left South Africa, nice man.

They must have nicked it from us Brits

 

[Charlie99]

Looking back at those two dives for a 3.3 - I remember filling up my BC so I could do a surface swim back to the port of entry a couple of times. I had to dump my air to swim quickly with the current to the pier and then filled it back up again to swim back to the entry/exit point. Here are my figures: Air used - 2250 psi; depth - 10'; bottom time - 34 mins. I guess filling up the BC twice when it is empty for the dives may use up a bit but I doubt it used up a lot. I remember that dive because it was one of the dives where I felt relaxed for most of it - practicing my bouyancy and maintaing position for five minutes just watching a crab. Yeah, I am suprised it was so high on that dive.

I don't get 3.3cfm.

My calculations are that you used 98*2250/2640=83.5 cu ft on the dive. About 2.4cf per minute actual consumption rate before depth correction. After multiplying by 33/(33+10) correction factor, its about 1.9cfm SAC.

Filling your BC on the surface is less than 1 cu ft (water weighs 64 pound per cu ft and I doubt you added that much lift).

1.9cfm isn't as outrageous as 3.3, but still pretty high, paticularly for a dive that you characterize as "relaxed for most of it". Using up an LP98 in 34 minutes on a 10' dive is definitely on the high side of air consumption rates.

Don't forget to include your surface swim if you are breathing off the reg while going to and from the descent point.

The whole point of SAC is being able to predict the gas volume needed for a dive that you haven't done before. So far, your numbers are all over the chart, making gas planning pretty difficult.