Remote photoplethysmography with consumer smartphone reveals temporal differences between glabrous and nonglabrous skin: Pilot in vivo study

Abstract

Photoplethysmography (PPG) is a noninvasive optical technology, with applications including vital sign extraction and patient monitoring. The PPG acquisition skin type may be of importance. Skin is either nonglabrous (~90%) or glabrous (~10%). Clinical PPG collection is typically from glabrous (fingerpad), while proliferating wearables collecting PPG, which may perform critical functions like arrythmia detection, often acquire from atypical sites. Glabrous skin has significant differences from nonglabrous, including microcirculation, yet comparisons between their PPG signals have not been well reported. Using a smartphone‐based remote/contactless PPG, a pilot dataset was collected from the hands (palmar/dorsal) of five healthy volunteers. The data shows statistically significant lead time (52 ± 36 ms) of glabrous over nonglabrous. Further, a trend of glabrous amplitude increase over nonglabrous (31%) was found. Although our study has a small number of participants, these results further the characterization of PPG skin differences, and can be used to inform development of PPG‐based devices.

Remote Photoplethysmography with a High-Speed Camera Reveals Temporal and Amplitude Differences between Glabrous and Non-Glabrous Skin

“…Firstly, we obtained statistically significant results to demonstrate that the PPG signal in glabrous skin is stronger than in non-glabrous skin. Prior to the current study, these results were derived on a single subject [ 19 ] or a small number of subjects [ 15 ], which did not allow any feasible extrapolation.…”

“…The experimental protocol was performed as in our previous study [ 15 ]. Briefly, subjects rested for 10 min in the collection area before the initiation of data collection.…”

“…All rPPG extraction and processing were performed in Matlab (Mathworks, Natick, MA) and in alignment with conventional rPPG methodologies [ 15 ]. Image frames were demosaiced to provide pixel intensity for each color channel (red, green, and blue), then a Gaussian filter (MATLAB imgaussfilt) was applied to reduce pixel noise.…”

“…We began to investigate this hypothesis in our previous work [ 15 ], where we used a consumer-grade camera (as embodied in a smartphone) to acquire rPPG signals at 60 frames per second (fps) to analyze the differences between glabrous (palmar) and non-glabrous (dorsal) skin in a pilot study. The video was acquired of both hands (one palm up and the other palm down) simultaneously since both were present in the frame, and the rPPG signals were isolated from each hand by segmenting the frame during post-processing.…”

1st Spring Biophotonics Conference in Porto

“…Burton et al used a smartphone‐based device to measure the photo‐plethysmography (PPG) signal from the glabrous and non‐glabrous areas of the skin in the hands of five healthy volunteers [7]. In this study, it was found that by measuring the amplitude ratio and temporal lag from the two types of skin, the collected data exhibited a statistically significant lead time of the glabrous signal over the non‐glabrous (by 52 ms), and a variable yet interesting trend of an increase in amplitude of the glabrous signal over the non‐glabrous (31%, but lacking statistical significance at α = 0.05).…”