Please Help..Bi-PAP AVAPS - Calling SWS..

[vikingblade]

hi guys. ive got a respironics bipap avaps coming to me on monday. i have a degenerative neuromuscular disease that is weakening my respiratory muscles and diaphragm. i was on a regular bipap pro 2 for the past 5 yrs, but ive had to up my inspiration pressure to 24, so..its really not an effective machine for me anymore. probably never was. ive read through a few of the avaps threads and posts by sws, banned and madalot. they have helped me to understand things a bit. but, i still had a few questions about the avaps, and was hoping to get some input from the experts here.

questions...

INSPIRATION TIME.. i understand that people in my situation do better with a longer inspiration, and that is definItely what i feel i need. my question is tho.. when running in s/t mode, what exactly does the Ti..inspiration time do.. my understanding is this..please correct me if i am mistaken..

Inspiration time is the maximum time the machine will allow me to inhale. BUT...it is not the minimum. meaning..if it is set at say 2 sec, and i attempt to inhale longer than 2, it will kick into epap. BUT..if i only inhale for 1.5 sec, even tho it is set at 2, i can still trigger it to epap before 2 is reached, if i stop inhaling. Is this correct??

my other question concerning inspiration time is.. if the above is true, does it also work that way for a non-spontaneous triggered inspiration.. meaning a timed, back up, or machine triggered inspiration? i have a hunch, that when i dont trigger an inspiration, or i dont keep up with the set bpm, AND the machine kicks in an inspiration, it will hold the inspiration for the entire set inspiration time, regardless of whether i stop inhaling or not.. Does anyone know for sure?

i have other questions as well, concerning BPM, Tidal Volume and Rise Time, but... dont wanna overwhelm with questions. THANKS FOR THE HELP

[Madalot]

Hello!

Very interesting questions posed here and I'm anxious to see the answers from the experts myself. Since you've read some of my threads, you know that I'm using a Trilogy Ventilator, but I am currently using it like your new machine -- S/T AVAPS. I don't know if different machines function differently.

Here's what I have found about Inspiration Time with the Trilogy. I increased my Inspiration Time from 2.0 to 2.7. The ventilator does have a backup and if I don't inhale on my own, the machine switches to IPAP to force a breath on me. And because my RR is incredibly slow when I relax, the machine DOES kick breaths on me fairly often.

If *I* initiate the breath, the Inspiration Time is based on MY breathing. If I stop inhaling before the 2.0 - 2.7 seconds, it switches to EPAP. The 2.0 - 2.7 is a maximum, but is not required, thus switching to EPAP if I don't inhale that full time.

However, if the breath is *Machine* initiated, it forces it for the full inspiratory time. That's where I ran into a problem because 2.7 is way too long for me a lot of the time. Not always, but a lot of the time. I was having a really hard time one night and reached over and changed the Inspiratory Time back to 2.0 after it seemed like the vent was pushing too much air on me too often for me to handle.

I don't know if this helps you, but it has been my experience. I'll keep an eye on this thread for more input from the experts.

[-SWS]

Welcome aboard, vikingblade.

Inspiration time is the maximum time the machine will allow me to inhale. BUT...it is not the minimum. meaning..if it is set at say 2 sec, and i attempt to inhale longer than 2, it will kick into epap. BUT..if i only inhale for 1.5 sec, even tho it is set at 2, i can still trigger it to epap before 2 is reached, if i stop inhaling. Is this correct??

Yes. That's exactly how the AVAPS Ti parameter behaves in S/T mode.

if the above is true, does it also work that way for a non-spontaneous triggered inspiration.. meaning a timed, back up, or machine triggered inspiration? i have a hunch, that when i dont trigger an inspiration, or i dont keep up with the set bpm, AND the machine kicks in an inspiration, it will hold the inspiration for the entire set inspiration time, regardless of whether i stop inhaling or not.. Does anyone know for sure?

In spontaneous (S) mode, the machine parameter called Ti is unavailable since that part of respiration is handled or guided by the human respiratory drive. In Pressure Control (PC) mode and Timed (T) mode, machine-parameter Ti is essentially fixed-duration IPAP delivery (instead of being a maximum or upper time-limit for inspiratory time as in the S/T case).

