Importance of Spont Cycle %

[SingleH]

Hi all,

Are there any guideline figures in terms what is an "accetable" Spont Cycle % range. Should it ideally generally always be above 70,80,90% etc

Assuming a user doesnt have an problem with spontaneous breathing, what should someone be expecting to see on a daily basis and how important is this figure in the context of managing other figures and events.

Is it more important to resolve events and compromise Spont Cycle, or if Spont Cycle is continually low, should you adjust settings to compromise slightly on another event parameter?

[Jay51]

resmed vauto spontaneous cycle    Great questions SingleH.  I found this thread.  The post by StuartC was very helpful to me.  

[SingleH]

Thanks for sharing that post, very useful and has triggered some thoughts in combination with your previous comments on CA's and their causes.


There isnt a lot of info in the Resmed Titration guide but it doesn comment on patient-device synchronicity

• To achieve patient–ventilator synchronization, you can customize the beginning and end of each inspiration with ResMed’s adjustable Trigger & Cycle technology.
  

• The Cycle sensitivity helps the care provider ensure appropriate breath termination for every patient, promoting patient-device synchroncity.
  

As you point out high PS or a long TiMax, could result in increased amount of inhaled oxygen. On that basis I had to reduce the Timax all the way from 3.0 down to 2.0 to get CA's down to about 0.7%.
However in doing so Spont Cycle went all the way from 85-90% to 40-60%.

At the moment figures are good (around 1.5 AHI a night) but:

If I increase TiMax, CA's will increase.
If I reduce PS, Flow limitations will increase.

This led me to think what else could be the cause. Cycle sensitivity could be adjusted to high, but according to the post from Stuart C, that will only work if your TiMax is long enough for it to be detected during that period, which currently appears to be too short.

The only parameter left is TiMin, based on the Resmed Titration guide and RR I originally used the "Restrictive" criteria of Timin 1.0 and TiMax 2.0.

Perhaps it not just the Timax that was causing over oxygenation, but having too long a TiMin also, as that is the guaranteed part of the inhalation. If Timin is too long this could possibly have the same effect? If true, some thoughts on next steps:

1. Incrementaly reduce Timin - if my understanding is correct the potential reduction in over oxygenation would possibly result in his breath being cycled earlier and possibly within the current 2.0 timax, thus improving spont cycle.
2. Incementaly reduce Timin, plus increase cycle sensitivity to high - if the machine is struggling to detect his efforts. If no change, then step 3a or b.
3a. Incrementally reduce Timin, and incrementaly increase Timax - in theory if the Timin is too long and causing the over oxygenation, I'm thinking it should be possible to extend the Timax out a bit longer if the Timin is reduced. 
3b. Incrementally reduce Timin and increase PS - I currently cant increase PS without triggering more CA's and I read that longer breathing cycles can be a sign of flow limitations. If I can increase PS his breathing cycle may reduce in duration resulting in a better spont cycle figure.

[Jay51]

You thinking looks good SingleH, IMO.  There are so many different variables in play in your dad's unique situation, that experimenting (like you have already done and have done a fantastic job so far IMO) may be the only way to know for sure which ideas will pan out successfully.  You could probably write your own titration guide at this point from all the experiments that you have done.

[SarcasticDave94]

Not trying to be a party pooper, but if you're needing deep diving into breath and machine timing, where is the line drawn that maybe an actual ventilator might be better? At a minimum an ST-A device with AVAPS...

I don't recall the history about the OPs circumstances.

[SingleH]

Thanks for confirming, its been a steep learning curve, but the patience and support of members such as yourself has made it possible.

Your piece of info on the different causes of CA's was the game changer that gave me an understanding how interlinked the different parameters are and why my changes were causing erratic CA results.

I now have events under control, hopefully the breathing synchronicity is the last part to address.

[SingleH]

Hi Sarcasticdave94, I do agree with you to some extent, unfortunately Im working within the confines of the limited support of UK healthcare which is not as advanced as the US on sleep apnea nor easy or quick to access equipment.

