What's that red curve in the Pressure graph? (Geek/nerd question)

[robysue1]

Folks,

I've been using SleepyHead right from the very beginning when JediMark was still in the process of writing it. (My old PR System One Auto BiPAP data helped JediMark tease out several issues with the code very early on way back in the early part of 2011.) And I know that JediMark wound up in a feud with the folks over on the other board and that SleepyHead eventually became an unsupported orphan program with no additional updates. Which wasn't an issue since I am still using a PR DreamStation Auto BiPAP that works with SleepyHead. So when I wanted to look at the data, I just kept using SleepyHead because it showed me pretty much everything I needed to see when I needed to work on sleep quality issues.

But now that I'm back on cpaptalk, I've discovered OSCAR and been pointed in the direction of SleepHQ. So I've downloaded OSCAR and joined SleepHQ as well.

Now I've got a question about a new piece of data that shows up in OSCAR, but not SleepyHead. In the following screenshot you'll see three curves in the Pressure graphs section:


Now I know the top (purple) curve is the IPAP setting as it varies through the night. And the bottom (green) curve, which sits at 4cm for most of this night, is the EPAP setting as it varies through the night. (On this particular night, the EPAP was raised to 5cm only after/during the initial set of events right at the start of the night. And those events are most likely SWJ events that occurred as I was still trying to get to sleep, so I'm not worried about them at all: They're typical for my data.)

But what the heck is the red middle curve in the Pressure graphs section representing? Average pressure? Or something else? Because it sure doesn't look like it could possibly be the actual pressure at the mask since it does not have the necessary breath-by-breath increases and decreases that would correspond to the machine switching between IPAP and EPAP.

Anybody know how the numbers for that red graph are computed?

[lynninnj]

Folks,

I've been using SleepyHead right from the very beginning when JediMark was still in the process of writing it. (My old PR System One Auto BiPAP data helped JediMark tease out several issues with the code very early on way back in the early part of 2011.) And I know that JediMark wound up in a feud with the folks over on the other board and that SleepyHead eventually became an unsupported orphan program with no additional updates. Which wasn't an issue since I am still using a PR DreamStation Auto BiPAP that works with SleepyHead. So when I wanted to look at the data, I just kept using SleepyHead because it showed me pretty much everything I needed to see when I needed to work on sleep quality issues.

But now that I'm back on cpaptalk, I've discovered OSCAR and been pointed in the direction of SleepHQ. So I've downloaded OSCAR and joined SleepHQ as well.

Now I've got a question about a new piece of data that shows up in OSCAR, but not SleepyHead. In the following screenshot you'll see three curves in the Pressure graphs section:


Now I know the top (purple) curve is the IPAP setting as it varies through the night. And the bottom (green) curve, which sits at 4cm for most of this night, is the EPAP setting as it varies through the night. (On this particular night, the EPAP was raised to 5cm only after/during the initial set of events right at the start of the night. And those events are most likely SWJ events that occurred as I was still trying to get to sleep, so I'm not worried about them at all: They're typical for my data.)

But what the heck is the red middle curve in the Pressure graphs section representing? Average pressure? Or something else? Because it sure doesn't look like it could possibly be the actual pressure at the mask since it does not have the necessary breath-by-breath increases and decreases that would correspond to the machine switching between IPAP and EPAP.

Anybody know how the numbers for that red graph are computed?

EPR pressure maybe?
Usually I have my EPR set on three and **there’s a line that runs exactly parallel to the pressure line separated by three. I don’t know if that’s what you’re looking at or not, sorry.

Edit: I **think so maybe?

[Rubicon]

Can you put up a 5-minute window and add Mask Pressure? I believe Pressure (red waveform) is updated only once per second so it's going to be very dampened, (whereas Mask Pressure is updated 25 times per second).

So the real question would be what's the plum-colored line (IPAP Set), but I think that simply reflecting what the PS is doing.

At any rate, Mask Pressure will give a more accurate picture of what's happening.

[Rubicon]

I believe Pressure (red waveform) is updated only once per second so it's going to be very dampened...

At least in any kind of bilevel therapy anyway.

[robysue1]

Can you put up a 5-minute window and add Mask Pressure? I believe Pressure (red waveform) is updated only once per second so it's going to be very dampened, (whereas Mask Pressure is updated 25 times per second).

Your wish is my command. Any suggestions on where you want that 5 minute window? There's not much going on with EPAP on this night.

So the real question would be what's the plum-colored line (IPAP Set), but I think that simply reflecting what the PS is doing.

At any rate, Mask Pressure will give a more accurate picture of what's happening.

Do PR Dreamstation Auto BiPAPs even record Mask Pressure?

[Pugsy]

Do PR Dreamstation Auto BiPAPs even record Mask Pressure?

I don't think so. I think mask pressure is limited to ResMed machines.

[robysue1]

Can you put up a 5-minute window and add Mask Pressure? I believe Pressure (red waveform) is updated only once per second so it's going to be very dampened, (whereas Mask Pressure is updated 25 times per second).

