My Apnea Story (Includes DS2, S9, low AHI, RERAs) - Help!

[gadgetmaniah]

@xxxxqwe, there doesn't seem to be a lot of obvious flow limitation in most of your screenshots, but I can see evidence of some flow limitation (FL) or irregularity which might indicate FL in a few of the screenshots, for example the third screenshot that you've attached. Based on your sleep study though, it seems like you do have UARS (since you had a RDI score and a low AHI score). So, I would still recommend trying out a bilevel machine to see if your sleep improves with higher pressure support. Perhaps you could rent one for a month or so. Just a suggestion.

@CorruptAlligator, to treat flow limitation, pressure support is needed. Sorry I wasn't clear enough in my previous post, but yes, EPR is pressure support. Pressure support (PS) refers to the difference between the inhale pressure and the exhale pressure. In a Resmed AS10, the EPR (pressure support) can only be set up to a value of 3. This means that you can only create a difference of a maximum of 3 cm pressure between your inhale pressure and your exhale pressure. So, if you set your pressure to 11 cm and set EPR to 3, the exhale pressure will go down to 8 cm when you exhale. This difference between the inhale pressure and exhale pressure is what is called pressure support.

In bilevel machines, since a larger range of exhale pressures can be set, we can also create a larger amount of pressure support (because, remember, pressure support means the difference between inhale pressure and the exhale pressure). So, for example, my current inhale pressure is 11 and exhale pressure is 6, which means a pressure support of 5. This is higher than what my previous machine, the AS10, could offer, which could only offer a maximum pressure support/EPR of 3.

However, I don't think there is a consensus about why a higher flow limit helps eliminate flow limits. I recommend you to read Dr. Barry Krakow's writings on this subject. I'll post some links if I can. I thought that a higher pressure support works to fight flow limits because of the added force that the large difference between the inhale and exhale pressure provides, preventing the airway from collapsing or partially collapsing. I'm not sure if this is the correct reasoning though. Whatever the reasoning, from what I've read a higher inhale pressure and a lower exhale pressure is what reduces flow limits.

Edit: Here is Dr. Barry Krakow's explanation about why bilevel works for flow limitation:

"To fully normalize sleep inspiration as well as sleep expiration, the inspiratory and expiratory airflow curves must be fully rounded on the pressure transducer tracing of airflow. To be fully rounded, each limb of the airflow curve needs its own distinct pressure. That is, higher pressure when you breathe in to round the inspiratory curve and lower pressure when you breathe out to round the expiratory curve. Hence, the use of bilevel." (https://sleepbreathe.org/response-to-sle...krakow-md/)

I'll try sharing some pictures from my own data to show you how a higher pressure support has made my flow rate more stable.

[CorruptAlligator]

@gadgetmaniah. I've read around about PS and it's effectiveness in reducing FL, but that's as far as the info out there tells me. I've not read anything yet that clearly explains the way it works. Best way to understand would be a visual animation with the flow rate and images of how flow is working inside the patient. Made by somebody that clearly understands beyond causal reasoning.

as far as flow limitation, I think I've had episodes last two nights that cause arousals. When looking at flow rate without zooming in, you can see at certain ranges the waveforms are thinner. That's what's happening, and I woke up at a point in time when it was thinner (and afterwards, I could see larger erratic swings where recovery breathing is happening.). What really doesn't make sense is, how does this waveform correspond to the FL level shown? I tried looking at it, and it sometimes doesn't correspond to flow rate waveform swing amplitudes. How much of a delay is there when FL is reflected based on the flow rate? At which point in the FL corresponds to flow rate diagrams?

Also, what flow rate waveform swing is considered a value of '1?' and what is less than one? What is the baselines to determine flow limitation in the flow rate phases? Because there are various levels of flow rate swings throughout the night (at least for me). What is considered normal and what is less?

Perhaps there is a good textbook on this subject matter? Is FL understood well enough to be taught on textbooks?

[cathyf]

Comparing an autoset with EPR of 3 and a vauto with PS of 3, the vauto dramatically lowers the reported flow limits.

HOWEVER -- (big but coming) the algorithms for scoring flow limits are complex and proprietary -- very opaque! I can see that the waveforms are different, however I'm still somewhat suspicious that the two machines may be reporting based on different calculations, and maybe the vauto just reports differently?

[xxxxqwe]

then i will have to get bipap soon and try
Thank you