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Opinion on Sleep Study
#31
RE: Opinion on Sleep Study
(12-22-2021, 10:22 PM)Geer1 Wrote: Ok she hasn't said that but that is how it came across because you/she are questioning both doctors, sleep study and the diagnosis. 

- She wouldn't say PAP therapy was BS, because she is much more gracious.   I certainly wouldn't say PaP therapy is BS having been on therapy for ~20 years I know what it has done (and continues to) for me.

The only thing that is being questioned is the sleep study. Others questioned why the sleep study was ordered originally, and while she(nor I)  doesn't grasp the reasoning for the original study, as the compliant patient that she is, she had no problem with going ahead with that study.

Where she has expressed concern is accepting a life-time routine of therapy, that seems to have had no measurable  on her life. (when she has been repeated been told by that best measure of PaP therapy is how good you feel now that your on it)

OK, enough on that.

For my benefit (and learning).... I think you said that flow limitations are not scored on home studies because home studies don't have EEG data. So there is something missing in my understanding about evaluation of flow limitations. 

My Respironics scores flow limitations without the benefit of EEG. And flow limitations, while scored, FL do not seem to rise to the level of an "event". 
More significantly (as I understand it) FL are scored on the basis of the shape of the inhalation as seen in the flowrate curve, rather than the observation of an actual obstruction (or partial obstruction). For example, a flat topped inhalation curve may be scored as a flow limitation because it suggests that inhalation was somehow impeded. (I would dare say that the overwhelming majority of my inhalation breaths are flat-topped or even bi-modal (imagine the profile of a molar tooth), both while I'm asleep as well as while I'm awake, and I am not conscious of any restriction or need for increased effort to breathe)

Her home study included a effort (strain) belt. The effort belt showed no differential during a period of FL. If there was a true restriction or flow limitation, should it be mirrored by increased effort?  

Thanks for bearing with me and trying to expand my understanding.
Have a nice Holiday
 
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#32
RE: Opinion on Sleep Study
It isn't that flow limitations aren't scored on home studies it is more so that what they cause (RERAs) are not scored. Although this home study indicated near constant flow limitations what it didn't do was score the RERAs associated with them. RDI (respiratory disturbance index) = AHI + RERAs/hr and in a case like this with near constant flow limitations I would expect another 5+ RDI from RERA's (just a guess). RDI is as important and actually more telling then AHI and is what most in clinic sleep studies use to diagnose SDB and what usually diagnoses UARS (which has AHI < 5 but with high RDI due to RERAs).

The best way to think of a flow limitation is like trying to breath through a straw. It isn't fun and it makes it hard to breath. One or two breaths doesn't create much issue but try doing it for half an hour or a full night. This extra effort can show up on effort belt data and I believe it did in the 2nd example (in that image of close up data). If you look at the top example and far left or right you will see the nice consistent effort level (3rd graph down below below flow and snore). If you look at the bottom example and especially over at the right where there were lots of flow limitations you can see how inconsistent and in the end increasing in amplitude the effort was because her body was trying harder to effectively breath through a straw. 

Flow limitations are treated differently by different manufacturers and doctors. Resmed has realized how important they are and targets them fairly aggressively with their algorithms. This helps avoid a lot of hypopnea and apnea by the machine proactively increasing pressure before the hypopnea, apnea or RERA occur. In some people increasing the pressure doesn't help overcome the flow limitation though (and in rare cases can even be detrimental) and that is where close examination of OSCAR data comes in. If you look at a period of flow limited breaths and the pressure increases and breathing returns to normal then the pressure helped. If the pressure increased and flow limitations remained until a sudden change of large amplitude breathing then the pressure didn't help and the large amplitude breathing you see is an arousal and probably a RERA (if flow limitation was significant). This is why I would be curious to see her OSCAR data because it is possible that the reason she is not seeing any change from using PAP is because she is only partially treated (AHI sounds for the most part under control but these periods of high effort and RERA may still be remaining).

Attached is an example of a RERA in OSCAR data. Note there is no flagged event because the machine cannot easily interpret RERAs without EEG data, as a human it is pretty obvious once you get to know OSCAR and your data. I can't help but wonder if one day these PAP machines will use artificial intelligence to self titrate.


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