I'm a recently-diagnosed user and I was originally supplied with a Respironics System One CPAP with it's associated humidifier and a ResMed Quattro Air full-face mask. After approximately 10 days of all-night use (I'm highly motivated for this therapy to work) I was still seeing AHI's of 15+ so my DME "sleep concierge" (as she calls herself) came by yesterday and provided a System One BiPAP/Bi-flex pump in place of the original unit. First night AHI was 12.5. (FWIW, I'm a stage 4 throat cancer survivor and my trachea is small due to radiation treatment scar tissue.)
Being a design consultant/engineer (entertainment/control systems) the first thing I did was hold down the two buttons (duh) to take a peek at the "protected" settings – which drives my DME berserk even tho I NEVER change anything without her approval (thus far). I noticed that the "hose" setting on the BiPap is set to "15H" even tho I have a 22mm hose. When asked, DME said "mismatch doesn't matter" but my Inner Engineer says "Phillips wouldn't have put the variable in there if it didn't matter". I'm sure my college fluid dynamics prof would have said that "the flow/pressure characteristics of different size hoses would indeed be different"... but whether or not it's important in this application I truly don't know.
Any info anyone can provide would be most appreciated.