Assessment of Vascular Health With Photoplethysmographic Waveforms From the Fingertip

Although the flow-mediated dilation (FMD) index is considered the most reliable indicator of vascular endothelial function, previous studies have proved that the dilatation index (DI) measured by the highly reproducible air pressure sensing system (APSS) is just as accurate in effectively determining endothelial function. Besides, not only is APSS cheaper than the instrument for FMD ratio measurement, but operation of the former is also simple to facilitate its domestic use. However, APSS had the pitfall of being time consuming because of the large amount of computation involved. This paper attempted to validate a new self-developed endothelial function screening (EFS) device that utilized the photoplethysmography (PPG) system for acquiring PPG waveform signals from the index finger through an infrared sensor and a pressure cuff for applying pressure on ipsilateral upper arm for eliciting reactive hyperemic response to assess vascular health. The mean peak amplitude of the signals during the hyperemic phase was divided by that of the baseline to produce an EFS ratio. About 52 volunteers of age 34.76 ± 15.23 years without history of cardiovascular diseases were recruited for vascular endothelial function evaluation using the EFS device and the APSS. Bland-Altman analysis showed good consistency between the EFS ratio and DI. Besides, linear regression analysis demonstrated highly significant correlation between the two sets of data (p