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

[chrisj]

I don't know of any way the cpap will know IF there is an antibacterial filter installed in order to compensate the reading.

ResMeds do
see page 16 of the manual
https://www.respshop.com/manuals/ResMed ... %20her.pdf
also mentioned on page 13 and what it can do to results and what they recommend to use in terms of resistance.
This is of course the AirSense 10 manual...but the S9 models had the same yes/no choice in their menu.
I assume that since there is a choice then they must compensate in some fashion but I have never seen it documented.

Of course maybe a moot point when talking about Respironics machines (which the OP here has) as I don't think there is a choice but my memory may have failed me.

To the OP here....about all you can do is use Encore Pro and see what it says for mask pressure. Maybe a bug in OSCAR software calculations for the DreamStation ASV for all I know. Encore Pro is available by request at the apneaboard forum but it is Windows only software and a real bitch to install and use.

Cheers Pugsy, I'll look into that.

[chrisj]

chrisj wrote: ↑Mon Apr 05, 2021 1:37 pm
They are the same thing as it's a closed loop system.

I don't think so. The two numbers are tracked separately by the machine and the software. Why do that if they are the same?

The machine doesn't measure mask pressure. It can't - there are no pressure sensors on masks.

A factored number is programmed into the machine or OSCAR. Meaningless. I've always ignored it.

*mask pressure* with a resmed machine (perhaps not applicable here) is a direct readout of *measured pressure* at the machine compensated for pressure drops caused by the humidifier, hose, antibacterial filters and the mask, whereas "pressure" is the *desired pressure*.

I'm not sure how Philips does "mask pressure" since the only machine that reports it (I think) is their AutoSV (and maybe AVAPS).

Yep, same on the Philips. The pressure reported at the machine is indeed the mask pressure, as indicated above I've verified this with a digital manometer and it's accurate to 1 d.p.

Pressure taken at mask connection point.

20210214_121622.jpg (219.65 KiB) Viewed 711 times

[ChicagoGranny]

Of course it measures mask pressure - the measurement is taken at the machine itself

WTH?? If the measurement is taken at the machine, it's the pressure at the machine. To measure pressure at the mask, a pressure sensor would be needed at the mask.

Unless there is some sort of kink in the hose, the difference in pressures is inconsequential.

[chrisj]

Of course it measures mask pressure - the measurement is taken at the machine itself

WTH?? If the measurement is taken at the machine, it's the pressure at the machine. To measure pressure at the mask, a pressure sensor would be needed at the mask.

Unless there is some sort of kink in the hose, the difference in pressures is inconsequential.

Nope... the pressure is taken at the machine, which is also internal to the same circuit. If there was a kink in the hose causing a total blockage, anything beyond the kink is no longer part of that circuit. As you can see from my picture above, the actual pressure measured at the mask is the exact pressure reported by the machine.

Older machines like the S7 used to have a sepeate pressure sensor line which connected to the mask, but newer machines have the pressure sensor integrated within the flow circuit itself.

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

[ChicagoGranny]

As you can see from my picture above, the actual pressure measured at the mask is the exact pressure reported by the machine.

In your photo, you are measuring the pressure at the machine. Your photo title, "Pressure taken at mask connection point", is not correct. You are taking the pressure at the hose connection point.

[palerider]

IOW - your AHI may not read correctly with an *Inline Filter* - it can read lower.

NOT CORRECT! This shows a fundamental misunderstanding of how machines determine AHI.
What *WILL* result from an uncompensated AB filter being in the patient circuit will be a LOWER than desired pressure at the mask which very well result in a HIGHER AHI than you would have had if the pressures had been proper.
Resmed goes to great lengths to compensate for the pressure restrictions in various parts of the patient circuit to get an accurate pressure at the mask.

I don't know

A lot of things. and it would be good if you'd stop talking like you did.

many Resmed's have a setting for an AB filter.

[palerider]

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.

