Plug-and-play, single-chip photoplethysmography.
Remote patient monitoring (RPM) relies on low-cost, low-power, wearable sensors for continuous physiological assessment. Photoplethysmographic (PPG) sensors generally require >10 components, occupy an area >300 mm(2), consume >10 mW power, and cost >$20 USD. Although the principle of PPG sensing is straightforward, in practice, a robust implementation requires a careful design including optical alignment, analog circuits, ambient light cancellation, and power management. This paper reports the first use of digital optical proximity sensors (OPS) for "plug-and-play" PPG. OPS have traditionally been used for distance sensing in smartphones and factory automation. Here we show that a digital OPS can perform PPG functions in a single 4×4 mm package which also provides a direct digital interface to a microcontroller. By exploiting its key features, a digital OPS can provide substantial performance advantages over existing state-of-the-art PPGs, including: i) 10X lower power consumption (200 µW) due to pulse operation; ii) high signal to noise ratio (>90), as a result of built-in optical barriers, filters, and ambient light cancellation; iii) 10X lower cost ($2 USD); and iv) 12X smaller area. We show single wavelength PPG measurements in multiple anatomical locations, including fingertips and earlobes. The results suggest that a digital OPS can provide an elegant solution for battery-powered, wearable physiological monitors. To the authors' knowledge, this is the smallest and lowest power PPG sensor reported to date.
Department of Family Medicine and Public Health Sciences at the Wayne State University School of Medicine, Detroit, Michigan, USA.
Deepak
D
Chandrasekar
Bengt
B
Arnetz
Philip
P
Levy
Amar S
AS
Basu
D006801:Humans; D008904:Miniaturization; D008991:Monitoring, Physiologic / Q000295:instrumentation*; D017156:Photoplethysmography / Q000295:instrumentation*