Double check with your DME about the monthly rental rate, $400 sounds high for a straight BiPAP or autoBiPAP, unless your rent-to-own period is a lot shorter then most or something. I know the allowable for Medicare for BiPAP ST (E0471) is $600-675, depending on where you are in the country, because that's what I have. I checked regular BiPAP (EO470), and it looks like its around $215-260 (depending on state). Medicare 2006 Fee Schedule for Respiratory Assist Device (RAD), Bi-Level Pressure Capability, without Backup Rate
Most insurance companies, including Medicare, will 'rent to own' equipment like CPAP & BiPAP for about 12-18 months; some insurance companies will purchase immediately or after 3-6 months, while others continue to rent forever & ever. Sometimes insurance companies may even pay for a CPAP outright, but rent or rent-to-own a BiPAP because of the difference in cost. You would have to speak to your DME's billing department directly to find out what your situation was and how many months your insurance had paid in & how many are left before you take ownership or what the deal is. Do you have insurance now and is it going to cover your BiPAP & related supplies? Is there a possibility the new insurance would cover the purchase of your machine? Your DME may write off the months you owe for then; I had something similar happen with some of my other medical equipment and my DME wrote off a lot of $$$$. At the least, maybe you can get them to accept an amount equal to Medicare's monthly rental, for the months you are responsible for.