Can slight arrythmia disrupt oximeters? Seems not?

[DavidEsp]

A question that has been nagging me...

Could slight (e.g. benign) arryhthmia violate assumptions required for an oximeter (e.g. O2Ring) pulse-rate measuring algorithm to produce reliable or even consistent pulse-rate (or even SpO2) results?"

I am no expert, just a websearcher, but from the following it seems neither of these imagined issues exist in reality.

I have read that for good devices (no idea if that includes O2Ring) "Cardiac arrhythmias do not decrease accuracy of pulse oximeters so long as saturation readings are steady."

And from the end of that (1991) paper, it seems this applies not only to SpO2 but also to pulse rate. Of course that's only from one paper, not specific to the O2Ring, but to me it sounds encouraging.

Any other knowledge or opinions?

[staceyburke]

The device is measuring the O2 in the blood - not anything to do with monitoring the heart.  So no a abnormal heart beat would not be detected or would it change the reading of the oxygen in you blood.

[DavidEsp]

That's right in theory (science), though in practice (engineering) it seems (as presented in the following article - that I just now came across) that various complications in the signal have to be allowed for, and one of the things oximeters rely on to to that is the pulsing of the blood.

Here's the article. The more we understand the nuances/idiosyncracies these devices the better we can work with them. Same as for people!

I had a vague memory that oximeters used pulsing somehow, but never knew how or why. So I have learnt something here.

I love that article, really thoughtfully put together. It presents the deeper principles and techniques of oximeters, in terms of pictures that one can absorb in stages. That tech author can communicate!.

So the pulse measurement is not just a "side addition" to the SpO2 measurement, they work together.

That article also shows in what way moving the finger about can disrupt the signal. Maybe that's why oximeters sense (and in some cases, like my O2Ring, record) movement. I'd imagine they simply ditch/disregard measurements during any significant movement, or perhaps they compute (e.g. average) them over longer periods of time and then interpolate - but I can see "it make's their job harder".

I always wondered why oximeters had movement sensors. Manufacturers would surely trim their chip costs by excluding such sensors if they were not strictly necessary (unless for whatever reason they were using some "inherited" or generic chip that had them as standard. But I very much expect they use their own tailored chip designs.

Always learning, and (as I'm discovering) sharing helps this, both for motivation and for uncovering "unknown unknowns" apparent to others.

I know I've been really wordy here, but please don't be put off by that, I'm just someone who always thinks and expresses like this.

Further feedback (from anyone) would be very welcome.

[mesenteria]

The pulse oximeters and wearable devices like smart watches and others that record pulses and SPO2 rely on light amplitude and feedback in the sensors.  Movement can change the angles of incidence and contact for the sensor, so knowing when movement might impede successful and veridical measurement is exceedingly important. It doesn't matter what the heart is doing to the measuring device.  The device merely reads electrical activity and SPO2, and records the numbers of changes it senses.  A heart in ventricular tachycardia, flutter, or in supra-ventricular tachycardia or flutter, will only result in a recording that shows abnormal values or inconsistent ones.  Atrial fibrillation will show a heart rate at rest higher than 95 and lower than about 130, with variance.  A pulse oximeter will show a concomitant change in SPO2, but it might not be able to specify what rhythm it is reading.  It doesn't matter to strictly SPO2 monitors.  More sophisticated devices will measure arrhythmias as well.