The difference between those latter two modes (PC mode and T mode) lies in how the machine is programmed to commence the transition from EPAP to IPAP (that's called the machine's "trigger"---and is directly related to the machine's BPM setting). Pressure Control (PC) mode will handle that machine-trigger from EPAP-to-IPAP the same way that Spontaneous/Timed (S/T) mode handles it: patient gets first-crack at triggering IPAP---otherwise a timed backup rate (BPM) will eventually kick in to provide that EPAP-to-IPAP transition.

In Timed (T) mode, the machine's fixed timing is always used to commence both transitions: 1) the machine transition from EPAP to IPAP (again, called the "trigger"---and is controlled by the BPM setting) as well as, 2) the machine transition from IPAP to EPAP (called the machine's "cycle"---and is controlled by the Ti setting).

i have other questions as well, concerning BPM, Tidal Volume and Rise Time, but... dont wanna overwhelm with questions. THANKS FOR THE HELP

Pass your questions along and we'll try to answer just as many as we can. Can't say we'll manage to answer them all... We head scratch plenty around this message board.

[vikingblade]

hi again.. thanks for the input madalot and sws... that was exactly the info i needed. both of your posts have helped me greatly. a lil bit of info about my previous and current settings...

on my previous machine..the bipap pro 2, i was on a straight forward s mode.. ipap of 24 and epap of 5. very high ipap i know. i slowly raised it over the years. i find i need the extra pressure to feel like im getting a deep breath without too much assistance from me. i just got the avaps and started with these settings..

s/t avaps mode
ipap min..20
ipap max..27
tidal volume..600
bpm..14
inspiratory time..1.5
rise time..3

luckily, my dr. is very casual with me, and has allowed me to tinker, if i stay in communication. the above settings were arrived at by us working together, as i couldnt complete a sucessful sleep study..couldnt sleep. we figured wed start here and change things as needed.. anyways, after only a little while on these settings, i soon realized i needed to adjust some things.. the ipap min felt too low after my usual 24, and the bpm of 14 was just too fast to keep up with. also, the inspiration time seemed a bit short. i experimented with the bpm.. 12, 10, 8, and finally settled on 6 for the night. felt the least aggressve and i figured id still have a back up breath in case of centrals. so...new settings..

s/t avaps mode
ipap min..24
ipap max..27
tidal volume..600
bpm..6
inspiratory time..1.9
rise time..3

my feelings today.. everything seemed ok except for couple issues.. i have an ongoing mouth leak issue. i use nasal pillows, and at my pressures, obviously some air forces my lips apart..making noise, leaking pressure and waking me up..its a drag. ive tried chin straps..no luck. i received a full face mask..mirage quattro with the avaps. it seems to work well, and will probably solve my mouth leaks. however, my hand weakness makes it impossible to take it off by myself if i need to. which makes it feel very trapping, scary and dangerous. plus just inconveinant. id have to page my wife in other room to come help, wake her up etc.. just to get a drink, take a pill etc.. so.. its just something ill have to work thru to find a solution..quick release or something.

another issue is.. when the machine kicks in a breath.. when i pause too long after an expiration.. and i guess im having a central.. when the inspiration comes, my throat makes a moaning, humming type sound..startles me awake all the time. weird thing is, this only happens when im pausing breath when sleeping or falling asleep. if im awake, and expecting the inhale, i dont get the sound. cant make it happen. but, as soon as i start to drift into sleep, my breathing slows or stops momentarily after exhale, the bpm kicks in the inhale, and my damn throat does the high pitch humm. any ideas??

sws..can u give me a better idea of how the bpm and inspiratory time work together.. im wondering if i need to increase my bpm a bit.. i seem to naturally pause for a few seconds after an exhale.. could this be causing a problem.. im unsure whether i should maybe increase bpm or Ti or both etc.. i hate the constant kicking in of the bpm if faster..just feels unnatural and wakes me, but, maybe 6 is too low??

another question i had... my tidal volume is at 600. the way i understand avaps is the pressure starts at the min ipap and slowly adjusts as needed, to the max ipap. now..my ipap pressure never seems to change. it just stays at the min ipap. could this be because my min ipap is already so high that its giving me the 600 tv already, and no need to increase? plus, i really have no idea what my tidal volume should really be.. ive asked my dr and rt and all i get is a weight or height generic range. i would think there would be a more accurate way to gauge it. my lung situation is quite a bit different from a typical person, so, i would think my tv may be different..dunno.

anyways thanks for reading my ramblings. any insight or opinions are appreciated.

