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[Pressure] Can you explain pressure measurement?
#21
(11-12-2015, 05:19 PM)eseedhouse Wrote: To a pretty fair approximation 10cm of water is about 1% of normal sea level ambient atmospheric pressure. Even the max most machines can deliver is about 2% of standard pressure. It's the difference between what the machine provides and the outside pressure that causes your breathing passages to open wider

So if the ambient pressure at your bedside is 1000 millibars then the machine at 10 cm of water will deliver about 1010 millibars to your nose throat and lungs. This is only an approximation, but it's a pretty good one. A really bad storm at sea level may drop the ambient pressure to around 980 millibars, and of course if you live on the hights it will be lower too.

Well . . . interesting. It just seems like when I open my mouth and let my machine blow (which will auto adjust up to 18cm) it seems like a giant WHOOOOSH of air coming out, not like what you'd get from a 1.8% change in pressure. But maybe that's just the way it is. Surprising, though.
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#22
(11-13-2015, 09:43 AM)spottymaldoon Wrote: Responding with my physicist's hat on, if it is set to 10 cm of water pressure then it will blow bubbles until the tip of the straw is 10 cm below the water surface - then it will stop!
Now, Spotty, now yer talkin'! That is actually a pretty easy experiment, isn't it? I can fill a bucket with water, immerse my mask while the machine is running, then mark the depth where the bubbles stop flowing. Which should be at a depth approximately equivalent to the max IPAP setting on my machine. If eseedhouse is correct, that is.

I'm gonna try it!
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#23
(11-14-2015, 07:46 PM)Tacoma Droner Wrote: Well . . . interesting. It just seems like when I open my mouth and let my machine blow (which will auto adjust up to 18cm) it seems like a giant WHOOOOSH of air coming out, not like what you'd get from a 1.8% change in pressure. But maybe that's just the way it is. Surprising, though.

Imagine you had a chamber from which all air had been removed. Punch a hole in it and you'll get a whoosh of air flowing in. Had you first increased the pressure of the air in the room by 1.8% it wouldn't have made much more of a whoosh.
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#24
Sonuvabitch! Spotty Maldoon is right! (And all you others who said the same thing.) Banana

Here's what I did. First, if you look at my profile you'll see my machine is a little too fancy for an experiment like this. So I went to my closet and pulled out one of my old BiPap machines, plugged it in, then reprogrammed it to straight CPAP, 10cm pressure, no auto on, no auto off, no ramp, no flex, nothing. Just 10cm of straight CPAP. Then I took a bare hose, attached it, and manually started the machine. Then I dunked the business end of the bare hose (with no mask of any sort) into a bucket of water.

The machine blew prodigious bubbles in the water when the hose end was a few centimeters below the surface. But as I lowered the hose deeper into the bucket, all blowing stopped. Nothing. Then I started to pull it out and the huge bubbles started again. By lifting the hose up, then lowering it down over and over again I was able to get a pretty consistent mark on the hose where the blowing stopped. I put a metric ruler next to me before I started so was then able to measure the length of hose that was immersed when the bubbling stopped.

Wow! 10 centimeters almost exactly! Dang! Amazing

That was cool.Cool
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#25
(11-14-2015, 07:50 PM)Tacoma Droner Wrote:
(11-13-2015, 09:43 AM)spottymaldoon Wrote: Responding with my physicist's hat on, if it is set to 10 cm of water pressure then it will blow bubbles until the tip of the straw is 10 cm below the water surface - then it will stop!
Now, Spotty, now yer talkin'! That is actually a pretty easy experiment, isn't it? I can fill a bucket with water, immerse my mask while the machine is running, then mark the depth where the bubbles stop flowing. Which should be at a depth approximately equivalent to the max IPAP setting on my machine. If eseedhouse is correct, that is.

I'm gonna try it!

Forget the mask (if possible) and just use the hose. Be careful and use a large container not filled to the top with water. Submerse the hose 7" or so (e.g., the length of a straw <g>) then turn on the machine. When you pull the hose upwards to see where the bubbles start it can make quite a mess so have your S.O. (and a towel) around for the show. Eat-popcorn Do this on the night stand and not the bed...
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