NotMuffy wrote:That would not be "Auto Bipap" in the Classic Algorithic Sense, in that all obstructive events would need to be managed by EPAP; in the CAS, IPAP (or PS) plays a significant role in the management of hypopneas and flow limitation (Popt).
and
NotMuffy wrote:However, the need (or choice) of moving to bilevel or autobilevel therapy is frequently based on seeking greater comfort while insuring effective therapy. This is achieved by setting EPAP at the lowest possible level (that which overcomes all obstructive apneas and addresses vibratory snores), then attacking other events (obstructive hypopneas and RERAs (algorithmically presumed as flow limitations) with IPAP.
This does describe how the PR System One BiPAP Auto works (except for one twist). The PS setting on the System One is the
maximum IPAP-EPAP allowed. Pressure levels work as follows:
- At the start of the night:
- EPAP = min EPAP and IPAP = EPAP + 2
Pressures are INCREASED as follows:
- When the machine detects hypopneas, RERAs, and flow limitations:
- If IPAP - EPAP < PS, JUST the IPAP is increased---until the problem is resolved OR IPAP-EPAP = PS OR IPAP reaches the max IPAP setting.
- If IPAP - EPAP = PS, then BOTH the IPAP and EPAP are increased---until the problem is resolved OR IPAP reaches the max IPAP setting.
- If IPAP = max IPAP, then neither IPAP nor EPAP is increased.
When the machine detects OAs and vibratory snores:
- If IPAP - EPAP > 2, JUST the EPAP is increased---until the problems is resolved OR IPAP-EPAP = 2 is reached.
- If IPAP - EPAP = 2, BOTH the IPAP and EPAP are increased---until the problem is resolved OR IPAP reaches the max IPAP setting.
- If IPAP - EPAP = 2 AND IPAP = max IPAP, then neither IPAP nor EPAP is increased.
It is important to note too, that the PR System One does use the Resprionics "hunt and peck" algorithm for raising the pressure periodically to see if the wave flow improves (as defined by that mysterious Popt variable) even in the absence of events. The hunt and peck algorithm ONLY raises the IPAP pressure, however. It does NOT affect EPAP if IPAP - EPAP < PS.
The S9 VPAP Auto, on the other hand, uses the PS setting as the
fixed difference between IPAP and EPAP. In other words, on the S9 VPAP Auto, it works like this:
- At the start of the night:
- EPAP = min EPAP AND IPAP = min EPAP + PS
Pressures are increased as follows: When the machine detects OAs, hypopneas, flow limitations, and vibratory snores:- If IPAP < max IPAP, then both IPAP and EPAP are raised (so IPAP - EPAP = PS at all times)
- If IPAP = max IPAP, then neither IPAP nor EPAP are increased.
So a pair of questions to NotMuffy:
1) Does this mean that the Resmed S9 VPAP Auto algorithm is the "Classic Bi-level Algorithm" and the PR System One BiPAP Auto's algorithm is attempting to better mimic what actually goes on in a bi-level titration study?
2) Which in your opinion is more likely to provide more comfort for a person who is being switched to BiPAP Auto primarily for comfort reasons? (I.e.for folks can't seem to sleep with straight CPAP/APAP and/or has serious aerophagia problems with straight CPAP/APAP even with pressure relief turned on.)
moresleep wrote:I don't know anything about the algorithym used, but those most likely vary considerably from machine-to-machine, anyway.
Yes they do, which should prompt people to exercise their due diligence before selecting a machine.
Ah, yes, but how is the user who is facing a choice between the S9 VPAP Auto and the PR System One BiPAP Auto supposed to exercise that due diligence: DMEs won't typically allow you to try out the blower for 15 or 20 minutes before you make the decision.