(06-18-2016 01:01 PM)nativedancer Wrote: My S9 is a vpap st, and I use the ST setting, which, as I understand it, compensates for any breathing variance. Also, I wonder how important the 90% data are to me personally? Finally, if I do not make use of Sleepy, how can I even determine the 90% factors?
Officially, mathematically, your 90 percentile IPAP pressure was the pressure your mask was at or below at least 90% of the time during the times you were inhaling. It is also the pressure you were at or above at least 10% of the time while inhaling.
Similarly, your 90% EPAP pressure would have been the pressure you were at or below at least 90% of the time while exhaling.
In ST therapy mode, I think when your pressure settings are 17.8/12.6 this means your inhale pressure will be 17.8 cmH2O all night, and your exhale pressure will be 12.6 all night. The difference is 5.2 which is called Pressure Support, the amount the pressure is boosted during inhalation. An ST machine is constantly switching back and forth between EPAP and IPAP in synchronization with your own breathing (or, if you stop, at the backup rate), but the machine does not auto-adjust EPAP or IPAP.
Your machine in ST mode has the backup respiration rate feature, meaning, even if you stop all breathing effort the machine won't stop cycling between EPAP and IPAP. The machine will continue cycling back and forth between 12.6 and 17.8, and when the pressure is 17.8 it will push more air into your lungs and when the pressure drops to 12.6 the air which had been pushed in will exit, keeping some fresh air circulating through your lungs each breath, keeping you perhaps halfway ventilated instead of in complete central apnea. Or, if instead of stopping all effort, if you merely lose about half of your respiratory drive and are exerting about half the effort you normally use when asleep and breathing on your own, perhaps with the machine helping you are getting completely enough air, even when you are providing only about half the breathing effort. Or, if instead of a central event there is an obstructive event, depending on how strong the obstructive event is, there might or might not be any airflow, even though the mask pressure continues to cycle between EPAP and IPAP.
The point is, all night the pressure the machine provided during IPAP was always 17.8 (assuming the Ramp feature wasn't used), and all night the pressure it provided during EPAP was always 12.6 (assuming the Ramp wasn't used).
So the minimum IPAP pressure and the median (50%) IPAP pressure and the 90% IPAP pressure and the max IPAP pressure were all the same, 17.8.
For those who are using bilevel ST mode or bilevel S therapy mode (same as ST mode except without the backup rate feature) or fixed-pressure CPAP therapy mode, the 90% pressure is not of interest. It is significant only to those who are using an auto-adjusting machine.
In an ST machine, it may be significant (or at least interesting) to know what percentage of breaths were patient-triggered (spontaneous) and what percentage of breaths were machine triggered. If all breaths are 100% patient-triggered, perhaps the the backup rate feature is not contributing a benefit (except as a form of insurance; it is there in case it is needed).