I have been lurking and learning for more than 10 months now and have achieved a lot by reading the posts. My experience appears somewhat different than most. I have not been well-served with a cpap machine jn “auto” mode. My sleep is broken by one or periods (1-2 hour duration each) that are dominated by clusters of what is identified as central (clear air) apneas. The vast majority of these events last 10-12 seconds and only a few are longer than 15 seconds. Resmed claims something like 85% success in distinguishing Obstructive from centrals – but even this small error rate drives my pressure up to max when auto mode is employed. By carefully logging when these clusters appear I have concluded that I am probably awake or at least switching in and out of wakefulness. I have also noticed that during these periods my average respiration rate drops from 12/sec to 8/sec and the tidal volume increases proportionately. I should note that I have been told by my doctor that I have a larger than average lung capacity. It is really not surprising that, during these periods of lower respiration rates a number of 10-second-events would be present – but are these apneas? These periods are often (perhaps always) accompanied by lucid dreaming.
I have benefited significantly from the beginning of my use of CPAP therapy. At my present fixed pressure of 7.4 in H2O my typical apnea rates are 0.0 to 0.3 for obstructive and 4-10 for central. Oddly enough on rare occasions when I consume three or more glasses of wine over an evening these numbers drop to as low as 0.0/0.0 respectively.
In my initial in-hospital overnight sleep test (12 months ago) I was diagnosed with moderate (45 AHI) apnea and 6 months later, on a bipap in-hospital overnight test I had no obstructive or centrals. Some periods of low respiration rate were noted but no low O2 saturation levels were reported.
I tried to do a home titration by carefully scanning my daily data and estimate what pressure would be appropriate if I disregarded the clusters. I came up with 8.5-9.0 and initially set the fixed pressure to 9. I dropped it slowly to 7.4 over the objection of the vendor - but she accepted the results (increased comfort and lower leak rate). The second sleep test was supposed to be a titration but it was a disaster (that's another story) except that it confirmed I was drifting in and out of sleep during the centrals.