I'm wondering if anyone knows what the averaging time is for the raw SaO2 data recorded in SHHS1?
I've had a look through the technical documentation and key publications, but I haven't had any luck finding this. The sampling rate (1Hz) hints that is may be a 2s averaging time (based on the Nyquist criteria) and the data itself appears to have a fairly quick physiological response; but I know a lot of the old Nonin oximeters were setup with default averaging times of 16 or 32s.
cheers and thanks,
the model used was Nonin XPOD 3011. Although we were not able to find the exact specifics of that one, we did find the specifics of its "low power" version XPOD 3011LP, which we could reasonably assume would be the same? If that was the case, there would have been the option to average over 4 or 8 beats. This means that if 4 beats was chosen, and assuming a heart rate of 60 bpm, the delay would be 4 seconds. Also, looking at the power spectrum of the signal, a lowpass filter with a ~4 s window does look plausible. Let me know if this makes sense!
That seems to match my impression from the data.
I guess the main concern will be whether the averaging time was consistently set across all the patients in the cohort. It might be hard to know now whether this was something that the hard-coded on the compumedics device or whether the collection centres had control over it?