Analysis of the Effect of Ageing on Rising Edge Characteristics of the Photoplethysmogram using a Modified Windkessel Model

Abstract

Ageing is one of the main contributing factors towards increasing arterial stiffness, leading to changes in peripheral pulses propagation. Therefore the characteristics of the photoplethysmogram (PPG) pulse, especially the rising edge and peak position, are greatly affected. In this study, the PPG pulse rising edge and corresponding peak position have been investigated non-invasively in human subjects as a function of age. Fifteen healthy subjects were selected and grouped in five age intervals, from 20 to 59 years, based on their comparable systolic-diastolic blood pressure and PPG amplitude. As expected, the peripheral pulse shows a steep rise and early peak in younger subjects. With age, the slope becomes blunted and in older subjects, the rise is very gradual and the pulse peak appears much later. Qualitative results were further verified by a modified 10-element Windkessel model to quantify the lumped parameter changes with ageing. This verification highlighted some specific changes in vascular parameters with aging. The rising edge could be considered as one parameter in determining the age-dependent vascular state.

The Role of Pulse Transit Time as an Index of Arterial Stiffness During Exercise

“…Whereas, in the majority of the studies this parameter was suggested as a blood pressure surrogate, PTT has gradually become a popular index of arterial stiffness (Kingwell et al 1997;Nichols 2005). Most importantly, pulse transit time has been used as a measure of vascular health and condition across life span (Safar et al 2003;Vaitkevicius et al 1993;Zahedi et al 2007) in different populations (Foo and Lim 2008).…”

An Efficient and Automatic Systolic Peak Detection Algorithm for Photoplethysmographic Signals

“…The valley between these two waves is called dicrotic notch. The location of the dicrotic notch changes from subject to subject and also depends on the age [18]. This prevents the use of simple threshold to detect systolic peaks as compared to peak detection in ECG.…”

Photoplethysmography analysis of artery properties in patients presenting with established erectile dysfunction

“…Next PPG signals were band-pass filtered (0.6-15 Hz) for removing the effect of the respiratory rhythm and higher frequency disturbances. These filters did not introduce phase delays or distortion to the waveforms [8]. A process of beat-by-beat pulse foot identification took place for best pulse selection.…”

“…Pulse foot was taken as the minimum value of the pulse for scaling the PPG AC amplitudes [8], systole point was determined as the maximum point of the pulse, dicrotic notch is determined as the third derivative's first negative to positive zero crossing point which occurred after the third derivative's positive to negative zero crossing point [5]. To ease visualization and comparison, the PPG AC amplitude normalization was done.…”

“…Arterial stiffness is the main player affects arterial functionality which is somehow inevitable with aging. Arterial stiffness has been found to have significant influence on the propagation of pulses to the periphery, affecting pulse timing and shape characteristics of the PPG [8].…”