Research On The Measurement Method Of Continuous Blood Pressure Based On Multiple Parameters

Blood pressure is an important physiological parameter,which can reflect the health condition of human body,and is also one of the main inducement factors of cardiovascular diseases.Assessment of blood pressure provides a reliable basis for the diagnosis and treatment of hypertension.Noninvasive continuous blood pressure measurement can achieve real-time monitoring of blood pressure changes,and has a positive effect on early prevention,diagnosis,evaluation and treatment of hypertension and related cardiovascular diseases.Non-invasive continuous blood pressure measurement based on pulse wave transmission time is rapidly developing,and the estimation results of this method have initially reached the international blood pressure standard.The accuracy of blood pressure estimation in elderly people has become the main factor restricting the large-scale promotion of this method.Therefore,it is very meaningful to study the optimization algorithm for patients with hypertension.The photoplethysmography(PPG)used in this paper is a kind of waveform that reflects the change of blood volume in human arteries by the intensity of optical signal.The pulse waveform contains a large amount of physiological information.The traditional BP algorithm mainly focuses on the PTT and the calibration method.However,the morphological characteristics of the pulse wave are rarely considered in the BP model.The mechanism of blood pressure formation and the physiological structure of blood vessel wall were analyzed.Combining the first derivative and the second derivative of pulse wave with the movement of blood vessel wall,it was found that the waveform changes of each period of pulse wave correspond to the movement of blood vessel wall.Extracting the main peak of the pulse wave and the feature point of the dicrotic notch,the pressure index(PI)characteristic parameters were presented.PI includes the elastic function of the artery and reflected wave arrival time,the results show that young people's PI value was significantly greater than the elderly population.The centered component of the PI spectrum moves in the low frequency direction with the increase of blood pressure,and is consistent with the change of the heart rate variability(HRV)spectrum.Low-frequency components are affected by sympathetic activity,and are closely related to vascular compliance and peripheral resistance.This indicated that PI can track high blood pressure at low frequencies.In addition,the pulse wave was divided into two parts by the dicrotic wave valleys,and the Area characteristics were defined to represent the amount of ventricular ejection.Combining PI with the original algorithm and Area feature as compensating factor,a new PI-based blood pressure estimation algorithm model was established.This article designed and completed a large number of clinical trials.In order to verify the predictive effect of PI-based blood pressure algorithm on resting status and post-exercise status of young people,a comparative experimental program of 31 people was designed.The new algorithm shows good fitness for rest and after exercise.In addition,a two-week geriatric follow-up test was performed on 63 subjects and the algorithm was validated.The results show that the optimized algorithm based on PI has significantly i mproved the estimation effect of patients with hypertension.