I use the same machine and mask. It is actually very hard to inhale through your nose and exhale through your mouth, especially after you fall asleep. What tends to happen is that air escapes continually though your mouth and makes a large leak. It may or may not affect your AHI results. But, it is most likely to give you a very dry uncomfortable mouth and throat. One way or another one really needs to stop the air loss through the mouth. A chin strap is a good first step if you cannot learn to keep your mouth closed even when sleeping. Some find that putting your tongue on the roof of your mouth behind your top teeth helps. It does when you are awake, but the trick is to also do it when you are sleeping. I have tried a few different chin straps and the Breathewear Halo is the best one I have found so far.
Another question: Is the starting "pressure" always '4'? During sleep, what pressure is reached?
When you start your machine up to go to sleep the display will show the starting pressure in the middle of the circle. In the top right it will also show the minimum and maximum pressure it is set for. It would be helpful if you would say what it is currently set at.
The very lowest pressure the machine can operate at is 4 cm. The minimum pressure can be set there, but for most that is not an ideal setting, and can you leave you feeling starved for air when trying to go to sleep.
Depending on how your machine is set up, you may be able to see a sleep report that reports the 95% pressure. That is the pressure at which 95% of the time during the night it was less than that. It is not the peak pressure, but is usually quite near the peak pressure.
But, if you really want to see what is going on with pressures and mouth leaks during the night I would suggest using a free software program called SleepyHead. Here is an example of what it can show you. That period of time from 3:00 to 3:30 is probably a mouth leak. Leak rate is high, and it has a fairly flat top to the curve indicating a constant but high leak rate. And the green trace in the pressure chart shows the pressure during the night as it responds to events. If you want more info on SleepyHead just ask.
When I start my machine, the number in the middle of the circle is '4'. At the top right, the display shows: Pressure 4.0 - 20.0. (There doesn't seem to be any way to change the minimum and maximum pressures). Ramp-up is 'Auto'.
I have to stay semi-awake so I can consciously keep my mouth closed so I can exhale through the nasal pillows. Then, after about one hour of use, I have to turn the machine off and remove the nasal pillows so I can fall asleep. (That defeats the purpose of the machine). What am I doing wrong?
Note: Apparently, this machine is a 'loaner' that is NOT set up so I can see the Sleep Report. After using it for 3 nights, I return it to the Sleep Clinic. A 'permanent' machine will then be shipped to me. When it arrives, I'll install the SleepyHead app so I can see the chart in your example.
If you have a spare SD card lying around from a tablet or camera, you could put it in the SD slot on the top left side of the machine. You can't really get the previous nights data back, but you can get data going forward. To read the data in SleepyHead you have to transfer the data from the SD card to a PC or Mac using a SD card reader.
The way that machine is set up it could be uncomfortable, because it is essentially in default out of the box for settings. The machine max and min pressure is 20 and 4 cm. Normally it would make more sense to say set the minimum pressure at 7 cm, set the EPR to 3 and Ramp only. That would then cycle the pressure on inhale to exhale from 7 cm down to 4 cm while you are awake. Then it uses 7 cm as minimum when you go to sleep. My guess is that they are just trying a wide open machine to see how you respond to pressure and whether or not it controls your apnea, and what pressure it takes.
On the mask issue you either have to learn to keep your mouth closed, or use a chin strap, or go to a full face mask which covers your mouth and nose.
Your machine is a good one, and I would try to get that same model (but with a SD card in it) for your permanent machine, if you are going to be prescribed one. Here is a link to a technical manual which gives you more detail on what the machine can do. See pages 4 through 11. In fact if you get to choose your machine I would ask for the ResMed AirSense 10 AutoSet for Her. The "For Her" model has an extra optional mode which can be useful to a male or female, if they need pressures in the lower range. You can set the machine to use it, or just use the standard mode. The price is the same.
How can I change the machine's default settings so the minimum pressure is 7 cm, the EPR is 3 and Ramp only?
That manual I gave you a link to explains in detail how to do it, if you feel confident enough to do it yourself. That is normally something that is adjusted by a sleep technician. That said, you would be just changing the Minimum Pressure to 7 cm, and the Ramp Start pressure to 7 cm also.
Gary, another thing to consider is calling your machine provider. This machine is capable of sending data to them, and they can change settings wirelessly as well. That may be a more prudent way to change things during a trial machine phase. Just tell them what issues you are having, and that you are not able to use it all night. That should concern them enough to make some changes to the settings to improve comfort.