Easier to breath! Why

[below_sea_level]

I was just playing around in the pool last night after our lesson doing flips, laying on my back and standing on my head. I noticed that it is very easy to breath when I was standing on my head but when I laid on my back it was a little harder to pull a breath through the regulator. Why is this?

 

[Walter]

Try that with a double hose.

Seriously, what regulator were you using?

 

[below_sea_level]

Scubapro R190ut:

 

[rmediver2002]

It is always going to be slightly harder to breath when lying on your back / facing towards the surface.

If the regulator cover is the highest point the air in the regulator is trying to get upward towards the surface and you have to offset that effect in addition to the resistance of the second stage when you inhale.

If the regulator is facing down like when you normally dive it, then that same air space is trying to travel upward into your mouth making the inhale slightly easier. (that is the resistance range the regulator is set to operate at)

The same thing applies to double hose regulators although of course the regulator in that case is attached to the cylinder.

I think this (the effect on a double hose) is often somewhat confusing to some people because i have heard it said also that the effect is from the difference in intermediate pressure on the first stage. 1) the pressure difference is not enough to signifigantly effect the first stage 2) if anything it would slightly increase the first stage pressure.

Good question to be thinking about though!!

Jeff Lane

 

[below_sea_level]

What do you guys mean a double hose?=-)

 

[rmediver2002]

Sea Hunt era gear...

http://www.vintagescubasupply.com/

 

[Walter]

"The same thing applies to double hose regulators"

Nope.

 

[DA Aquamaster]

With a double hose reg, the diaphragm that detemines the "ambient" pressure in the intake hose is located a few inches above the position of the mouthpiece and your chest in a normal swimming position. this makes the reg slightly hard to breathe compared to a single hose reg. It is a little better if you are swimming slightly head up, perfect to a little on the positive side if you are vertical and will force feed you if you are on your back as the diphragm is a few inches below the mouthpiece.

The advantage of the single hose reg is that it detemines the ambient pressure right at your mouth and which makes breathing a no brainer.

When head down vertically in the water, there is the potential for air to bleed out the exhaust valve in the second stage an this in turn reduces the pressure in the second stage making it breathe easier and/or freeflow. When on your back, the diaphragm in the second stage is a couple inches shallower requiring you to overcome that 2" or so of water pressure to breathe.

 

[rmediver2002]

Walter "The same thing applies to double hose regulators"

The effect with a double hose regulator when swimming upside down is the same concept but with the regulator being lower than the mouth piece the air traveling upward through the hose creates a negative pressure area beneath the diaphragm causing the regulator to free flow.

This is similar in function to an airlift...

DA Aquamaster With a double hose reg, the diaphragm that detemines the "ambient" pressure in the intake hose is located a few inches above the position of the mouthpiece and your chest in a normal swimming position. this makes the reg slightly hard to breathe compared to a single hose reg. It is a little better if you are swimming slightly head up, perfect to a little on the positive side if you are vertical and will force feed you if you are on your back as the diphragm is a few inches below the mouthpiece.

The advantage of the single hose reg is that it detemines the ambient pressure right at your mouth and which makes breathing a no brainer.

When head down vertically in the water, there is the potential for air to bleed out the exhaust valve in the second stage an this in turn reduces the pressure in the second stage making it breathe easier and/or freeflow. When on your back, the diaphragm in the second stage is a couple inches shallower requiring you to overcome that 2" or so of water pressure to breathe.

Yes these are factors in the operation of the second stage but they are also being effected, with newer second stage designs to a greater extent, by the effects of the air routing.

The negative pressure phase being created behind the diapragm has the most effect on the regulator function and performance.

The path the air is following through the regulator also determines this negative pressure area. Second stages designed currently normally port the air flow in a manner so that with each inspiration as the air is traveling out the regulator it is also creating a negative pressure phase in its wake effectively reducing the effort required to breathe.

Jeff Lane