EPAPmin and minimum EPAP

[tmoody]

As I look over my SH data, I note that not only is my minimum EPAP on a given night below EPAPmin=8.5, but so are both the median and the average. Last night's average EPAP, according to SH, was 8.12; the median was 8.4.

Out of curiosity, last night I turned off flex and tried Rise Time=1. I didn't notice any difference in comfort. A couple of brief CAs snuck through, but that was probably a coincidence. And as I just noted, my average EPAP pressure was still below EPAPmin. I'll leave it on Rise Time=1 for a few days and see if I notice anything.

I'm not trying to say that this is a problem in need of a solution. I'm just trying to understand what's going on.

[robysue]

Out of curiosity, last night I turned off flex and tried Rise Time=1. I didn't notice any difference in comfort. A couple of brief CAs snuck through, but that was probably a coincidence. And as I just noted, my average EPAP pressure was still below EPAPmin. I'll leave it on Rise Time=1 for a few days and see if I notice anything.

That's just plain weird and my theory certainly can't explain that kind of weird behavior.

But then my min EPAP = 4cm, and the machine can't go lower than that, so maybe that's why this kind of thing never shows up in my data.

Can you post some data perhaps?

[tmoody]

Can you post some data perhaps?

Okay, here's last night. I'm just looking at the SH summary data in the "statistics" box on the left. As you can see, EPAPmin is set to 8.5, but the min and med values for EPAP for the night are 8.4. If I hover over the EPAP label, it says the avg. was 8.47, which rounds up to the correct value. I know I wrote in the previous message it was 8.12; that must have been a mistake. Maybe the 8.4 is a SH rounding error?

[justMongo]

I agree. In fact it's a truncation. Instead of rounding to the nearest tenth, they just drop the the digit in the hundredths place.
May not be intrinsic to Sleephhead; could be the data came from a machine summary; and PR drops the digit.

[tmoody]

I agree. In fact it's a truncation. Instead of rounding to the nearest tenth, they just drop the the digit in the hundredths place.
May not be intrinsic to Sleephhead; could be the data came from a machine summary; and PR drops the digit.

In earlier nights, the difference is more pronounced, but during those nights I had flex going. So I'll keep it on Rise Time=1 and see if the minimum EPAP pressure SH records stays closer to actual EPAPmin.

I do wonder why my maximum IPAP in a given night seldom goes much higher than about 12, even though the EPAPmax value is 23. Last night's maximum was 9.5, but I still had 26 hypos during the night. From my reading on this forum and in the manual (I still don't pretend to have a clear understanding), the whole point of having a variable EPAP with a fairly high maximum is to have enough "ceiling" to increase EPAP pressure to get rid of OAs and HAs.

I'm not complaining. 26 HAs is still about half of what I was getting on APAP. I'm just curious about why the ASV doesn't bump EPAP pressure a bit higher on those HAs. I guess this question is a bit OT for this thread.

Edit: Because the latter question about maximum EPAP is off-topic, I'm directing back to this thread: http://www.apneaboard.com/forums/Thread-...#pid158978, so this thread can stay on the EPAPmin issue, if there's anything left to say about it.

[PaytonA]

I am not an ASV guru by any stretch but it sounds to me like you might benefit from a little higher Minimum EPAP. Just my thought.

Best Regards,

PaytonA

[robysue]

I do wonder why my maximum IPAP in a given night seldom goes much higher than about 12, even though the EPAPmax value is 23.

I am not an ASV expert by any means. But it looks like there is some kind of algorithm programed into the machine that dynamically determines a reasonable "local max IPAP" value that is based on both the current EPAP value and parameters that are determined by the shape of the inhalations in the flow rate graph. It looks as though the machine wants to use as little extra IPAP pressure as needed when it starts triggering inhalations. If a little extra IPAP doesn't work to stabilize the breathing OR if the breathing gets ragged in some specific way, it looks like the "max IPAP" algorithm kicks in and increases the local max IPAP so that the machine can add more extra IPAP when it needs to trigger inhalations. Clearly, the local max IPAP only reaches the max IPAP setting when the machine is finding the need to trigger lots and lots of inhalations---i.e. the machine's noninvasive ventilator properties are being used at their max capability to trigger the inhalations.

Last night's maximum [EPAP] was 9.5, but I still had 26 hypos during the night. From my reading on this forum and in the manual (I still don't pretend to have a clear understanding), the whole point of having a variable EPAP with a fairly high maximum is to have enough "ceiling" to increase EPAP pressure to get rid of OAs and HAs.

You are using a PR System One ASV. I am not sure if the "Auto EPAP" algorithm used by your machine is similar to the "Auto BiPAP" algorithm used by the simpler PR System One BiPAP Auto machine. But it looks like it might be.

In the PR Auto BiPAP's "Auto" algorithm, EPAP is increased for clusters of OAs, clusters of OAs mixed with Hs, and snoring. Clusters of Hs result in an increased IPAP, not an increased EPAP.

In your data, there's a distinct cluster of just Hs right before 1:30. It's clear that the EPAP did not increase in response to those Hs. It's less clear, but it appears that the actual IPAP was increased during the cluster and then was lowered after the cluster of Hs appears to clear up. It would be useful to zoom in on the time frame of 1:15 to 1:45 to see exactly what is happening to the IPAP during and right after that cluster of Hs.

I'm not complaining. 26 HAs is still about half of what I was getting on APAP. I'm just curious about why the ASV doesn't bump EPAP pressure a bit higher on those HAs. I guess this question is a bit OT for this thread.

It looks like the PR ASV "auto EPAP" algorithm is similar to the PR BiPAP Auto's "auto" algorithm. See my comments above.

Edit: Because the latter question about maximum EPAP is off-topic, I'm directing back to this thread: http://www.apneaboard.com/forums/Thread-...#pid158978, so this thread can stay on the EPAPmin issue, if there's anything left to say about it.

I'll post there as well.