[Madalot]

hi again.. thanks for the input madalot and sws... that was exactly the info i needed. both of your posts have helped me greatly.

I'm sorry you find yourself needing this equipment for the reasons you do, but am grateful to see you posting here. I think that while our situations are a bit different, they are similar enough that we can help and learn from each other. Because of what I've been through, I understand what you're doing and the settings you're discussing. But I'm always anxious to read what the experts (-SWS and others) have to say about this.

sws..can u give me a better idea of how the bpm and inspiratory time work together.. im wondering if i need to increase my bpm a bit.. i seem to naturally pause for a few seconds after an exhale.. could this be causing a problem.. im unsure whether i should maybe increase bpm or Ti or both etc.. i hate the constant kicking in of the bpm if faster..just feels unnatural and wakes me, but, maybe 6 is too low??

I'm interested in this one too. I think it's very possible that -SWS and others have addressed this in some of my threads, I'm anxious to see what he says here.

As far as the mask situation is concerned, I know exactly what you mean on that. I went to a full face mask after only 3 days because I am a serious mouth breather (sinus and congestion issues). I decided that taping my mouth or using a strap weren't options for me as I would panic if I couldn't open my mouth if I felt it necessary, thus sticking with the FFM. But what you said about needing to be able to release it quickly is another big thing with me. I found the F&P 431 the easiest one I've used thus far in that regard. I like the Respironics Comfort Gel, but the headgear and release are too difficult for me to use. On the 431, it's a matter of pushing on a clip and it releases the headgear.

I can't remember if I mentioned this or not (having some serious memory troubles recently), but my initial settings in AVAPS were very similar to yours. My RT would only lower the settings in miniscule amounts at first and I finally got my doctor to order a significant change. My tidal volume was at 550 initially and my RT would drop it to 525, then 500, etc. My doctor finally lowered it to 400, which is where we have left it for a few months now. I've got my BPM at 7 because like you, much faster was hard for me to keep up with sometimes.

Once again, I'm grateful that you are posting here, vikingblade. I think we both know that what works for one of us may not work for the other, but I do think it will help us in comparing a bit.

[-SWS]

Hello, again, vikingblade and Madalot!

another issue is.. when the machine kicks in a breath.. when i pause too long after an expiration.. and i guess im having a central.. when the inspiration comes, my throat makes a moaning, humming type sound..startles me awake all the time. weird thing is, this only happens when im pausing breath when sleeping or falling asleep. if im awake, and expecting the inhale, i dont get the sound. cant make it happen. but, as soon as i start to drift into sleep, my breathing slows or stops momentarily after exhale, the bpm kicks in the inhale, and my damn throat does the high pitch humm. any ideas??

I suspect the above upper-airway noise might be what's called "stridor":
http://www.google.com/#hl=en&source=hp& ... 6c9e19fcb7

If it really is stridor, it might be related to airway dynamics of neuromuscular weakening and machine ventilation of that upper airway. Stabilizing chin or tongue position just might help with that in some cases.

Next I'll post about the relationship between Ti and BPM.

[Madalot]

Next I'll post about the relationship between Ti and BPM.

I'm looking forward to it. And if you've already provided this information in my threads, my apologies for not remembering. I've been having some memory issues here lately! But I'm following this thread and will watch for it!!

Thanks again for helping those of us with problems that are "outside the norm."

[-SWS]

For purposes of this discussion, here's a quoted AVAPS reference from an older post:

what AVAPS guide says for S/T mode:

1. Set the target tidal volume, either to 110% of the displayed patient
tidal volume when ventilated on S/T mode or to 8 ml/kg of ideal weight.
Adjust depending on patient tolerance and clinical outcomes.
Target Vte may be set from 200 ml to 1500 ml.

