A Review of Photoplethysmography-based Physiological Measurement and Estimation, Part 1: Single Input Methods

Photoplethysmography is a non-invasive and easy to administer optical method used primarily to measure blood oxygen saturation, but also used widely to estimate and measure various other physiological parameters. This paper reviews several physiological parameter estimations that have been done with just this waveform signal, i.e. heart rate, lipid profiling by morphological PPG analysis, blood glucose, ankle brachial pressure, and respiratory rate. Additional physiological estimations which use additional input measurements are reviewed in Part 2 of this paper. The different methods and signal processing techniques based on the principle of operation are discussed in this review. The validity of each of these optical measurement techniques are reviewed where the results were compared with the results obtained using the gold reference standards. Future research considerations for non-invasive wearable devices for physiological parameter measurements are also highlighted in this review which could be helpful for future research.