USD mistral questions

[luis]

The actual work of inhalation and exhalation is done by the lung muscle, but the sensation of the work done by those muscles is not very acute.

What are more acute are the pressure sensors on your inner ears. That is where differential pressure is measured by the human body. IMHO, that is the actual reason why many divers think that the vertical distance between the regulator diaphragm and the mouthpiece is important. Your ears just happen to be close to your mouth.

In reality when your lips form a seal with the mouthpiece, your respiratory track becomes part of the air duct system. When the mouthpiece is out of your mouth the system has being modified.

So the bottom line from my observations (also looking at some research data for re-breather WOB as a function of counter-lung position, etc.) is that even though the actual work is done on the lungs, the inhalation effort sensation is measure at the pressure sensors in the inner ear.

If you look straight up with your single hose regulator (truly position yourself to maximize the vertical water column distance between your ears and the regulator diaphragm) you will notice a slight breathing effort change.

Also in a double hose just a very slight body inclination with the head looking somewhat forward will raise your ears to about the same level as the regulator diaphragm.

[captain]

From personal experience I know Luis is right and explanation in the book is wrong. One can simply remove the mouthpiece and raise and lower in in relation to the diaphragm and see. It is also the principle used to purge the hoses. By raising the mouthpiece above the diaphragm a free flow is induced. The lungs play no part other than sensing the increase or decrease in suction effort.

[Fibber McGee]

I agree with you, Luis...I guess my explaination wasn't quite so good...while you can induce free flow by removing the mouthpiece and holding it higher than the reg, once it is in your mouth, the air path is from the reg through the hoses, mouthpiece, windpipe, and to the lungs...the distance and routing makes little difference so long as the regulator and lungs are in close proximity to eah other....I suppose you could run the hose from the reg to the surface and back down to the diver and it would make little difference other than the frictional losses of moving the air through the longer pathway.

...Hmm, gets me thinking...Has anyone ever tried using smooth hoses? You know, the lind without any corrigations? ...if you can find one that won't collapse and is still flexible...it may make for reduced breathing effort. or maybe it would be too small a difference to tell???

[Nemrod]

A. I find the diagram useful if not totally accurate.
B. I am a skeptic with the "ear" hypothesis
C. I have experimented with using a large tube, simply as an experiment, to see if there were noticeable reductions in breathing effort. I did not find any subjective difference. Using a magnehlic or other instrumnets, a manometer inserted into the loop, might reveal actual differences but subjectively I found none. I did this experiment several years ago when there was a discussion of the super stretch hoses and the opinions of several (including me) that they seemed to breath easier. No real explanation or conclusive proof was ever realized.
D. Wearing the tank(s) "caveman" style dragging behind so low they bump my calves has no positive value IMO as long as you have good horizontal trim.

Nem

[JES]

The actual work of inhalation and exhalation is done by the lung muscle, ....

Your lungs are not a muscle. It is the action of your diaphragm that allows you to breathe.

Breathing is largely driven by the muscular diaphragm at the bottom of the thorax. Contraction of the diaphragm pulls the bottom of the cavity in which the lung is enclosed downward. Air enters through the oral and nasal cavities; it flows through the larynx and into the trachea, which branches out into the main bronchi and then subsequent divisions. During exercise, the diaphragm contracts, forcing the air out more quickly and forcefully. The rib cage itself is also able to expand and contract to some degree, through the action of other respiratory and accessory respiratory muscles. As a result, air is sucked into or expelled out of the lungs, always moving down its pressure gradient.

[Bryan]

Bill Haley and the Comets, one of rock and roll's pioneer groups actually began their career's as Bill Haley's Saddle Pals - a country music act.

[JES]

Bill Haley and the Comets, one of rock and roll's pioneer groups actually began their career's as Bill Haley's Saddle Pals - a country music act.

Very true, although me thinks you're trying to say we've drifted off topic...

