Default Settings On Resmed S9 Vpap Auto?

[DoriC]

This is my PM conversation with McSleepy as I didn't want to hijack the OP's thread and I'm taking his suggestion to bring this question to the forum. I've never thought of asking before but I think I may be onto something regarding Mike's breathing sometimes that doesn't register as an apnea on the data but I do watch the green pressure gauge sometimes stop midway between exhale/inhale and then finally complete the inhale. He's not in any distress and sleeping quietly. It sometimes registers as a CA but I don't think it is because CAs only appear when he's turning or restless and holding his breath. Anyone else have experience with these settings? Where is Mollete/Sludge when you need him??

Jan 10, 2014 1:35 pm
by McSleepy

.Hello, Dori,
I'd be happy to help with as much as I can, even though the subject matter really is quite complex and requires good understanding. However, it is certain that those little settings can make a big difference. In my case, I was close to rejecting the machine because it wasn't working for me with its default settings (the DME was of no use, as you can imagine). I was both having difficulty sleeping with the default settings and my AHI was higher (not sure, I think above 10). After making the appropriate adjustments, my reported AHI is now near zero.

Before I could provide specific explanations, you need to tell me in which mode Mike is using the machine - S (spontaneous, which is straight bi-level) or VAuto (which is an automatic mode) because some settings are available in one or the other mode, only. And, finally, I am wondering whether this might benefit other forum members and bring it to a public discussion, rather than private messaging. This way, my writing would also be vetted by other members, in case I am wrong about something.


What you are describing happening to Mike appears to indeed be caused by the default limit on Ti, which is 2.0 seconds: if he triggers IPAP but takes longer than 2.0 seconds to complete his inhalation, the machine would drop the IPAP pressure and switch to EPAP. I don't know that it would appear as the pressure gauge stopping its scroll of ">>>>"'s, but it might. This is valid in all modes and is one of the first things I changed (to its maximum of 4.0 seconds). I guess, most people have trouble with higher pressures as it is different than your natural breathing (hence the "ramp" features on all constant CPAP machines). I guess it also guards against the central apneas, where the patient is stuck in inhaled state (must not apply to stomach-sleepers), but I don't see how 4 seconds would be bad - it's not even enough for a hypopnea. To me, however, it is the exact opposite - I need my high pressure to help me fill my lungs, and fill them quickly, or I wake up.

The important thing is that Mike feels happy with the machine and his data shows good results (low AHI). If not, you'll need to go deep into the plethora of settings on the machine. If yes, then you could experiment, but make sure you don't make anything worse in the process.


Re: Switching to Bi-Level - What to expect?

Sent at: Thu Jan 09, 2014 11:15 pm
by DoriC

Subject: Switching to Bi-Level - What to expect?
Hi McSleepy, I don't think I've ever seen any discussion about these settings so I just left them on default. You may know that I'm the caregiver for my hubby's therapy and sometimes I watch the green pressure gauge while he's sleeping and at times it gets hung up in the middle and stops before it eventually goes to the end. I was thinking he was having some sort of event but now I'm wondering if it's a timing thing because if he has an apnea I can usually hear it. It sounds like Mike might benefit from adjusting the trigger settings but I'm not sure how to do that and the manual is too technical for me to understand. I know you can't advise me but I'd really appreciate a better understanding of what these settings mean and how to adjust them. Thanks and regards, Dori

Re: Switching to Bi-Level - What to expect?

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uto

McSleepy wrote:
I wouldn't worry about the transition, at all, if I were you. For me bi-level CPAP was a lifesaver as I could not tolerate constant CPAP. But it might require some adjustment in the beginning. For example, during my titration study they tried bi-level and it didn't work. Probably because they had me sleeping supine (way too many wires and sensors) and I can't sleep on my back, and with the higher pressures of bi-level, and being the very first time on a CPAP machine, it was very hard on me. But after struggling with constant pressure for a week or two, my doctor prescribed a bi-level and it took immediately. Normally bi-level is meant to make it easier on the patient; if your doctor thinks you need bi-level, I think you definitely will benefit from it.

