Research Of Inflatable Noninvasive Blood Pressure Measurement Algorithm

The blood pressure is one of the most important physiological parameters, which can reflect the status of human cardiovascular function, and it provides important basis in clinical diagnosis and observing treatment effect. The blood pressure is closely related to many cardiovascular system information, such as heart rate, peripheral resistance, hemal wall elasticity, blood volume and blood physical state, etc. Using electronic sphygmomanometer to monitor in family has an important help in preventing cardiovascular abnormal events.The blood pressure measurement is divided into invasive and noninvasive method. The invasive method is the gold standard of the international recognition method. This way is the most accurate, but extremely inconvenient and generally limited to critically ill patients or open heart surgery patients. Noninvasive method is simple and easy, which has been widely used in clinic. In the noninvasive blood pressure measurement method, the method of the cuff pressure theory is mature and conducive to implementation, and it becomes the preferred device in manufacturers. Traditional cuff pressure measuring method is based on the upper arm which twists cuff and measure the blood pressure on the process of cuff deflated. The measurement discussed in this paper is wrist cuff winding, and the blood pressure is measured in the process of cuff inflated, the wrist sphygmomanometer has characters with low cost and convenience. It is a kind of ideal self-service monitoring equipment.This paper is based on the pneumatic blood pressure measurement. In blood pressure signal acquisition, processing and results, I did following work:1. We use the MPXV5050GP pressure sensor included in the cuff to collect the mixed signal of static pressure and pulse wave, and transmit to PC.2. Analyse the details of the pulse wave pretreatment method based on wavelet transform First of all, according to the characteristics of the pulse wave signal to select the wavelet basis. Then we use wavelet threshold denoising method to remove the noise, and the threshold denoising method respectively adopt forcing denoising method, the default threshold denoising method and the given threshold denoising method. We use analog signal to denoise with above-mentioned methods and work out the SNR to compare them, and select the best denoising method to remove the mixed signal of cuff pressure. Finally we complete the separation of static pressure and pulse wave. 3. We use the threshold value method to extract feature points of pulse wave peak. and set a threshold to remove the interference pulse peak value points. Then we use the gaussian curve fitting. We compared one gaussian fitting, quadratic gauss fitting, and double linear fitting, and selected the best fitting curve to complete the pulse wave envelope drawing.4. We use the improved amplitude coefficient method, which can find the systolic pressure, diastolic pressure position of the corresponding amplitude ratio more precise. Then complete the systolic pressure, diastolic pressure calculation. Finally verify the result of the accuracy of the systolic pressure, diastolic blood pressure by probability statistics knowledge and acquire the conclusion.