Open Access

Sebastian Zaunseder, Vincent Fleischhauer

• Photoplethysmography imaging (PPGI) can yield far- reaching statements on the health state in a convenient way. The presented work investigates the morphology of PPGI signals upon stimulation in comparison to the be- havior of contact PPG signals. We use own experimental data of 39 healthy volunteers recorded during a cold pres- sure test (CPT). We analyze PPGI signals from the face and from the forearm together with contact PPG from the finger and the earlobe. Signals’ morphology is assessed by means of four common features at three time intervals around CPT. Our results show significant differences upon stimulation for most features from finger and earlobe PPG (p < 0.001). Even PPGI signals show significant differ- ences upon stimulation, though forearm signals’ analysis is hampered by a lower signal quality. Beyond a general effect of stimulation, there are differences in the signals’ behavior according to the recording setup. E.g., finger and forearm signals show stronger and even morePhotoplethysmography imaging (PPGI) can yield far- reaching statements on the health state in a convenient way. The presented work investigates the morphology of PPGI signals upon stimulation in comparison to the be- havior of contact PPG signals. We use own experimental data of 39 healthy volunteers recorded during a cold pres- sure test (CPT). We analyze PPGI signals from the face and from the forearm together with contact PPG from the finger and the earlobe. Signals’ morphology is assessed by means of four common features at three time intervals around CPT. Our results show significant differences upon stimulation for most features from finger and earlobe PPG (p < 0.001). Even PPGI signals show significant differ- ences upon stimulation, though forearm signals’ analysis is hampered by a lower signal quality. Beyond a general effect of stimulation, there are differences in the signals’ behavior according to the recording setup. E.g., finger and forearm signals show stronger and even more persistent effects upon stimulation than earlobe and facial signals. Our study highlights the importance of recording setup. While care must be taken when knowledge or methods are transferred from contact PPG to PPGI, the found behavior opens novel analysis opportunities if multiple PPG signals are available.…