AHI still erratic, time to wingding?

[palerider]

I don't see how that quote out of a 20 year old paper is relevent, however, I do note that you are regarded with high esteem around these parts, so I've got to wonder what I'm missing.

I would say the first thing would be to realize is that old does not equate to irrelevancy.

nor does it automatically make it relevant....

thank you for the non-answer, it really helps.

[College3girls]

Mom's RT had to cancel Tuesday- (after I drove the hour to get to Mom's ). The visit has been rescheduled for Thursday afternoon, so I will try again.

In the meantime, Mom has had a string of 3 nights with a good or at least reasonable AHI with readings under 6 or lower.

Robysue and Sludge, we are still working on getting the sleep study(s).

The SD card with the APAP that was used for a year went back to the DME along with the machine, but I do have some of her data on sleepyhead on both my computer and on Mom's computer. Depending on how Thursday works with the RT, I'll get more info posted, as soon as my time allows. ( New job is keeping me extra busy with less time to get this all to the forum.)

[Sludge]

In the meantime, Mom has had a string of 3 nights with a good or at least reasonable AHI with readings under 6 or lower.

Is that on the previous settings or have you done any wingdinging?

[College3girls]

Mom's settings are still at the range proposed by Robysue a week or so ago. IPAP lowered from full range to 21 and EPAP raised from 10 to 13. With these settings, the majority of time her AHI is below 10, and actually frequently below 5. She did have one really high night of 25. Maybe Pugsy's aliens paid a visit.

I know an even more narrowed range of 21/17 has been suggested, and possibly a trial of straight pressure. Everything is kind of waiting on the sleep study paperwork and the RT appointment tomorrow afternoon.

The leaks that used to wake her have been conquered and the mask is no longer leaving red marks that last all day. The gel pad on the bridge of her nose solved all that. She feels she is sleeping soundly all night, and she is sleeping longer, usually at least 8 hrs.

[Sludge]

IPAP lowered from full range to 21 and EPAP raised from 10 to 13. With these settings, the majority of time her AHI is below 10, and actually frequently below 5. She did have one really high night of 25.

If our position is going to be that all (or most) of the events are central, then increasing EPAP (or increasing anything, really) may not be the best wingding here.

[Sludge]

PEEP optimization procedure according to optimal Xrs. The upper panel shows tracheal pressure and the lower panel shows respiratory system reactance (Xrs) measured at end-expiration over time during a representative positive end-expiratory pressure (PEEP) optimization procedure. PEEP was increased up to 20 cmH2O, and then decreased in one-minute steps of 2 cmH2O while Xrs was continuously monitored. When Xrs started to decrease, PEEP was increased back to 20 cmH2O and finally set to the PEEP level corresponding to the maximum Xrs.

[College3girls]

I'll keep you posted on what happens tomorrow. How many days in a row of an AHI at or below 5 are needed before a determination of correct therapy is made? While things are still erratic, they are much improved over what they were at the start of VPAP. I'm as anxious as everyone else to get my hands on the titration study to see what it show. Keep in mind however, that the mask fit during that titration was awful. Having a mask that is comfortable has been half the battle, and that alone is making a big difference.

[Sludge]

Is the eyesight of FOTResMed 20/20 at high pressures?"

Therefore, if we attempting (in this case anyway) to label FOTResMed inaccurate, there should at least be some logic to do so.

So if we are to make an assumption as (apparently) drastic as above (namely, the ResMed FOT algorithm is a LSOS) we must offer our reasons (as occasionally syllogistic as they may be):

• FOT has been around a long time.
• FOT is not rocket science. You vibrate the airway and see what shakes out (so to speak).
• FOT will measure the resistance in it's path.
• FOT cannot tell you what the resistance is from.
• A lot of things increase airway resistance.
• In the case of the pig, simply jacking up the BiPAP will do it (although technically, they changed compliance).
• The ResMed FOTorithm may work by having a pre-set fixed resistance and using that as the differentiation point for open or closed airway.
• The FOT signal is undoubtedly dampened by leaks, and there is always a planned leak in xPAP therapy.
• The more pressure, the bigger the leak.
• FOT may be disturbing to the patient, which may be why it is not commonly used to identify and treat all respiratory events (which it can if it wants to).
• Or the "good" FOTorithm could be patented.
• Which I doubt or somebody would be using it.
• Although Weinmann's using it at 20Hz.
• But their signal is calibrated, which "IMHO" offers a huge advantage in sensitivity.
• Or it only works if you have a good FOTorater, and then we're back to where we were

  20 years ago

• But what "IMHO" happened was that Respironics came out with pulse technology to identify central ("clear airway") apneas, ResMed had to put something on the table, and thus were "forced" to throw out what they had.

[Sludge]

Note to self:

• F&P Simplus full face mask promotes CO2 washout when mouth breathing because of design;
• Consider nasal restriction/obstruction responsible for obstructive apnea identification if nasal breathing; and
• Sure seems like people forgot what the A10 Rule was all about.

[robysue]

IPAP lowered from full range to 21 and EPAP raised from 10 to 13. With these settings, the majority of time her AHI is below 10, and actually frequently below 5. She did have one really high night of 25.

If our position is going to be that all (or most) of the events are central, then increasing EPAP (or increasing anything, really) may not be the best wingding here.

I agree here. I'd be exceptionally cautious about increasing the minimum EPAP.

I know an even more narrowed range of 21/17 has been suggested, and possibly a trial of straight pressure. Everything is kind of waiting on the sleep study paperwork and the RT appointment tomorrow afternoon.

Increasing the min EPAP from 13 to 17 is a huge increase, particularly if it's done all at once.

