How can you have an Obstructive Apnea without a Flow Limit?

General Discussion on any topic relating to CPAP and/or Sleep Apnea.
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Chris33022
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Joined: Wed Mar 30, 2022 5:46 pm

Re: How can you have an Obstructive Apnea without a Flow Limit?

Post by Chris33022 » Tue May 17, 2022 1:11 pm

Thank you ChicagoGranny and Lazarus. I understand better now.

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Pugsy
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Location: Missouri, USA

Re: How can you have an Obstructive Apnea without a Flow Limit?

Post by Pugsy » Tue May 17, 2022 1:16 pm

Chris33022 wrote:
Tue May 17, 2022 12:30 pm
based on how TheLankyLefty27 explains it in his YouTube videos, that one OA I had looks to me like a real OA because there is a strong increase in breathing right afterwards, as if it's maybe gasping. Jason says that one way to recognize a CA is that the breathing resumes exactly as it was beforehand, with no increase, no gasping.
Some time ago when ResMed first came out with the FOT thing to help sort out central apneas from obstructive apneas there was some documentation available where ResMed released a comparison of a machine flagged central to a human flagged central apnea. They did a lot of machine comparison to human attended PSG results. There was minimal difference in the name calling between machine flagged events and a human flagged event. Something like maybe around a 1% difference (or maybe a little less) between machine scored events and human scored events.

And of course we also have to remember that even humans aren't always 100% correct.... :lol: :lol:

Your event above does also look more obstructive than central to my eyes as well. Is it possible the machine named it wrong??....yeah, I suppose it is possible but it's a real long shot. Nothing out there is ever 100% perfect...even the humans...so we have to accept the possibility of the machine getting it wrong but with ResMed I would say the chances of that happening are extremely rare.

Now if it had been a Respironics machine involved...I have seen that brand get it wrong on more than one occasion.
I remember once seeing the Respironics machine flag a truck load of OAs when they were definitely centrals. I have never seen a ResMed machine do that.

I don't remember ever seeing the exact criteria that needs to be met for a FL flag but it very well could be that in your situation you didn't meet one little parameter that needed to be met for a FL flag. Maybe something like a difference in flow rate of 1% or something like that. Maybe your flow rate was just 1% below whatever is measured to earn a FL flag.
Impossible for the eye to see but the machine's sensors would "see" the difference.

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Chris33022
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Re: How can you have an Obstructive Apnea without a Flow Limit?

Post by Chris33022 » Tue May 17, 2022 2:00 pm

Thanks, Pugsy, that's interesting.