S 9 Detailed Graph of Apneas, Flow, Flow Limitations

Thanks to help from friends here, I now have Flow showing on my report.

I'm requesting input on interpreting these graphs, specifically on what happens during a Central apnea and an Obstructive apnea.

Here's the Detailed Graph for the whole night, then the graphs after zooming in on the 5 minutes of the apenas








My question is: The graph shows a decrease in flow, just before each apnea, which makes sense to me. The Minute Ventilation seems to stay within my normal range. But why doesn't the Flow Limitation dip down?

Is it to do with what the trigger for the apneas? I find this stuff fascinating, and would like to better understand it.

Thanks for any input.

bump

I think there is some hesitation to answer the questions because they are such good ones. I will take a stab at them, but I am sure I will get some of it wrong. Hopefully someone more knowledgeable will correct what I get wrong.

The machine responds to snores and to certain changes in the flatness of the flow that indicates obstruction. For some of us, an obstructive apnea can hit out of nowhere, though. If it wasn't preceded by the kind of snore or the kind of changes in breathing that trigger an increase in pressure, that obstructive apnea will sneak through.

If you had had several breaths where the top of the flow curve had been chopped off, the machine would have said to itself "her breathing is changing in a way that indicates her airway is closing, let's raise pressure to prevent an obstructive apnea!" But not every obstructive event has those precursors, especially for some of us.

Hope that helps and that I am not too wrong on that.

jeff

Thanks Jeff, that does make sense.

Hi Katie...

I also have been giving this issue and some others some thoughts... I am not quite ready to pose my other questions just yet. But, I will give this a try.

According to the definitions provided by ResMed in their Data Management Guide: Flow should be available (graph) as long as we are breathing properly w/o assistance. Flow Limitation should not occur normally and should be flatline. But, when Flow Limitation occurs, it show as deviation from flat and decreased Flow should be the result. If the Limitation is sufficient and for over 10 seconds, then an Apnea occurs.

Enter the Auto Flow Generator: When Flow Limitation increases, then the Generator pressure is increased to deal with the Limitation until Flow is restored as it was for your first event in "marked as 10 seconds" presumably the pressure was still at a higher level for the second event and dealt with the Limitation beforehand but was insufficient to deal with the "instantaneous" Obstructive Apnea Event with a higher level that was your second Obstructive during the 5 minutes. Any other explanation for this requires that there be a Flow Limitation for any Obstruction Event or that it was scored wrongly as Obstructive and should be Central???

What do you think???

Nord

my head hurts

Nord, thanks for your response. I'm in cpap mode right now, so don't know if "the machine responds" at all. It just chugs along at the same pressure, no matter what. When I was using the S8, 10.6 cmH2O was as high as I could go, without getting severe aerophagia. Since my AI was low (.2), I decided to just stay there. So for me, it's not so that I'm trying to eliminate all apneas. It's more learning about the data from the software, and how to best use that information.

I'm thinking about doing a trial on apap in a week so, with a very narrow range, to see what the graphs look like. On cpap, the S9 seems to cause less gas than the S8 did, so I'm hoping it will be the same in apap mode.

Hi Katie,

Looking at the first graph, I presume you're trying to zoom in for the second graph at where you have the cyan coloured lines? Just prior to 4am, so around 3:45am?

If I look at the 5 minutes graph (2nd one) it shows the first apnea at 4:23am (12) and another at 4:27am (18). But if you compare that with your top graph, there's no apeans in this time frame between 4am and 5am. Are you sure both graphs are from the same day?

Also on the top graph the Minute Ventilation seems to spike quite a bit around the Apnea event but you're not seeing that spike on the detailed graph.

On the Obstructive event (18) I would expect the Flow limitation graph to drop because you're hitting an Obstructive Apnea at this point and you should be seeing a reduction in flow but your graph is showing a flat line.

Hi All

I have been going over this and perhaps the answer lies in the definition for from the Data Management Guide: " Flow Limitation is a measure of partial upper airway obstruction. This measure is based on the shape of the inspiratory flow–time curve. A flat shape suggests upper airway obstruction." The obstruction is not measured separately - it is based totally on the shape of your Insipation of your Flow Graph.

Therefore when your inspiration flow does not show flattening... there will be no Partial Obstruction and of course when there are no Inspirations during an Apnea Event... there will be no Flow Limitation. Since it is all relative to the Flow Graph there are no measurements and presumably as we have discovered... little accuracy by measurement of obstruction. It only records the shape of your Inspiration.

If your Inspirations on your Flow Graph are consistent and in the correct shape for an obstruction then it records correctly. Perhaps we begin having Centrals and during the time that we are having a Central... the obstruction takes place in the airway and it is recorded as Obstruction during the Apnea Event...

Nord

dave21 wrote:Hi Katie,

Looking at the first graph, I presume you're trying to zoom in for the second graph at where you have the cyan coloured lines? Just prior to 4am, so around 3:45am?

If I look at the 5 minutes graph (2nd one) it shows the first apnea at 4:23am (12) and another at 4:27am (18). But if you compare that with your top graph, there's no apeans in this time frame between 4am and 5am. Are you sure both graphs are from the same day?

