On the Analysis of Fingertip Photoplethysmogram Signals

Abstract

Photoplethysmography (PPG) is used to estimate the skin blood flow using infrared light. Researchers from different domains of science have become increasingly interested in PPG because of its advantages as non-invasive, inexpensive, and convenient diagnostic tool. Traditionally, it measures the oxygen saturation, blood pressure, cardiac output, and for assessing autonomic functions. Moreover, PPG is a promising technique for early screening of various atherosclerotic pathologies and could be helpful for regular GP-assessment but a full understanding of the diagnostic value of the different features is still lacking. Recent studies emphasise the potential information embedded in the PPG waveform signal and it deserves further attention for its possible applications beyond pulse oximetry and heart-rate calculation. Therefore, this overview discusses different types of artifact added to PPG signal, characteristic features of PPG waveform, and existing indexes to evaluate for diagnoses.

Glycemic Control, Hand Activity, and Complexity of Biological Signals in Diabetes Mellitus

“…To the best of our knowledge, PPG pulse amplitudes are closely related to central or peripheral autonomic nervous, cardiorespiratory, and vascular controls [17], whereas ECG R-R intervals, the classic biological signals mostly used for the entropy analysis, are mainly influenced by autonomic nervous activity. Since the PPG pulse amplitudes are compromised by a wide range of physiological functions, the complexity of PPG signal series might be more sensitive than heart rate variability as a short-term estimate of autonomic and vasomotor dysfunction in diabetes.…”

“…The magnitude of fingertip photoplethysmographic (PPG) pulse amplitudes is multifactorially influenced by arteriosclerosis, respiratory cycles, cardiac output, blood flow, and pulse pressure [17]. Theoretically the MSE or refined MSE of PPG pulse amplitudes can represent the complexity of cardiovascular and autonomic nervous system network.…”

Investigation of peripheral photoplethysmographic morphology changes induced during a hand-elevation study

“…Furthermore, the peripheral PPG pulse has been described as becoming ''damped, delayed and diminished'' with increasing severity of vascular disease [1,8]. In order to quantify these morphological changes, various features of the ac PPG pulse have been extracted and analysed [9,10].…”

“…Much of the current work in the area of PPG morphology analysis, involves applying calculations commonly used on arterial blood pressure waveforms, such as Augmentation Index (AI) or Reflection Index (RI), to the ac PPG signal because of this relationship between pressure and volume [10,12]. As the PPG wave propagates along the arterial tree, wave reflections are induced, with the most prominent reflection site being the bifurcation of the abdominal descending aorta [13].…”

“…As the PPG wave propagates along the arterial tree, wave reflections are induced, with the most prominent reflection site being the bifurcation of the abdominal descending aorta [13]. However, the application of variables such as AI and RI also assumes that as the PPG wave moves from central arteries to the periphery, the more resistant vessels in the peripheral vasculature will induce reflection of the wave [10]. This concept is taken from the arterial blood pressure signal, which has been shown to be a summation of forward and reflected pressure waves.…”