Reported mask pressure 'capped' to 15.88 cmH20 by OSCAR?

[chrisj]

Of course it measures mask pressure - the measurement is taken at the machine itself... the air pressure within the hose, and within the machine body where the sensor is, is equal to that within the mask...

This is incorrect, the pressure at the mask is NOT equal to the pressure in the mask, unless no air is flowing through the patient circuit.
Resistances to airflow cause lowered pressure (to avoid cough drop comments) at each stage of the circuit between the blower motor itself and your face. whether you have a humidifier attached, what diameter and length of tube, filters, and mask type (ever noticed the "System One Resistance"?) all affect the actual pressure, *AT THE MASK*. The machines have to compensate for these flow resistances by increasing the pressure at the machine.

it's how the machine compensates for mask leaks by increasing the pressure when it senses a drop.

Totally incorrect, the machine increases the FLOW to compensate for leaks, in order to *maintain* pressure.

Mask pressure is the only figure that matters, as that's what a physician's prescribed setting pertains to.

Again, incorrect. many Philips machines never even report mask pressure, just target pressure.

Most doctors don't have any idea what 'mask pressure' is.

To address a couple of points if I may

"the pressure at the mask is NOT equal to the pressure in the mask"

It's as near as makes no difference. Obviously there are *very* slight pressure variances, and obviously I'm aware some are caused depending on what components are present in the circuit - but these are accounted for as the machine knows which components are connected and the mask type (resistance) is user specified. The point is, we're talking about a 14 cmH20 difference between actual and that reported in OSCAR here.

"Totally incorrect, the machine increases the FLOW to compensate for leaks, in order to *maintain* pressure."

OK, if we were being pedantic about it you could state it that way, however my assertion was indeed correct. By increasing flow, it is of course increasing pressure to compensate for the drop in pressure caused by the leak. A PAP unit is just a 'fan in a box'.. not exactly rocket science.

"Again, incorrect. many Philips machines never even report mask pressure, just target pressure."

Mask pressure is of course the only figure that truly matters - whether it's close to the target pressure or not. It doesn't matter what's 'reported', the actual delivered pressure is based on measurement within a closed circuit. Anyway, as we're talking about a 14cm difference that's a different story...

[chrisj]

In a vaccum, generally speaking pressure is pressure no matter which location it is sampled at.

This isn't a vacuum, and your theory is faulty because that statement is only valid in a static system. A cpap patient circuit is a very dynamic system.

I've measured pressure differentials of over 10cmH2O between the humidifier outlet and the mask on my VPAP AUTO when taking deep breaths.

For my measurement purposes it is indeed as good as a static system, as the manometer pressure measurements discussed were being taken in a static cicruit (no significant leaks, no breathing). Of course there will be pressure variances in a dynamic system, as nothing has instant propagation.

I'm not interested in that though as it doesn't really address the original problem which was the machine hits 30 but OSCAR always reports max 15.88.

[chrisj]

Re: Sanitizing a used machine?
Post by SleepGeek » Mon Apr 05, 2021 8:27 pm

palerider wrote: ↑Mon Apr 05, 2021 8:07 pm
When you post *bad* advice, it will be corrected,
I guess YOU are *KING OF THIS FORUM*?
YOU have run many people away from this *Helping Forum*.
AND Still at it, I see.

Get busy ....
viewtopic/p1381301/Reported-mask-pressu ... l#p1381301

LOL, and the very next day he did And yes, I've abandoned this post now as a result - it's clear there are some highly strung people here and just came for help and advice.

Thanks to those of you who attempted to offer helpful answers anyway

22519427_1713477958702702_681984384952417100_n.jpg (77.28 KiB) Viewed 855 times

[Pugsy]

the original problem which was the machine hits 30 but OSCAR always reports max 15.88.

Well....maybe the problem is with OSCAR and all this bullshit fighting and arguing is just a herd of studs tryout for stud leader.

Flow rate is NOT the same thing as pressure and increasing flow rate does NOT mean increasing the pressure and the reason we nit pick on certain details is because we prefer to use correct terms. Believe it or not or use "pressure" and "flow rate" interchangeably if you wish but that doesn't make it correct.

I find it totally amazing when people ask for ideas and then go shoot those ideas down and be rude about it.

Now no one says you have to like the ideas, believe the ideas or implement the ideas....but the polite thing is either thank someone for their time and then move on and maybe just totally ignored their ideas but to keep arguing about advice is just plain rude. Good way to get a person on a list where no one would piss on you if you on fire on their front porch and really needed help.

