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. 2012 Aug;8(3):215–219. doi: 10.2174/157340312803217184

Fig. (2).

Fig. (2)

(a) the relationship between the photoplethysmogram terminologies (PPG”o”, PTG”+”, and DVP “*”) and the number of publications through years. (b) The relationship between the cumulative sum of PPG” solid curve”, PTG “dashed curve”, and DVP” dotted curve” terminologies with their number of publications. It is clear that the use of PPG is increasing exponentially over time.