+- Apnea Board Forum - CPAP | Sleep Apnea (https://www.apneaboard.com/forums)
+-- Forum: Public Area (https://www.apneaboard.com/forums/Forum-Public-Area)
+--- Forum: Main Apnea Board Forum (https://www.apneaboard.com/forums/Forum-Main-Apnea-Board-Forum)
+--- Thread: Flow limitation and wave form question (/Thread-Flow-limitation-and-wave-form-question)
Flow limitation and wave form question - KallyA - 05-16-2019
I have had a couple of weeks of not so great sleep, and am still trying to figure out what is keeping me so tired. Here I am considering what is happening with flow limitation and wondering if I need to get a handle on it. I'm attaching an all night view and a close up of a section with a lot of flow limitation. I notice there tops on the inspiration is flat and that there seems to be a lot below the line. Is there anything else of note? How does the wave form in the flow chart relate to the pressure and flow limitation? And is there any relationship to the aerophagia I am battling?
Thanks ahead for your input!
[attachment=12013]
[attachment=12012]
RE: Flow limitation and wave form question - Gideon - 05-16-2019
The ASV algorithm is especially brutal for aerophagia since to resolve central events it spikes pressure fairly high fairly fast.
To reduce aerophagia you would need to reduce this higher pressure without compromising the "forced" breath. This would be accomplished by slowly lowering the Max PS
The issue with flow limitations is best resolved by increasing min Pressure support. You want to maintain sufficient PS differential to be able to mitigate a central event.
I would set your min PS to 4 and see what happens. That is tackling the flow limitations first.
Because your high pressures are so high I don't think you will be able to significantly reduce your Aerophagia.
RE: Flow limitation and wave form question - jaswilliams - 05-17-2019
The flow limitations on an ASV show when despite running at max pressure support it was still unable to initiate a non restricted breath. You are running into a challenge with your machine, to clear your events it has to use its max pressure of 25 this is causing your aerophagia if you reduce the max pressure support you may reduce your aerophagia but your Hypopnoeas and UA’s will rise. I actually found my aerophagia was reduced when not wearing the collar so I had to ditch mine but that may not be the same for you. Over time your body will get used to the pressure changes of the ASV and the sleep disruption will reduce.
RE: Flow limitation and wave form question - Sleeprider - 05-17-2019
Flow limitation is common with ASV therapy, and Jaswilliams explanation is a good one. We have seen this in a number of individuals. There are some optimization techniques that might improve your results. These would involve using ASV auto mode and lower EPAP minimum pressure as well as possibly increasing the minimum PS to minimize flow limitation when the machineis not triggering higher pressure support to overcome centrals. The close-up segment you posted from 00:07 to 00:10 shows flow limited breathing that your ASV is attempting to resolve with PS of about 3 to 6. I think you will find the mask pressure graph offers a bit more detail on the machine response than the pressure graph when looking at details like this.
RE: Flow limitation and wave form question - KallyA - 05-17-2019
Thank you so much for all of your responses. I called my sleep center to ask if they could turn down the pressure. Dr. is out until Monday, sleep tech took the day off. They warned me not to turn down the PS on my own due to “liability issues.” It's a new machine and I am on the thirty day compliance period for Medicare, and my supplemental could have issues this, so it looks like I will have a couple more miserable nights. Fortunately, I got an appointment with Dr for Monday afternoon. Meanwhile .. keep the cervical collar or not? My sleep study titration was done without a collar. I added it this last week to address large leaks. Here are the graphs for last night--full night and worst part. Note I forgot the collar during the first part and had to readjust it, then the large leaks stopped. The second chart shows large leaks gone, but increased events. Is the collar use related to events?
[attachment=12018]
[attachment=12019]
RE: Flow limitation and wave form question - jaswilliams - 05-17-2019
The reason for more events with the collar on is due to the leaks the machine could not tell what was going on and so was unable to flag, the second part of the night looks horrible, dispite pushing max pressure you were still not adequately breathing
RE: Flow limitation and wave form question - KallyA - 05-17-2019
(05-17-2019, 04:35 PM)jaswilliams Wrote: The reason for more events with the collar on is due to the leaks the machine could not tell what was going on and so was unable to flag, the second part of the night looks horrible, dispite pushing max pressure you were still not adequately breathing
hmmm. You sound tired. The early part with the leaks I did not have the collar on. Later with the collar on, no leaks, but lots of events.
I don't know how the collar relates to events yet, only that it reduces leakage. I have had the cervical collar not tight enough, found lots of leaks, tightened it and leaks stopped, so I know there must be an optimal tightness. I'm still new to it.
RE: Flow limitation and wave form question - sheepless - 05-17-2019
it took me a while to figure it out too. his point is that the machine flags are not accurate during substantial leaks like you had without the collar. had it been accurate it would have flagged more, just as it did when you reduced leaks with the collar.
RE: Flow limitation and wave form question - Sleeprider - 05-18-2019
Kally, I want to clarify, that my suggestion was not to turn down the pressure but to try ASVauto mode with a lower minimum. That lets the machine auto titrate as needed without making you deal with high pressure all the time. Again, please ask your doctor to switch to ASVauto mode, with epap min 8.0, EPAP max 11.0, PS min 3.0, PS max 14.0. This would be an easy change for you to make yourself and see if it works or not. It is easy to try this, and return settings to the fixed ASV mode if it doesn't work out.
I think continue using the collar.