Synchronous Monitoring of Heart Beat and Cerebral Blood Flow Pulsation Based on Near Field Coherent Coupling

Simultaneous monitoring of heart beat (HB) and cerebral blood flow pulsation (CBFP) has important clinical significance for reducing the incidence, mortality and disability rate of cardiovascular and cerebrovascular diseases. However, there is no safe, reliable and effective method for synchronous monitoring of them in practice. Near-field coherent coupling (NCC) obtains physiological signals by demodulating the modulation information of complex impedance changes in biological tissues with the advantages of non-invasiveness, strong penetrability, and real-time monitoring. A synchronization monitoring system of HB and CBFP was constructed in this work based on the NCC principle and software defined radio programming technology. In order to investigate its feasibility of monitoring the heart-brain coupling activity (HBCA) changes in different states, the HB and CBFP signals of 6 healthy volunteers at rest and after exercise were collected synchronously and analyzed. Furthermore, the heart-brain delay time (HBDT) in the two states was compared by moving cross-correlation analysis. The results show that the size of heart rate obtained by the NCC and physiological monitor is very close with an average relative error of 4.7%. The waveforms of HB and CBFP in time domain before and after exercise were relatively consistent, which meets the heart rate and the basic characteristics of CBF impedance map. The frequency of HB and CBFP after exercise were obviously higher than that at rest. CBFP is delayed from the HB and has the same frequency. It is consistent with the mechanism of the same frequency and different phases between cardiac vibration and intracranial blood supply. The HBDTs at resting state in all 6 volunteers are less than those after exercising with an optimal consistency. These results prove the possibility of NCC monitoring HB and CBFP. In addition, it has the potential in non-invasive, real-time monitoring of HBCA.