Can the Resmed s9 machine detect all apneas?

[Matty332]

G'day,

Man I am on a roll with the questions tonight! I suppose if you don't ask you don't know.

Does anyone know if the Resmed s9 machine detect all apneas including central and other weird ones? Or just obstructive. Thanks again.

[NewBMW]

I have an S9 Elite and according to my SleepyHead Software, it detects hypopnea, apnea, clear airway and obstructive and gives me a number for each one as well as AHI for the session.

[robysue]

Does anyone know if the Resmed s9 machine detect all apneas including central and other weird ones? Or just obstructive. Thanks again.

ALL apneas are detected in the same way: An apnea of some type is scored when the airflow drops by 80% or more from baseline for a period of at least 10 seconds.

When the S9 detects a potential apnea in progress (i.e. the airflow has dropped by at least 80% from baseline for about 6 seconds or so), the machine starts doing the FOT algorithm to test the patencey of the airway. If the FOT algorithm indicates the airway is closed, an OA is scored if the event continues for at least 10 seconds. If the FOT algorithm indicates the airway is open, a CA is scored10 seonds if the event continues for at least 10 seconds. If the FOT data is inconclusive, a UA (unknown apnea) is scored if the event continues for at least 10 seconds.

[gatnus]

I believe my S9 is detecting some central apneas that aren't real. I've had 2 sleep studies and both have shown zero central apneas, but yet every night, my S9 shows about up to 2 centrals of 10-20 seconds in length per hour.

[NewBMW]

Am I understanding this correctly? To have a recordable event on the S9, it must last 10 seconds
1) If the airway is blocked, it is obstructive
2) If the airway is partially open it is a CA

If the airway is cleared by the pressure of the CPAP before 10 seconds has passed, nothing is recorded.

Thanks,

Lee

[Pugsy]

Am I understanding this correctly? To have a recordable event on the S9, it must last 10 seconds
1) If the airway is blocked, it is obstructive
2) If the airway is partially open it is a CA

If the airway is cleared by the pressure of the CPAP before 10 seconds has passed, nothing is recorded.

Pretty much correct. #2 might need to be clarified a bit.
A partial opening could be a partial collapse or partial reduction resulting in a hyponea.

A Central (Clear Airway) doesn't necessarily mean partial opening...only that no air is moving and no indication of collapse...full or partial...It is an open airway cessation of breathing. Hold your breath for 15 seconds...that is pretty much a 15 second clear airway cessation of breathing.
Airway is open but no air is moving.

[robysue]

I believe my S9 is detecting some central apneas that aren't real. I've had 2 sleep studies and both have shown zero central apneas, but yet every night, my S9 shows about up to 2 centrals of 10-20 seconds in length per hour.

Like all PAP machines, the S9 does not have an EEG. So it can't tell when you are awake or when you are asleep. Since wakeful breathing is much less regular than sleep breathing is supposed to be, it's not uncommon for machines to score events that would not be scored on an in-lab PSG because the EEG would indicate the event took place while you are awake.

Like all PAP machines, the S9 lacks the belts around your chest and abdomen that measure effort to breath. Hence the S9 cannot score central and obstructive apneas in the same way it's done on an in-lab PSG. In the lab, an apnea requires a complete cessation of air flow for 10 seconds or more. If the belts indicate you are trying to breathe, the event is scored as an OA, and assumption is that no air is getting through because the upper airway has collapsed. If the events indicate you are not trying to breath, the event is scored as a central apnea (lab CA). No effort is made to determine the patency of the airway since the problem appears to be that your brain forgot to send the signal to breathe. It's possible that the airway is also collapsed---and if you start trying to breathe after the start of an apnea and the air does NOT start flowing into your lungs, that's scored as a mixed apnea on the PSG.

For machine scored events, all the machine has to go on is airflow. The definition of apnea varies a bit from brand to brand: Some use an 80% decrease in airflow from baseline; some use a 90% decrease in airflow from baseline. The decrease has to last at least 10 seconds. Since there's no way to measure whether you are awake or not, the machine just assumes that if you are masked up, then you are asleep. Since there's no way to measure whether you are trying to breathe, the machine tests for the patency of the airway. If the airway is obstructed, an OA is scored (and the machine's makers pressume you were making an effort to breathe). If the airway is clear, a clear airway apnea (CA) is scored, and the usual assumption is that since the airway is open, the problem must be that you are making no effort to breathe. Hence the auto algorithms are set up to NOT respond to machine-scored CAs since they are likely to be central apneas (if you are asleep) and pressure increases can trigger additional problems with CAs in some folks.

