dsm wrote:One thing we all need to appreciate is that with such a small gap between epap & ipap, the mechanism for dealing with centrals is all but negated.
To explain ...
The PS mechanism doesn't respond to centrals only to the 4 min Peak Flow Target. The Central mechanism is purely the breathing timing (set from the back-up rate) & probably the reason why the RT set a back-up BPM of 10 - if Wendy drops below 10 BPM then the Central mechanism kicks in but if the epap to ipap gap is a mere 1 CMs or 2 CMs the central mechanism has little pressure to get Wendy breathing again. If Wendy doesn't breath in (due to a central) the PS algorithm sits there waiting until she does, it is not time driven but is flow target driven. The back-up rate is the timing by which the machine on its own flips from epap to ipap but if the pressure isn't enough & the central persists then PS doesn't get activated.
To me a
- 2 CMs gap is the bare minimum epap to ipap gap for a normal user
- 3 CMs is more optimal for normal users
- 4 CMs starts to benefit people with centrals
- above 4 CMs gap is best recommended by an RT & they can set it as high as 8 CMs for serious cases
The actual AI & HI numbers if relatively small (say under 4 or 5) can be acceptable if the centrals are being dealt with & no desats are occurring.
I agree with SD's desire to get Wendy breathing deeper & slower. But, we do need to think about the extent that backup rate is needed.
Cheers
DSM
Doug,
Yes but that is the protocol for that machine it calls for setting backup BPM at 10 when set manually, that is where you set backup when obstructive events are addressed and centrals are present. I believe that is where her doctor last left it. But at this point we are rolling back for a second to improve the obstructive AHI getting obstructive events as low as possible then those other settings will get adjusted to correct settings. I agree they are low,
Normally backup BPM is set -2 below the spontaneous rate. But at this point in the game we are hoping that number comes down even from last night's 17 (dropped by 2 from 19.5 from last night increase to EPAP), so putting backup in "Auto" mode for the time being seems logical. If her spontaneous BPM drops as a result of the changes the Auto mode should automatically handle the back up rate for her within 2-4 breaths, so one less thing to worry about, again following mfg protocol for settings.
I'd like to see her down in the 15 BPM avg. range if possible, from my perspective she is breathing too fast and too shallow exhausting more Co2 in the process which only contributes to centrals showing up.
She's on the high end of the normal breathing scale at 19.5, that most likely is due to the asthma, but if her RR can slow down a bit I see that as a good thing towards avoiding her CA threshold.
I also think you are right her EPAP needs to go to 7 then we can increase the PS by moving IPAP Minimum up. IPAP Min was at 8.0 baseline from her doctor when she started (but again, protocol calls for first bringing IPAP Min down to within +1 of EPAP until obstructive or AI is eliminated) or where you want it, then move it up for greater PS as you suggest.
As you know moving EPAP up or down will have a dramatic impact on HI seen and that part is already handled by the machine automatically, that is why HI is nearly always at zero. As you know this machine is manual setup on EPAP like a CPAP, so that is what is happening here manual titration of EPAP until AI is more desirable.
My understanding she is scheduled for another PSG, would be nice for her to have that and find out her settings match what they find in the lab, so these are short term settings anyway. Of course we can't see the centrals, we can only see how much time she is spending in spontaneous breathing mode, if she is staying close to that 99% rate she can't be spending too much in the backup mode (I haven't see her Encore reports, just going by raw data), but I was suspect with the old settings machine was ever switching to backup, appears it does.
But what we don't know is if this machine "probes" on backup rate like it does on other machines, meaning any change seen in the spontaneous usage may have been from the machine probing for back up mode settings. I haven't seen the report to know if that happened. But I think she will be fine in the Auto mode for backup for time being until the EPAP is established as BPM can be a moving target. Once spontaneous settings are found the backup can be switched to manual with better values used.
SO is her drop in spontaneous breathing seen from 99% to 97% a result of the moving/changing IPAP working pressure?
We know that moving pressure too fast can cause that, but I would suspect this machine was designed to compensate for and/or reduce that risk. Last night working IPAP moved from 7.0 cm to 12.8,
or a maximum PS of 6.8 cm (i.e. IPAP avg=12.8 -EPAP=6.0 =6.8 PS). Granted that PS of 6.8 came from the machine's Auto algorithm. That drop in spontaneous breathing could have come from that algorithm finding that IPAP pressure. Just sorta following machine protocol established by the mfg and so Wendy understands it as we go.
Again, her numbers are not really that bad, just trying to improve the conditions seen while keeping her centrals at bay or so that she knows she is getting the best therapy she can expect from the machine. If she knows what a particular setting does or doesn't do she'll be able to fine tune her own settings for optimal therapy.