(02-20-2014, 02:43 PM)Kate Wrote: I have an ASV machine.
What is mask pressure? It seems to be different from the pressures that I have set (4/8). It varies between 8 and what I believe is I believe 17.
Quote:The graph looks like an almost solid blue line between 8 and 15 with spikes to 17. It does not look like anything I've seen from other people.
Mask pressure is the pressure delivered at the mask by the machine. The pressure curve shows just the current set pressure for the EPAP
pressure on your machine, if I recall correctly.
It sounds like your EPAP pressure is allowed to range from 4cm to 8cm as the machine responds to OAs, Hs, Flow limitations, and snoring. Or perhaps you are using the ramp and the initial ramp EPAP is 4 cm.
But an ASV machine is only prescribed when a person has real problems with central apneas
. And an ASV machine has a couple of other important setting for explaining why your mask pressure graph looks the way it does. Those setting are the min PS
and max PS
pressure will always be between EPAP + min PS and EPAP + max PS. And the variation in the mask curve (if you zoom in far enough) will show how the pressure is increased from EPAP to IPAP and then decreased back to EPAP as you cycle through inhalations and exhalations.
It's also worth pointing out how the ASV machine treats central apneas by monitoring the frequency and depth of the inhalations. When the machine's ASV algorithm is not happy with your overall breathing effort
, it will then step in and start "triggering" breaths: In other words, the ASV algorithm will start increasing the IPAP pressure drastically
in an effort to force you to inhale. In ASV mode, it is possible for the IPAP to suddenly increase over a few breaths up to where it is 10cm (or more) higher than the EPAP pressure.
The docs who treat us and the engineers who design our equipment also seem to believe that a pretty significant difference in IPAP and EPAP pressure may
help the CO2 overshoot/undershoot cycle that is at the root of central sleep apnea from developing in the first place.
So if I had to make a guess, I'd guess than your EPAP is hovering around 8cm most of the night and that your max PS setting is at least 9cm. It sounds as though you are spending much of night with
IPAP = 15 (and spikes to 17 when the machine is triggering inhalations)
EPAP = 8 (so the machine is running at or near max EPAP most of the night OR your machine actually has a fixed EPAP = 8 and you are starting the night off with a ramp period where the starting ramp EPAP pressure is 4cm)
Quote:What is making this happen? The mask almost lifts off my face when I have the machine going.
What's causing the mask to almost lift off your face is that rather large difference between and EPAP = 8cm and an IPAP in the 15-17 cm range. It is, alas, part of what's expected when using an ASV to treat central apneas. And learning to deal with it is, an unfortunate part of needed an ASV machine to treat problems with central apneas. Mask liners might help.