The second study, as others have said, is important.
Some people have "adverse" reactions to the CPAP pressure as they increase it. The reaction is to have more Central events as the pressure is increased even though the Obstructive events cease. This does not mean the person has Mixed Apnea. It is just something that happens to some people. They would be able to determine this as they do the study.
Some people cannot breathe out against the pressure, especially someone with low lung function due to lung issues or heart issues. The face he is having heart issues is important. You want him to have the optimum pressure determined.
Once he has the second test and once you know the pressure, then you can find out your out of pocket expense. What happens after the "rental" period ends? Usually the rental period is to make sure they don't fork over money for a machine and then he not use it. It is all about compliance. If the patient is compliant, some insurance companies then go into a kind of "rent to own" deal with the supplier. You continue to pay the 20% until the machine is yours. If your out of pocket money is more than buying one outright from Supplier #2
, then get it on your own.
BUT this means you are also on your own for supplies for the machine, such as hoses, filters, and replacement humidifier tubs. And make sure the insurance will still cover the cost of the mask if you buy your own machine.