The reason presumably to keep our mouth shut is to avoid breathing through the darn thing, and conversely, letting air escape through it. For best results we need to sleep breathing, inhaling and exhaling, through our cute little nosies. OK... But how to do that? In some cases folks think they cannot breath through their nosies. But yeah, in many or most cases they can. Just hook up one of our cute little cpap machines with a pillows mask to the end of your nose, fire it up and see how much better your nose performs than you ever gave it credit to be able to do.
As I mentioned to my friend Eric a little while ago, it's really not about keeping your mouth closed. In fact, a closed mouth can simply create a place for air to build up until your cheeks poke out in all directions and something pops. You can actually spend the better part of the night sounding like "The Little Engine That Could." Or maybe "Puff, the Magic Dragon." But not getting great results from your cpap therapy.
So it's not about keeping your mouth closed.
It's about being able to sleep with your jaw remaining forward in a natural, but not "clenched" state. It's about using one of the most amazing tools God ever invented for something other than eating and kissing. It's about making an air-seal with the tongue at the roof of your mouth. Something you can't do if the jaw isn't hanging around in the forward position.
A little test: Sit back, relax, and allow your jaw to drop backwards. Now being all relaxed and such, your mouth probably natural tries to stay a little open? If you force it closed, then the odds are pretty good that you won't breath through it. But apply a nice stream of cool refreshing air from your cpap through your nose and see if your cheeks don't start to look like balloons. Until they pop. Even if you glue the darn thing shut, the cheeks will still fill up, then sooner or later -- pop.
The other thing you can't really do all that well when the jaw is laying back is block the airway with the tongue.
Now, move the jaw forward so that your teeth meet, or are close together, but nothing is forced. Don't even try to make sure your mouth is securely closed, that is not important. Now place your tongue on the roof of your mouth to make the airtight seal. Notice how you can inhale and exhale through your nose even when your mouth is open.
Some of us can do all that while we sleep without any assistance. Some of us (me included) need to use a chinstrap to help get it done.
What a successful chinstrap will help you do is keep your jaw from falling backwards when you go to sleep and your body relaxes. With it forward, your tongue can take it's proper place at the roof of your mouth which creates the air seal. A very effective air seal as a matter of fact. Once you're good at it, you can open your mouth and listen to all the funny noises even.
There is a technique involved with a chinstrap that needs to be used:
1. It's not about lots of force, but rather a gentle encouraging to keep the jaw forward. If you use a lot of force your jaw will tense up, your teeth will clinch, and during the night the whatsitcalled gland in between your jaw and your ear will begin to hurt like crazy go nutz. So gentle encouragement. Not force.
2. About comfort: I don't like wearing a chinstrap. I do find that odd, because I don't mind wearing a mask. But chinstraps bother me. So for me, the best chinstrap is the very simple single strap things that are as minimalistic as possible. Lots of people do better with the ruby-reds, or equivalent that suck up your brains. But not me. I like something as small as possible. And I wear it under my P10 mask so that when I get up in the night I can remove my mask without fooling with the chinstrap.
3. The conventional wisdom is to wash them frequently. I try to wash mine at least once a month, when I also wash my socks. But don't make the mistake of putting an "almost-dry" chinstrap on when you go to bed. It's not a good thing.
So mastering the technique of breathing through your nose while maintaining a seal in your mouth with your tongue is something that will allow you a much more pleasurable cpap experience.
There are those among us that simply use full face masks thinking that it will not matter if they breath and exhale through there mouths. They are misguided. They are being kept from migrating to the P10 pillows mask. Which of course sooner or later everyone will use. Resistance is futile.