fig1

Figure 1. We show the details of feature extraction in Figure 1A and B. (A) parameters used in HR, PTT, PIR, SI, and AI calculations; (B) The extraction principle of feature SYM. HR: heart rate; PTT: pulse transit time; PIR: PPG intensity ratio; SI: stiffness index; AI: augmentation index; SYM: symmetry; PPG: photoplethysmogram; ECG: electrocardiogram; dPPG: derivative of PPG; sdPPG: second derivative of PPG; I_L: minimum amplitude; I_H: maximum amplitude.