My two cents:
I'd put off buying a machine for a while and just continue with the rental machine. The reason why is this: With the growing number of central apneas, there's a chance that you might have
complex sleep apnea, which is diangonsed when a person who has OSA develops persistent problems with central apneas only after starting PAP therapy. Approximately 10% of new PAPers have problems with pressure induced centrals. Sometimes the problem will resolve itself in the first couple of months and no change in machine is needed. But sometimes the problem does NOT resolve, and the person is eventually moved to a more expensive machine---typically an ASV machine or a BiPAP ST machine that can trigger inhalations. A standard PR System One Auto BiPAP is not the same thing and is not designed to trigger inhalations. Since you report a growing AHI made up of a lot of centrals, there's a chance that you will eventually be switched to an ASV or a BiPAP ST, and that's why I recommend continuing to rent instead of purchasing a BiPAP or a Resmed S9 VPAP Auto right away.
The usual criteria for moving a person from BiPAP to an ASV or a BiPAP ST machine are:
- A treated AHI that remains above 5.0
A treated CAI that remains above (or at least close to) 5.0
CAs make up at least 50% of the events that continue to occur while on PAP therapy
There is some flexibility in interpreting these criteria when a patient is also reporting that they continue to feel bad while on PAP therapy---particularly if the patient initially felt better---i.e. that the patient felt better before the CAs started to emerge.
I'd suggest that you take a list of written questions with you to the follow-up appointment with the sleep doc, along with your data.
Finally, a comment on an important pair of differences between the System One Auto BiPAP and the Resmed S9 VPAP:
1) On the System One, the IPAP and EPAP vary independently of each other unless one of the following happens:
- IPAP = EPAP + min PS and EPAP needs to be increased. In this case, both IPAP and EPAP will be increased.
IPAP = EPAP + max PS and IPAP needs to be increased. In this case, both IPAP and EPAP will be increased.
IPAP = EPAP + min PS and IPAP can be decreased. In this case both IPAP and EPAP will be decreased.
IPAP = EPAP + max PS and EPAP can be decreased. In this case both IPAP and EPAP will be decreased.
But on the Resmed S9 VPAP Auto, the IPAP and EPAP are not allowed to vary independently of each other. In other words, IPAP and EPAP are always increased and decreased together and by the exact same amount. The difference between IPAP and EPAP remains constant on the S9 VPAP, whereas it can vary on the System One BiPAP Auto.
2) The System One BiPAP Auto has Bi-Flex, which offers a small (variable) decrease in EPAP pressure at the beginning of every exhalation. In other words, when Bi-Flex is turned on, at the beginning of each exhalation, the pressure can drop a bit below the EPAP setting as a form of additional exhalation relief beyond that provided by dropping the pressure from IPAP to EPAP. The S9 VPAP Auto does not have any additional exhalation relief beyond the drop from IPAP to EPAP. If you are currently using Bi-Flex and you like the way Bi-Flex feels, this could be a potential issue when switching to a Resmed S9 VPAP.
