Waking up at night wth shortness of breath after using cpap.

My father has recently been instructed to use the cpap machine. He's been using it for 3 nights I believe and every night he's used it he says he wakes up in the middle of the night and is short of breath. It's not something that he can just take a few deep breaths and the goes away either. He feels like he can't get a good breath for about 20 minutes. (Forced yawning helps). How much of a concern is this? Will this go away? What should be done? This has never happened without the machine. He says he's fine for the first 4 hours of the night sometimes than he is awoken by this. Any input would be greatly appreciated. Thanks

Just wondering what pressure he's using on the cpap? The pressure on a cpap can be set low enough that you can get the feeling that you're not getting enough air. When I first got my cpap it was set up with a ramp from 4 to 10cmH2O...When the night started it was hard for me to breath, I felt like I wasn't getting enough air...so I turned the initial ramp pressure up to 6, and then turned off the ramp completely shortly after that. Then no problems.

So if you could give some more information about what cpap he has, and what pressure he's using, that would be very helpful. If it isn't that, then it may be something that needs a doctor's attention. But more information would be really helpful.

Thanks.

And is he taking any medication, and does he use the humidifier (at what setting)?