Dryness can be a serious issue for people using CPAP, here are some ways to alleviate this: Increase your humidity. The most common fix to dry mouth is adjusting the humidity level on your CPAP machine. You may just require a higher setting than what you are using. Try a different mask. You may be using a nasal mask and your mouth may be falling open, resulting in a dry mouth. Visit your provider to trial a full mask to see if this helps alleviate your dryness. Review your medications with your pharmacist or physician. Often, medications on their own can cause dryness, and combined with your CPAP, can cause troubles. If this is the case it is best to have a review of your medications.