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hypopnea duration
#1
hypopnea duration
I posted this in the oscar beta test forum; it was suggested I put it here.  recently I noticed that in the overview page 'total time in apnea' was sometimes blank even though the ahi graph showed events.  turns out that the 10 second entry for each hypopnea was removed from oscar.  my response: 

an h has to be at least 10 seconds to be flagged, no?  if not assigned at least 10 seconds, will h be included in the 'time in apnea' statistic?  and the 'total time in apnea' graph?  if not, I would prefer to go back to counting them as 10 seconds; still not precise but more accurate than not including duration at all.
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#2
RE: hypopnea duration
It turns out the info is not provided by the machine.  The goal of OSCAR is to be accurate and REPORT what is reported by the machine.  If or more likely when we bring that back you will know what and how it was determined.
Fred Bonjour - Project Manager and Lead Tester for OSCAR - Open Source CPAP Analysis Reporter

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#3
RE: hypopnea duration
As far as I know, Resmed does not report the duration of hypopneas. SleepyHead arbitrarily assigned 10 seconds to them. The aim of OSCAR is to try and report, as honestly as possible, the data of each CPAP. Since Resmed doesn't record the time, OSCAR shouldn't be injecting data that doesn't exist. I believe this subject is still open.

I hope this answers your question.
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#4
RE: hypopnea duration
yes, I understand the reasoning but haven't seen a response to: the fact that it has to be at least 10 seconds to be flagged (so it isn't entirely arbitrary) and the question about whether time in apnea and total time in apnea is off by not including something for hypopnea. if the statistic and chart include some time associated with hypopnea, I'm less concerned.

are you saying that nothing oscar reports is a calculation (in oscar)?
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#5
RE: hypopnea duration
by no means is everything in OSCAR wrong. This is one that was.
OSCAR calculated Compliance differently in different places, (in one spot it did not count skipped days) This has been corrected.

Issues that are found are validated and entered into a tracking system. Many of the issues have come from outside the team. The OSCAR team believes strongly in fixing all validated issues that are found. Many are discovered in this very forum.
Fred Bonjour - Project Manager and Lead Tester for OSCAR - Open Source CPAP Analysis Reporter

Download OSCAR
New to Apnea? Helpful tips to ensure success
Soft Cervical Collar
Mask Primer
Dealing with a DME
Organize Charts
Optimizing Therapy
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#6
RE: hypopnea duration
sorry, I don't follow, bonjour. was that meant for this thread?
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#7
RE: hypopnea duration
Coming back to the original question - I think it could be re-phrased as "Should the total time in apnea include time in hypopnea? If so, how is it to be calculated?"

My view is that apnea is effectively a cessation of breathing and total time in apnea is a very useful statistic. Hypopnea, while not to be ignored, is not a complete cessation of breathing. Adding time in hypopnea to time in apnea would give an answer just as wrong / misleading as not including it. Given that we don't actually know the duration of hypopneas, perhaps the best we could do is say time in apnea is one reasonably accurate statistic and time in hypopnea is not less than the number of hypopneas x 10 seconds.
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#8
RE: hypopnea duration
Total time in Apnoea is a statistic that is unique to Sleepyhead/Oscar we need to define what it contains and how it can be used p. This thread is a useful discussion of those concepts, there is no right or wrong answer just a consensus that the team need to agree.


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#9
RE: hypopnea duration
I don't know what should be done in this case, but I hope you won't mind a question about machines and reports (and particularly about PR Dreamstation's Hypopnea reports).

The vast majority of my reported events are hypopneas, and at least one definition I've found says that's a 50% drop in airflow plus EEG arousal or reduced SpO2.  Since I don't have electrodes or a finger monitor, the Dreamstation must be looking at something else to flag hypopneas.  Looking at the flow rate, I don't see any clear signature it might be keying on.  (There's often a slightly-longer period between breaths, but it's only a second or two, and not in a sequence that's otherwise exceptional.)  The OSCAR UI shows a duration, though, so the Dreamstation must be identifying something as the start and the end (right?)
           

I'm thinking that if I knew what was getting flagged, I'd have some basis for trying to figure out what was causing it, and from there to stopping it from happening.  Otherwise, it feels like I'm just chasing a number that doesn't have any particular significance.

Since you seem to be some of the OSCAR devs, a couple other quickies:

* Can OSCAR accept / display heart-rate data?  (I'm working on a way to record data from a Bluetooth heart rate monitor, and I'd like to see it correlated with my respiratory data.)

* What is the resolution of the pressure data?  The UI makes it look continuous (in time and value), but that seems like it would be a lot of data!
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#10
RE: hypopnea duration
>>>an h has to be at least 10 seconds to be flagged, no?<<<

Well, I'm not so sure. We have to find the definition that ResMed is using... back in a bit... Ahh, page 19 of the Clinician's Manual: 
     "A hypopnea is when the respiratory flow decreases to 50% for at least 10 sec."

The American Society of Sleep Medicine page https://aasm.org/aasm-clarifies-hypopnea...-criteria/ is different:
    "The peak signal excursions drop by ≥30% of pre-event baseline...PAP device flow..."

I think the difference there is between peak flow rate and average flow volume, but I'm not sure.

So, at least 10 seconds... but exactly how long? We don't know. And decreases to 50% from what base value? Presumably the average during some previous time period. But how long? And if it's a moving period, the average will decrease during the hypopnea time interval. This will sure confuse things. And, as far as I can tell, ResMed has never answered these questions in public.

Now back to the original question: Should Total Time in Apnea include the time in hypopnea? Well, no, because a hypopnea is not an apnea, even if we knew how long these hypopneas lasted. 

There's no doubt that we should keep track of hypopneas; they do disrupt our sleep. My own Total AI is quite often zero, my AHI runs between 1.5 and 3. But before we can create a Total Time in Hypopnea we have to decide - computably - when they start and end. And we have to remember that we are being as arbitrary as the people that decided it wasn't an apnea unless it lasted at least ten seconds.
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