RE: Flow Limitation Units in Statistics
Not in any way intended to be derogatory, if you require a highly detailed flow limit chart, this could indicate the flow limit activity are for some reason part of poor therapy on PAP. Yes this is just based on speculation as I don't recall seeing a full OSCAR nightly sleep session. If that were supplied, we'd be able to help get PAP therapy better optimized.
INFORMATION ON APNEA BOARD FORUMS OR ON APNEABOARD.COM SHOULD NOT BE CONSIDERED MEDICAL ADVICE. ALWAYS SEEK THE ADVICE OF A PHYSICIAN BEFORE SEEKING TREATMENT FOR MEDICAL CONDITIONS, INCLUDING SLEEP APNEA. INFORMATION POSTED ON THE APNEA BOARD WEBSITE AND FORUMS ARE PERSONAL OPINION ONLY AND NOT NECESSARILY A STATEMENT OF FACT.
RE: Flow Limitation Units in Statistics
(03-24-2021, 04:14 PM)pholynyk Wrote: So the digial values run from 0 to 100 and get scaled to values between 0.0 and 1.0. As you can see, only two digits of precision is appropriate, and there are no dimensional units supplied.
While every signal in an edf file uses 16 bits, in this case, only 7 bits are required.
Ahhhhh!! I see!
completely different from what I thought... (In other words, everything that I said before
is just ignorant kibbitzing
)
I can clearly see that my FL's are driving the pressure spikes.
What I
think I'm seeing is two distinctly different kinds of value zero -- the machine reports zero when it sees breaths that are not flow-limited, AND it also reports zero when it sees a flow rate waveform which doesn't fit the specific sort of breathing pathology that we are talking about as a "flow limited or not." Given what I know about Fourier transforms (which is not much, but the guy I sleep with is a theoretical physicist who's tried to explain it to me
) what I think I'm seeing is that lots of breaths are being evaluated for flow limitations but a whole lot are not.
As a software engineer, I look at the data that the ResMed engineers are putting on the card, and the form that they are using, and that SD card looks to me like a debugging tool, designed to make sure that the machine behaves as they intend it to behave in all of their various test cases. But any usefulness for monitoring what the heck is going on when we use the device is a side effect and not very interesting to them. After it leaves the factory all that they care about is whether it works as it's designed to work. Which really really really sucks, because the data that they are (basically accidentally) giving to us is incredibly useful and valuable to us. But the sleep doctors don't think that it has any value, and because this is a prescription device the sleep doctors are the customers and not us.
RE: Flow Limitation Units in Statistics
Yes that last sentence is on target. Include doctor and DME's as the customer and then that explains why we're in a challenging state on feeling with PAP machines.
INFORMATION ON APNEA BOARD FORUMS OR ON APNEABOARD.COM SHOULD NOT BE CONSIDERED MEDICAL ADVICE. ALWAYS SEEK THE ADVICE OF A PHYSICIAN BEFORE SEEKING TREATMENT FOR MEDICAL CONDITIONS, INCLUDING SLEEP APNEA. INFORMATION POSTED ON THE APNEA BOARD WEBSITE AND FORUMS ARE PERSONAL OPINION ONLY AND NOT NECESSARILY A STATEMENT OF FACT.
RE: Flow Limitation Units in Statistics
In some of my puttering with OSCAR data, I have taken to plotting the flow limits in dB's. That is 10 x log10( flow_limit ). What this does is to allow one to see the lower level flow limits that are being registered by the machine. A linear scale is very poor for seeing both large and small values simultaneously. A logarithmic scale is much better for this. Unfortunately, for most individuals, it is hard to interpret. For people with an engineering or scientific background, it is a natural way to present data. That being said, the dynamic range of flow limits is only 20dB due to how it is recorded.
Independent of the paragraph above, there needs to be an alternate set of metrics for the flow limitations. As currently implemented, they can indicate "train wreck" status, but at levels below wreck status there's insufficient (dynamic) range for the metric to be useful. Under CPAP Statistics, my Flow Limitation index says it has been zero (0.00) for the last 5 months. I've had good days and some bad flow limit days in that interval. 0.00 implies all is perfect. It is not perfect.
RE: Flow Limitation Units in Statistics
I have not observed consistency in what this index means between different users, or even different nights. It seems to be relative to a moving time and can even change through the night. Only Resmed charts flow limitation, and there is considerable variation between manufacturers. Resmed charts flow rate at 25 Hz while Respironics is 5 Hz. Oscar does not create data, it reports it. I would not look for anything different unless there is a policy change from the development team.
RE: Flow Limitation Units in Statistics
Yeah, I definitely see that OSCAR is just reporting the data. I'm questioning more what the machine is recording -- there's zero, and then there's other zeros
Take this snippet:
[attachment=31156]
where my A10 is reporting this:
[attachment=31157]
I'm claiming that the zero that the machine is recording during the apnea is a very different thing than the zero that it records between 00:46:19 and 00:46:37. And the zero that's on either side of the event is different than the zero during the event.
Given that the machine reacts to the data, it's obvious that the machine isn't treating its zero as a zero -- it starts raising the pressure as soon as the OA starts:
[attachment=31158]
I'm thinking that if the pressure is rising while the FL is recording zero, then it's not really zero, and the machine isn't acting like it thinks that it's zero
