I also find that colds are easier with my CPAP, since the CPAP is pushing air in it seems to keep my nasal passages a little more open. Also, when I have a cold I turn up the heat on my humidifier a notch -- that always helps me.
I have also noticed "little signs" about myself -- if I find myself randomly "sniffing" (frequently) throughout the day -- when I finally do realize it** -- I know that I need to turn up my humnidifier because I am sniffing due to being to dried out.
**most of the day I am in a fog and have no idea what I am doing or why
