A Simple Basic Question I Should Know about Air

I am almost a 1-year user of CPAP (nasal pillows) and have recently been having issues again. But a non-CPAP friend asked me the physics of the therapy.
In my case, I have a very large tongue and very small airway and jaw (due to prior orthodontics work in the 1960's and teeth pulled to bring my jaw in) (Another topic for another time). My friend asked what is it in the "air therapy" that allows the air to open the airway when the machine senses you stop breathing? Is it the pressure of the air going down the throat, like pushing a closed door open that opens up the throat? Sorry for the ignorance.

Exactly, a little bit of pressured air. No more, no less.

Thanks Julie. So this "pressurized" air opens up our throats and we start breathing again? And the other question is, how long does it take for the machine to know we stopped breathing? Seconds? Minutes?

Luthie2006 wrote:Thanks Julie. So this "pressurized" air opens up our throats and we start breathing again? And the other question is, how long does it take for the machine to know we stopped breathing? Seconds? Minutes?

that's not how it works, actually. the machine doesn't do anything when you stop breathing, because it can't. now, some machines (ASV) WILL kick into action when they sense you having a central apnea, but that's a wholly different thing than what your autoset does.

think of your airway like a weak straw, that isn't strong enough to stay round on it's own.

if you suck on that straw, (much like when you inhale) then it'll collapse and you can't get any air through it. now, if someone were to blow gently on the other end of that straw, they'd puff it up a little, so when you started to try to breath in through it, it would stay open.

that's the basics of what cpap does. it is very little pressure, remember it's measured in centimeters of h2o, you can see that pressure with a straw and a glass of water. if you're on 10 centimeters pressure, then stick the end of a straw 10cm into a glass of water, and blow... if bubbles come out, you've made at least 10cm of pressure! (10cm is just under 4 inches)

what your autoset WILL do is sense that you've had a couple apneas within a certain amount of time, and it will raise the pressure, hoping to prevent you having further ones. it will also raise pressure if it senses snoring, or flow limitations since those often happen before apneas.

https://www.youtube.com/watch?v=-gie2dhqP2c

Thank you. I always thought that the machine was a "smart" machine and senses when we stop breathing or struggling to breath and that it forces more air down our airway. I think I understand, Pale Rider and Julie.

Luthie2006 wrote:Thank you. I always thought that the machine was a "smart" machine and senses when we stop breathing or struggling to breath and that it forces more air down our airway. I think I understand, Pale Rider and Julie.

As has been said or implied, these "Auto" machines have sensors and programs which are designed to interpret "air flow". Not all users have the "textbook" airflow that these machines and their programs (algorithms) were designed for. So, that's why it's important for the users to monitor their therapy with software. They're supposed to blow enough air into our airways to stint our them open or keep them open so we can breath "normally" during the night, but they're NOT "ventilators" which make you breathe.
And, based on the amount of time it takes (usually at least 10 seconds) for their programs to analyze and record the "events", many of those events can be over with. The "Autos" primarily respond with increased pressure to Flow Limitations and Snoring because that's what the programming has told them to do. Not everyone has Flow Limitations or Snores which precede their apnea events.......so, sometimes the pressure increases aren't necessary and can disturb the sleep of the user.


Den

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Good article from ResMed explaining how APAP works:

Somewhat basic but still a good explanation:

http://www.resmed.com/us/en/healthcare- ... apnea.html#

Thanks all! Simple physics I think.