Yes, by taping my mouth.

Taping my mouth shut only solves a part of the problem, as my tongue and jaw still collapse downwards when sleeping.

Given I've been a mouth breather for most of my life however, this is good enough until I've acquired some better oral habits.  Baby steps.

BUTEYKO BREATHING! My myologist has even corrected people's deviated septums by having them do lots of Buteyko breathing exercises. No matter how bad your maxilla is, almost everyone can get their nasal passages de-inflamed enough to be able to breathe through their nose. Buteyko breathing exercises force you to exhale heightened amounts of CO2 through your nose, which acts as an anti-inflammatory for your nasal passages. The basic exercise is: While moving (ideally walking slowly, but can be sitting and swaying side-to-side, or standing and marching in place), take one normal breath in, and one normal breath out. Then (yes AFTER exhaling), close your mouth and hold your nose with your hand. Count how many steps you can last before feeling hungry for air. Go 1-2 steps PAST that point, then (keeping your mouth closed) breathe in through your nose. Breathe normally (keeping your mouth closed) for half a minute or so, then repeat.

The two most prominent techniques I've heard of people using with success are: taping the mouth, and chewing (before bed).

Taping the mouth, I have found, forces the body to get used to breathing through the nose. It seems more than willing to do this as well!

As @WrongNotes mentioned above, the other part of the problem is that even if you can keep your lips together whilst sleeping, that doesn't ensure that your jaw is closed! Chewing gum seems to solve this problem, and I have heard of people chewing gum right before bed in order to get their jaws used to being closed.

@snaaaaakes

I've heard plenty of good things about Buteyko, and that's half the problem for me - I can't tell if it genuinely works or is just a never ending sales pitch for Patrick Mckeown.

But maybe I'm just being overly sceptical.   It sounds like you've had some success with it?

My issue is that I'm severely lacking chest/thorax expansion, meaning I cannot inhale a good volume of oxygen.  Do you know if Buteyko is helpful for improving such an issue?

Cheers.

Posted by: snaaaaakes

BUTEYKO BREATHING! My myologist has even corrected people's deviated septums by having them do lots of Buteyko breathing exercises. No matter how bad your maxilla is, almost everyone can get their nasal passages de-inflamed enough to be able to breathe through their nose. Buteyko breathing exercises force you to exhale heightened amounts of CO2 through your nose, which acts as an anti-inflammatory for your nasal passages. The basic exercise is: While moving (ideally walking slowly, but can be sitting and swaying side-to-side, or standing and marching in place), take one normal breath in, and one normal breath out. Then (yes AFTER exhaling), close your mouth and hold your nose with your hand. Count how many steps you can last before feeling hungry for air. Go 1-2 steps PAST that point, then (keeping your mouth closed) breathe in through your nose. Breathe normally (keeping your mouth closed) for half a minute or so, then repeat.

Great that you shared Buteyko, but just to clarify: the airways dilate from the CO2 in your bloodstream, not from air actually passing through your nostrils.

Basically, every single cell benefits from higher CO2 levels and receives more oxygen (CO2 is a catalyst for oxygen reception via the Bohr-Werigo effect). Blood vessels arteries and veins all dilate. This is the number 1 benefit of Nose breathing: it forces you to breathe less and maintain a higher CO2 level.