I should also point out that there are many adjustments on your new machine to help you customize it to your needs. My observations are from the S8 version of that machine, but I'm sure the S9 has those and probably more. For example, you can set the rate of pressure increase (from very gradual to an abrupt hit; I like the latter); the sensitivity to inhalation (from the machine requiring a significant inhalation effort to trigger, to immediately cranking up the pressure upon the slightest hint of pressure change in your airways; I like the latter); the minimum and maximum durations at IPAP level, and so on. I recommend you obtain a clinician's manual and study those.

Good luck!

McSleepy



Top

[McSleepy]

This is a very long topic and could take a lot of time, so, it being Friday night, I'll just get this started. Hopefully, others will join.

First, I should start with a disclaimer that I'm using an S8 and referencing its manual, while Mike is using an S9, which could potentially have different parameters (or a different meaning to the same-named parameters). It is very difficult to know what exactly could be happening when Dori observes the S9's pressure indicator stop its left-to-right scrolling, but my guess is that the Ti max limit is encountered, so I'll try to explain the Ti max and min parameters as I understand them. I'll get to the others in following posts.

I should mention that the machine has different modes and some parameters are only defined in one or the other. Furthermore, I'll only focus on S (fixed bi-level) and VAuto (bi-level with automatic adjustment), and mostly on S, because that is the one I use. Constant-pressure mode is not why you'd get this machine and ST (spontaneous/timed mode) is too complicated and rare to discuss.

With bi-level machines, such as this one, when the patient tries to inhale, they trigger a higher pressure, IPAP; when they try to exhale ("cycling"), the pressure switches to the lower EPAP level. In auto mode, there is a pressure support (PS) setting, which is the difference between the IPAP and EPAP, and a range of minimum and maximum pressures, but triggering and cycling is the same (except, different parameters are available to adjust those). For various reasons (specific to various pulmonary conditions), it is desirable to put time limits on the process. Ti max is the maximum duration of the IPAP level and Ti min, the minimum, respectively. Factory defaults are 2.0 seconds for Ti max and 0.3 seconds for Ti min. If the patient slows down their breathing, they might hit the Ti max limit, in which case the machine would switch to EPAP before they are ready, thus causing them to "fight" the machine (i.e., to try and inhale at the lower EPAP level). For me this is the main reason for arousals - not being able to inhale fast enough, and sufficient volume of air. An event like that would not register as apnea or hypopnea because the flow does not stop, but causes arousal, nonetheless. Kind of like with UARS.

I changed that setting to its maximum of 4.0 seconds and is working great for me. Maybe because I sleep on my stomach, I have no problems with getting "stuck" in inhaled state (my weight expunges the air), so no harm can be done there. The other value, Ti min, could be left alone, but I noticed that my breathing rate was getting real fast (like over 20 BPM) and I set Ti min to 2 seconds to limit it. It sometimes bothers me because I'd try to exhale but the machine maintains the IPAP, even though I'm trying to exhale, but I can live with that, better than with >20 BMP breathing rate.

I don't know what the policy of this board is, but I could also post the page from the clinician's manual where those parameters are explained.

The family is waiting for me, I'll continue later on; I hope someone finds this helpful.

McSleepy

[McSleepy]

Sorry for taking so long to pick this up again (very busy). Here's the next installment.

The most-important settings for me refer to subjective comfort and would probably be not that important for Mike as, if I understand it correctly, he is not very communicative when it comes to giving you feedback on his CPAP treatment. Those are the trigger and cycle sensitivity ("Trigger", "Cycle") and the pressure rise time ("Rise time").

"Trigger". When the patient initiates an inhalation, the machine senses the reverse flow and begins the transition from EPAP to IPAP. We all know that's how bi-level CPAP machines work. However, the S8 and S9 have a way to adjust the threshold at which this switch occurs. The manual does not explain whether it triggers on the flow magnitude or the rate of its increase, or some other measure, and only provides subjective units ("VERY LOW/LOW/MED/HIGH/VERY HIGH"), but you can clearly feel the difference.

"Cycle". This very much like trigger but the opposite: it defines the switch point from IPAP to EPAP. That is, when the patient is finished with their inhalation, as soon as they start exhaling, the machine would detect this and start lowering the pressure. This is the main motivation for bi-level modes as it avoids having to fight the high pressure when trying to exhale. The settings are the same as trigger and the default is medium ("MED").

