A significant difference in detecting hypopnea events exists among the H 2012, H Rec and H Alt definitions. The 2007 AASM "Recommended" definition tended to result in lower AHI than the other two definitions.

Current evidence suggests that the nasal mask is better tolerated, requires lower pressure to eliminate obstructive respiratory events, and is associated with a better sleep quality and better PAP therapy compliance. Nevertheless, the best mask is the one that patient will wear.