Spontaneous triggered breath percentage (Bi-level S/T)

My percentage of spontaneously triggered breaths varies greatly depending on what type of mask I use, using the exact same settings (except changing the mask type). With a FFM, I spontaneously trigger the device 99% for a night of sleep. If I wear my P10 nasal pillows and tape my mouth shut, and have low 95% leak levels, I spontaneously trigger the device anywhere from 40 - 90% of the time. I assume this is due to some type of mouth leak, perhaps during exhalation? I seal my mouth shut with 3M paper tape though, and my 95% value for leaks was 6l/min last night.

Is this problematic? Are backup initiated breaths very different than ones that I initiate myself?

I would just wear the FFM but I have great difficulty falling and staying asleep with the mask even though it's comfortable enough and doesn't leak; the air feels much stronger and as the pressure vary in VAPS mode I can really notice the swings with the mask covering my face and inflating up and down. I barely notice the P10 even with higher pressures and it's much easier for me to fall asleep.

I can't speak directly regarding the S/T machine's backup rate, etc. but my ASV machine has a backup rate as well.

On my machine, the difference between a breath taken spontaneously and one triggered by the backup rate is one of pressure differential.
When my machine is "breathing for me", it switches the IPAP/EPAP pressures between 25 IPAP and 10 EPAP until I begin breathing on my own again. On my own, the pressure differential hovers around 17/10. These numbers were arrived at through experimentation and consultation with my pulmonologist/sleep doctor who prescribed the machine. In my case, lots of hypopneas were happening (as compared to my prior AutoBiPap machine, and we tried to fix that by modifying the pressures and still keep the backup pressures sufficient to provide good ventilation. I had one night in which I was in backup mode for 2.5 hours so this is a real concern if the pressures are insufficient.

What your machine does in that circumstance depends on the programmed pressure differential in your setup. It is likely that you may have a similar pressure profile so that "backup" breaths provide better ventilation than patient triggered breaths. You should check with your doctor to get the details of how this works on your machine with your settings if you think this might be an issue.

On the subject of the FFM v nasal mask, have you tried using a soft cervical collar to see if that helps with any leak issues? Nasal masks are likely to be better for you providing leaks are under control.

JDS74 wrote:I can't speak directly regarding the S/T machine's backup rate, etc. but my ASV machine has a backup rate as well.

On my machine, the difference between a breath taken spontaneously and one triggered by the backup rate is one of pressure differential.
When my machine is "breathing for me", it switches the IPAP/EPAP pressures between 25 IPAP and 10 EPAP until I begin breathing on my own again. On my own, the pressure differential hovers around 17/10. These numbers were arrived at through experimentation and consultation with my pulmonologist/sleep doctor who prescribed the machine. In my case, lots of hypopneas were happening (as compared to my prior AutoBiPap machine, and we tried to fix that by modifying the pressures and still keep the backup pressures sufficient to provide good ventilation. I had one night in which I was in backup mode for 2.5 hours so this is a real concern if the pressures are insufficient.

What your machine does in that circumstance depends on the programmed pressure differential in your setup. It is likely that you may have a similar pressure profile so that "backup" breaths provide better ventilation than patient triggered breaths. You should check with your doctor to get the details of how this works on your machine with your settings if you think this might be an issue.

On the subject of the FFM v nasal mask, have you tried using a soft cervical collar to see if that helps with any leak issues? Nasal masks are likely to be better for you providing leaks are under control.

My machine uses an "intelligent backup rate" where you set the target patient rate at your actual spontaneous respiratory rate (the machine can learn this value over a course of 20 minutes or so). The variable backup rate is designed to stay out of the way at 2/3rds of your actual spontaneous rate, and only kicks in when your rr falls below 2/3rds of your rate. It applies that backup rate until you make a spontaneous breath again, and then it resets to 2/3rds of that new spontaneous breath rate.

For whatever reason I don't think I'm making adequate inspiratory effort through my nose...either that or maybe my spontaneous respiratory rate is a lot lower when breathing through my nose only??? I could always set my target respiratory rate real low to see if it's a case of 1) not triggering the device, or 2) my rr falling when breathing through the nose.

I tried a cervical collar but it was an uncomfortable fit and felt really awkward - I didn't last more than a few minutes with it on. And my leaks with the nasal pillows are not bad - 95% level was 6L/Min so I don't see that mattering much.

Well, I used my FFM last night (Simplus) with a static backup rate of 12 in S/T mode (not with iVAPS enabled) and my patient triggered breaths were 98%. I also notice I blew off more CO2 (minute ventilation rate was higher and so was my average respiratory rate). A set IPAP/EPAP also seems to play nicer on my mask and synchronizing with my breathing.

I think at some periods during sleep my breathing becomes vary shallow (hypoventilation) causing the backup rate to kick in. I don't think it's a case of not triggering the inhalation - my respiratory muscles aren't THAT weak and I also don't suffer from central apneas as far as I know.