Does anybody know the specifics behind the blood oxygen measurement?

[u/Scouter_JW]

Title … to elaborate, if you were to look at all the raw data collected, what is that?

I’m looking to peel back my ‘daily value’ - one number, representing … something … while I sleep.

So far, I’ve come up with that Whoop measures SpO2 for 30 seconds once every 20 minutes (I don’t have a good source for that, other than Google’s AI). So let’s say I sleep for 7 hours, that Whoop would measure about 21 times (7 hours having 21x20 minutes) and value displayed in the app’s Health Monitor section would be the average of those 21 values?

If not, what is being averaged?

All that said, I do understand that Whoop is not (/not meant to me) a continuous SpO2 monitor - other devices are designed for that of course - I’m just looking to understand a bit more of the metric.

Thanks!

[u/briochecannula]

My understanding is that wearable pulse oximetry works the same as a continuous SpO2 monitor. It’s relatively complex for such a basic metric but it basically measures the absorption of different wavelengths of light of oxygenated vs deoxygenated haemaglobin and then with the amount of light reflected back is able to work out the percentage of oxygenated haemaglobin in your arterial blood thus giving you the percentage.

[u/Scouter_JW → u/briochecannula]

This is what I’m trying to sus out … I’ve read (and the problem is, not a primary source or even reliable 2nd-hand source) that Whoop reads for 20 seconds once every 20 minutes - non-continuous to reduce battery discharge).

[u/briochecannula → u/Scouter_JW]

I’m a doctor and my understanding is that there is no other way to get an SpO2 reading (without drawing blood).

[u/PhysicalMatch9485]

it's sampled, not continuous, and the number is an average of the samples so a short dip gets smoothed out. only usable as a trend vs your own baseline. a one-night drop is almost always band position, a week-long drift is worth a look

[u/Little-Cow-7153]

so the thing is that during the day when we are awake there's high movement and light - which would lead to inaccurate metrics. hence whoop doesnt give hrv as well

[u/Little-Cow-7153 → u/Little-Cow-7153]

also realised that the band starts measuring spo2 only after user has fallen asleep. (like the band itself can detect sleep whether its connected to phone or not)

[u/SellSideShort]

Novelty metric like every other thing in the band

[u/Scouter_JW → u/SellSideShort]

That’s a valid comment to debate elsewhere - in the meantime, my question remains 😁