Central Apneas and Respiratory Rate

[deltadave]

Oh you think you're the cat's banana.

You're just mad 'cause you didn't think of that.

BTW, did you ever consider that the straight line of the Tidal Volume would be that even if it did Breath-by-Breath Calculation, it is simply waiting for the next breath?

[NotMuffy]

Oh you think you're the cat's banana.

You're just mad 'cause you didn't think of that.

BTW, did you ever consider that the straight line of the Tidal Volume would be that even if it did Breath-by-Breath Calculation, it is simply waiting for the next breath?

OK then Mr.-Know-It-All, why doesn't the Respiratory Rate and Minute Ventilation drop when the Tidal Volume finally registers?

[Muffy]

Oh you think you're the cat's banana.

You're just mad 'cause you didn't think of that.

BTW, did you ever consider that the straight line of the Tidal Volume would be that even if it did Breath-by-Breath Calculation, it is simply waiting for the next breath?

OK then Mr.-Know-It-All, why doesn't the Respiratory Rate and Minute Ventilation drop when the Tidal Volume finally registers?

Speaking from a purely clinical point-of-view, it would make sense to suspend Respiratory Rate during periods of apnea. If it were an obstructive apnea, while flow (and consequently Tidal Volume) would hit zero, underlying repiratory effort would continue, and thus reporting Respiratory Rate = 0 would be inaccurate.

[StillAnotherGuest]

Oh you think you're the cat's banana.

You're just mad 'cause you didn't think of that.

BTW, did you ever consider that the straight line of the Tidal Volume would be that even if it did Breath-by-Breath Calculation, it is simply waiting for the next breath?

OK then Mr.-Know-It-All, why doesn't the Respiratory Rate and Minute Ventilation drop when the Tidal Volume finally registers?

Speaking from a purely clinical point-of-view, it would make sense to suspend Respiratory Rate during periods of apnea. If it were an obstructive apnea, while flow (and consequently Tidal Volume) would hit zero, underlying respiratory effort would continue, and thus reporting Respiratory Rate = 0 would be inaccurate.

It may be a combination of all of these factors, as well as the sampling window for Respiratory Rate. ResMed uses a 5 Breath Average in the VPAP III Series, and perhaps that calculation carries over here, with the possible exception that the first breath following an apneic event is excluded.

This hypothesis (SAGpothesisVIII) may be demonstrated in the following example of bradypnea:



While this incredibly slow rate should have registered 4-5 BPM at some point, it would appear that (1) tidal volume and rate calculation are effectively suspended as the algorithm waits for a pure patient breath following an FOT scout; so consequently (2) nearly every breath is excluded, and the algorithm must go back and search for 5 clean secondaries, leaving the RR at 16.00.

[NotMuffy]

Data recording is not suspended during a central.

I did not say "Data recording is suspended", I said "data point update" is suspended. That string of 19.0s is self-refreshing and used for nothing other than drawing a line. If Respiratory Rate was truly being updated, then it would progressively fall as Texpiration becomes progressively longer. However, as noted by the previous posters, RR is apparently (1) calculated at inspiration of the next breath, and (2) suspended during certain criteria. These criteria may include respiratory events (apneas, but not hypopneas) and FOT scouts.

[-SWS]

Oh you think you're the cat's banana.

You're just mad 'cause you didn't think of that.

BTW, did you ever consider that the straight line of the Tidal Volume would be that even if it did Breath-by-Breath Calculation, it is simply waiting for the next breath?

OK then Mr.-Know-It-All, why doesn't the Respiratory Rate and Minute Ventilation drop when the Tidal Volume finally registers?

Speaking from a purely clinical point-of-view, it would make sense to suspend Respiratory Rate during periods of apnea. If it were an obstructive apnea, while flow (and consequently Tidal Volume) would hit zero, underlying repiratory effort would continue, and thus reporting Respiratory Rate = 0 would be inaccurate.

Funny banter... good content.

Speaking from an algorithmic PAP-treatment point of view, I would add that rate type feedback variables are probably maintained with larger granularity (temporal scope) based on algorithmic analysis and treatment objectives----far more than graph-reporting objectives. By contrast to those longer-scope rate variables, shorter-scope---and even instantaneous flow-based variables---are necessarily maintained for tasks such as SDB event detection or per-breath proportional assist calculations.

[LoQ]

[DreamDiver]

Lots of bran in those muffins this morning...

[LoQ]

[LoQ]

Maybe this is just too dumb of an idea, but has anybody given any thought to the chance that since they are reporting respiratory rate in BREATHS PER MINUTE, what you are seeing in the respiratory rate during an apnea are the number of breaths in the minute prior to the point on the graph you are examining? You would have to stop breathing for a whole minute for the respiratory rate, when given in BREATHS PER MINUTE, to go to zero, wouldn't you?

[M.D.Hosehead]

Following.

[NotMuffy]

Maybe this is just too dumb of an idea, but has anybody given any thought to the chance that since they are reporting respiratory rate in BREATHS PER MINUTE, what you are seeing in the respiratory rate during an apnea are the number of breaths in the minute prior to the point on the graph you are examining? You would have to stop breathing for a whole minute for the respiratory rate, when given in BREATHS PER MINUTE, to go to zero, wouldn't you?

I don't think it's a 60-second floating window, and I believe this example demonstrates that it's a 5 breath floating window instead:



There is a pause following breath 11, long enough to to trigger a small FOT scout. RR drops during the 5 breath floating windows that include the pause, and peak RR occurs once the pause is excluded. The highlighted 5 breath window excludes the breath that terminates the FOT scout.

[-SWS]

...this example demonstrates that it's a 5 breath floating window

Also following. That earns a new Muffin pan... or NotMuffin pan if you prefer... or even a miniMuffin pan/not-pan.

[LoQ]

I don't think it's a 60-second floating window, and I believe this example demonstrates that it's a 5 breath floating window instead:

Interesting example. I looked at half a dozen central apneas in my data, and a couple of obstructive apneas. I could not find that pattern. I dunno. I also have no alternate explanation for your example, so I concede.

[LoQ]

The gospel according to Muffy is found here:
The Muffin Bible
That must be where he gets all of his charts and stuff.