n00b question about air pressure

Thanks for this forum -- there's so much here to try to absorb! I have a question about air pressure.

I am a new CPAP user -- two nights so far, the first of which I spent with strep throat. (Surprise! Have some antibiotics!)

I was given a ResMed AirSense 10 Autoset, with an AirFit A10 full-face mask because I sleep with my mouth open, thanks to a bad nose. It feels like the machine ramps up from a nice, gentle airflow to a howling wind that flaps my cheeks and whistles around the mask and brings me wide awake.

I've fussed with the straps and tried resettling the mask, but only turning off the machine and turning it back on again (I work in IT, and it's how we fix everything) slows down the air to where I can actually breath.

Is this more likely to be an issue with the mask not fitting my weird-shaped head, or with the target air pressure being high? And is it set so high based on my home sleep test, or just a kind of default setting?

Thanks for any advice, and any pointers to FAQs that I may have overlooked.

- Will

Use the available software to see what the pressure is doing.
https://sleep.tnet.com/equipment
If there is a big change maybe you just need to adjust the mask to the higher pressure to start with.
Or maybe a different mask would work better.

But first...check to see exactly where the pressure is going when you start having problems.

Also check to see if you are using EPR (exhale relief) and if you are at what setting.

Don't know about all the various settings? Check out the manual as it explains how to get to the menu where you can see all the various setting menus.
https://sleep.tnet.com/home/files/resme ... -guide.pdf

Fair enough: the answer is usually in the data!

I don't think there's an SD card in my CPAP machine's card slot. If I put one in there, will it stop reporting data to the DME, or will it do both?

The SD card has no effect on cellular communication with the DME, who only cares about hours of use.
YOU want more info, so get your own sd card.

Where are you looking for the SD card slot? The blank slot that is easily seen isn't for the SD card.
Instead the SD card is hidden just left of the LCD screen on the side and you have to open the little door with a fingernail. Shown in the manual. There are 2 little doors...the top one is for the SD card.
If nothing in there then any generic SD card will work and having the SD card doesn't stop any transmission or data collection.

You will need the SD card to be in the slot to get the detailed graphs you will want to see exactly what the pressure is doing. The machine will store some summary data in its internal memory but it doesn't store the detailed stuff.
If the SD card isn't in the machine during the night you won't get any detailed graphs.

Yeah, I saw the card slot. (It has the standard SD card logo on it.)

I will pop one in before bed tonight and make sure it's formatted properly.

wenestvedt wrote: howling wind that flaps my cheeks and whistles around the mask and brings me wide awake.

since you're new, here's a little perspective on pressure...

The machine has a pressure sensor right at the outlet, it measures pressure typically in centimeters of water. ie, how much pressure it takes to push down that many centimeters of water. you can feel *exactly* how much pressure that is by sticking a straw in a glass of water, and blowing. four centimeters is slightly over 1/2 inch. so, stick a straw 1.5 inches in a glass of water, and blow.. if you got bubbles to come out, you've just blown harder than 4cm/h2o pressure.

the maximum pressure your machine can create is 20cm/h2o, that's just under 8 inches.... so take a tall glass and stick a straw 8 inches into it... blow. you've just blown harder that 20cm/h2o.

now, as to that rush of air, like I said, the machine is set to create a specific pressure. pressure is the result of resistance to flow. when there's no resistance (or very little) like when your mask is off... the machine creates MORE flow, to try and get pressure. but there's no resistance, so the air just blows out, so the machine tries harder, spinning the fan faster, and faster, till it's at full speed, trying to make some pressure, pushing against nothing.... so you get a huge amount of flow with no pressure. it's like turning on the garden hose and letting all the water run out, it doesn't go very far, big flow, low pressure, but if you put your thumb over the end, the flow goes way down but the pressure goes up, and the water shoots a much longer distance.

as soon as you put your mask on, the machine senses the the increasing pressure, and slows the fan down. (it checks maybe a hundred times a second, maybe more, depending on the model.) it slows the fan down till there's only that very gentle 4cm/h2o of pressure, that you blew bubbles with. and none of it is blowing up your nose... where would it go? if it was actually blowing up your nose, you'd eventually explode! no, the air, and that gentle pressure, is just sitting there, until you do what you normally do, until you inhale, THEN air goes up your nose, into your lungs, giving you the oxygen you need to live. then you exhale and the air comes back out your
nose, against that tiny bit of pressure... and flows out the vent holes in the mask.

as to the whistles and noise... look into 'mask liners' check out padacheek.com.

