An experimental study of pulse wave measurements with magnetic induction phase shift method

BACKGROUND: Pulse wave monitoring is widely used to evaluate the physiological and pathological states of the cardiovascular system. OBJECTIVE: High-sensitivity ring sensors were designed, and a simultaneous acquisition platform based on National Instruments T-Clock technology (NI-TCLK) was used to achieve simultaneous pulse detection using both the traditional method and the magnetic induction phase shift (MIPS) method. METHODS: The excitation signal had a frequency of approximately 10.7 MHz and power of about 20 dBm. A total of 30 volunteers (adults, aged 20–30 y) were selected to corroborate the feasibility of our measurement system. The subjects wore the proposed sensor on their right-hand forefingers and for reference, the piezoelectric pulse sensor on the left-hand forefinger. The pulse waves of these 30 subjects were measured over 2 min each. RESULTS: The phase shift of the magnetic induction detection signal ranged from 0.6–0.8 degrees. Comparison of detection results for the same subject between the two methods showed that the pulse rate measured by magnetic induction exhibited fewer deviations and better stability than the traditional method. In addition, spectral analysis indicated that the pulse frequencies obtained using the 2 methods were concentrated between 1–3 Hz and were regular in the 1.5 Hz frequency region. CONCLUSIONS: These results prove that the magnetic induction pulse wave can be used to accurately measure pulse wave features.