[Bryan]

Bill Haley and the Comets, one of rock and roll's pioneer groups actually began their career's as Bill Haley's Saddle Pals - a country music act.

Very true, although me thinks you're trying to say we've drifted off topic...

Your Jedi mind tricks wont work on me.....

[JES]

Your Jedi mind tricks wont work on me.....

The Force can have a strong influence on the weak-minded. You will find it a powerful ally.

[luis]

The actual work of inhalation and exhalation is done by the lung muscle, ....

Your lungs are not a muscle. It is the action of your diaphragm that allows you to breathe.

Breathing is largely driven by the muscular diaphragm at the bottom of the thorax. Contraction of the diaphragm pulls the bottom of the cavity in which the lung is enclosed downward. Air enters through the oral and nasal cavities; it flows through the larynx and into the trachea, which branches out into the main bronchi and then subsequent divisions. During exercise, the diaphragm contracts, forcing the air out more quickly and forcefully. The rib cage itself is also able to expand and contract to some degree, through the action of other respiratory and accessory respiratory muscles. As a result, air is sucked into or expelled out of the lungs, always moving down its pressure gradient.

You are correct. It was early this morning and I was in a rush (I was running late to do some diving). I should have at least said the muscles associated with the lungs, but more accurately would have been the diaphragm and thoracic muscles. I think we can all agree that the work is perform there.

At the same time the fact that our primary pressure sensor is in the inner ear can not be ignored. Again I think we can all agree that it is the inner ear where we sense pressure differences.

Now all you have to do is put it all together with our diving experiences (and other data that is available). Human beings do get tricked very easily do, many times our perception is tricked by many factors.


The diagram is a very simplistic picture that has a simplified explanation of basic hydrostatic pressure…very simple physics. Where it is inaccurate is in the human physiology. Again, I agree that the work in done in the lung area, but most of the sensation comes from the inner ear.

Talking about the diagram, I don’t think anyone really looks like exactly like that in any of those positions. In the horizontal position specially, we normally look forward at about a 45 degree angle.

[usddude]

Bill Haley and the Comets, one of rock and roll's pioneer groups actually began their career's as Bill Haley's Saddle Pals - a country music act.

Geez that guy Bryan, ya just gotta luv'im.

__________________

Divers in the know dive Phoenix !

[Bryan]

Going backwards a little bit to the original questions on the Mistral as a regulator.

When used on cylinders with 1800 or less it will breathe on par with any double hose. It does breathe a bit harder when you use it at 3000+ psi at the start of a dive but gets better and better as the pressure decreases. At higher pressures the HP seat may wear a bit more quickly but I have enough in stock to last us all for 10+ years. I have used mine at 3000+ for at least 4 years now and it still has the original HP seat that it came with in 1975.
Mistrals move air like a jet engine! They make a unique WOOOOSH sound as the air flows down the hose that is unique to single stage regulators and you can pick them out underwater by their sound without seeing the label.
With very few moving parts and only one 0-ring they are about as bullet proof as a regulator comes. Once the lever height is set correctly they need almost zero maintenance. Rinse in clear fresh water after diving, let it dry and it's good to go. If you have a leatherman tool and a crescent wrench you could rebuild one in the field with no problem.
9 out of 10 dives I use a Mistral and if I could only have one double hose it would be the one without a second thought.

[capn_tucker]

What Bryan said. 1-stage regs rule!

[usddude]

I have dove my Jet-Air a lot and I love it. I recently acquired a Mistral black powder coat that has passed through Bryan's hands. Never have dove a Mistral but am waiting on the day! I wish Luis could come up with a Phoenix Mistral. I guess it can't have a LP port but HP ports seem possible.

Maybe some day I can say>>>
__________________________
Divers in the know dive Phoenix MISTRAL!!!

and it will be reality!!

[Bryan]

A cost effective long yoke to fit Mistrals so they can use banjo fittings is all that is needed. A Phoenix type nozzle would be overkill and ruin the simplicity that makes them great.