Thank you, palerider -- your explanation of pressure makes a lot of sense.

This evening I popped a 2GB SD card into the machine, which it happily accepted. Curious, I held down combinations of buttons until it switched into clinical mode, which is some pretty lame security. :7) Anyway, from there I saw that my AHI last night was 5.7, and that the pressure is set to go up to 20. So that makes sense that, when the mask leaks enough air, the pump really revs up in order to try for that 20cm!

Tonight I will have the data written to the card, and I already installed SleepyHead so I can look at it tomorrow morning.

Thanks again, all!

wenestvedt wrote:and that the pressure is set to go up to 20. So that makes sense that, when the mask leaks enough air, the pump really revs up in order to try for that 20cm!

the pressure *could* go up to 20, but it's highly unlikely that it did.

the fastest that the machine ever revs up to is when you take off the mask... (just fyi).

if you hold your ear to the blower, while you've got the mask on, you can probably hear it speeding up and slowing down, to maintain pressure as you breath.

You are wearing an Airfit F10 mask. I hated that mask as I constantly had leaks. I then went to the Fisher & Paykel Simplus where it was more tolerable but only while using liners. Since you are so new at this, call your DME and ask to be fitted to another mask. Try either the Airfit F20 or the Mirage Quattro. Both are Full Face. Depending on the type of sleeper you are, these mask tend to seal much better for an "active" sleeper.

Last night was better still: the strep throat is on its way out, and I had fewer of the constant leaks again -- but a couple of times it woke me up.

Here's a screenshot of what SleepyHead captured:


(Did I do that right?)

I got up to go to the bathroom a little before midnight and turned off the device. And around 2:00, there was a lot of leaking and the pressure went up and eventually I turned it off and on again and went back to sleep.

Well your machine never went to 20.
Don't need the snore graph...replace it with the Flow limitation graph next time.

Did you end up on your back right before that first wake up and the little cluster of events?

It's obvious that you need more pressure at some parts of the night and not others. The usual culprits for rather dramatic pressure change needs are sleeping on your back or REM stage sleep. Your clusters of events are within the time cycle that we might see REM happen.

You need more minimum pressure because from what the machine's minimum is now it can't get to where it needs to be quickly enough to prevent those clusters of events (no matter what the cause). We sometimes have to give the machine a better headstart. I would say maybe try 7 or 8 minimum instead of the 4 cm.

Also happening is you fit the mask for 4 cm and it goes up to 10 or 12 and what works well in terms of fit doesn't work so great at 10 or 12 cm. Fit it to the 7 or 8 new minimum maximum and there's a better chance that the seal will still work if you go to 10 or 12 again.
You may not go to 10 or 12 or whatever if the minimum pressure is more optimal. Can't promise you that the pressure won't climb so high but I have seen it happen enough that it might. These machines work best by preventing the airway from collapsing in the first place and not trying to fix something after the fact.
More baseline (minimum) pressure helps hold the airway open better and lessen the chance of the airway tissues collapsing and if they do try to collapse the machine has a better headstart to get to where it needs to be to stop them.

So more minimum pressure for 2 reasons...will help with leak control and you need a better baseline pressure to give the machine a running start to better deal with those clusters of OA events.

Higher minimum pressure, got it. I will try tonight!

Any obvious reason the mask might fit well at bedtime and not as well four hours later? Is the stubble on my face enough to break the seal?

And thank you!

Four hours later poor fit besides the pressure needs?
Most likely facial oils more than beard stubble I would think.
I think if you fit the mask to 7 or 8 pressure instead of 4 that it stands a better chance of fitting better 4 hours later.
If it is facial oils you might want to look at a mask liner.