Good observation--I didn't look at the times, I just zeroed in on the 2 apneas, so they would show in the Detailed Screen. Yes, they are the same day. I don't know why the time is not synchronized. Any ideas?

Also on the top graph the Minute Ventilation seems to spike quite a bit around the Apnea event but you're not seeing that spike on the detailed graph.

I think the spike doesn't look the same, because of the different scales--on the Navigation pane it's 0-8, but on the Detailed pane, it's 0-15. I'll have to change that on my Options. But the spike is around 8 l/min in both graphs.

On the Obstructive event (18) I would expect the Flow limitation graph to drop because you're hitting an Obstructive Apnea at this point and you should be seeing a reduction in flow but your graph is showing a flat line.

Yes, I don't understand this, and that's my question. Thanks for your input Dave, I'm really enjoying learning about the capability of this software, and what the data means.

Thanks Nord, this is starting to make sense to me now. What you're describing is a "mixed apnea". From Sleep Apnea--the Phantom of the Night, page 63:

"We frequently see another type of breathing pause during sleep. Usually these events begin with a central apnea, yet when the patient tries to initiate breathing there is an obstruction. No airflow results because the throat is now blocked. These apneas are referred to as mixed apneas because they include elements of a central apnea and an obstruction. New information suggests that the airway narrows slightly during central apnea. In a patient with an obstructive component this could cause obstruction as breathing resumes. Usually, treatment of obstructive sleep apnea eliminates these occurrences. Only rarely do mixed events begin with an obstruction and proceed to become a central event."

I appreciate your input, this is a great learning opportunity.

KatieW wrote:Good observation--I didn't look at the times, I just zeroed in on the 2 apneas, so they would show in the Detailed Screen. Yes, they are the same day. I don't know why the time is not synchronized. Any ideas?

If you open it up again do you still see the wrong time values? I'm not sure why these wouldn't be in-sync. I'm wondering whether the screen cached badly as I notice that sometimes dragging the scroll bars around parts of the screen don't always update properly. Sometimes it's more noticeable than other times.

KatieW wrote:Thanks for your input Dave, I'm really enjoying learning about the capability of this software, and what the data means.

I agree, it's great looking and reviewing over the stats and understanding better at how to be treated by the CPAP technology when in a lot of our cases, nobody reviews our data anyway.

dave21 wrote: I agree, it's great looking and reviewing over the stats and understanding better at how to be treated by the CPAP technology when in a lot of our cases, nobody reviews our data anyway.

As I understand it... nobody else even owns the software; not the DME's, not the RT's, not the Sleep Centre's and not my M.D. Either they believe it is not worth it; they think/hope no one will ask them any difficult questions; or they want to reduce our shared time together...

Nord

Nord wrote:... As I understand it... nobody else even owns the software; not the DME's, not the RT's, not the Sleep Centre's and not my M.D. ...

In my experience that's not the case. I've used three different DMEs. All three had the software to read the data. They just often did NOT read it.

My sleep specialist simply requests the data report from the data from the DME. However, some doctors also have the software.

Nord wrote:... Either they believe it is not worth it; they think/hope no one will ask them any difficult questions; or they want to reduce our shared time together... ...

It might be all three.

I liken it to the same thing as data from my blood glucose monitor. I once asked my endocrinologist if he wanted to see the data from my blood glucose monitor. His answer was striking (and applicable here): "Good lord, no! I don't need to see it! YOU need to see it. Your body no longer automatically controls your blood glucose. You need this data to keep your blood glucose under control."

That's what we should do with the sleep efficacy data. Just keep things under control.

JohnBFisher wrote:

Nord wrote:... As I understand it... nobody else even owns the software; not the DME's, not the RT's, not the Sleep Centre's and not my M.D. ...

In my experience that's not the case. I've used three different DMEs. All three had the software to read the data. They just often did NOT read it.

My sleep specialist simply requests the data report from the data from the DME. However, some doctors also have the software.

Nord wrote:... Either they believe it is not worth it; they think/hope no one will ask them any difficult questions; or they want to reduce our shared time together... ...

It might be all three.

I liken it to the same thing as data from my blood glucose monitor. I once asked my endocrinologist if he wanted to see the data from my blood glucose monitor. His answer was striking (and applicable here): "Good lord, no! I don't need to see it! YOU need to see it. Your body no longer automatically controls your blood glucose. You need this data to keep your blood glucose under control."

That's what we should do with the sleep efficacy data. Just keep things under control.

It's probably a little different where I come from... my info comes from dealing with/talking with 3 DME's. Two of them do not offer machines that record any data other than compliance. The other DME supplied me and does not usually offer Data recording machines. She told me after 15 years experience and being an RN as well, that no Doctor's that she knows have the software. My own Sleep Doctor that I have seen twice - I know doesn't have it.

Almost no one has AutoPAP's as they require separate prescription and made difficult to get except outside the Medicare system, provided an M.D. will make an exception. Our medical system makes it M.D. and Government centralized.

That makes it difficult to make individualized decisions... but on the plus side many things are covered either partially or fully. For example - Sleep Centres for studies or titrating are pretty reasonably priced at approximately $400/night and the government pays 100% twice per year... making AutoPAP's less necessary.

Better in some ways... NOT in others.

Sorry about the theft of your thread Katie... politics should be left for the dinner table...

Nord