[palerider]

It's ASV, so if no breaths are taken it will progessively attempt to deliver them at increasing pressure levels until it tops out - hence by simply blocking the hose at the mask the machine will revert to it's backup rate, and progressively deliver stronger and stronger breaths at 12 BPM (iirc) until it hits 30cmH2O - the max output pressure of the DreamStation BiPAP autoSV.

Don't be surprised it it doesn't do what you think it will, you're doing "tests" outside of the machines operational parameters.

[palerider]

Yep, same on the Philips. The pressure reported at the machine is indeed the mask pressure, as indicated above I've verified this with a digital manometer and it's accurate to 1 d.p.

20210214_121622.jpg

I have connected differential manometers at the machine and at the mask, the pressures are indeed different. You're measuring at the wrong place

[palerider]

Of course it measures mask pressure - the measurement is taken at the machine itself

WTH?? If the measurement is taken at the machine, it's the pressure at the machine. To measure pressure at the mask, a pressure sensor would be needed at the mask.

Unless there is some sort of kink in the hose, the difference in pressures is inconsequential.

The pressure at the machine is almost *never* equal to pressure at the machine.

"Mask pressure" is a *calculated* value, as I said above, claps now have the computing power to calculate what the pressure is at the mask by measuring the outlet pressure at the mask and factoring in all of the air flow resistances from that point to the patients face.

If you set it wrong, you get the wrong pressure, like saying you have a small diameter hose when it is a normal diameter one. The time I did that, I thought the machine was faulty.

[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.

[ChicagoGranny]

"Mask pressure" is a *calculated* value, as I said above,

Yeah, that's what I meant by "factor."

"Calculated" is a better word.

[SleepGeek]

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

Look at you arguing with yourself. That is exactly why any obstructions in the flow circuit will *dampen* the signal and calculation of events. YOU are a perfect example - YOU think your treatment is effective and your behavior says otherwise.

Resmed goes to great lengths to compensate for the pressure restrictions in various parts of the patient circuit to get an accurate pressure at the mask.

Fortunately the OP is *NOT* using a resmed so all of your BS about what Resmed does is like Pugsy says

Of course maybe a moot point when talking about Respironics machines (which the OP here has) as I don't think there is a choice but my memory may have failed me.

So MrKingRider (MKR) you apparently didn't get any sleep lastnite (again) and have derailed yet another thread here on cpaptalk. Six (6) consecutive posts of absolute BS from *THE KING*.

Who wants to start a GoFundMe collection to get MrKingRider his much needed medicine so he will stop his babbling and derailing? he certainly doesn't know how to help anyone - including himself.

So, do you think that the OP is incapable of understanding the discussion and you have to interpret it for him?

Oh I think he understands, he's not been able to make you understand.

What, exactly, do you think you're adding to this thread?

This what YOU need to ask yourself each time YOU sit down at the keyboard.

If seems that it's just so you can stand on your soapbox and tell everybody that I'm stupid, something that I'm pretty sure they could figure out on their own, unless you think they're all stupid too.

I never had a soapbox. I thought I'd never reach you - Finally something we ALL agree on.
What a workout. /Peace

[Pugsy]

ENOUGH with the PERSONAL attack shit. ENOUGH.
Further such crap will be removed.

Get back on topic or posts will be removed.

PERSONAL ATTACKS AND NAME CALLING ARE NOT being on topic.

THERE WILL BE ZERO FURTHER NAME CALLING SLURS......ZERO...or the entire posts will be removed.

OFF TOPIC POSTS....bickering, name calling, fighting, shit chit chat....will be removed. That's a promise.

[chrisj]

As you can see from my picture above, the actual pressure measured at the mask is the exact pressure reported by the machine.

In your photo, you are measuring the pressure at the machine. Your photo title, "Pressure taken at mask connection point", is not correct. You are taking the pressure at the hose connection point.

To clarify, no I'm not - the manometer is connected to the mask connnection point at the end of the 6ft hose, not the hose connection point at the machine.