(04-11-2013, 10:37 PM)GrammaBear Wrote: Frequently I will wake up with a headache in the morning and I've never had many cpap problems until recently. My AHI is anywhere from 0.2 to 2.5.
My husband suggested that maybe my headaches and the higher CO2 level could be because I cover my head with our blankets.
The reason most CPAP machines cannot be set to pressures below 4 cmH2O is because at pressures lower than 4 the stale air might not be flushed out fast enough. The higher the pressure, the less likely it is that stale air is being re-breathed. Since your profile says you are using a minimum pressure of 11, there really cannot be any problem that you aren't getting fresh air.
Being under the covers will have absolutely no effect on how much fresh air you are getting, unless the machine's air inlet is also under the covers. (And, no doubt, that's not the case.)
If your mouth opens and you have mouth leaking under the covers, this would only increase the air flow. There would be plenty of fresh air but (because of the large leak) the pressure in your throat would probably be too low to keep your airway open. So large leak can prevent the machine from preventing apneas. Apneas often cause headaches.
Having a "good" AHI below 5 does not tell you whether the apneas were short (merely preventing you from reaching deep, restful sleep) or long (causing serious Oxygen desaturations, perhaps leading to headaches and other more serious problems).
I suggest it would be best if you can see if you can manage to download and use ResScan or SleepyHead to monitor your sleep data. You have a great machine for that, and people here on the forum to help you figure out how to do it.
In any case, I think the fact that recently you have started having headaches shows it would be very helpful to take a close look at your machine's data, to be sure your Sleep Apnea is being adequately treated.