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. 2017 Jan 27;32(1):97–107. doi: 10.1007/s10877-017-9975-4

Fig. 9.

Fig. 9

The red finger PPG signal (green trace) and the ECG signal (blue trace) acquired from a volunteer towards the end of the cold exposure, along with the peaks detected (red trace) by the peak detection algorithm. The amplitude of the red finger PPG signals was sometimes so weak that the peak detection algorithm could not distinguish between the heart beat peaks and the noise peaks