I don't know how you'd be able to fine-tune this without Mike's feedback, but there is a slight possibility that cycle is responsible for the stopping of the inhalation progression (if that is, indeed, what is happening). It is possible that he makes slight pauses in his inhalation that are detected as the start of exhalation. If that were the case, decreasing the sensitivity (i.e., going to low or very low) could help. In my case, the salvation was setting cycle to very low and trigger to very high as I use this mode to assist my breathing (very controversial, I know, but it makes the difference between high AHI and zero).

"Rise time" (in S mode). This setting determines how quickly the pressure will transition between EPAP and IPAP. It is measured (roughly) in milliseconds and varies between some "MIN" setting (probably the best the machine can do, under the circumstances), and then from 150 to 900, in 50ms increments, with the default being "150". If Mike were to use S mode, I think the default would have worked for him, unless, like me, he has a very high lung capacity and needs more pressure and time to fill his lungs. Luckily, one can get a good idea about this by looking at the graphs: a high tidal volume, like mine, would be between 400 and 800 mL. You need more pressure, and quickly, to satisfy a higher tidal volume demand. I've alternated this setting between "MIN" and "150", and they both work well (probably the same since I'm at high altitude, go Broncos!)

"Exhalation" (in Auto mode). This setting determines how quickly the pressure will transition between IPAP and EPAP. It is measured in some subjective units and the options are: slow, medium, and fast. The default is "MED" and is purely subjective, although, like cycle, it could lead to false positives, so trying the LOW setting is a possibility.

Those are the main settings that I feel are relevant. As always, my opinion is just that, so don't take it as medical advice (like sleep doctors know much, anyway), but I hope it could help in better understanding the operation of the machine.

McSleepy

[DoriC]

I almost missed your reply, thanks for the detailed explanation. I'm sure it will of interest to others as well. I'll have to read it a few more times to really understand it but because of my situation I would really be leery of making those changes unless it was really impacting Mike's therapy. After thinking about it I'm pretty sure a few small pressure tweaks and controlling his leaks is all I'm capable of handling without expert supervision. In general, he's doing pretty well and I shouldn't be expecting perfection. Thanks again for taking so much time to post this excellent information.

[Taringa542]

A very good read, as Dori says, I will also have to read several times to absorb it all

[digitalepiphany]

I've noticed that I've been having to breathe fairly quickly just to keep up with the changing IPAP and EPAP. This feels counterproductive to me, as we would normally slow our breathing when sleeping. It's also been causing my heart to race, as if I' hyperventilating. I'm going to change the Ti Max to 3 tonight and see how it goes.

Thanks for all the great info.

[digitalepiphany]

Also, could you explain a little more abut Rise Time and Tidal Volume? I'm using an ST, not an S, but I looked at my tidal volume, and the median is 480. Since it's in the same ballpark as yours, I'd like to know a little more about that.

Thanks again.

[McSleepy]

I've noticed that I've been having to breathe fairly quickly just to keep up with the changing IPAP and EPAP. This feels counterproductive to me, as we would normally slow our breathing when sleeping. It's also been causing my heart to race, as if I' hyperventilating. I'm going to change the Ti Max to 3 tonight and see how it goes.

Thanks for all the great info.
= = = = = = = = = =
Also, could you explain a little more abut Rise Time and Tidal Volume? I'm using an ST, not an S, but I looked at my tidal volume, and the median is 480. Since it's in the same ballpark as yours, I'd like to know a little more about that.

Thanks again.

Those are very complex issues and I'm really afraid that I might provide some information that could lead to misunderstanding the problems, but I guess, this is what we do on this message board, so I'll give it a shot.

In your case the machine has more functions - it actually tries to "police" your breathing explicitly, and for that purpose, it has an additional parameter that can be adjusted: the respiratory rate in breaths per minute. However, that would only come to play if your respiratory rate were to slow down, and you seem to indicate that the opposite is happening to you. That is actually good: if your never miss spontaneous breaths (and there is a statistic for that in ResScan), it means you don't really need an ST machine, and, even better, the condition for which it was prescribed may not be there anymore (or ever).

If your breathing seems excessive, in frequency or minute ventilation (you should look at that parameter, it is basically the tidal volume multiplied by the respiratory rate), then you have to first try to explain what is happening. There are factors that are undesirable, in which case you'd want to reconfigure the machine to help you correct that; but there are cases when you don't want to do it. For example, if your respiratory rate is too high and causes shallow breathing, which could be corrected by forcing down the rate, but compensate for it by increasing the tidal volume, thus keeping the minute ventilation the same, then it is a good thing and you should do it. I believe that was my case and that's why I did that adjustment. But, if your respiratory rate has increased because you don't have enough tidal volume, or for any other reason you are unable to achieve the required minute ventilation, then you should in no circumstance limit your breathing rate but seek the reason for the problem, instead.

