Keeping mouth open

[Made]

I have posted on this forum before about how to keep my mouth open or more exactly how to keep my oral airway open.

As I have both a Deviated Septum and Nasal Polyps I have to use a full face mask (Simplus or Vitera)

If during the night my oral airway closes my Resmed S10 reponds to the nasal flow limitations by increasing the pressure up to maximum.

The question I have is how can my oral airway close but I still have restricted nasal breathing

[PeaceLoveAndPizza]

You said it yourself. If your mouth is closed the air has no path other than the nose. If the nose is flow restricted then the machine has to increase pressure as needed until it finally hits max. The nasal conditions causing the restricted flow are still there.

I used an oral appliance for sports from Shock Doctor called Max Airflow 2.0 that is basically a teeth guard with a slight gap between the teeth allowing me to mouth breath. I see a few on Amazon, may be worth a go.

[G. Szabo]

The question I have is how can my oral airway close but I still have restricted nasal breathing

I have posted Alaxo Hybrid Stent with CPAP - Therapy Thread ( 1 2 3 4 ). which you might want to read. 
You can also buy a shorter version, which mitigates your nasal blockage and is much easier to tolerate.

[Made]

I have got it
Even though I am using a full face mask its only the first few minutes before I go to sleep that I mouth breath.
This is very apparent when I have got up for a comfort break and have been unable to get back to sleep.
I think that the back of my throat is closing rather than my mouth closing.
The big question is how do i prevent it closing

[SarcasticDave94]

Throat collapse is likely the airway collapsing which is what properly set up CPAP machines work to prevent.

[Made]

But my nasal airway is still open

[G. Szabo]

But my nasal airway is still open

I am confused, you complaiend before your nasal blocade. 
- If you have a nasal blockage, you can resolve it with a short version (4") of the Alexo stent. 
- If your tongue sleeps back, restricting the flow, then you should sleep on your side and try to tape your mouth. 
- If your airway collapses, you should increase the pressure as SarcasticDave94  implied.

[Made]

My left nostril has a polyp ,which can be controled with steriod nasal spray, which acts like a valve allowing inhale but blocking exhale.
My right nostril has a deviated septum which restricts the air flow in both directions.
This does mean that when I breath through my nose it sounds pretty noisy because of the restriction

If my tongue is slipping back how do i prevent it as I need to keep my oral airway open

Lastly with the pressure at 20cm there is still the same amout of flow restrictions

Increasing pressure does not fix a deviated septums and nasal polyps. Its only surgery which can do this but its considered to be to risky.

Also as im on blood thinners puttting stents into my nose could cause bleeding which could be difficult to stop

[G. Szabo]

My left nostril has a polyp ,which can be controled with steriod nasal spray, which acts like a valve allowing inhale but blocking exhale.
My right nostril has a deviated septum which restricts the air flow in both directions.

It means that you either have to try the stent in your left nose and simultaneously fix your tongue position with mouth taping and side sleeping, or you should live with highly pressurized mouth breathing and mitigate your tongue movement somewhat by side sleeping.

I have never experienced bleeding with the 5" stent (although I do not have a polyp), so you might want to try the 4". Discuss with your MD the risk of some bleeding versus surgery. 

Do you sleep on your back?

[Made]

I have been trying out  a couple of nasal masks but something I dont understand.
I can use them with my mouth open with no leakage 
I read about trying to keep your mouth shut when using a nasal mask to stop leakage but I dont get any leakage.
Why