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How are Pulse Change events determined?
#11
RE: How are Pulse Change events determined?
Selfcoacher, can you point us in the direction of the literature? At some point we are planning on revising the pulse oximetry handling, so it would be good to have reference to point to.
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#12
RE: How are Pulse Change events determined?
(01-29-2022, 07:22 PM)StuartC Wrote: Thanks for the reply.  I had more-or-less reached that conclusion.  

Two things then become interesting to me.  1) The impact, if any, of the number of arousals indicated by pulse change (much higher than AHI). 2) That I seem to be the only one interested in these observations on my charts because the neither my doctor, nor the CPAP consultants, nor even the sleep tech who did my sleep study seem to pay any attention to them (did make my GP's eyes open for a moment though).

I have not tried to match pulse increases against increased flow limitation.  I am pretty good at seeing things on charts so it might not be showing up.  Also, my flow limits generally occur in clusters that correlate to low SpO2 along with some variable breathing patterns, which the sleep studies show to be happening mainly during REM.  With that much going on at the same time, working out a root cause is tough.  

One thing I can rule out in my case is response to pressure changes as I am on fixed pressure.  Oh, maybe one other thing, I switched to an Evora Full mask and leaks are largely a thing of the past.
 
On one of the graphs there are flow limits and movements.  On the other one leaks.  All potential causes of arousals.  It is difficult to get the timing precise though as syncing the wellue and the cpap is not easy.

You should shoot for less than 10 arousals/pulse rises per hour, no matter the cause.  You should not count the drops in heart rate and you should not count awake times.
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#13
RE: How are Pulse Change events determined?
I agree that heart rate increases are more significant than decreases. The current numbers reported by OSCAR are still useful though and I see a high correlation between my PLMI (calculated from direct measurements of leg movements) and the OSCAR reported pulse change rate. There are some instances where OSCAR sees 2 drop events following an increase, and others where OSCAR doesn't report a drop event (due to the decrease being slower) but I would expect that the current reported value is close enough to double the value you would get by just counting increases.

This paper "Relationship between Arousal Intensity and Heart Rate Response to Arousal" (https://dx.doi.org/10.5665%2Fsleep.3560) finds that there is significant correlation between level of arousal and the heart rate increase level. And "The Sleep Apnea–Specific Pulse-Rate Response Predicts Cardiovascular Morbidity and Mortality" (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8483223/) concludes "Individuals with OSA who demonstrate an elevated ΔHR are at increased risk of cardiovascular morbidity and mortality. This study identifies a prognostic biomarker for OSA that appears useful for risk stratification..."
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#14
RE: How are Pulse Change events determined?
Hi kappa, thanks for the interesting links. Nice find and good reading.

If I understand the findings in the 2nd of your references (Azarbarzin, Scott and others) this researches the Delta HR in response to OSA events, not just the Delta HR over the course of the whole night? If so, a good reason to reduce one's OSA count!

Good to know!
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#15
RE: How are Pulse Change events determined?
Hi SevereApnea, that study was looking for heart rate changes in a time window around apnea and hypopnea events and did not consider rapid heart rate changes outside of this. So yes, reducing OSA is a good thing. I still think there's value in looking at pulse change events for the entire night - one might have sleep arousals due other factors such as PLM.

Here's another paper: "Autonomic Arousals as Surrogates for Cortical Arousals Caused by Respiratory Events: A Methodological Optimization Study in the Diagnosis of Sleep Breathing Disorders" (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6927566/) that looks at heart rate acceleration (HRa) as a proxy for EEG arousal measurement.
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