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Help understand the different machines
#21
(06-22-2014, 04:29 PM)jcarerra Wrote:
(06-22-2014, 04:06 PM)robysue Wrote: Auto PAPs do NOT raise the pressure during an apnea; they wait until the event is over to respond.

The rationale is simple: CPAPs and ordinary Bi-levels are NOT ventilators. In order to try to force an inhalation (i.e. "blow through the obstruction") the machine would have to jack up the IPAP really, really HIGH--as in by 10-12 cm of additional pressure or more. And that kind of pressure change can cause its own problems with sleep continuity.

In other words, CPAPs and APAPs work by preventing the vast majority of events from occurring in the first place.

OK, but my musing has to do with why it is EPAP being raised vs. IPAP?

When the airway collapses completely, it typically collapses during the exhalation. More EPAP makes it harder for the aiway to collapse during the exhalation.


Quote:And does the image look like RERA?
oops nevermind--those were called OAs so can't be RERA by definition.
Those OAs look like they might just be mis-scored CAs to me. They have a very distinct pattern that is common to CSA and CompSA patterns:
  • Big breaths which blow off too much CO2 lead to
    less urge to breath which leads to
    shallower and shallower breaths which leads to
    blowing off too little CO2 as the breathing becomes shallower and a (central) apnea at the nadir of the cycle, which leads to
    Big breaths which blow off too much CO2 ...
And the cycle repeats over and over in roughly the same amount of time until something happens to break the CO2 overshoot/undershoot cycle. That "something" is typically an arousal or an awakening.

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#22
(06-21-2014, 04:35 PM)jcarerra Wrote: 3. Finally, I have an opportunity, assuming things progress, to get at a terrific price a Respironics 750p which I think is
"Respironics PR System One REMstar BiPAP Auto w/ Bi-Flex"
(does 750p automatically equal precisely and totally that?

Yes. That's a good machine. I wish I had one.
Sleepster
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#23
(06-22-2014, 04:29 PM)jcarerra Wrote: OK, but my musing has to do with why it is EPAP being raised vs. IPAP?

Hi jcarerra,

Have you ever tried to suck something thick through a weak straw, like a milkshake or slushy partly-frozen slurpy, which, if you sucked too hard on the weak straw, would collapse or partially collapse the straw, until sucking on the straw harder actually reduced the amount getting through the straw? (I have.) The same fluid dynamics are sometimes evident in our Flow waveforms.

The early symptoms of this approaching problem are evident as "Flow Limitation", where the Flow is actually higher at the very start of inhalation and then the flow reduces because the suction created by our lungs during inhalation (or, to be more precise, because of the Venturi effect in our airway at the start of inhalation) has caused our airway to partially close off, lowering the rate of airflow we can get through our airway.

The most vulnerable time for an obstructive apnea to begin is at the end of EPAP or when the inhalation is just beginning and the machine has not yet switched to the higher IPAP pressure. If our airway is already closed off or nearly closed off at the end of EPAP, the suction of starting to inhale can be enough to cause the airway to finish collapsing completely, before the machine switches to IPAP.

As robysue mentioned, if the airway has already collapsed by the end of exhalation or at the very start of inhalation, a very large increase in pressure from the machine may be needed to re-open the airway. Machines with a "back up respiration rate" (such as ASV machines) will make that large increase in Pressure Support in order to end the apnea, but most machines just wait for the apnea to end. If EPR is turned on, after a fairly long time (such as 10 or 15 seconds, if memory serves) the machine will return to normal IPAP pressure, but it may be too small of an increase to help.

Take care,
-- Vaughn
Membership in the Advisory Member group should not be understood as in any way implying medical expertise or qualification for advising Sleep Apnea patients concerning their treatment. The Advisory Member group provides advice and suggestions to Apnea Board administrators and staff on matters concerning Apnea Board operation and administrative policies - not on matters concerning treatment for Sleep Apnea. I think it is now too late to change the name of the group but I think Voting Member group would perhaps have been a more descriptive name for the group.
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#24
(06-22-2014, 05:24 PM)robysue Wrote: Those OAs look like they might just be mis-scored CAs to me. They have a very distinct pattern that is common to CSA and CompSA patterns

The pattern is missing half of the typical sinusoidal oscillation (gradual-buildup, gradual slow-down) characteristic of Cheyne-Stokes Respiration (CSR).

The smooth, sinusoidal tapering off is present, but instead of a smooth and gradual restarting of breathing, the restart is abrupt, as with obstructive apneas.

The pattern does not look like simple CSR, but perhaps a combination of CSR plus relaxation/obstruction before the central apnea ends, which may explain why the machine scored these apneas as obstructive.

It is not that the apneas were not obstructive, but that they were both central and obstructive. (Central apneas which, by the time each central apnea ends, have transitioned into obstructive apneas.) This pattern may give new meaning to the term CompSA (Complex Sleep Apnea), which I think usually means central sleep apnea caused by Constant Positive Airway Pressure therapy.

Wikipedia article on CSR, with picture showing the characteristic gradual breathing transitions in CSR:
http://en.wikipedia.org/wiki/Cheyne-Stokes

.
Membership in the Advisory Member group should not be understood as in any way implying medical expertise or qualification for advising Sleep Apnea patients concerning their treatment. The Advisory Member group provides advice and suggestions to Apnea Board administrators and staff on matters concerning Apnea Board operation and administrative policies - not on matters concerning treatment for Sleep Apnea. I think it is now too late to change the name of the group but I think Voting Member group would perhaps have been a more descriptive name for the group.
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#25
Wow. You guys (and gals) are just nailing it. Well, I don't mean to say pinning exactly what is happening, but that your analysis is perceptive.

Just quick hits here...

Don't think Cheyne-Stokes was ever on the table for the reason you state---it just doesn't look like it--just "periodic breathing" .

This makes immense sense to me:
"They have a very distinct pattern that is common to CSA and CompSA patterns:
Big breaths which blow off too much CO2 lead to
less urge to breath which leads to
shallower and shallower breaths which leads to
blowing off too little CO2 as the breathing becomes shallower and a (central) apnea at the nadir of the cycle, which leads to
Big breaths which blow off too much CO2 ..."

That pattern is ALWAYS present during my clusters, and sometimes I see it other places along the timeline (not a lot), unscored as an apnea--which I judge to be because the "tail end" of the shallow breaths get small but not zero and/or shallow/zero breath time does not last long enough. But that shape is "my shape"-- a few stronger than normal breaths (recovering from the almost non-breathing leading into it), followed by declining volume, followed by near zero volume or zero. Then repeat.

I don't know how to discern if these are centrals or CSA+OSA or CompSA or what.

Here is an interesting article--the first one in the item--on CSA and CompSA
http://www.resmed.com/au/assets/document...0933r1.pdf

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