Dynamic Cerebral Autoregulation Capacity Detection System Research

Cerebral autoregulation (CA) is a most important mechanism that involves micro-dilatation and micro-constriction in brain capillaries to maintain relatively stable cerebral blood flow in response to changes of systemic blood pressure when blood pressure changes within a certain range. CA is one of the parameters of cerebral dynamics characteristics, generally used to measure the degree of cerebral arteriosclerosis. The less cerebral autoregulation are arterial sclerosis of cerebral as usual, and then likely give rise to high blood pressure, stroke and other cardiovascular diseases. The changes of kinetic parameters are often earlier than the morphological in the field of cardiovascular disease, and that the dynamic cerebral autoregulation is often significantly lower has occurred in the early stages, Thus the detection of dynamic cerebral autoregulation can make the diagnosis of cardiovascular disease become more timely and accurate.Detection of dynamic cerebral autoregulation usually uses the pressure from outside to change the arterial pressure to form the disturbance signal, such as leg banding method, Valsalva manoeuvre, etc. The phase difference between the arterial blood pressure and the dynamic flow velocity are used to measure the dynamic cerebral autoregulation in the disturbances. The traditional method has several disadvantages:on the one hand, the accuracy is not high because of needing to impose external disturbances; on the other hand, it is difficult to promote because ambulatory blood pressure monitoring equipment is expensive.In this paper, the movement of chest muscles in normal breathing condition instead of the movement of the external pressure to introduce is used for the system of dynamic cerebral autoregulation by the type of KJ-2V2U transcranial Doppler ultrasound analyzer and the type of HK-2000H pulse sensor. Firstly, the synchronous dynamic blood signal and pulse signal are collected, and then the blood velocity signal is extracted from the blood signal. Secondly, the dominant intrinsic mode function that has the same frequency with respiratory rate is extracted by EMD. Thirdly, the instantaneous phase of dominate intrinsic mode function are calculated by Hilbert transform. Finally, dynamic cerebral autoregulation is measured using the instantaneous phase.The simulation experiments are performed to evaluate the proposed and used approaches. In the simulation experiments, firstly, the synchronization of the pulse and blood signal is controlled by the CSocket of KJ-2V2U and the COM of HK-2000H. Secondly, the two-way signal is collected precisely Synchronization. Thirdly, the blood velocity signal is extracted from time-frequency distribution of blood signal. Fourthly, the dominant intrinsic mode function that has the same frequency with respiratory rate is extracted by EMD. Finally, the instantaneous phase of the dual dominant IMF is calculated by Hilbert transform, and then dynamic cerebral autoregulation is measured using the difference between the two. The results show that:the system is not only able to complete the requirements of the dynamic cerebral autoregulation, but also to improve the traditional methods of experimental study presented; the movement of chest muscles in normal breathing condition instead of the movement of the external pressure to introduce is used for the formation of disturbance; the pulse sensor instead of the ambulatory blood pressure monitoring equipment is used for the detection of ambulatory blood pressure. The system has higher accuracy, lower risk and lower system cost than traditional system.