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Hypoapnea algorithm and pressure
#1
Hypoapnea algorithm and pressure
[attachment=20172]I have a couple of general doubts regarding the increase in autocpap pressure. I don't know if it happens only on the resmed airsense10 autoset model or it is on all machines.
1.-Why doesn't an increase in pressure occur when hypoapnea is detected?
2.- According to the graphics I see, the hypoapneas do not always follow the same criteria, I am confused. Sometimes they are marked as hypopnea and in others when the graph visually looks the same, hypopnea is not declared ...
That algorithm seems to use different parameters on each occasion, don't you think?
Attached screenshot with the flows marked.
And at the bottom of the graph, there is the pressure graph, with respect to the number 1 doubt and it is seen that it remains unchanged, at 6.8, which is the minimum autocpap pressure
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#2
RE: Hypoapnea algorithm and pressure
Hard to read in your graphic but hypopneas is based on flow because the machine cannot measure blockage. So more specifically a hypopneas is measure by a reduction in flow. Reduction from what? Measured normal flow. What is measured normal flow? A moving average of flow for a period of time prior to an event. My guess is they do not eliminate all sub normal flows from this average so when multiple events occur within this moving avg normal rate drops raising the 2nd hypopneas above the threshold for declaring a hypopneas. This can be even clearer when viewing RERAS that are not labeled but are preceded by long periods of flow limits.
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#3
RE: Hypoapnea algorithm and pressure
An auto CPAP responses to events is not immediate it does not work that way, the events occur the machine thinks about it and then may raise pressure if deemed appropriate
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#4
RE: Hypoapnea algorithm and pressure
(02-21-2020, 09:21 AM)bonjour Wrote: Hard to read in your graphic   but hypopneas is based on flow because the machine cannot measure blockage.  So more specifically a hypopneas is measure by a reduction in flow.  Reduction from what?  Measured normal flow.  What is measured normal flow? A moving average of flow for a period of time prior to an event.  My guess is they do not eliminate all sub normal flows from this average so when multiple events occur within this moving avg normal rate drops raising the 2nd hypopneas above the threshold for declaring a hypopneas.  This can be even clearer when viewing RERAS that are not labeled but are preceded by long periods of flow limits.

The graphics reflect only that the machine does not follow a uniform pattern, that is all I wanted to show. In identical events, some are labeled hypopnea and others are not labeled. In this little piece of sample, the one indicated, there is no flow limitation, Bonjour, so that would not be the explanation, it seems to me. On whether RERA shows more or less, no idea, because as I said yesterday, I can not see RERA with this machine. By the way, Bonjour, I sent you yesterday in a private serial number and model number as requested. Do you already know what date my Resmed machine is?
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#5
RE: Hypoapnea algorithm and pressure
(02-21-2020, 09:21 AM)bonjour Wrote: Hard to read in your graphic   but hypopneas is based on flow because the machine cannot measure blockage.  So more specifically a hypopneas is measure by a reduction in flow.  Reduction from what?  Measured normal flow.  What is measured normal flow? A moving average of flow for a period of time prior to an event.  My guess is they do not eliminate all sub normal flows from this average so when multiple events occur within this moving avg normal rate drops raising the 2nd hypopneas above the threshold for declaring a hypopneas.  This can be even clearer when viewing RERAS that are not labeled but are preceded by long periods of flow limits.

Explanation of the graphic that I have sent, so that it is well understood, Bonjour. The first chart is the complete IAH chart; The clearest area highlighted is the one that is enlarged for analysis in the second graph, (the one below the first), those 13 minutes are highlighted. The third graph is the interval between one episode of the hypoapnea and the next and shows an area with the same time pattern and flattening of the flow wave and which, however, is not marked as hypopnea. Immediately below is the graph that shows an enlarged area between two other hypopnea that contains two episodes that may be hypopnea but that the machine does not detect. Why? I don't know and it's because of that curiosity I was asking. I understand that not everything in this world of CPAP has an answer, of course. Thanks
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#6
RE: Hypoapnea algorithm and pressure
I did not see your model and serial number.  I have not read all the posts since yesterday.  

The events do follow a pattern, BUT you do have to understand what the interpretation is based on.  In the case you cited here the 'normal' value was decreased because of the earlier hypopnea thus losing the determining criteria for hypopnea.    

