Constant Pulmonary Airway Pressure machine. To mine this sites for all threads, go back to the main page, then click the "Search" button near the top, and search on "apnea". There are only 11 or so threads, but you can get what everyone has said before.
I use one, and it does help. Cheaper and better than losing a job because you keep falling asleep there, or better than dying and killing your family as well when you fall asleep while driving. There ARE other things that can at least contribute to apnoea (English spelling), the largest (naturally) of which is being overweight. It's a factor in my case, but it's not the only one - my father and at least one brother both have it, and they're not overweight.
DO find out what new prices are, then buy a good second hand one if you can. You can make BIG savings, but remember you'll probably want to buy new mask and tubes, air filters and humidifer bowl if it uses one.
Remember that you will need either to be able to adapt the air pressure of one you buy, or pay an expert to do it.
Think about sleep arrangements. The machine does make a noise at night. You can get used to it - it's no worse than an air-conditioner, but it IS there. The machine also delivers more air than is needed to breathe - that's why it works. The "more air" (pressure) keeps the pulmonary airways open, but it means there's a bit of a draft as well. Again, not unbearable, but don't be surprised by it later. If necessary, stand a pillow on edge between your pillows to block the wind - sleeping in separate beds is NOT a good idea.