jedimark wrote:
Now, I have a couple of BIPAP / VPAP / VPAP/ST / ASV Questions you may be able to help me with.. I've probably asked this before, but I was way too foggy for any of it to sink in. (Forgive me if any of you have explained this to me before, I really am a little slow sometimes.)
Does EPAP on any of these machines types vary, or is it set to a constant? If it varies, what determines the range? I'm assuming for BIPAP the Pressure Support is constant distance between EPAP & IPAP.. but what happens on ASV or ST machines where IPAP is variable? Does EPAP remain constant then?
My answers are for the PR BiPAP Auto---when run in both "fixed" mode and "auto" mode and with Bi-Flex turned OFF. (See the note about Bi-Flex at the end of this discussion.)
Fixed Mode with no RAMP: If you don't use the ramp feature, then EPAP and IPAP should both be constants.
Fixed Mode with a RAMP: If you DO use the ramp, then starting EPAP = ramp setting (default is 4cm) and starting IPAP = starting EPAP + 2. Both EPAP and IPAP ramp up to the full setting in a linear fashion I believe. But since the IPAP setting is typically greater than EPAP+2, that means that the IPAP line is steeper than the EPAP line. So during the ramp period, the PS = IPAP-EPAP is not a constant: PS starts at 2cm and ends at IPAP-EPAP. So we get the following ranges:
- Ramp setting <= EPAP <= Set EPAP pressure duing ramp time; EPAP = Set EPAP once the ramp is over.
- Ramp setting + 2 <= IPAP <= Set IPAP pressure duing ramp time; IPAP = Set IPAP once the ramp is over.
Important note about PS on the PR System One BiPAP machines. When running in AUTO mode, the PS on the PR BiPAP Auto is NOT a constant. The machine's PS setting is the
maximum distance allowed between EPAP and IPAP; the
minimum distance allowed between EPAP and IPAP is equal to 2cm. In other words, when a PR BiPAP is running in Auto mode, we get
- 2 <= actual PS <= PS setting on machine where actual PS = IPAP - EPAP at the current time.
AUTO mode with no RAMP: At the beginning of the night, EPAP=min EPAP and IPAP = min EPAP + 2. The two pressures are largely allowed to vary independent of each other. So without a RAMP, the pressure ranges are as follows:
- min EPAP <= EPAP <= max IPAP - 2
- min EPAP + 2 <= IPAP <= max IPAP
AUTO mode with a RAMP: Just like in Fixed mode, EPAP starts out at the ramp setting and IPAP = ramp setting + 2cm. As long as there are no "events", EPAP and IPAP increase linearly to where they reach EPAP = min EPAP and IPAP = min EPAP + 2. If any events occur, the machine will increase the appropriate pressure by a cm or two and then continue ramping up from there. Once EPAP = min EPAP, then the pressures change based on the Auto algorithm and the two pressures are largely allowed to vary independently f each other. So with a RAMP, the pressure ranges are as follows:
- ramp setting <= EPAP <= max IPAP - 2
- ramp setting + 2 <= IPAP <= max IPAP; once the ramp period is over, min EPAP <= EPAP and min EPAP + 2 <= IPAP.
A NOTE about Bi-Flex turned ON: I don't know if the machine records the subtle differences in EPAP that are caused by the "extra-relief" and "rounding" that you get when Bi-Flex is turned on. Unlike the Resmed EPR algorithm, the PR Flex systems apparently do not reduce the pressure by the same amount on each exhalation----the amount of relief depends on how forceful the exhalation is: The larger and more forceful the exhale, the more relief is provided. My understanding of Bi-Flex is that the pressure increases back up to the full EPAP setting sometime around halfway through the exhale. And then there's some kind of "rounding" that takes place when you start your inhalation that is to gentle the transition from EPAP to IPAP. I'm sorry I'm so vague here, but I didn't like Flex and turned it off within a few days of getting my PR BiPAP Auto.
What are the most important statistics to show for a line in the prescription changes table?
For example, for BIPAP it shows a table containing the date range, number of data days, AHI, EPAP, IPAP, EPAP 95%, IPAP 95%
(Flex/EPR types will be added to this list soon, I haven't forgotten.)
On the BiPAP Auto machines, PS and PS 95% would be nice since PS is NOT a constant on these machines; on the Resmed machines, PS is a constant and hence not really needed.
Final note: Right now SH always shows my "Flex = 2" even though I haven't used Flex in months and months. (I briefly did an experiment with both Flex and Rise Time some time way back in March 2011. It would be nice if SH could pick up my Rise Time setting. Rise Time is only available if Bi-Flex is turned completely off; so most folks don't know about it or care about it.
