Abstract
A new finger-photoplethysmography (FPPG) using an integrating sphere (isFPPG) is proposed to enhance light collection ability with higher accuracy and sensitivity, towards practical non-invasive measurement of blood constituents, especially alcohol (BAL) and glucose (BGL). Preliminary study with a laser-based experimental setup was made using two representative wavelengths, 1160 nm that is the window in the absorption spectra of water and BAL, and 1600 nm in which water absorption is high but it is suitable for BGL detection. Simultaneous measurements were conducted with a conventional transmittance FPPG (tmFPPG) and with the isFPPG at the fingertips of the index fingers in both hands of 10 healthy young volunteers. We measured the signal-to-noise ratio (SNR) and the sensitivity of the two methods. SNR obtained by the isFPPG with 1600 nm was significantly higher than that by the tmFPPG. Sensitivity with 1600 nm was also higher than that with 1160 nm, suggesting that isFPPG is superior to tmFPPG, especially in the wavelength regions where water absorption is very high but there is potential for the detection of blood constituents including BGL.
