I've used a regular mask (just over the entire nose, not full face) for over 20 years, but since it's no longer made, I thought I'd try a nasal mask. I ordered a Dreamwear Nasal Mask by Philips Respironics, used their measuring template and landed on medium. When I tried it, it was very comfortable, but two problems were apparent immediately. First, the exit vent opening that passes air out of the mask is very small, so there was a noticeable increase in pressure that the cpap didn't respond to. Second, because the exit opening is so small, it doesn't pass enough volume out after and exhale, so I was doing a lot of rebreathing, resulting in a drop in blood oxygen. Ultimately, it's going back, but I have no idea what to try next.
I ordered from cpapman.com, and so far it's been disappointing since the original owner sold the company. The "support" person didn't even understand basic cpap, and could only parrot a script he'd been given. His response to my rebreathing complaint was "Most patients take some time to adapt to the cpap before they're comfortable with it". Um...20 years, full compliance every night...I think I got it.
All input is welcome.