This problem is compounded by psychological factors (and which problem isn't?) The breathing changes significantly under different circumstances. The minute ventilation in a state of deep sleep can be really low (while adequately ventilating your lungs, no drop in SpO2), and it can increase tenfold during a period of stress (e.g., waking from a nightmare). My minute ventilation is normally around 5-6 L/min but I've had stress-induced periods (half-awake, trying to fall asleep) when it had shot above 25 L/min. So, the real question is how to distinguish between what your actual needs are and what your mind feels it needs at a given moment.

It is very possible (although it isn't quite clear from your description) that the machine is actually causing your increased respiratory rate. In that case, it only makes sense to correct those factors and return to what would be your natural rate. If you do determine that you can get good ventilation with a slower respiratory rate, you could start by increasing your Ti Max, which would simply lift a restriction that few people would ever need. However, you might have to go further (like I did) by increasing Ti Min, which is no more lifting a limitation but imposing one, and that could be tricky. For example, people who tend to have central apneas where they get stuck in an inhaled state (with full lungs) could get in trouble with this. Like I said, I sleep on my stomach and I rather have the opposite problem (get stuck in exhaled position), but you should carefully consider this option.

For a given timing of your machine-supported breathing, the minute ventilation would be fixed. Let's say your inhalation continues 2 seconds and because of your physiology (e.g., respiratory effort) and the constant pressure (IPAP), the flow and, thus, the volume of air pumped into your lungs, should be a given constant. Now, the S8/S9 can vary the rise time: the time it takes for the pressure to transition from EPAP to IPAP. Let's compare the two extreme cases (assuming IPAP must be eventually reached): instantaneous increase and it taking all of the 2 seconds. In the former case, the rising slope would be vertical and the time/pressure graph (assuming an instantaneous cycle, i.e., fall from IPAP back to EPAP) would look like a rectangle. In the latter case, the slope would be significant and the graph would look like a saw-tooth. It is rather obvious that the area of the two graphs is very different, the latter could be half of the former. That means, you are filling much lesser tidal volume and to maintain the same minute ventilation you have to increase the effort or the breathing rate, but the times are limited by the machine. Probably the most important aspect of this conflict is that your body is feeling unhappy and is trying to resolve the problem but has to fight the machine for it. If you are able to lift those restrictions by adjusting the parameters accordingly, then all is good. Otherwise, it gets really complicated.

If this were simple(r), the sleep medicine science would have resolved all issues by now. I hope they do one day, so we don't have to try and figure it out ourselves.

There is a lot of information about this on the Net, here is a very helpful Wikipedia article: http://en.wikipedia.org/wiki/Respiratory_minute_volume.

McSleepy

[Sludge]

I don't know what the policy of this board is, but I could also post the page from the clinician's manual where those parameters are explained.

Policy?

We don't need no stinkin' policy!

VSynch Leak Management



Trigger Sensitivity



Cycle Sensitivity

[Denial Dave]

This is great information. . It's time for some tweaking of my settings!

[McSleepy]

Just thought of something to add here: if you feel like varying some of those settings does not seem to make a difference (especially as far as comfort is concerned), try setting (temporarily) the pressures significantly higher than you normally have them. This will exacerbate all the effects and might help you figure out which settings work best for you.

McSleepy

[Denial Dave]

thanks.... personally, I've always thought that the machine switched from IPAP to EPAP faster than it should for me.....which resulted in my breathing faster than normal.... I haven't found any difference from my changes yet....

Dave

[DoriC]

Dave, which changes did you make??

[Denial Dave]

Ive been playing with Ti settings. Nothing major.

[McSleepy]

thanks.... personally, I've always thought that the machine switched from IPAP to EPAP faster than it should for me.....which resulted in my breathing faster than normal.... I haven't found any difference from my changes yet....

Dave

Extending Ti min should help with that - that's what I did to slow down my RR. Mine is at 2.1 sec and my RR climbed down to ~15 (from over 20). What is yours currently?
McSleepy