In-Vitro Investigation of Flow Profiles in Arteries Using the Photoplethysmograph

The flow profile in the artery reflects the health status of the vessel and generally the arterial system. The aim of this pilot study was to investigate in-vitro the effect of flow profiles on reflective photoplethysmography (PPG) signals at different steady state flow rates and levels of vessel constrictions. A simplified model of an arterial system was built, consisting of a steady state flow gear pump, PVC vinyl tubing, reservoir and a clamp with a micrometer gauge. The blood mimicking fluid (2.5% India ink and water solution) was pumped through the model. It was found that the waveforms of the PPG signals fluctuate irregularly and the magnitude of the frequency components was increased below 60 Hz in cases of turbulent flow (Re = 2503). These preliminary results suggest that PPG could be the basis for new technologies for assessing the profile of the blood flow in the artery. Future studies have to be carried out with pulsatile flow and more complex models that are more similar to the human arterial system.Clinical Relevance- The PPG signal reflects changes in the flow profile caused by the stenotic rigid vessel.