* Participants undergo PSG, lying on their backs while their breathing route is recorded for about 30 minutes.
* The participants are then put on their prescribed airway pressure support with the first randomized mask, and their breathing is recorded again for 30 minutes.
* The mask is switched to the second mask, and the same procedure is repeated.
Participants are then moved to the sleep laboratory for the night where they are provided with beds.
* They continue NIV therapy with the last mask used during the awake test.
* After at least 60 minutes of recording, participants are awakened to switch back to the first mask. They are then allowed to sleep uninterrupted for the rest of the night.
