wow, it looks like dr. warwick himself has tried to weigh in on this thread!
i wanted to say, i have tried both the Hill Rom and Respirtech. for those of you who are interested, there have been a lot of other threads on this you should search for. my input is that i liked the Respirtech better because i feel the product is superior and the people at the company are very helpful and kind.
the only advantage to the Hill Rom is that is it slightly quieter and more easily portable. for me, these weren't big enough of a deal to outweigh all the other stuff.