UARS, diagnostic sleep studies, surgery and ASV!

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xsara
Posts: 14
Joined: Thu Jun 02, 2011 6:54 pm

UARS, diagnostic sleep studies, surgery and ASV!

Post by xsara » Tue Nov 25, 2014 2:58 am

Hello,
I am wondering if people would consider the flow limitations data analysis from an S9 Autoset to have the same level of detection for UARS as a nasal pressure transducer in a sleep study?

The reason I ask is, I have had a total of four sleep studies, only one of which I believe used a pressure transducer, vs a thermistor in the others (http://www.medscape.com/viewarticle/494651_4).

The three sleep studies that used a transducer showed an RDI of 0.5, 1.1 and unknown. The sleep study with the transducer shows an RDI of 27. The two most recent sleep studies displayed very fragmented sleep, with 4% and 8% late-onset fragmented REM.

The S9, when I manage to wear it for a very limited period of time, is often riddled with flow limitations.

Do you think that the S9's data would be more diagnostic than a sleep study that uses a thermistor?

I am unable to tolerate the S9 Autoset (I have tried every combination of settings and masks over three years), and am seeing my ENT surgeon tomorrow to look at a surgical intervention (modified uppp and tongue coblation channelling), for which I have read all of the opposing views. I have a 2mm tongue base gap whilst awake, a large uvula and a flappy palate!

If the surgery doesn't assist, I am hoping that it may increase my xPAP tolerance. My intention then would be to try ASV (from secondwind, as I can't justify the money to try BiPAP first, in the event that it doesn't work).

Look forward to any thoughts.

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Additional Comments: Former S9 Autoset user

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49er
Posts: 5624
Joined: Mon Jan 16, 2012 8:18 am

Re: UARS, diagnostic sleep studies, surgery and ASV!

Post by 49er » Tue Nov 25, 2014 4:03 am

I am unable to tolerate the S9 Autoset (I have tried every combination of settings and masks over three years), and am seeing my ENT surgeon tomorrow to look at a surgical intervention (modified uppp and tongue coblation channelling), for which I have read all of the opposing views. I have a 2mm tongue base gap whilst awake, a large uvula and a flappy palate!

If the surgery doesn't assist, I am hoping that it may increase my xPAP tolerance. My intention then would be to try ASV (from secondwind, as I can't justify the money to try BiPAP first, in the event that it doesn't work).

Look forward to any thoughts.
Hi Xsara,

I am going to leave the technical details about flow limitation to other posters but wanted to address the surgery issues. As one who may be in a similar position to you, the first step is to address your nasal potency before considering any other major surgeries by either conservative or surgical methods. How is that?

If it isn't an issue, then my question is how were your issues diagnosed? The reason I am asking is that I have read on other boards that in order to increase your chances of having the most effective surgery, it is advisable to undergo a sleep endoscopy so the exact obstructions can be pinpointed. I guess I would be asking the surgeon how he/she knows that these are the obstructions that need to be addressed if that wasn't done?

For example, my sleep doctor said I had a large tongue for my mouth but in my opinion, that may not necessarily translate to needing some type of tongue procedure without undergoing the sleep endoscopy to confirm that there is an obstruction. Does that make sense?

Have you also looked at the Inspire Procedure? It seems alot less invasive than the other procedures although of course, keep in mind, I am not a doctor.

Finally, before undergoing any surgery, make sure you understand exactly what the surgeon expects the success rate to be regarding AHI so you are a fully informed patient.

49er

49er

OKCSleepDoc
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Re: UARS, diagnostic sleep studies, surgery and ASV!

Post by OKCSleepDoc » Tue Nov 25, 2014 8:14 am

49er, happy to help with the technical details. The answer is that it would be hard to say. Resmed flow limitation analysis is done by calculating a "flattening index". They basically try to figure out how flat the flow curve is and assign it a value. I believe it is somewhere between 0.0 and 0.3. The closer the flattening index is to 0, the more quickly the machine responds by increasing the pressure (so it responds with more pressure to more flow limitation). This is not really how one would calculate an RDI using a nasal pressure transducer. Typically a nasal pressure transducer allows sleep labs to capture/mark more hypopneas as it is more sensitive to changes in airflow than a thermistor. However because the method used to mark these events are completely different between Resmed, Respironics, and Sleep Study, I don't think you can really compare them exactly to one another. The other thing to keep in mind on the Resmed is that it is a computer that does not monitor sleep staging. So any flattening on the flow curve, whether due to you being awake, leak, etc is going to still potentially count towards the flow limitation index (I am sure they have some algorithm that tries to filter some of that out but it is proprietary so no one really knows how they do it).

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49er
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Re: UARS, diagnostic sleep studies, surgery and ASV!

Post by 49er » Tue Nov 25, 2014 8:51 am

OKCSleepDoc wrote:49er, happy to help with the technical details. The answer is that it would be hard to say. Resmed flow limitation analysis is done by calculating a "flattening index". They basically try to figure out how flat the flow curve is and assign it a value. I believe it is somewhere between 0.0 and 0.3. The closer the flattening index is to 0, the more quickly the machine responds by increasing the pressure (so it responds with more pressure to more flow limitation). This is not really how one would calculate an RDI using a nasal pressure transducer. Typically a nasal pressure transducer allows sleep labs to capture/mark more hypopneas as it is more sensitive to changes in airflow than a thermistor. However because the method used to mark these events are completely different between Resmed, Respironics, and Sleep Study, I don't think you can really compare them exactly to one another. The other thing to keep in mind on the Resmed is that it is a computer that does not monitor sleep staging. So any flattening on the flow curve, whether due to you being awake, leak, etc is going to still potentially count towards the flow limitation index (I am sure they have some algorithm that tries to filter some of that out but it is proprietary so no one really knows how they do it).
Thanks and very informative. Also, glad to see you posting again.

49er