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Question about SH analysis of a rare 0 AHI night
#1
Since I had such a miraculous night last night with no "called" events, I thought it would be an interesting case study for some of the SleepyHead data analysis fiends on here. Smile

It's fairly easy to understand pressure changes in response to an apnea or hypopnea event, but what I'm trying to understand is why my pressure changes fairly significantly across my therapeutic range when there are no events. What is the trigger?

I had no snore or leak (not pictured), and the only graph that seemed to correlate with the pressure adjustments was Flow Limitation, so is that how the Airsense A10 decides when pressure changes are needed in general?

I've noticed that SleepyHead always "calls" events on the Flow Rate graph, and when I zoomed into this graph during one of the pressure rises (attached below), I did see some small disturbances in the baseline - maybe these are the beginnings of events detected by the machine, so it raises pressure before the event actually gets to 10 secs and gets an official call?

   

Zoomed view of Flow Rate during one pressure change:

   
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#2
ResMed scores FL by the shape of the inhalation waveform. "Flat-topping" indicates FL.
FL is one of the triggers for pressure rise to try prevent a full OA before it happens.

I'm not sure that you didn't have apnea that it didn't score. Your second flow graph looks like there might have been 3 in that time.
You need to zoom further in near 01:10, 01:13 and 01:19 and examine the flow data plot. Looks like the FOT algorithm was activated; and the flow essentially zero. FOT starts at 4 seconds after breathing stops. An Apnea is only scored if it lasts at least 10 seconds.
So, how long are those 3 apparent zero flow periods? If greater than 10, perhaps the machine is awry. If less then it will not count as an apnea.

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#3
Neither my machine nor SH called any events. The stops in the Flow Rate appear to be less 10 secs
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#4
(01-22-2016, 09:43 PM)Possum Wrote: Neither my machine nor SH called any events. The stops in the Flow Rate appear to be less 10 secs

OK, that's why they are not scored.

Admin Note:
JustMongo passed away in August 2017
Click HERE to read his Memorial Thread

~ Rest in Peace ~
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#5
I have used a new REMstar Pro M Series Model # 400M by Philips Respironics since 2009. The Apn-hyp Indet average since then has been around 3.6. Since January 1it has fallen to around 0.08. Any reason for this? Am I Healed?
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#6
(01-25-2016, 09:51 AM)edfarrell Wrote: I have used a new REMstar Pro M Series Model # 400M by Philips Respironics since 2009. The Apn-hyp Indet average since then has been around 3.6. Since January 1it has fallen to around 0.08. Any reason for this? Am I Healed?


Hi edfarrell,
Welcome to the forum!

Unfortunately you are using an older machine that gives no useful data.
If you have been running an AHI of 3.6 since 2009, I would think there would be room for improvement. Your recent AHI of .08 is suspect, and there would be no way of knowing without looking at data.

Mabye it's time to updgrade to a newer machine. Preferably a data capable APAP.

Don't know if you have insurance, but if not, check out the many online suppliers listed above (Suppliers List).

Supplier #2 offers gently used and new open box machines.
OpalRose
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#7
(01-25-2016, 10:07 AM)OpalRose Wrote:
(01-25-2016, 09:51 AM)edfarrell Wrote: I have used a new REMstar Pro M Series Model # 400M by Philips Respironics since 2009. The Apn-hyp Indet average since then has been around 3.6. Since January 1it has fallen to around 0.08. Any reason for this? Am I Healed?


Hi edfarrell,
Welcome to the forum!

Unfortunately you are using an older machine that gives no useful data.
If you have been running an AHI of 3.6 since 2009, I would think there would be room for improvement. Your recent AHI of .08 is suspect, and there would be no way of knowing without looking at data.

Mabye it's time to updgrade to a newer machine. Preferably a data capable APAP.

Don't know if you have insurance, but if not, check out the many online suppliers listed above (Suppliers List).

Supplier #2 offers gently used and new open box machines.

Actually his machine gives pretty good data, but you need a Smart Card reader (Mako-Infineer DT3500) and EncoreBasic. As far as speculating on the sudden improvement, who knows? Dont-know
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#8
Possum, looking at your charts, you have 3 breaks in therapy through the night, so while the numbers look good, I don't know that I'd trade with you. At 1:10, 1:13 and 1:18:30 you have some pretty strange stuff going on with fluctuating flow rates. If you zoom in on those it might be interesting to see, but I'd guess you barely missed scoring a hypopnea with that reduced flow, and a Respironics machine would have scored it.

Flow limitation is a major trigger of pressure increases in all auto CPAP machines. Zoom in closely in the period preceeding a pressure increase, and see if you notice the inspiration curve flattening out. Happens to me all the time. FWIW, I often get <1 AHI, but have never managed to earn a zero from my machine. Congrats.
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#9
(01-25-2016, 11:05 AM)Sleeprider Wrote: Possum, looking at your charts, you have 3 breaks in therapy through the night, so while the numbers look good, I don't know that I'd trade with you. At 1:10, 1:13 and 1:18:30 you have some pretty strange stuff going on with fluctuating flow rates. If you zoom in on those it might be interesting to see, but I'd guess you barely missed scoring a hypopnea with that reduced flow, and a Respironics machine would have scored it.

Flow limitation is a major trigger of pressure increases in all auto CPAP machines. Zoom in closely in the period preceeding a pressure increase, and see if you notice the inspiration curve flattening out. Happens to me all the time. FWIW, I often get <1 AHI, but have never managed to earn a zero from my machine. Congrats.

Well, now you have me somewhat worried. Do you think the fluctuating flow rate is suggestive of Cheyne-Stokes? Wondering if I should have my doctor take a look. ResScan did not detect CSR breathing, and I'm still unclear on whether SleepyHead does so.
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#10
Not at all! All that means is that for a short period of time, flow was less than at times when inhale and exhale volume was normal for you. I don't see any periodic pattern that is a concern in that graph. All I was suggesting is it might be interesting to zoom in on the breath by breath level where the low-flow is apparent. It's clearly not serious, and not even scored as an event. If you want scary, I'll show some of mine. Smile
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