I think that OSCAR is off with the max masked pressure because of a calculation issue because it is trying to report something the machine most likely doesn't report based on data points that it has available within the software code. OSCAR is far from perfect...it is NOT the HOLY BIBLE. I don't know if the Respironics machines even have an official max mask pressure data recorded....get ENCORE PRO and see what it says...if it says anything. That is the only way to know.

You totally ignored my previous advice about Encore Pro. It was good sound advice and the only thing that would give us an idea if OSCAR was just maybe wrong....and it very well could be as simple as OSCAR being wrong.

But if you don't want to know and all you want to do is nit pick and fight and not do what is the ONLY possible solution to figuring out if OSCAR has a bug in it...that's fine by me....but quit stinking up the forum with all this in fighting and shit throwing and temper tantrums.

The little cartoon....cheap shot and while you might think it funny....I don't. Just tells me that you want to be a stud herd leader and not really have your question answered. Make fun of people and not really dig for answers.

Have a nice day.

[BlueDragon]

Just a quick one - my Dreamstation autoSV is set with an EPAP min of 9, ps 3.0 -> 21, yet no matter what happens OSCAR is showing 15.88 as being as high as the 'mask pressure' ever goes - I know it goes higher than that though as the machine itself says it does. If I stop breathing for a lengthy period eventually it'll max out at 30, but OSCAR only ever shows 15.88 max.

Do you have y-axis range set for the Mask Pressure plot, or is it set to AutoFit? The way the mask pressure graph is topped is similar to what you see when a the plot is being restricted by a y-axis limit.

If you would like me to take a look at how OSCAR is seeing your data, make a zip of your SD card (use Help/Troubleshooting/Create ZIP of data card) and upload it to my Dropbox folder at https://www.dropbox.com/request/REp6AH7LCGyeOcXfOokH.

[palerider]

To address a couple of points if I may

"the pressure at the [machine] is NOT equal to the pressure in the mask"

It's as near as makes no difference. Obviously there are *very* slight pressure variances, and obviously I'm aware some are caused depending on what components are present in the circuit - but these are accounted for as the machine knows which components are connected and the mask type (resistance) is user specified. The point is, we're talking about a 14 cmH20 difference between actual and that reported in OSCAR here.

Actually, there can be sizeable differences between the machine and the mask, as you breathe, the air has to flow past the various resistances, and that all causes pressure drops. I've measured 10cm difference between the machine and mask using a differential manometer.

"Totally incorrect, the machine increases the FLOW to compensate for leaks, in order to *maintain* pressure."

OK, if we were being pedantic about it you could state it that way, however my assertion was indeed correct. By increasing flow, it is of course increasing pressure to compensate for the drop in pressure caused by the leak. A PAP unit is just a 'fan in a box'.. not exactly rocket science.

No, your assertion was incorrect.

You don't understand the system, or the incredible amount of math and computation that goes into making that "fan in a box" spin at just the *exact* right speed to correctly generate a desired pressure at the end of a circuit, taking into the resistances that are added by all the things that are dropped into that circuit between the 'fan in a box' and your face.

Increasing flow to compensate for increased leak does *NOT* increase pressure. you can put your manometer on the end of the circuit and vary the amount of leak, the pressure will stay the same, as the blower is ramped up and down to compensate for the varying leak by increasing and decreasing the air flow.

People have this *WRONG*, many people think that the machines increase pressure because of leaks, they *DO NOT* increase pressure, in fact, modern auto machines will in fact decrease the commanded pressure in the event of severe leaks, in an attempt to get the mask to seal again.

You can say it's being 'pedantic' all you want, but what you said is simply wrong.

"Again, incorrect. many Philips machines never even report mask pressure, just target pressure."

Mask pressure is of course the only figure that truly matters - whether it's close to the target pressure or not. It doesn't matter what's 'reported', the actual delivered pressure is based on measurement within a closed circuit. Anyway, as we're talking about a 14cm difference that's a different story...

It may be all that 'matters' but it still doesn't exist in most Philips machines, just another reason I prefer Resmed.

[palerider]

In a vaccum, generally speaking pressure is pressure no matter which location it is sampled at.

This isn't a vacuum, and your theory is faulty because that statement is only valid in a static system. A cpap patient circuit is a very dynamic system.

I've measured pressure differentials of over 10cmH2O between the humidifier outlet and the mask on my VPAP AUTO when taking deep breaths.