Target Vte Chart (sorry it lost formatting, assumes ideal weigh, height more important, 59"=420ml, 75"=660ml etc.):

HEIGHT 59" 61" 63" 65" 67" 69" 71" 73" 75"
IDEAL
52.0 Kg 55.5 Kg 59.0 Kg 62.5 Kg 66.5 Kg 70.5 Kg 74.5 Kg 78.5 Kg 83.0 Kg
WEIGHT
VTE IF
420 ml 440 ml 470 ml 500 ml 530 ml 560 ml 600 ml 630 ml 660 ml
8 ML/KG

2. Set IPAP limit.
-IPAP max = 25 to 30 cm H2O depending on patient pathology
-IPAP min = EPAP + 4 cm H2O

3. Set respiratory rate 2-3 BPM below resting respiratory rate.

4. Set inspiratory time for the controlled breaths.
-Set Ti between 25% and 33% for obstructive patients.
-Set Ti between 33% and 50% for restrictive patients.

5. Adjust rise time to the patient’s comfort.
-Obstructive patients prefer short rise times from 1 to 4 (100 ms to 400 ms).
-Restrictive patients prefer long rise times from 3 to 6 (300 ms to 600 ms).

Nothing in these suggested settings is intended to supercede established medical protocols.

[-SWS]

Here's an image that might help with the upcoming discussions in this thread as well.

[-SWS]

And a relevant excerpt from another thread:

I would like to see us discuss Inspiration Time and how that might change ones breathing to a particular scenario. Respironics keeps resorting to 1.2 seconds when it sees a problem, I wonder why they choose that value? With the range of that setting seems it could vary quite a bit.

Well, unfortunately I didn't turn up much by the way of Google. But two general characteristics of inspiration time have to do with either achieving a certain tidal volume, a certain I:E ratio, or both.

In certain cases of COPD, for instance, clinicians might try to achieve more expiratory time by influencing the I:E ratio. To accomplish that they need to factor BPM and IT together. BPM yields the total time spent in I + E. Of that total time spent in I + E, a set inspiratory time (IT) will drive the ratio of how much time is spent in each. The IT setting will specifically account for time spent in inspiration; and almost all of the remaining time will be allotted for expiration (there are also slight intervening pauses between respiratory phases only slightly contributing toward that total remaining respiratory time).

Alternately, IT can be used to help with central dysregulation since IT directly helps regulate the amount of inspired O2---while indirectly regulating the rate of expired CO2 (via expiratory time implicitly defaulted or remaining by employing the IT and BPM parameters). A shorter IT or inspiratory time period amounts to less O2 volume inspired, which can supposedly help with periodic breathing. Again, if IT is employed toward I:E ratio-adjustment (by also utilizing the BPM parameter), a clinician can even influence CO2 expiration rates via the time allotted for the expiratory phase relative to inspired volume. However, that's not the same as directly influencing CO2 retention via additional appropriate methods.

So when the autoSV titration guide says "Set Fixed Rate to a minimum of 10 BPM... Start I time: 1.2 seconds" we can at least see how those 10 BPM and 1.2 second IT parameters play against each other ratio-wise: here the I:E ratio would be 1.2 sec to 4.8 sec (which can be numerically reduced to an I:E ratio of 1:4). However, that "minimum of 10 BPM" recommendation tells us that the starting ratio might favor a somewhat smaller E number. Regardless, if we compare that against a default setting of 1:1 or say an acceptable spontaneous 1:2 ratio, we can see that Respironcics implies that central apneas can be countered, at least in part, with comparatively shorter inspiratory volumes and times.

However, also bear in mind that the AutoSV's BPM setting is only a backup setting, and that faster spontaneous breathing rates by the patient will diminish time spent in E while still holding the above 1.2 second inspiratory time constant. Recall that BPM is typically set at the patient's spontaneous rate minus 2. Here setting BPM rate much closer to a machine-affected or influenced spontaneous rate can allow the clinician to additionally impose tighter control over time spent in E. Allowing for BPM as a non-salient backup rate (as opposed to either tightly enforced or purely timed mode scenarios), the above spontaneous I:E ratios can thus be more accurately estimated during periods that are free of central dysregulation by also including that BPM offset of 2 into the above ratio calculations. Easier yet: just calculate that I:E scenario of a non-salient backup rate using the patient's measured spontaneous BPM, rather than employing machine backup rate along with spontaneous offset.

