Jourdain - as you confirm, sleep aponea is serious, every time the sufferer's breathing is interupted, the heart kicks up additional work to re-start it, which can lead deventually to damage and even a heart attack in his sleep.
When diagnosed, my incidents were over ninety an hour, and as you say, the sufferer is unaware of what is happening.
The device takes a little getting used to, but if it is like mine, they can actually monitor and adjust it remotely from the hospital, without the need for me to take the machine in.
It may need adjustment to get the optimum air level right, a bit of trail and error.
The machine does have two buttons, one to switch on and off, and next to it, a button to re-set it to its first setting, for when he is going to sleep.
He may find that when the machine detects stoppages, and increases the air flow, it wakes him up, and he will neeed to press the re-set to stop the force ten gale blowing into his face!
Good luck with it.