You can use a Resmed AirSense with a nose pillow or a face mask. I only use the nose pillow. It covers the nostrils. You breathe through the nose. The mouth stays uncovered. If you manage to keep the mouth closed while sleeping, this is enough. Between the tube and the nose pillow there's a piece with two mesh vents. When the CPAP increases the pressure, some air is vented through the meshes. When you breathe out, most of the breathed air leaves by the vents. I feel the air: when breathing in only a little and when breathing out a lot. It is a fine mesh creating some resistance but it works because when you breathe out, you temporarily increase the pressure and the mesh lets your stale air out. However when the mesh gets wet by condensation, not enough stale air is vented and you get the feeling of not having enough air. It feels like the head being under the blanket. The first time this happened I was confused. Now I know to recognize and to avoid this situation. If the room air is very cold, this can happen because the air you breathe out can condensate. If you use an air moisturizer, you need to find a balance between temperature and too much moisture. You need to position the tube such that moisture can't flow downwards to the nose pillow.

This all sounds a bit complicated and dangerous, but in reality this works surprisingly well. It really works and it is helpful. I know CPAP devices are a nuisance and need a lot of time and dedication to get used to, but they are able to fix sleep apnea. They give me a good sleep. I needed about three months to find the sweet and deep sleep we humans all need thanks to this bloody contraption. It is a hate-love relationship.