@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.