Moreover if PS remains set to 4, then a setting of min EPAP = 17 forces the min IPAP = 21, so essentially settings of min EPAP = 17, max IPAP = 21 means the pressures will be fixed at 21/17 all night long. And we know your mom seems to be a high risk of long chains of what look like misscored CAs once the pressure gets up around IPAP = 21.

So increasing min EPAP seems like a very bad idea to me.

Fixed pressures might still be a good idea, but I think the fixed IPAP would need to be lower than the current max IPAP = 21. I don't have a good guess as to how much lower ...

I'd suggest extreme caution as far as increasing either the min EPAP or max IPAP settings, even if the RT tells you to do so because of the large number of "OAs" being scored.

How many days in a row of an AHI at or below 5 are needed before a determination of correct therapy is made? While things are still erratic, they are much improved over what they were at the start of VPAP.

I know it sounds frustrating, but the answer is "it depends". I think it's important to look at the overall trends in the data, rather than individual good and bad nights when you are trying to make a decision about the dial winging.

And in this case, I think that the "trends" you want to keep an eye on are:

• The frequency of the really bad nights. One or two bad nights in a two week period is one thing; one or two bad nights out of every four nights is something else.
• Length of the worst of the clusters each night. A 15-minute bad cluster is one thing, a two-hour one is something else entirely.
• Pressures at which the really bad and really long clusters occur at. It's worth noting if the worst of the clustering continues to occur mainly when the IPAP pressure is running at or near 20cm. It's also worth noting just how far (and how quickly) the pressure rises at the beginning of each cluster.

Unless the RT has a better idea to try (and increasing the min EPAP pressure or the max IPAP are NOT better ideas IMHO), then I'd be inclined to leave the settings were they are for at least 2-3 weeks (maybe even a month) unless its clear that the frequency of the really bad nights remains really high.

And if the number of really bad nights does remain high, then I'd seriously consider lowering the max IPAP rather than increasing the min EPAP.

[robysue]

PEEP optimization procedure according to optimal Xrs. The upper panel shows tracheal pressure and the lower panel shows respiratory system reactance (Xrs) measured at end-expiration over time during a representative positive end-expiratory pressure (PEEP) optimization procedure. PEEP was increased up to 20 cmH2O, and then decreased in one-minute steps of 2 cmH2O while Xrs was continuously monitored. When Xrs started to decrease, PEEP was increased back to 20 cmH2O and finally set to the PEEP level corresponding to the maximum Xrs.

Just trying to see whether I understand what these two graphs are supposed to say.

The top chart is the PEEP, and PEEP is the external positive air pressure applied to the system? This PEEP data seems to be a range of values (represented by vertical line segments) for each time value. Is it totally off base to think of the min value of each of those line segments as "EPAP" and the max value as "IPAP"?

The bottom chart is Xrs = respiratory system reactance. But what exactly is respiratory system reactance? Is it some kind of measure of how stable the breathing pattern is? The higher the Xrs, the better? (Given the NEGATIVE numbers on scale on the Xrs chart, "higher Xrs" actually means the Xrs is closer to 0, and "lower Xrs" means the Xrs is further from 0.)

When Xrs started to decrease, PEEP was increased back to 20 cmH2O and finally set to the PEEP level corresponding to the maximum Xrs.

So that explains the funny looking "bump" in the PEEP graph around t = 460 to t = 500.

Xrs was not being monitored during this time?? (There are no dots on the Xrs graph for this time frame.) And then there was one more Xrs reading taken after the PEEP was lowered back to the optimal PEEP and it's right around the same height as the max Xrs value(s) at around t = 240. Was this to confirm that the optimal PEEP (around 10 cm H2O) really is optimal for this particular person?

Finally, is there any significance to the fact that the lengths on those vertical line segments in the PEEP graph get shorter as the PEEP is lowered?

[Sludge]

Increasing the min EPAP from 13 to 17 is a huge increase, particularly if it's done all at once.

But how did we even get to 13?

[Sludge]

Is it totally off base to think of the min value of each of those line segments as "EPAP" and the max value as "IPAP"?

That is exactly what it is.

But what exactly is respiratory system reactance?

The reactive component of respiratory impedance, Xrs incorporates the mass-inertive forces of the moving air column in the conducting airways, expressed in the term inertance (I) and the elastic properties of lung periphery, expressed in the term capacitance (Ca).

This is critical because if you will note in the Figure, a fixed VT is being used. At high PEEP (or EPAP) PS needed to send in this constant tidal volume was 25 cmH20, while at ideal pressures, it only took 10 cmH2O!!!

BTW, this was on a bunch of drowned pigs (later sacrificed to look at other stuff), but hey, you really couldn't do this on a real person.

Anyway, this shows that if you overly inflate lungs, they become less compliant, and there is a point of no return. Consequently

EPAP, especially high EPAP, is not just a number with infinite range!!

Finally, is there any significance to the fact that the lengths on those vertical line segments in the PEEP graph get shorter as the PEEP is lowered?

It is all the significance.

[Sludge]

Returning to our hypothesis (these are ALL central), the point of bringing up this lung behavior is to offer an explanation for the supposed error, namely:

If the lung is over-inflated, does FOT interpret the Xrs as obstruction, when the airway is, in fact, completely open?

I mean, is the cut-off for OA/CA via FOT the same for everybody (unlike SomnoSmart, which appears to calibrate based on the individual)?

So now you have this tiny lady, over-inflated, maybe some other factors (see above), how do we know any of it is correct?

[Jay Aitchsee]

Note to self:

• F&P Simplus full face mask promotes CO2 washout when mouth breathing because of design;

Sludge, is this compared to other masks? That is, does the Simplus promote more CO2 washout when mouth breathing than other FFM? If so, does that mean mouth breathing Simplus users could be inclined to experience more Central Apneas than mouth breathing users of other types of FFM? Is this a result of purposeful design or happenstance?