erratic flow rate graph on ASV normal?

[jaredihnen]

        I have been using my new ASV unit for a few days now.  It took me a couple nights to get used to letting the machine assist my breathing. I do feel like I am sleeping OK a good portion of the night now. AHI is nominal. But instead of air hunger waking me up now, I am wake up feeling like I am breathing against the machine.  My Oscar shows what seems to be erratic breathing and mask pressure fluctuations at times.  Is this a normal occurrence with ASV users, or perhaps some setting adjustments would be in order?

Also,  there are frequently periods of time that my flow rate graph shows waning volumes, whereas I was expecting the ASV to give me the pressure needed to maintain consistent tidal volumes.  

Could these inconsistencies be simply indicators of different sleep cycles?

Thanks for your insight!

[SarcasticDave94]

I would try the ASV in ASV Auto to gain an EPAP range. 6-12 or so I'm thinking.

The ASV may give decent tidal volume, etc. but I think that will come as a byproduct of treating CA. Even though it is an Adaptive Servo Ventilator, the ventilator that actually shapes breath mechanics is true ventilation, likely not what you're really after. It's still requiring you to spontaneous breath mostly, exception being during the Central. It'll kick PS up then, but it's not doing timed breathing for you, again like real vents ST, ST-A, AVAPS modes.

[jaredihnen]

Ahhh... I see.  I recall seeing one of ResMed's ASV marketing material showing a diagram that looked like if your average tidal volume was 300ml and you started an hyponeic phase, it would provide PS sufficient to reach that 300ml average.  Looking closer at the marketing material it says that the machine is targeting an average minute ventilation from the previous 90 sec.  I guess I was expecting the machine to maintain a fairly constant tidal volume throughout the night.