How does CPAP work? Doesn't make sense

[JDS74]

This thread remnds me of a heated discussion I overheard many years ago ( hard not to considering the volume) which came to an end with the comment "You're trying to confuse me with facts ...I'm talking about principles!"

[DonaldST]

That was probably an argument with me way back in the day. =D

CPAP is the exact same thing as intubation. CPAP is (Continuous Positive Air Pressure) and it has been used since the 1930s. It was first used for infants which were born with a collapsed lung. They would put the infant on room air and then slowly increase air pressure untill the lung inflated intself.

Years down the line, in the mid to late 60s, sleep disorders were observed (some were already known, some where not) by a great group of researcher who would forever be regarded as the 'Fathers of Sleep Science' but that is a story all unto itself. For over a decade there was absolutely no treatment for OSA (obstructive sleep apnea) other than tracheotomy. Where as I am I certain you can understand how popular that treatment was with patients you have to understand that OSA, in it's most severe cases was completely untreated in that day and age and there were large groups of patients who did opt-in for a trach. Unless you work in medicine, it may be difficult to fully appreciate just how bad OSA can get with some people. I sometimes have patients that get brought in via wheelchair because they can't maintain consciousness anymore.

In the early 80s (I will spare you the details) the idea for an adult version of CPAP came up as a possible treatment for OSA. The device would act like intubation but with out a tube. By pressurizing the air that the patient breathes, their throat would inflate like an air matress and insure that the patient could breath on their own.

THAT IS IT.

That is all that CPAP does. You need to throw out all of these mentions of the tongue resting in a particular place at a particular time. Throw out all these ideas that CPAP can some how retrain a person to breath in a certain way. Throw out all these ideas about bi-level devices that act as a ventilator with out a negative pressure. These are all ideas and concepts of NON MEDICAL, Patients and former patients who enjoy getting on the internet and speculating wildly. The reason you became confused is because you were listening to them.

All a CPAP device does is pressurize the air that you breath. It is not rated in psi. psi is a completely different form of volume measurement. It is measured in cwp. Centimeters of water pressure. If you live at 6500 feet and you hop in a car and drive to pheonix arizona.... that is a 2cwp change in the air that you are breathing. CPAP only takes this a little bit further by providing positive pressure and using a mask that leaks that pressure there by allowing you to inhale oxygen and exhale c02 in an environment that is so pressurized that it can not collapse. If anyone has ever been to a 8 year old's birthday party you may have seen one of these...



Same premise.

[StuUnderPressure]

Strong evidence exists that it helps with ED.

IMHO, that IS improper use of the "hose".

[Dr Philip]

CPAP is the exact same thing as intubation. CPAP is (Continuous Positive Air Pressure) and it has been used since the 1930s. It was first used for infants which were born with a collapsed lung. They would put the infant on room air and then slowly increase air pressure untill the lung inflated intself.

They did not use CPAP in the nineteen thirties. They used PEEP positive end-expiratory pressure which is just applied pressure against exhalation. They were very similar. Easy to confuse.

[MRRPM]

Boy, a lot of conflicting info in here! Someone said that "they" had CPaP in the thirties, then someone else comes along saying that "they" did not have CPaP in the thirties. Which is it? Same person also thinks that we breathe in O2 & breathe out CO2. I myself know this is not completely true, as we breathe in whatever is in the room, and exhale whatever is in the room, minus a little O2, that our lungs remove from the room air. How do people get to thinking our atmosphere is made from one element? How do they get to thinking that we exhale one other element? If we were exhaling only CO2, mouth to mouth resuscitation would not be possible.

Another person comes along saying that this is not physics, to the contrary, everything in the physical world is physics, hence the name. I have a few family members that are nurses or otherwise trained in the medical field, ALL of them were required to take physics courses as part of their education.

As to how this works, I'm starting to piece together how this works, a little from one, a little from another. I still do not like the fact that we are rebreathing some of our air. It just seems like there should be some other way. I would guess that there prolly is, but like a lot of other things, it may be cost prohibitive.

[ChicagoGranny]

All I'm asking for is an explanation that agrees with the laws of physics.

I'm starting to piece together how this works, a little from one, a little from another.

Pick and choose. The scientific method.

6:00 a.m. It is unsubcribe time for me.

[SleepyBobR]

MRRPM, I hope you "piece it together" enough to start using your CPAP machine to treat your OSA. I have to say your obsession with re-breathing really is ridiculous. It just isn't happening enough to matter. Hell, you re-breathe your own air (or someone else's or your dog's) all the time when sleeping or sitting still and breathing normally without a CPAP. So what? All that matters is that the mix you breathe meets your body's requirements for O2 and maximum CO2. If the air in your bedroom meets those requirements you will be fine with your CPAP.

[rkuntz123]

Mr RPM,
You appear to be yanking everyone's chain here, all of whom are genuinely attempting to help you understand. So I'll give it one more try, using your numbers vs my equipments characteristics as an example, before abandoning this thread.

