[Equipment] What machine is a step up from VPAP Autoset 25?

[diamaunt]

And the pressure is increased.

sleepster better be careful lest he turn into a weather balloon!

[Sleepster]

Without looking at the graphs, I'd put my money on flow limitations.

Here's the last 5 minutes before the ramp shut off. I'm new to ResScan so take pity. The Flow Limitation graph axis goes from 0.0 to 0.2 even though it's not shown on the axis label (What the heck are those things labeling the Flow Limitation axis?).

[diamaunt]

instead of your flow being a nice rounded wave, it's disturbed at the top, and in worst case, flattened.

here's a resmed video: https://www.youtube.com/watch?v=3Ehb7U78P5w

[robysue]

The Flow Limitation graph axis goes from 0.0 to 0.2 even though it's not shown on the axis label (What the heck are those things labeling the Flow Limitation axis?).

Those icons are supposed to suggest the degree of flow limitation. The nice round "hump" at the bottom is (roughly) the shape of a perfect inhalation. The thing in the middle is a very typical flow rate pattern for one well known kind of flow limitation and is used to indicate a partially compromised airway. The flat line on the top is the flow rate for an apnea and is used to indicate a seriously compromised airway.

Here's the last 5 minutes before the ramp shut off. I'm new to ResScan so take pity

First question: Did the ramp go off RIGHT AT the time the pressure increase starts? It's important to realize that the Resmed S9 will NOT increase the pressure in response to events, flow limitations, or snoring that takes place during the ramp period. Indeed, as I recall, the S9 doesn't even flag OAs, Hs, or CAs that happen during the ramp period.

Here's a marked up copy of your graph:



The parts of the Flow that correspond to the Flow Limitations are circled. In the first flow limitation, there's an inhalation with a clear double peak, which is interpreted as a flow limitation by the scoring algorithm. I'm a bit surprised there's not an increase in pressure caused by this flow limitation; but you said the ramp was on, and I think that must be why there's no increase in pressure.

On the second FL, the changes in the inhalation are more subtle and hard to see at this resolution. It looks, however, as though there is a small reduction in the airflow into the lungs (the amplitude of the peaks is smaller). This reduction is NOT severe enough to be flagged as a H, but it probably is the reason the S9 decides to increase the pressure just after the ramp goes off.

[Sleepster]

First question: Did the ramp go off RIGHT AT the time the pressure increase starts?

Yes, precisely 20 minutes after the machine was started, give or take maybe 5 or 10 seconds. And that may be approximately as precise as we can get due to the machine's sampling rate. I say this because I see misalignments of that magnitude, like the "vertical" arrow you drew on the graph that's not really vertical even though it may signify an alignment.

This reduction is NOT severe enough to be flagged as a H, but it probably is the reason the S9 decides to increase the pressure just after the ramp goes off.

Good to know, and thanks for the help. Another night's data will be an interesting thing to see.

Do you know what the units are for Flow Limitation? I set the graph axis to a maximum of 0.2, but 0.2 what?

[Sleepster]

instead of your flow being a nice rounded wave, it's disturbed at the top, and in worst case, flattened.

here's a resmed video: https://www.youtube.com/watch?v=3Ehb7U78P5w

Thanks. That's a very nice animation and it goes to show that there's more to SDB than can be measured with an AHI.

[zonk]

instead of your flow being a nice rounded wave, it's disturbed at the top, and in worst case, flattened.

here's a resmed video: https://www.youtube.com/watch?v=3Ehb7U78P5w

Thanks. That's a very nice animation and it goes to show that there's more to SDB than can be measured with an AHI.

Scroll down to to the bottom of the wiki home page
http://www.apneaboard.com/wiki/index.php...=Wiki_Home

and here http://www.apneaboard.com/wiki/index.php..._%28SDB%29

[diamaunt]

instead of your flow being a nice rounded wave, it's disturbed at the top, and in worst case, flattened.

here's a resmed video: https://www.youtube.com/watch?v=3Ehb7U78P5w

Thanks. That's a very nice animation and it goes to show that there's more to SDB than can be measured with an AHI.

that's the truth!

[robysue]

Do you know what the units are for Flow Limitation? I set the graph axis to a maximum of 0.2, but 0.2 what?

Nope. I don't know the units for Flow Limitation. As I recall, the units for FL don't appear anywhere in the ResScan documentation.

In SH the FL numbers always are between 0.0 and 1.0. And the tool-tip thingy reports the meaning of the scale as:

• Flow limitation
  Graph showing severity of flow limitations
  (Severity (0-1))

So I've always suspected the numbers represent some kind of a normalized "statistical score" for the shape of the inspiratory part of the flow rate graph where

• 0.0 = no distortion = fully open airway, and
  1.0 = severe flattening = fully collapse airway

---

First question: Did the ramp go off RIGHT AT the time the pressure increase starts?

Yes, precisely 20 minutes after the machine was started, give or take maybe 5 or 10 seconds. And that may be approximately as precise as we can get due to the machine's sampling rate. I say this because I see misalignments of that magnitude, like the "vertical" arrow you drew on the graph that's not really vertical even though it may signify an alignment.

Yep. I remember those problems in my own Resmed data. Back in 2010 there was also a Resmed/ResScan bug that also involved clock drift between the time stamps on the Flow curve vs. some of the other curves. The more you turned the machine off and on, the worse the clock drift problem got.

[archangle]

A number of people have reported that the S8 detects more apneas than the S9. Consensus seems to be that the algorithms are less stringent. Which one is more accurate is up for debate.