Figure 6.
The theoretical model for analyzing the variation of blood pressure by the virtual work principle. (A) The parameters used to analyze the real stress acting through the virtual displacement of the blood radius δr. r and h: radius and thickness of the blood vessel, respectively; Pbp and Pex: blood pressure to the blood vessel and the external pressure by other tissue, respectively. (B) A model for the light transmission path through pulsating arterial blood, non-pulsating arterial blood, venous blood and other tissues over several cardiac cycles. IAC: alternating current; IDC: direct current [30]. Copyright 2014, Wiley. (C) Typical PPG signals with motion artifact, including slow and fast squeezing of the skin-like systems, bending the wrist and clenching fist, corresponding to sections 1–4. (D) Schematic of the optical path and tissue changed by external stress.