Regarding my Dads condition, he has scoliosis, not super extreme, but does have some lung restriction and somewhat poor muscle control when breathing in and out. He has been fit and healthy his whole life and did many sports, however more recently in later life he developed heart problems which I believe was due to undiagnosed sleep apnea at the time. He had surgery and his heart is good and all parameters normal, however I believe the surgery affected his chest wall muscles and he didnt do any physio post surgery either. Since doing more physio recently and using the Bilevel I have noticed improvement in that area so I think the machine is re-training his breathing muscles.

When I started out on this, I did think the ST-A with Ivaps would be the best choice, but could only get my hands on a second hand trial unit. I saw pretty good results with it straight away for the first few days. I also tried S mode which did not work at all for him. Unfortunately the machine developed a serious noise problem and it had to be returned. As Im sure you know the iVAPS mode has some really brilliant features like the auto adjusting EPAP mode and the auto adjusting PS range. This was really helpful in his case as he sometimes needs a high EPAP to clear apneas but this mode avoids sending the IPAP sky high. That is one of the major deficiencies of the Vauto. It would be so useful to have those two features, but I guess they are "advanced features" and why the iVAPS unit costs so much more.

Anyway to cut a long story short, as suggested on this forum, I bought a unit from a recommended second hand supplier. I decided to opt for the Vauto for the following reasons:

Event reporting in Oscar seems to be a little bit more comprehensive on the Vauto than the iVAPS.
More expertise on the Vauto than Ivaps on the forum.
I read that users had found pressure delivery more comfortable than volume delivery.

I would have liked to have tested iVAPS more as out of the box it was producing good results and I suspect the various auto modes, were handling all the fine tuning that I have had to learn and implement in a slightly more manual fashion. Nevertheless the Aircurve 10 has produced full uninteruppted nights of sleep where figures have been in the 0.0 to 0.5 range, so this machine is able to deliver good results too. The spont cycle is the last figure I'm trying to correct and as I know I can get a higher Spont figure at the compromise of PS, I'm fairly confident that the Oxygenation/CO2 aspect is the likely cause. I certainly dont want to continue to have to adjust and test things endlessley as that isnt a working solution. As you suggest a line has to be drawn, but as events are now stable on a daily basis, I'm hoping this is the last piece of the puzzle.

[Sleeprider]

COPD patients frequently require a lower TI Max setting to preserve expiration time and avoid "stacking", where the lung does not adequately expire the previous breath, and subsequent breaths enter an already partially filled lung. So it's an important tool in people with a restricted expiratory airway or non compliant lungs. When Ti Max is excessive, we will often see inspiratory effort sustained too long of a healthy respiratory cycle time or rate, so these individuals can be prompted to cycle by shortening the TiMax. We still want adequate tidal volume, and we achieve that withing the allowed inspiratory time using higher PS. Your reaction to the events your dad was experiencing was appropriate and maintains an appropriate cycle time to prevent stacking, which may be the cause of what you observed as CA. When the lung is already full due to inadequate expiration, there is no place for inspired air to go. With an open airway and no flow a CA is recorded. Respiration is a balancing act, and inspiration and expiration volumes must be equal, or we begin to see the problems you observed. Using a shorter TiMax is simply a cue to turn off inspiratory effort, especially inpatients with hyperinflation tendency or poor lung compliance that require longer expiration time be preserved.

[SarcasticDave94]

FWIW what Sleeprider posted is what I dealt with myself, air stacking. Time controls are your friends. You may be in need to balance all trigger, cycle, Ti settings to get things working decent.

Surprising the VAuto has as many time controls as it does. I don't recall if you'd gotten the manual, but you'll want it to guide in the settings.

[SingleH]

Thanks Sleeprider, a lot of new info in your response, so will need to digest that!

As I understand it Scoliosis(Restrictive) is the opposite of COPD(Obstructive), in Resmeds titration guide they have two suggested settings that are almost opposite in terms of Timin,max and tigger and cycle.

In your comments you mentioned Timax, but what about Timin? Could having a Timin that is too long (currently at 1.0 second) potentially cause breathing stacking also? Resmed give a guideline for restrictive breathing, but there is no real quantification as to "how restrictive" someone is. My dad was assesed as having some "mild" restriction. Could a long Timin be enforcing too much oxygenation and also causing breath staking. He typically takes short shallow breathes when awake so could the long Timin be lasting too long thus stopping him cycling.
The IE ratio from the past couple days is this with 58-66% spont cycle
IE 1:1.3
IE 1:1.41