[-SWS]

Here's an image that might help with the upcoming discussions in this thread as well.

In the above picture we can see that inspiration begins at the trigger point. The rise time is a nested sub-component of overall inspiratory time. The cycle arrow points where expiration begins.

In that picture one breath, or complete cycle would be from the trigger arrow to that same spot on the next breath where we might place another trigger arrow. While Inspiratory time is given as a Ti value, the remainder of that same breath's time can be derived from BPM and Ti.

The time for one complete breath, "Tc" would be 60/BPM
The time for inspiration is "Ti"
The remainder of that same breath would expiration at (Tc-Ti)
So the I:E ratio could be derived as: Ti:(Tc-Ti)
=============================================

If you knew a BPM and Ti pair of values, then you could calculate the I:E ratio and see how it happens to fit with obstructive versus restrictive recommendations for I:E. Alternately, if you knew a BPM and a target ratio, then you might calculate your target Ti. Essentially there's a three way relationship, requiring that any two be known or targeted to calculate an outstanding third component. In PC mode, the calculations are exact. In S/T mode, the calculations lend useful ranges or limits---since breathing itself is largely spontaneous within those limits.

Any thoughts or questions? Additional ideas or concepts to add?

[-SWS]

Here we did one similar calculation on Madalot's past ratios:
viewtopic/t52784/viewtopic.php?f=1&t=51 ... te#p480784

[unadog]

Tired tonight folks, I didn't have time to go through all of this in detail right now. I'll read it again tomorrow.

I was just thinking about Madalots Ti. If I remember correctly, she has had it set at 2.0. She tried to adjust it the other night, then moved it back. I forget what she has her BPM set at.

It seems like it would help to have some ranges in mind when trying to tweak her Ti. So if we look at some common BPM rates, we can quickly get a lower limit (using the restrictive guidelines) and an upper limit for Ti, when I:E 1:1.

-Set Ti between 33% and 50% for restrictive patients

SO:

BPM - Tc - 33% Ti - 50% Ti

15 - 4.0 - 1.3 - 2.0

12 - 5.0 - 1.65 - 2.5

10 - 6.0 - 2.0 - 3.0

8 - 7.5 - 2.5 - 3.75

6 - 10.0 - 3.3 - 5.0


Having those quick parameters in mind might help her try to "tweak" her Ti without stray too far from where the predicted value is.

Especially right now, as we can't find DirectView software anywhere, to get her access to her data as she is trying to optomize her settings (with help from her doctor and DME.)

Anybody have an idea about where to get it?? Even if just one person had an install of DirectView, if they could grab the data files and run reports for a few of the folks here struggling with their AVAPs, with limited DME support (and DMEs with limited understanding), that would be a great help!

Cheers,
Michael

[-SWS]

Unadog, I couldn't help but notice that you converted vikingblade's thread into a dial-winging campaign for Madalot. You admit you're too tired to read the details above, and yet you're more than happy to devise ventilation settings for patients on a message board whom you've never medically screened.

I would also guess that you're not medically qualified to treat ventilator patients with highly complicated health problems in person---let alone on a message board when you're too tired to read.

Vikingblade, Madalot, I'm not here to dial wing. I'm adamant that should be done between clinician and patient in medically complicated cases. Good luck!

[Madalot]

Unadog, I couldn't help but notice that you converted vikingblade's thread into a dial-winging campaign for Madalot.

Vikingblade, Madalot, I'm not here to dial wing. I'm adamant that should be done between clinician and patient in medically complicated cases. Good luck!

Hi guys --

Unadog -- you know how much I appreciate what you're trying to do for me. Absolutely, positively.

I don't want to hijack vikingblade's thread with my issues. And I want to respect SWS's comfort zone about what he's willing to do and not do.

-SWS -- thanks for posting the information (again I'm sure because I've become braindead) about Inspiration Time, Trigger and Rise Time. I hope it helps vikingblade figure things out. And I'm going to read it thoroughly tonight.

I respect the fact that you share information, but do not support or condone a patient changing their settings without their medical team's orders or approval.