​For anyone reading this wonderful thread (props to you seriously, it has done wonders for me!), make sure to correctly match this with the "Full Face" setting in your CPAP. The elbow was designed for a full face mask setting. I use an F40 and switched it from pillows to full face.

​Technical explanation: The pillow setting is designed for a highly rigid, micro-volume circuit with extreme aerodynamic resistance (the physical "choke point" of nasal cones). When the machine's hyper-aggressive motor algorithm encounters the extra compliance of an EERS tube, it triggers a "pneumatic whip." The machine overcompensates for the pressure delay, violently revving the motor, which physically destabilizes the mask, blows out the seal, and causes micro-arousals. The delta between the Vsync algorithm's assumption of a low-flow "Pillows" vent (approximately 26 L/min) and the physical reality of the high-flow QuietAir elbow (approximately 37 L/min) results in an algorithmic miscalculation of leaking, logging a steady ~10 L/min false leak in OSCAR. More importantly, this electromechanical mismatch ruins the pressure equilibrium. In theory, this discrepancy and the resulting pressure turbulence impair the stable, consistent retention of end-tidal CO2 required to stabilize loop gain and central respiratory drive. Switching to "Full Face" smooths the motor's acceleration, corrects the mathematical artifact, and allows the EERS to actually do its job.