Note: In order to make it easier to see the green EPAP line, I've changed the y-range on the Pressure graph to 3-9 instead of 4-9.

Here's a 5 minute snippet from the SWJ near the beginning of the night. You may have to click on the image an open it up to see those Pressure lines correctly.


Here's a 5 minute snippet from much later when the PR machine is going through one of its "searches" by adjusting the IPAP. You may have to click on the image an open it up to see those Pressure lines correctly.

At any rate, Mask Pressure will give a more accurate picture of what's happening.

Yes, but .... PR machines (at least mine) don't record Mask Pressure. Or at least there's no "Mask Pressure" curve that I can select in OSCAR.

[robysue1]

EPR pressure maybe?
Usually I have my EPR set on three and **there’s a line that runs exactly parallel to the pressure line separated by three. I don’t know if that’s what you’re looking at or not, sorry.

Edit: I **think so maybe?

Nope. The red curve not "EPR pressure".

I am using a PR DreamStation Auto BiPAP. EPR only applies to Resmed CPAP and APAP machines, and EPR is in some sense equivalent to a PS setting on a bi-level machine like mine. In other words, on a Resmed CPAP/APAP, the EPR setting is the difference in the pressure on inhalation and the pressure on exhalation. Since you are using a Resmed APAP your top pressure line is the pressure the machine is using when you are inhaling and the lower line is the pressure the machin is using when you are exhaling, and with and you have EPR = 3, those two lines should always be 3 units apart.

On my Auto BiPAP, the PS setting is the difference between my IPAP (inhalation) pressure and my EPAP (exhalation) pressure. Because of the PR Auto BiPAP algorithm and my machine's settings, my PS is allowed to vary between 3 and 5 cm. In other words, my top purple (IPAP) curve is always somewhere between 3 and 5 cm higher than the bottom (EPAP) green curve.

On the night in question, my EPAP stayed at 4cm for almost the entire night. The EPAP did increase up to 5 cm between 2:15 and 2:40---that's the green bump that is visible near the left of the graph. Because the y-axis starts at 4cm, my EPAP curve is on the x-axis except for that one visible "bump". On this same night my IPAP varied from 7 cm to 9cm. Most of the increases in IPAP pressure are due to the PR "search" algorithm where the machine is testing to see if increasing the IPAP pressure makes my breathing more stable, less stable, or about the same. The sawtooths in the IPAP graph correspond to the "search" algorithm doing its thing and concluding that there no good reason to increase the IPAP pressure. The pressure increases in IPAP between 5:20 and 6:20 appear to be driven by the machine's response to a series of flow limitations that are scored during that time. My EPAP does not increase during those times because the PS is still less than 5, so the machine is allowed to increase only my IPAP instead of both pressures.

The red curve lies between the IPAP pressure and the EPAP pressure and it is clearly not equal to IPAP - EPAP. So whatever that red curve is measuring, it's not the PS setting (i.e. EPR) that my machine is using at that point in time.

[Pugsy]

Is BiFlex turned on?
If on...at what setting?

[robysue1]

Is BiFlex turned on?
If on...at what setting?

Nope. I can't stand BiFlex---it feels like it starts increasing the pressure before I'm done exhaling.

Way back when in January 2011 I quickly discovered that I preferred to turn BiFlex OFF and I use a Rise Time setting of "3", which provides the slowest transition from EPAP to IPAP as I recall.

[Rubicon]

Well that's a stumper!

It begins it's rise prior to machine changes, seen clearly at the beginning of the night:

[Rubicon]

I think it might be

Average IPAP Over a 2-Minute Window

https://www.documents.philips.com/asset ... 013046.pdf

[lynninnj]

The red curve lies between the IPAP pressure and the EPAP pressure and it is clearly not equal to IPAP - EPAP. So whatever that red curve is measuring, it's not the PS setting (i.e. EPR) that my machine is using at that point in time.

Thanks for the informative reply. I realized after I sent my post that you aren’t using apap.

My apologies.

I hope you can figure it out.

[palerider]

The red curve lies between the IPAP pressure and the EPAP pressure and it is clearly not equal to IPAP - EPAP. So whatever that red curve is measuring, it's not the PS setting (i.e. EPR) that my machine is using at that point in time.

Thanks for the informative reply. I realized after I sent my post that you aren’t using apap.

My apologies.

I hope you can figure it out.

And, philips machines don't do EPR, that's a Resmed thing.

[lynninnj]

The red curve lies between the IPAP pressure and the EPAP pressure and it is clearly not equal to IPAP - EPAP. So whatever that red curve is measuring, it's not the PS setting (i.e. EPR) that my machine is using at that point in time.

Thanks for the informative reply. I realized after I sent my post that you aren’t using apap.

My apologies.

I hope you can figure it out.

And, philips machines don't do EPR, that's a Resmed thing.

Thank you.

I wish there was a delete option on the posts. I realized I made the error right after posting.