Variability of photoplethysmography peripheral pulse measurements at the ears, thumbs and toes

Pulses radiating to the periphery after each heart beat can be detected by photoplethysmography (PPG). A multi-site PPG measurement and analysis syste m is described for beat-to-beat analysis of the pulse waveforms, Waveforms were collected from the right and left ear lobes, thumb pads. and toe pads of 30 normal subjects whilst they performed paced breathing. The median coe fficients of variation for pulse amplitude were: ears and thumbs 11%,. and toes 14%, Significant differences in pulse transit time of 4ms (to foot of pulse), and 14ms (to peak of pulse) between the right and left toes were de tected (right lagging left, p < 0.01). The median pulse transit times (to f oot) were: ears (0.133s), thumbs (0.199s), and toes (0.301s), with coeffici ents of variation: 2.8%, 2.2, and 1.6%, respectively. The median pulse tran sit rimes (to peak) were: ears (0.397s), thumbs (0.436s), and toes (0.515s) , with coefficients of variation: 1.4%, 2.0%, and 1.5% respectively. The au thors have utilised signal processing algorithms to calculate beat-to-beat measures of pulsatility, and determined normative data for multi-site PPG p ulse assessments.