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Palatal prolapse or VAuto misplacement of 0-axis baseline?
#1
Palatal prolapse or VAuto misplacement of 0-axis baseline?
My sense is that the zero-axis is about 0.1 liter lower than depicted by the OSCAR FR curve and by my replication of its form from the same SD card data. The effect being that what plots as expiration has to be leak. 

Two E waves with elevated E-curves lying on the zero axis show no expiration at all and, IMO, are accurate in that, but leak should be shown. No leak is shown for the entire duration indicated. 

Is my thinking wrong or the algorithm wrong? 

The lower, blue-colored FR curve shows the basis of my calculated inspiration and expiration volumes (sums of .04 sec X incremental FR strips as shown by the bottom bar or bristle graph).

When summed the whole series of I and E volumes adds up to a residual -0.21 liters, confirming my thought that equality of I and E volumes works itself out in the course of 2 - 4 waves. One looking at the bars can see (or imagine) that. But it looks like the algorithm wrongly imposed that base setting regime here.  

My fragment of understanding--misunderstanding?-- of the algorithm is that it uses a balancing of (a series?) of I and E volumes to set the zero axis. Looks like it is misplaced in all but two instances here. 


   
I have no particular qualifications or expertise with respect to the apnea/cpap/sleep related content of my posts beyond my own user experiences and what I've learned from others on this site. Each of us bears the burden of evaluating the validity and applicability of what we read here before acting on it.  (Disclaimer use permitted by sheepless)

 
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#2
RE: Palatal prolapse or VAuto misplacement of 0-axis baseline?
Why not both?

You are using pillows, so if the palatal prolapse is sealing off your nose from your airway then the machine isn't part of your airway loop during the prolapses. So the machine sensors are literally out of the loop, knocking on a firmly closed door.
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#3
RE: Palatal prolapse or VAuto misplacement of 0-axis baseline?
(03-18-2022, 11:36 PM)cathyf Wrote: Why not both?
Yes, correctly both. PP and misplaced baseline, the latter for all but two expirations.
I have no particular qualifications or expertise with respect to the apnea/cpap/sleep related content of my posts beyond my own user experiences and what I've learned from others on this site. Each of us bears the burden of evaluating the validity and applicability of what we read here before acting on it.  (Disclaimer use permitted by sheepless)

 
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#4
RE: Palatal prolapse or VAuto misplacement of 0-axis baseline?
So no leak is present and inhale/exhale volume appear similar, I fail to understand what makes you think there is an issue with the data?

I interpret this as a partial palate obstruction limiting exhalation flow rate. Brief normal exhalation rate slamming the palate partially closed and then you effectively having to exhale out through a small straw against pressure. When slamming shut some of the breaths briefly hit 0 flow rate and a couple of the exhales do stay at 0 flow rate for the entire time. Many of these exhales have snore/flow variation present indicating level of obstruction is varying which makes sense.

Imo this is what expiratory palate restriction looks like much like how we know inspiratory flow limitation looks like.

Could leak calculation be playing some very minor role in the data? Maybe but imo it is not causing misplacement of the 0 flow rate.
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#5
RE: Palatal prolapse or VAuto misplacement of 0-axis baseline?
(03-19-2022, 12:23 AM)2SleepBetta Wrote: Yes, correctly both. PP and misplaced baseline, the latter for all but two expirations.

Further to my other response if you correct 0 to exhalation flow rate you would have big inhalations breath after breath and no exhalations. Lungs obviously don't work that way and I fail to see how a leak rate calculation could explain this.
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#6
RE: Palatal prolapse or VAuto misplacement of 0-axis baseline?
Physically I think these exhalations end up looking near flat at a low flow rate for the following reasons.

Exhalation is driven by gravity and muscle tension. This combination creates an internal pressure and as air is exhaled this pressure decreases. I believe as this internal pressure decreases and comes closer to the CPAP pressure on other side of the palate the palate starts to open up slowly increasing the area of open airway. The larger open airway combined with smaller pressure maintains a similar flow rate. Then eventually spontaneous inhalation starts (muscles start expanding chest/diaphragm) and this pops the palate prolapse back open and inhalation of then next breath starts.
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#7
RE: Palatal prolapse or VAuto misplacement of 0-axis baseline?
(03-19-2022, 01:12 PM)Geer1 Wrote: Further to my other response if you correct 0 to exhalation flow rate you would have big inhalations breath after breath and no exhalations. Lungs obviously don't work that way and I fail to see how a leak rate calculation could explain this.

Exactly, so the answer had to be that if volumes of single or successive combined "expirations" are in balance with single or successive combined successive inspirations then the "expirations" all had to be unshown leaks--according to that wrong line of thinking.

My problems were (a) inability to get my head around the right-angle upturn of the expiration curve being a sudden burst of expiration which quickly and straight-line smoothly became a high slope inspiration wave and (b) being flummoxed by noticing, for the first time ever, some positive and zero read-out values below the 0-axis at cursor locations just before airflow changed to inspiration. Noticing one by accident, I looked at others and should have copied those. Drafting this, I found a couple of barely noticeable instances to include here. 

I'm guessing those almost microscopic things, artifacts?, arise from pixel or other granularities of some kind at different zoom levels, vertical and/or horizontal or from how the algorithm sets and maintains the 0-axis by balancing TV with expirations. It's not reasonable to expect our devices to render needless accuracy. But noticing the discrepancy when puzzling over palatal prolapse, while knowing of cathyf's bizzare FR curve episodes, I simply drew the wrong conclusion.

Thank you, Geer1, for your clear explanation. 

Given the PP context where it is relevant, is it not true that gravity, except maybe in the case of the obese, comes into play as atmospheric pressure to help elastic rebound expel CO2 laden air after inspiration--that requiring little muscular effort in quiet breathing.  

   
I have no particular qualifications or expertise with respect to the apnea/cpap/sleep related content of my posts beyond my own user experiences and what I've learned from others on this site. Each of us bears the burden of evaluating the validity and applicability of what we read here before acting on it.  (Disclaimer use permitted by sheepless)

 
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#8
RE: Palatal prolapse or VAuto misplacement of 0-axis baseline?
If you play with your mouse/cursor you will realize that the value displayed matches where your mouse cursor is rather than the green line. For whatever reason the green line is usually left of the mouse cursor 1-2 pixels. Play around with it enough you will find that you can move the mouse cursor and see value change without the green line moving.
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