Hi, welcome to the forum, the side effects of using CPAP are Mask leaves marks on face, Nasal bridge discomfort, Nasal congestion, Dry
nose during use, Dry
or red eyes, Ear pain etc. In some cases it can cause prolific rhinitis along with nasal drip.
Such accumulation of postnasal drip on the posterior of the tongue dorsum, Poor oral hygiene, Improper dental care, Mouth breathing and infection of the sinus or throat are the causes known to cause the bad breath.