The time-variable photoplethysmographic signal; dependence of the heart synchronous signal on wavelength and sample volume

✍ Scribed by H. Ugnell; P.Å. Öberg

• Publisher: Elsevier Science
• Year: 1995
• Tongue: English
• Weight: 916 KB
• Volume: 17
• Category: Article
• ISSN: 1350-4533
• DOI: 10.1016/1350-4533(95)00008-b

✦ Synopsis

The photoplethysmqraphic signal (PPG) f ram f orearm skin and the ECG were recorded simultaneously from healthy subjects. The optical signal was &rived with a jibre-@tic probe which consisted of 61 j&-e pairs. The peak-to-peak averaged a.c.-signal was calculated. The dependency of this signal and the signal-to-noise ratio (SNR) on the light wavelqth and on sample volume was studied. The light intensities used at 560 nm were 0.015 and 0.029 mWmmm2 and at 940 nm we used 0.029, 1.37 and 2.77 mWmm-'. A theoretical model for calculation of the sample volumes was also developed. The amplitu& and SNR of the a.c.-signal at 560 nm is larger than at 940 nm at the same intensity (0.029 mWmm-'). At 940 nm using 1.37 and 2.77 mWmmm2 the a.c.-signal increased with the number ofjibre pairs (volume) while the SNR was little afferted. At 560 nm it is suggested that the major con,tribution to the a.c.-signal is pulsations in the ascending arterioles and at 940 nm from pulsations in the larger vessels deeper in the tissue volume under study.