Evaluation of blood pressure by analyzing the fluctuation frequency of oxygen saturation in palmar digital vein

This paper presents a non-contact measurement method for the evaluation of human blood pressure. A reflection type optical imaging system was developed to interactively capture the human palmar back images with illumination of dual light sources. By a continuous measurement, the variation of oxygen saturation in palmar digital vein could be monitored. The fluctuation frequency of the oxygen saturation was also obtained by FFT algorithm. Through the comparison with electronic sphygmomanometer, the study succeeded in establishing a relationship between the natural blood pressure of human and venous fluctuation frequency. Also, the influence of external pressure for blood vessels on fluctuation frequency was studied. The results show that the fluctuation frequency of oxygen saturation linearly increases with the natural blood pressure or external pressure decreasing. The proposed innovations represent a solution for remote medical diagnosis technology with low risk of infection and high biocompatibility.