There are two types of sleep apnea, Central and Obstructive. They differ from causes. Obstructive is a blockage or collapse of the upper airway (could be from large necks, tongues, etc) and central is a result perhaps a neurological or central nervous system lapse. Both can be independent or mixed. Mixed is starting to become more and more common. The important thing is to continue to use the equipment. I have seen a great deal of improvement in many CPAP users. Generally the gov will cover 75% of the cost of the CPAP unit under a program called the ADP (Assisted Devices Program), Oxygen coverage falls under the HOP (Home Oxygen Program). Both programs are for Ontario.
Again,
The important thing is to continue to use the equipment.
Hope this helps with some background info.