Plethysmography by Fiber Bragg Gratings Embedded in Silicone Patches

In this article, a plethysmography sensor, based on fiber Bragg grating (FBG), is proposed. The FBG has been embedded within a proper silicone soft patch to improve the sensitivity of the sensor to external force/pressure, allowing it to measure the plethysmographic waveform. Simulations on the COMSOL Multiphysics software have been conducted to analyze the sensitivity to the pressure exerted by the heart pulse wave on the plethysmographic sensor, and to design the shape of the patch. Experimental results show that the proposed simple, inexpensive, and minimally invasive sensor can measure the sphygmic wave with a clear distinction between the cardiac systole and diastole peaks, key data on the cardiovascular status of the patients. In addition, from the second derivative of the plethysmographic signal (SDPTG), it is possible to trace the accelerated plethysmography which waveform contains important information related to cardiovascular rigidity.