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Help with SH Flow Rate?
Help with SH Flow Rate?
I was just looking over some SleepyHead data and have some questions about what I’m looking at. Would love to hear from the SleepyHead experts on here that could shed some light. Note I use Resmed AirCurve ASV. UF1 and UF2 are set to defaults. A few screenshots with subsequent commentary:

[Image: EIKnl9w.png]
On this one, two questions: why did the machine not flag the UF2 as hypopnea? The duration was 11 seconds. Just less oxygen desat I guess? But doesn't the loss of flow only need to be 30%? Regardless, the machine doesn’t look like it responded, why not? Secondly, what is up with the mask pressure? It stays frozen on EPAP pressures for 20+ seconds. Did I have some weird long exhale? But then how would it have flagged a hypopnea? Seems like the machine was slow (nonresponsive) to respond to the hypopnea anyhow. 

[Image: ksaqa6U.png]
Seems to be abnormal on all metrics, but nothing is flagged. A very erratic flow rate, along with a dip in pressure. Why would the machine do this?

[Image: RO0CYXO.png]
This tagging doesn't make any sense. Where is evidence of hypopnea (after the UF2 and UA)? 

Really hoping to get a better grasp of these metrics...and also ensure nothing is wrong with the machine. Thanks!
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RE: Help with SH Flow Rate?
I don't know a lot about your specific machine, but the traces and the events look ok. I don't think your machine is malfunctioning.

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RE: Help with SH Flow Rate?
I think that what looks like a drop in the inhale pressure is an artifact of the digital calculation. You can't really have two different pressures in one place at the same time.
It's as if there is a filter capacitor that gets charged up while you are inhaling, and discharges while you are not. If you inhale often enough, that inhale pressure stays up. if not, it starts sagging down to the exhale pressure.
That may not be how it really works, it just seems to me that's what it's like.
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RE: Help with SH Flow Rate?
I am not that familiar with ASV machines but on your first chart the event that is marked as a hypopnea looks more like an apnea to me and it appears to last long enough to be an apnea. It looks to me like it scored the hypopnea based on the flow prior to what looks to me like a complete cessation of breathing. There is one spot where the flow might have crossed the zero line just enough for the machine to sense it (even though it is not very visible) and call it the beginning of another breath. That would make it too short duration to score it as an apnea. A hypopnea is defined as a reduction of breathing of 30-50%. I believe that Resmed uses something more toward the 50% reduction.

The second chart looks to me like an apnea that was not quite long enough to be scored as an apnea.

In the third chart you have an apnea that the machine scored as an unidentified apnea but gave you some pressure support "kicks" in an attempt to get you to take a breath. I would guess from the lack of response to the "kicks" that the apnea was obstructive or maybe it was a CA that took a while to respond. As I am sure that you are aware the ASVs do not attempt to determine whether an apnea is OA or CA so they get scored as unidentified.

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