Why is my AHI so high?

jnk wrote: the best way to keep the ipap from going too low on that machine is to make sure the epap isn't set too low. Right?

Or maybe my brain lesions are acting up. If so, never mind.

jnk

On that particular machine yes. IPAP settings vary by machine, your VPAP may have a IPAP "Minimum" setting separate from the IPAP "Maximum". But with the Remstar Bipap Auto it does NOT have a IPAP "Minimum" setting at all.

The only Minimum and Maximum settings it has for pressure is IPAP Maximum and EPAP Minimum. Once set, that is the maximum "range" pressure can move up and down between those two markers. It is shown on the Encore Reports as the top and bottom bar in the pressure graph.

"Working pressure" of its auto algorithm works between that range and is shown on the report in the center of that upper and lower range. Those move up/down as events dictate.

Pressure support has its own Minimum and Maximum and it falls in the center of those two, seen as seperation between IPAP and EPAP "working pressure". Higher the PS the greater the distance seen on that report. You will notice on the Encore reports that IPAP and EPAP pressure never get closer than 2 cm together (i.e. you won't see 12/12 cm pressure on this machine). You can make it wider using a higher PS value but you cannot make it any lower than 2 cm as that is the hard-coded minimum Pressure Support (PS).

One way to look at it, is if you "stack" IPAP pressure on top of EPAP pressure in a tube or column, EPAP would be on the bottom Pressure Support in the middle and IPAP on top. By increasing the maximum PS you lengthen the height of that column without changing the height of the other pressures. How much you control that height can impact your respiration rate or manipulate how it handles an event. That is the "band" of Pressure Support I spoke of above.

On that particular machine IPAP Max only controls how high that tube of pressure can get. EPAP for the most part does most of the work like CPAP pressure, allowing IPAP to climb higher on its own with greater separation allows you to address those residual events like HI while maintaining a consistent lower EPAP pressure resulting in greater tolerance. Manipulation of those two pressures and tube height can also impact your respiratory rate. In other modes (like Bipap/Bilevel) there may be other settable parameters such as Rise Time etc.. With this machine it has digital autotrak, which automatically adjusts the rise time etc. on its own.

Other types of Bipaps may have a IPAP minimum setting such as the AdaptSV or S/T models but this one doesn't.

Thanks, Snoredog, for all that info.

Yeah I find the approach of BigEd's machine fascinating. In some ways it makes more sense than my machine's approach in that it allows the distance between experienced ipap and experienced epap to vary overnight.

On my machine the clinician (or, user) sets the distance between ipap and epap, and that distance always remains constant, no matter what, overnight. The clinician/user sets a minimum epap and a maximum ipap (or leaves the machine at the preset 4-20). That general approach makes sense to me too, but it is definitely coming at SDB from a different angle, seems to me.

I wonder which works better in practice? My assumption would be that either approach would work fine, as long as the approach was elegantly executed. But I hear some feel that one machine's approach might be better for some people and the other machine's approach might be better for others. I'm gonna go looking for those threads, I think, just out of curiosity, if I can find them, to see which people benefit most from which machine, if that's ever been hashed out.

Please pardon my hijack, BigEd.

jnk

jnk wrote:
Please pardon my hijack, BigEd.

Not a problem. I now have a great understanding of how my machine works.