not to fragment the existing thread on the sinus infection/ CPAP topic, but I wanted to break off separately some links on the subject that were generously compiled by j n k:

"Our results suggest that patients using CPAP therapy either with or without heated humidity seem to be at an increased risk of upper airway infections compared to conservatively treated patients."--http://content.karger.com/ProdukteDB/produkte.asp?Aktion=ShowFullte...

" . . . It is best to avoid using CPAP when you have a cold or sinus infection . . . Sometimes the congestion remains in the ears and sinuses after the acute symptoms of the cold are gone. If you develop headache or ear pain on CPAP, speak with you sleep specialist. In the interim you may try decongestants or antihistamines. Check with your doctor before you take these medications. . . . " -- http://www.sleepapnea.org/resources/pubs/wrong.html

"Patients using heated humidifiers without regard to good hygienic practices in maintaining their humidifiers by thorough cleansing and replacing their breathing tubes showed a dramatic increase in upper airway infections, compared with those who cared for their equipment regularly, when examined over a 6-month interval . . . " -- http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2556912/

You may want to listen to Dr. Krakow discuss related sinus issues:

http://sleeptreatment.com/allergy-video-series