FYI, there are a lot of flow limitations in that graphic, granted a number of them are minor, but they are there.
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#7
RE: Hypoapnea algorithm and pressure
(02-21-2020, 11:49 AM)bonjour Wrote: I did not see your model and serial number.  I have not read all the posts since yesterday.  

The events do follow a pattern, BUT you do have to understand what the interpretation is based on.  In the case you cited here the 'normal' value was decreased because of the earlier hypopnea thus losing the determining criteria for hypopnea.    

FYI, there are a lot of flow limitations in that graphic, granted a number of them are minor, but they are there.

Bonjour, I find this fascinating that says that one hypopnea changes to some extent the values for the consideration of another hypopnea if it is very often. I've always thought that, although I don't have a confirmation! On the limitation of flow, I also believe that there is, when studying the waves, but the machine does not mark it as such. Can it be broken? I have to value it.
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#8
RE: Hypoapnea algorithm and pressure
On ResMed I view the FL chart as an indication of how serious the FLs are overall. I look at the expanded Flow Rate chart if I need to see details. I ALWAYS see far more than is flagged. On RERAs, they are an indication that FLs are occurring because by definition they are a series of FLs ending in arousal. ResMed uses a 'flatness' index to indicate a FL. Respironics, well that is more of a mystery. I use any indication of FL on a PR machine as a reason to dig a but further, especially since PR CPAPs do not do a good job of treating them.
On ResMed I see .25-.33 as a level that really starts to impact an individual, though a few are hypersensitive to these changes.

Think about the algorithm, How do you determine "normal" You know nothing about the individual, All you can do is measure flow and pressure, what is 'normal'. Without question, over the years the algorithms will get more sophisticated, 'smarter' if you will. You see it a bit in the ASV and newer IVAPS algorithms.

I very much doubt that your machine is broken. But it gives you an idea of the knowledge of some of the so called experts on the forums.
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#9
RE: Hypoapnea algorithm and pressure
(02-21-2020, 12:35 PM)bonjour Wrote: Think about the algorithm, How do you determine "normal"  You know nothing about the individual, All you can do is measure flow and pressure, what is 'normal'.
So well stated.  This is something we all need to remember.  There have been no studies to actually determine ‘normal’ sleep.

I would think that someone without any discernible apnea or hypopnea events still has some degree of limitation.  It is beyond reason that any human being has continually perfect wave forms without any disruption over an 8 hour period.  Just turning over or swallowing interrupts the flow.

John
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#10
RE: Hypoapnea algorithm and pressure
(02-21-2020, 12:35 PM)bonjour Wrote: On ResMed I view the FL chart as an indication of how serious the FLs are overall.  I look at the expanded Flow Rate chart if I need to see details.  I ALWAYS see far more than is flagged.  On RERAs, they are an indication that FLs are occurring because by definition they are a series of FLs ending in arousal.  ResMed uses a 'flatness' index to indicate a FL. Respironics, well that is more of a mystery.  I use any indication of FL on a PR machine as a reason to dig a but further, especially since PR CPAPs do not do a good job of treating them.
On ResMed I see .25-.33 as a level that really starts to impact an individual, though a few are hypersensitive to these changes.

Think about the algorithm, How do you determine "normal"  You know nothing about the individual, All you can do is measure flow and pressure, what is 'normal'.  Without question, over the years the algorithms will get more sophisticated, 'smarter' if you will.  You see it a bit in the ASV and newer IVAPS algorithms.

I very much doubt that your machine is broken.  But it gives you an idea of the knowledge of some of the so called experts on the forums.

Bonjour, in relation to the flow limitation, I have read in the wiki that in general if they coincide with increases in pressure, they are flow limitations induced by the pressure of the CPAP. I have the feeling that all my flow limitations are of that type. Am I right? Add capture [attachment=20184]
I will ask you some questions about it, which seems to understand a lot about this topic and I want to learn if it doesn't bother you.
1.-The waves of the flow limitation that I observe are at peak in the expiratory part. Must be like this?. They are like sawtooth, rather than as waves at the bottom. I add capture [attachment=20187]
2.-In previous post comments that from .25-.33 flow limitation is already to investigate more, it is important. I add capture. [attachment=20186] What should I look at? The IAH index does not mark anything in that section, the pressure is maximum and there is no leakage.
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