Heart Rate in power spectrum: what to look at?
I'm not sure I post this in the right place but I hope for advices.
I'm quite confused with the power spectrum of my data.
We used to check the signal quality by looking at the heart rate peak in the PSD of our HbO data.
However when looking at it in the PSD of intensities I do not understand what I got: in some channels, I can perfectly identify the heart rate peak in the PSD of intensities, but it disappears in the HbO PSD. Is there any reason?
Also, I've read that finding the HR peak eanbles ensuring the physiological validity of the data. I was wondering if no seeing the peak must lead to channel rejection, and if it was better to look at it in HbO than in intensities (we have 3 wavelengths in our system, so 3 "intensities")?