Photoplethysmography (PPG) is a low-cost vascular optics technique that can detect blood volume changes in the microvascular bed of tissue, usually from measurements collected non-invasively at the skin surface. The PPG waveform comprises a pulsatile (‘AC’) physiological waveform which is attributed to cardiac synchronous blood volume changes, superimposed on a slowly varying (‘DC’) baseline with various lower frequency components attributed to respiration, sympathetic nervous system activity and thermoregulation. Although the origins of these key components are not fully understood, it is generally accepted that they can provide valuable cardiovascular information. There has been considerable interest in PPG in recent years and this is attributed to developments in wearable sensors, demands for low-cost portable technology, availability of low- cost/miniature semiconductor components, and advances in computer-based pulse wave analysis techniques including AI. PPG has been used in a wide range of devices, including for measuring oxygen saturation, blood pressure and cardiac output, assessing autonomic function and assessing peripheral vascular disease. Considerable work continues across the globe in advancing the technologies involved, creating innovations in PPG sensing, pulse analysis and applications.
Kyriacou and Allen, as co-editors, are proud to announce a new holistic and state-of-the- art book on Photoplethysmography (published by Elsevier, November 2021) covering the history, scientific principles, genesis of the PPG waveform, technology, pulse analysis, cardiovascular applications and clinical monitoring, cuffless blood pressure measurement, imaging, and future trends and directions. This mini-symposium will include talks by leading PPG experts on some of the key topics covered in the book, including tissue oxygen measurement, assessments of vascular disease and autonomic function, cuffless blood pressure measurement, as well as wearable sensors.