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Diseases. 2018 Sep 17;6(3). pii: E81. doi: 10.3390/diseases6030081.

Innovative Multi-Site Photoplethysmography Analysis for Quantifying Pulse Amplitude and Timing Variability Characteristics in Peripheral Arterial Disease.

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Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne NE2 4HH, UK.
Northern Vascular Centre, Freeman Hospital, Newcastle upon Tyne NE7 7DN, UK.
Northern Medical Physics and Clinical Engineering, Freeman Hospital, Newcastle upon Tyne Hospitals NHS Foundation Trust, Newcastle upon Tyne NE7 7DN, UK.


Photoplethysmography (PPG) is a simple-to-perform vascular optics measurement technique that can detect blood volume changes in the microvascular bed of tissue. Beat-to-beat analysis of the PPG waveform enables the study of the variability of pulse features, such as the amplitude and the pulse arrival time (PAT), and when quantified in the time and frequency domains, has considerable potential to shed light on perfusion changes associated with peripheral arterial disease (PAD). In this pilot study, innovative multi-site bilateral finger and toe PPG recordings from 43 healthy control subjects and 31 PAD subjects were compared (recordings each at least five minutes, collected in a warm temperature-controlled room). Beat-to-beat normalized amplitude variability and PAT variability were then quantified in the time-domain using two simple statistical measures and in the frequency-domain bilaterally using magnitude squared coherence (MSC). Significantly reduced normalized amplitude variability (healthy control 0.0384 (interquartile range 0.0217⁻0.0744) vs. PAD 0.0160 (0.0080⁻0.0338) (p < 0.0001)) and significantly increased PAT variability (healthy control 0.0063 (0.0052⁻0.0086) vs. PAD 0.0093 (0.0078⁻0.0144) (p < 0.0001)) was demonstrated for the toe site in PAD using the time-domain analysis. Frequency-domain analysis demonstrated significantly lower MSC values across a range of frequency bands for PAD patients. These changes suggest a loss of right-to-left body side coherence and cardiovascular control in PAD. This study has also demonstrated the feasibility of using these measurement and analysis methods in studies investigating multi-site PPG variability for a wide range of cardiac and vascular patient groups.


cardiovascular variability; heart-rate variability; peripheral arterial disease; photoplethysmography; pulse

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