DMR, we first had our respiratory therapist come by and work with Dave while he was on his back in bed. The settings were better, he got a more comfortable mask, but side sleeping caused problems with his mask slipping. Then today, at our ALS Care Team appointment, our pulmonologist tweaked it some more (we had brought it with us), recommended a pillow made especially for side sleepers with bi-paps, then determined that as long as Dave used it at least 4 hours per day while in his recliner to get used to it, he could later change over to using it for naps and then nighttime sleep. Perhaps your respiratory guy or gal from your DME supplier would come by, or you could do what we did and take your NIV with you to your next appointment. Best of luck!