Uim100c

In all, 57 healthy volunteers (34 men and 23 women) ranging from 22 to 60 years of age (mean (SD): 29.5 (5.9) years of age) participated in the PPG study. None of the participants had psychological or neurological disorders. All subjects provided their informed consent for inclusion before they participated in the study. The study was conducted in accordance with the Declaration of Helsinki, and the protocol was approved by the Institutional Review Board of the Seoul National University Hospital (IRB No. C-1703-045-837).
An MP150 data acquisition system (BIOPAC Systems, Inc., Goleta, CA, USA) simultaneously recorded a finger photoplethysmogram as a reference and the foot photoplethysmogram at a sampling rate of 500 Hz. As a reference, finger PPG was performed using a qualified PPG module (PPG100C, BIOPAC) with a paired (TSD200, BIOPAC) infrared (IR) LED and PD. A Velcro strap was used to fix the LED-PD pair to the middle fingertip of each participant’s right hand. The foot photoplethysmogram was recorded using a universal interface module (UIM100C, BIOPAC) and LED-PD pairs on a printed circuit board.

We performed a stress-inducing experiment with five sessions: BA-S, MIS-S, MOS-S, SES-S, and RE-S. In BA-S and RE-S, a black cross mark was displayed on a white background on the monitor. The difference between BA-S and RE-S is their order during the experiment. The flow of our experiment is shown in Figure 1. The length of each session is four minutes. Whenever each session finished, the subject rested for 10 min to reduce the effect of the previous session. All experiments were performed while the subjects were seated in a comfortable chair.
Three physiological signals were measured from each subject during the experiment: a photoplethysmogram (PPG), electrodermal activity (EDA), and skin temperature (SKT). The physiological signals were obtained using the Biopac PPG100C, Biopac EDA100C, and UIM100C systems (Biopac System, Inc., Goleta, CA, USA). The PPG sensor was attached to the index finger, EDA sensors were attached to the middle and ring fingers, and the SKT sensor was attached to the thumb of the non-dominant hand. Each physiological signal was sampled at 400 Hz according to the manufacturer’s instructions, using the Biopac Acknowledge 4.2.0 software (Biopac System, Inc.). Figure 1 shows the overall experimental procedures.