I made this adapter to go out the back of my AirSense 10 CPAP machine sideways rather than straight out. I also used a hose clip to bring it around the side of the machine for front exit: http://www.thingiverse.com/thing:3759686. The right-angle exit makes it much easier to place the CPAP machine in limited space.

This comes in two parts, the elbow and the coupler. I made the elbow out of standard PLA, and it's from the Tinkercad parametric elbow tube shape, customized for the CPAP 22mm OD to fit standard hoses. I put a standard-ish 15mm ID on the elbow.

The coupler I made out of TPU to make it a little more stretchy for a good and adaptive fit. You can make it out of PLA but you may have to chamfer the inside to fit the other parts.