Machine scored hypopneas are also based only on airflow. Again, the actual definition can vary from manufacturer to manufacturer. But typically a machine-score hyponea requires 40% or 50% decrease in airflow from baseline. Because air is still getting through, the machine usually doesn't try to determine the patency of the airway. The assumption is that you are trying to breathe, but the airway is partially collapsed.

A Central (Clear Airway) doesn't necessarily mean partial opening...only that no air is moving and no indication of collapse...full or partial...It is an open airway cessation of breathing. Hold your breath for 15 seconds...that is pretty much a 15 second clear airway cessation of breathing.
Airway is open but no air is moving.(emphasis added)

Maybe I'm just weird at holding my breath. But when I've done this experiment, the "event" seems to be just as likely to be scored as an OA as a CA. I think it may have something to do with an unconscious tongue position when I'm holding my breath.

[Pugsy]

Maybe I'm just weird at holding my breath. But when I've done this experiment, the "event" seems to be just as likely to be scored as an OA as a CA. I think it may have something to do with an unconscious tongue position when I'm holding my breath.

I guess I should have qualified my holding your breath example a little more. I meant it only to explain the mechanics of a central apnea. No effort to breathe and no airflow.
I didn't really mean it as a way to see a central or clear airway on the data. When I have purposely held my breath...sometimes I see a "central" and sometimes it gets flagged as obstructive. To me all it proves is that the machine isn't perfect and just a limitation I live with.
Very close in that at least it scores something but just not perfect. Another reason that I don't get horribly excited with a few "centrals" from time to time. The machine isn't perfect and even if it was...a few centrals are normal anyway.

[billbolton]

including central

If the central is detectable by FOT, then yes..... see http://www.resmed.com/us/assets/documen ... -paper.pdf

and other weird ones?

It doesn't have a paranormal detection capability

Cheers,

Bill

[avi123]

As I understand it, according to Dr Michael Berthon-Jones, who has been Resmed's Chief Designer of their Autoset machines,
we should not rely on the HI (hypopneas Index) values that these machines indicate.
Be it central or obstructive hypopneas.

Dr Berthon-Jones said it in an interview, like this:

Q. Why doesn’t ResMed's AutoSet respond to
hypopnoea?

A. When you are lying quietly awake, or when you
first go to sleep, or when you are dreaming, you
can have hypopneas (reductions in the depth of
breathing) which are nothing to do with the state of
the airway. For example if you sigh, which you do
every few minutes, you usually have a hypopnea
immediately afterwards. This can also happen if
you have just rolled over and are getting settled, or
if you are dreaming. And the annoying thing is that
when you are on CPAP, this tendency to have what
are called central hypopneas - hypopneas that are
nothing to do with the state of the airway - is
increased. If you make an automatic CPAP device
that responds to hypopneas, you will put the
pressure up to the maximum while the patient is
awake.

Q. Do you think there is a misconception clinically
that all hypopneas should be treated ?

A. For simple obstructive sleep apnea, central
hypopneas should not be treated. They are not a
disease. Everyone has them. And they don’t go
away with CPAP.

There is a rare and important exception: central
hypopneas due to heart disease. This is called
Cheyne-Stokes breathing. CPAP does help with
that.


P.S.

May I uggest that we should prefer using Apnea Index instead of AHI?
This is b/c the AHI includes hypopneas values in it and as such my idea would agree with Dr Berthon-Jones (see above) and also with Dr Collin Sullivan (see the report mentioned in my signature line). A better value would be to take the Apnea Index (Obstructive Index+ Central Index) and add to it the Flow Limitation (= UAR+ RERA).

Since the S9 shows the Flow Limitation (FL) only in a graph, we possibly could estimate its value index from the graph. Any idea how? I don't see any idea in this thread:

viewtopic/t68900/ResScan-Flow-Limitation-Chart.html

Howver, since the S9 decides on the value of the FL to show in the FL graph by evaluating the flatness of of the respiration wave we could do the same . We could look at the flow waves and decide on a value index. See this: I need to find it.

No, this is not it b/c it does not give values. It seems to me just a symbolic illustration.



Is this anything:

viewtopic/p542310/viewtopic.php?f=1&t=5 ... ow#p542280

[BasementDwellingGeek]

Thanks for that post , avi123. I have seen a scraggly waveform and wonder what it meant. I sometimes waken to pst, pst sounds as air leaks out of my mouth. I tighten my mouth and go back to sleep.


This forum is a plethora of information. I can now relate that to the scraggly waveform as expiratory mouth breathing.