Your numbers:
Tidal volume 0.5 Liter
Hardware volume 0.3 Liter

Real world measurements:
Mask to blower fan discharge = 96 Inches
Mask to bypassing vent = 1.5 Inches
Hardware (used air) volume that is NOT directly bypassed and could possibly be rebreathed is (1.5/96) x .03 or 0.0046875 Liter

Note: there is a more than sufficient volume of turbulent air passing through that vent at all times to flush any and all of the 0.0046875 Liter of used air left in the hardware's spaces in the pause (approximately 1 sec in my case) that exists between the completion of exhalation and the start of inhalation.

The only rebreathing, I'm doing on my system, is that portion of my tidal volume that stays in the air passages from my lungs to my nose and I would argue based on how my sinuses have responded to CPAP is that the hardware is actively flushing some of those passages of used air as well.

If you play dumb and counter with "but the internal shape and volume of my mask is different so your numbers can't be valid" my response will be:

Long version "I know that, but it doesn't matter, your system just like mine was very carefully engineered to perform just like mine does despite any inaccuracies in my back the envelope calculations".

or

Short version "Troll, you know too much"

I don't like being on CPAP but it's saving my life, Get on with CPAP, or not, it's your choice.

[49er]

Short version "Troll, you know too much"

Hmm, I don't think this person is a troll.

I know from personal experience that issues will come that I have questions about in which I know I could ask people until eternity and not be satisfied with the answers. So instead, I do a google search so I don't annoy people:)

I understand the frustration but really, I don't think this is a deliberate attempt to be annoying. Of course, I am not an expert and this is just my opinion.

49er

[chunkyfrog]

@MRRPM: All you need to do is BREATHE. --and take a pill for your anxiety.
The CPAP machine was INVENTED in the 1980's, but the physics has been around much longer.
If you are indeed the genius you believe you are; how about working on a cure?

[jamiswolf]

If it, (or anything) doesn't agree with physics, it is snake oil.

Wrong, wrong, wrong!

If cpap violates the laws of physics...then it's magic

Snake oil...in common usage doesn't do what it claims.
Just wanted to clear that up.

Try this video...has lots of visuals

https://www.youtube.com/watch?v=AUXYjPbNwqg

Jamis

[rkuntz123]

49er,
My apologies about suggesting the possiblity of Trolling. But Mr RPM who after leading with the term "tidal volume' which is a pretty exact physiological concept seems to be playing dumb to multiple well reasoned explanations of the mechanical concepts involved.

Perhaps it is my bad, but IMO it's time Mr RPM decides if he's going to follow his Doc's advice or not and stop using the I Don't Understand whine.

If he does start he may discover that a BIG problem with PAP therapy is the sometimes user unfriendliness of the hardware and you guys here on CPAPTALK dot com are absolutely great at helping people like he and I get started. So, 49er a big Thank YOU to you and all the other wonderful caring folks that frequent this locale.

[49er]

49er,
My apologies about suggesting the possiblity of Trolling. But Mr RPM who after leading with the term "tidal volume' which is a pretty exact physiological concept seems to be playing dumb to multiple well reasoned explanations of the mechanical concepts involved.

Perhaps it is my bad, but IMO it's time Mr RPM decides if he's going to follow his Doc's advice or not and stop using the I Don't Understand whine.

If he does start he may discover that a BIG problem with PAP therapy is the sometimes user unfriendliness of the hardware and you guys here on CPAPTALK dot com are absolutely great at helping people like he and I get started. So, 49er a big Thank YOU to you and all the other wonderful caring folks that frequent this locale.

Excellent points rkuntz and thank you for your apologies.

49er

[robysue]

+1 to rkuntz123's last two posts.

[Hose_Head]

Ok, I see, see if this makes sense: Since pressure from the machine, is low, really low, one wouldn't think that there would be enuf pressure to open anything, but... the surface area of the tongue would be rather large, and as we know, it's soft & relaxed. So it doesn't take much pressure to raise it a small amount, to keep us breathing. Kinda like those low pressure bags that are used to raise entire vehicles, in vehicle turnovers.

All I'm asking for is an explanation that agrees with the laws of physics. If the tech works, it must not break even one of these laws, so far, I'm getting it, with some help from some on here, sorta piecing together what's happening. If it, (or anything) doesn't agree with physics, it is snake oil.

If it helps you to understand by analogy, then think about your airway (not your tongue) as being kept open by a spring. For people that do not have sleep apnea the spring is strong enough to keep the airway open even when they are relaxed and asleep. For people who have sleep apnea the spring is not quite strong enough and the spring needs a small bit of help from the low pressure of an xpap machine to open it.

The analogy is incomplete, but if it helps you to understand why a low pressure xpap can help you breathe when asleep, then go for it.