Hi, Tracy, the "target volume" on AVAPS can be set as low as you need it to be. Yours is probably set too high, so the machine is amping up the pressure more than you can handle (and likely need). It is a good idea, though, to run in AVAPS mode if you are experiencing air hunger, because that way your pressure can adjust according to your stage of sleep. I can tell you how to adjust it, or you can ask your RT to do it -- my gmail is lmgelb. Not knowing your height and condition, I would start the Vt at 400 or so and stop at the point where you have less air hunger and can handle the air flow. There are other settings like the length of each breath that might bear some adjustment as well. It's also possible the EPAP or range is set too high, if your IPAP is 21. Some RTs/docs don't like large intervals, though they can be very helpful in MND.