(05-18-2014, 07:59 PM)BiBob Wrote: what is the criteria for selecting PS?
Initially, Pressure Support (PS) is most often set for comfort. Later, it may be optimized to improve sleep quality.
At the tail end of an overnight titration, after an adequate pressure has been identified which largely prevents apneas and hypopneas, the technician may explore the effect of increasing PS in order to further reduce Respiratory Effort-Related Arousal (RERA) events, which are arousals from sleep caused by respiratory effort but not accompanied by apneas or hypopneas. The number of RERA events per hr is not included in the AHI.
Sometimes excessive daytime sleepiness continues to be a problem even after the AHI with CPAP treatment looks fine, and sometimes RERAs may be the reason; RERAs may be preventing deep restorative sleep, and increasing the PS may help this.
But too high of a PS can also cause problems, so higher PS is not necessarily better and for some patients may lead to excessive Central Apneas (more than 5 per hr and outnumbering obstructive events).
I don't think central apneas are more alarming than obstructive apneas. (I think a central event if shorter would be preferable to a longer obstructive event.)
The PS will also have an influence on your blood Oxygen level (SpO2). If the SpO2 is too low or too high it can cause problems.
So I recommend buying a recording Pulse Oximeter. A great target range for SpO2 is 96% to 94%, or perhaps a little lower while sleeping. If the average SpO2 is below 90%, increasing the PS will tend to raise SpO2. If the average PS is above 96%, decreasing PS will tend to lower SpO2.