rested gal wrote:Snoredog wrote:My understanding is the 420e only scores CA's on line 2 when it hears cardiac oscillations associated with an open airway. So for the CA's found on line 2, it hears cardiac oscillations associated and is 100% accurate in those detections.
That's what I'm questioning..that 100% accuracy of the 420E in being correct - always correct - when it says "Now, THAT's a central apnea." I always thought the 420E would be right about that. Now I wonder.
At the same time the 420E was chalking up those centrals for me, the PSG equipment was saying "centrals = zero."
to be honest, I really don't know
where that "100% accuracy" claim even came from?, was it from some study? I know the help screen/manual includes info from some study (from memory, brain fade here) that only 60% of central apnea has an open airway present, the other 40% may be closed.
SAG's interpretation above of the 420's ability to detect cardiac oscillations over a closed air way is new to me. I thought it was looking for those associated with a inhale. Is cardiac pulsation the same thing? (I'm no cardiologist).
So if your airway is closed and you are experiencing a central apnea, are you not having an obstructive apnea at that point? If you were manually scoring these, where would you report the
central event with the closed airway? Let's see, the airway is blocked, there is no airflow, that is a obstructive apnea to me.
For examples sake, lets say machine detects 10 central apnea. Based on that help screen study, 6 of those 10 (avg) would have an associated "open" airway, if the airway is open the machine can hear/sense the cardiac oscillations and see absence of airflow.
So it is looking at 2 parameters in determining if the event is central, then if it is to respond, additional parameters such as current delivery pressure, command on apnea value. That by itself makes the 420e much more accurate then the latest auto's on the market which only look at absence of airflow and the latter parameters.
So if we assume that 6 of those 10 had open airways with cardiac oscillations, then they would be scored on line 2 as "Apnea/CA". The other 4 centrals would be scored under line 1 as simply Apnea (obstructive).
So if the 420e scored those 4 centrals (with the closed airway) as "obstructive" on line 1, then it would be technically incorrect when scoring those 4 events or would it?
So based upon the 420e's own admission, the 420e is 60% accurate in scoring central apnea, BUT of those it scored on line 2 it would be 100% accurate based upon its own selection criteria. By simply looking at the additional parameter of cardiac oscillations, the 420e is obviously more accurate in differentiating the event than nearly all other cpap autos on the market.
I wonder what the real difference is with the AdaptSV type machines, are they simply doing a better job with differentiating central apnea from obstructive? Are they also listening for cardiac oscillations like the 420e has been doing for years?
The sensor contained in the Remstar for example has always been able to detect cardiac oscillations just like the 420e but for unknown reasons they never implemented it within the firmware/software, the ability to do so has always been there. I know the S7 Spirit wasn't capable of doing that, the S8 now is, but they didn't implement it either. Maybe PB has the patent on that, I don't know.
Lab PSG accuracy: You have more experience with that than I on that front, but my understanding is those are "manually" scored and subject to the interpretation of the tech doing the scoring observing and interpreting the event on the EEG. Is the lab's transducers any more accurate/sensitive than the ones used inside the machine? I don't know, I know Dr. Sullivan has questioned the accuracy/sensitivity of the lab transducer in the past.
We pulled up the Honeywell (think it was the 9000 series) transducer/Phenumotach sensor once, if I recall correctly the device is pretty accurate and sensitive enough to actually sense CO2 levels. After seeing that I brought up the question why they didn't take advantage of that function/feature in the design of the AdaptSV machines, seems to me if you are going to pay so much attention to dead space and mask exhaust rates that the machine could detect changing CO2 levels. But I guess while the device may be capable of actually doing that, getting it do do that accurately from the end of a 2m hose is a bit of a challenge.
Notice that the 420e has the smaller pressure sensor line right at the mask, then some of the Resmed SV style machines have the same, are they measuring pressure (sure they are) or are they also measuring CO2 levels, who knows.
When you think about it, finger pulse oximeter is not very accurate either.
I know we have seen many patients show up here with Zero CA's listed on their PSG reports then they have another titration with another tech and they magically appear (are they like me I didn't have any night before last). How do we know?
I know with my own case, I don't have them every night and other nights I may have a dozen (making no changes to the machine). Last night I had 2 at what appear to be about the time I was in REM and yet the night before I had zero and I woke up at 4AM wide awake and couldn't get back to sleep, reason I looked at the report, I didn't have any obstructive apnea, no centrals only about 6 or so hypopnea. Last night when I had the 2 CA's logged, I actually felt better today.
I sold my house and in the process of moving near Sacramento, so i've been doing alot of work packing so I've been pretty dead by the time night comes around.
After seeing numerous Remstar reports and LCD data, I have a much higher confidence level with the 420e being accurate with its data than say the Remstars. I think the Encore reports are much more accurate than the LCD and there can be many reasons for that.
I mean when you look at it, Silverling software has been out what 6 or 7 years now? with not many changes that I can tell, about all I've seen from 3.0 was them adding the additional machines to the library when they came out with the 420 series and later the 425 series. 3.0 worked as well as 3.2, if they came out with 3.3 don't think i would buy it.
