Changing from APAP to Bilevel

[alps]

After 17 years on CPAP/APAP my new doctor after a recent split night sleep test has prescribed a bilevel.

About a year and a half ago I moved from Michigan to Denver, CO.  In Michigan my apap set at 8-12 worked well.  Rarely had readings over 5 AHI with most night 2-4.  Almost immediately in Denver my AHI  numbers began going up.  Also they were inconsistent from night to night (I use Sleepyhead to monitor).  My average readings were from 12 to 15.

I went to sleep doctor and after my recent sleep test concluded Bilevel was needed.  My new prescription is a 9/5 setting with Biflex of 3.  I know something about Bilevel but could use a little more info.

I have ordered the Resmed Aircurve 10 VAuto (I believe it also has a place to set it as an S which is a fixed mode).  My question is about the Biflex setting of 3.  How does this work on the Aircurve 10 Vauto or S depending on which mode it is in.  Any expertise here would be appreciated!  Thanks.

[Sleeprider]

BiFlex is a proprietary pressure relief for Philips Respironics bilevel machines.  Its function is to round the flow transitions from IPAP to EPAP and back to IPAP.  Think about bilevel pressure in a square-wave instead of a sine wave, and that is what you get without BiFlex.  See the rounded shapes for BiFlex 1, 2, and 3 below.



In Resmed, the pressure is "rounded" by EasyBreathe™.  It serves the same function, but does not have multiple settings.  Easy Breathe must be manually set in S mode, but is always on in Vauto.  The EasyBreathe wave form looks like ocean waves, and in my opinion (having used both bilevels), the EasyBreathe is more comfortable.  In the case of Resmed, the mask pressure is graphed, and you can see the shape of the pressure curve in that chart.  Here is one of mine.


While you have been titrated to 9/5 bilevel pressure, if you want to use VAuto mode, just set the EPAP min to 5.0, EPAP max to 5.0 and PS (pressure support) to 4.0.  This will provide 9/5 pressure full time with Easybreathe on.  You can of course increase that range of EPAP from 4.0 to 6.0 and with PS at 4.0 will get between 8/4 and 10/6 bilevel pressure in auto mode.

If your events since arriving in Denver have been mostly central apnea, this is not necessarily a fix.  Have you been to higher altitudes at the ski areas yet?  What are your events like up there?

[alps]

Thanks Sleeprider. Very helpful explanation and data.

My events since being in Denver have been divided mainly between obstructive apneas and hypopneas....with hypopneas usually the larger number. Central apneas have been only occasionally indicated.

I have not yet spent any overnight times at the higher altitudes.

[Sleeprider]

You're going to really like the bilevel machine. I made the same change a few years ago and would never look back. Since you do have more OA and H events (obstruction), I strongly recommend using the Vauto mode and allowing it to go higher. EPAP is what controls OA on bilevel, and 5 cm is very low for someone with obstructive events. I think I would set EPAP min to 5, EPAP max to 9 and maintain the PS of 4 (IPAP max 13). Using bilevel on auto mode is really the way to go. I think you might be surprised that you need more than 9/5 pressure.

[Walla Walla]

Just a small correction. On the settings it will read EPAP 5 PS 4  IPAP 13. There's no max EPAP.

Sleeprider is overworked with ASV machines. 

[Sleeprider]

Just a small correction. On the settings it will read EPAP 5 PS 4  IPAP 13. There's no max EPAP.

Sleeprider is overworked with ASV machines. 

Yeah, I even have that machine and can't keep it straight.  

[alps]

Thanks for the correction Walla Walla.

And Sleeprider thanks for the tip on using the auto and setting it in a higher range for OA's.

This place is always a wealth of knowledge!!!!!

[trish6hundred]

Hi alps,
WELCOME! to the forum.!
Good luck as you continue CPAP therapy and also with your new machine.

[holden4th]

I went from APAP to BiPAP of my own volition to see if I could lower my RERAs. This has worked very well and the comfort of being able to use pressure support makes this a step up from APAP.

[Sleepster]

On the settings it will read EPAP 5 PS 4  IPAP 13.

Just to help you understand this perhaps a little better, alps, those settings will show on your machine's screen as

Mode VAuto
Max IPAP 13
Min EPAP 5
PS 4

Assuming you're not using ramp or the machine has ramped up fully if you are, the EPAP minimum setting of 5 plus the PS setting of 4 will mean that you'll have an IPAP of 9 when you start your therapy. Then, if the machine determines from your breathing patterns that you need more pressure it will start to raise both EPAP and IPAP, always keeping them different by 4. The IPAP can increase up to that maximum setting of 13 making the EPAP 9. And if the machine determines that your need for the higher pressure has diminished, it will start to lower it, but never go below where you started.

The advantage of the VAuto mode over the S mode is this ability to change the pressure as needed.

If you do choose S mode then the closest you could get to those prescribed settings would be, I suppose, IPAP 9 and EPAP 4, that would be roughly equivalent to a Respironics BiPAP set to IPAP 9 and EPAP 4 with Bi-Flex set to 3.