Age-related changes in the characteristics of the photoplethysmographic pulse shape at various body sites

It is accepted that older subjects have increasing arterial stiffness resulting in changes in the propagation of the pulse to the periphery, and thereby influencing the peripheral pulse timing and shape characteristics. However, this age association with pulse shape is less clear in younger subjects and for different peripheral measurement sites. The aim of this study was to determine the association between age and changes in pulse shape characteristics at the ears, fingers and toes. Photoplethysmography pulse waveforms were recorded non-invasively from the right and left sides at the ears, index fingers and great toes of 116 normal healthy human subjects. Their median age was 41 years (range 13-72) allowing four distinct age groups to be considered (subjects younger than 30 years, 30-39 years, 40-49 years and 50 years of age or older). Normalized ear, finger and toe pulse shapes were calculated, for the whole subject group, and for the subjects within each age group. The differences in shape, relative to the oldest group, were also calculated for two distinct regions of interest: the systolic rising edge and the dicrotic notch of the pulse. Subtle, gradual and significant changes in the pulse shape were found at all sites with overall elongation of the systolic rising edge (p < 0.05) and damping of the dicrotic notch (p < 0.05) with age. The overall age-related changes in multi-site PPG pulse shape characteristics at the ear, finger and toe sites have been demonstrated and quantified. Age-matched normal ranges must be considered when evaluating pulses from patients with possible vascular disease.