For my measurement purposes it is indeed as good as a static system, as the manometer pressure measurements discussed were being taken in a static cicruit (no significant leaks, no breathing). Of course there will be pressure variances in a dynamic system, as nothing has instant propagation.

I'm not interested in that though as it doesn't really address the original problem which was the machine hits 30 but OSCAR always reports max 15.88.

And how long are you running the machine at 30? is the machine reporting the data properly? is Oscar throwing out your spurious numbers because it doesn't report 100% of the data? just like all the software will throw out outliers.

The only way that you're going to get valid data is to put a high rate pressure transducer on the hose at your mask, sleep all night, and compare the data against what Encore and Oscar report.

[palerider]

but OSCAR only ever shows 15.88 max.

I am confused about one thing, it says IPAP Max 16.38 on the image you posted.

[Hang Fire]

Just a quick one - my Dreamstation autoSV is set with an EPAP min of 9, ps 3.0 -> 21, yet no matter what happens OSCAR is showing 15.88 as being as high as the 'mask pressure' ever goes - I know it goes higher than that though as the machine itself says it does. If I stop breathing for a lengthy period eventually it'll max out at 30, but OSCAR only ever shows 15.88 max.

Do you have y-axis range set for the Mask Pressure plot, or is it set to AutoFit? The way the mask pressure graph is topped is similar to what you see when a the plot is being restricted by a y-axis limit.

Wouldn't it be hilarious if this entire kerfuffle was because he had the y-axis range set incorrectly?

[palerider]

I think it's more likely that he's performing experiments, and the machine isn't having it. If the machine doesn't detect breathing, it often won't report *anything*. But we didn't see data from the 'experiments', just from a sample night.

[BlueDragon]

Just a quick one - my Dreamstation autoSV is set with an EPAP min of 9, ps 3.0 -> 21, yet no matter what happens OSCAR is showing 15.88 as being as high as the 'mask pressure' ever goes - I know it goes higher than that though as the machine itself says it does. If I stop breathing for a lengthy period eventually it'll max out at 30, but OSCAR only ever shows 15.88 max.

Is this a bug? or maybe I'm misinterpreting the information. Screenshot attached.

Found the answer: it's a bug in the CPAP machine! From the list of machines supported by OSCAR:

Dreamstation BiPAP & ASV
Note: It turns out that the 1130X series has the same bug that the 900X series has: it clamps the mask pressure to 127 rather than 255. As a result, the maximum mask pressure the machine will report in its data is 15.875 rather than 31.875. If you look at the actual delivered EPAP and IPAP, however, you see the correct pressures being delivered.

Almost certainly somebody accidentally used a signed integer instead of unsigned on these machines: that's appropriate for flow waveform, which can vary from -128 to +127, but it's not appropriate for mask pressure, which can only be positive. Other PRS1 machines (including the predecessor to the 900X) got this right.

Again, this simply a data reporting issue, and it's in the data reported by the machine, so official reports look just the same: mask pressure never exceeds ~16 cmH2O despite the waveform report graph having a scale of up to 30.

So there is nothing anyone can do about it. Just ignore it.

If your machine is not in the 900X or 1130X series, let me know which machine you have.

[ChicagoGranny]

Found the answer: it's a bug in the CPAP machine! From the list of machines supported by OSCAR:

Thank you, BD. Pugsy nailed it on the first page of this thread.

Maybe a bug in OSCAR software calculations for the DreamStation ASV

[SAG]

Found the answer: it's a bug in the CPAP machine! From the list of machines supported by OSCAR:

Thank you, BD. Pugsy nailed it on the first page of this thread.

Maybe a bug in OSCAR software calculations for the DreamStation ASV

I think what BlueDRagon is saying is the problem is inside the Device NOT OSCAR, which makes sense.

Good job BlueDragon.

Unfortunately, the OP will never know. afaik he has not posted since.

LOL, and the very next day he did And yes, I've abandoned this post now as a result - it's clear there are some highly strung people here and just came for help and advice.

Thanks to those of you who attempted to offer helpful answers anyway

How can you undo the damage done?

[BlueDragon]

Right, the problem is in the machine, not in OSCAR.

I have PM'ed the original poster.

[ChicagoGranny]

I think what BlueDRagon is saying is the problem is inside the Device NOT OSCAR, which makes sense.

Right, the problem is in the machine, not in OSCAR.

Oh yeah guys, thanks for the correction.