Gain Pulse Transmit Time And Use Based On Peripheral Artery Pressure Waveform

Pulse transmit time (PTT) is an important physiological parameter for assessment of cardio-cerebral vascular status and reflection of some disease information; it is calculated by peripheral arterial pressure signal, and fartherly gaining pulse wave velocity (PWV). The two parameters are independent predictor of cardiovascular disease partially reflected the vascular damage, with non-invasive, inexpensive, safe and simple operation, etc. So they has a wide range of application and social significance for evaluating body healthy in clinic, and are accepted easily by doctors and patients.The variation wave of peripheral arteries pressure signal is acquired because of the serious influence of several factors to measurement process. These factors include experimental conditions, such as selective sensors, measurement position and environment temperature as well as the individual variations such as hemodynamic parameters, blood component and cells, age, physiological and pathological status. The high accuracy of PTT is rather difficult to calculate by the various waves, which leads to poor reducibility and limit of its application in clinical medicine.In this paper, analysis on radial arterial pressure wave signal was in different ages of the asymptomatic subjects, the methods of calculating PTT were presented in time domain, frequency domain and time-frequency domain based on previous studies, their computed results were assessed validity by correlations and Bland-Altman analysis. And dissertation focused on further research on the fundamental algorithm in calculating PTT non-invasively to improve it widely used in clinical.Firstly, the definition of PTT and PWV were given, and the importance of non-invasive detection of these parameters. Then in recent years methods and their classification of calculating PTT at home and abroad were summarized and discussed in depth. We analyzed the problems in different existed methods and proposed the scientific issues and technical difficulties of our research project.Secondly, we analysed in-depth characteristics and application of the radial artery pressure wave signal. In order to acquire and display peripheral artery pressure signal, an overview of the measuring pulse instrument and its hardware structure were presented in our laboratory independent research. On the other hand, the paper mainly focused on analysis system software implementation, first we described the MCU software design in detail, second introduced the system block diagram of the PC software, include of the main interface of software, the test window of cardiovascular function and results window of measurement. At last, the radial, carotid, femoral and dorsalis pedis artery pressure waveform were measured in strict accordance with the measurement procedures, and superimposed display all periods wave. So these will be the foundation for further study of peripheral artery pressure wave signal.Thirdly, according to processing method of the radar and communications signal, the superimposed wave can be recombination noise characteristics in the time domain, and we boldly proposed a method of detection key point e by superimposed wave in the radial artery pressure signal, its operating theory and method were given in detail. The PTT values of289asymptomatic subjects were computed by this method, its correlations with age and AI were discussed. Thus the results show some defects of this method for calculating the strange bread wave, and the location of the point e in wave is still no way to identify accurately, so we study them in the frequency domain for further research and exploration.Fourthly, we improved algorithm of the frequency domain analysis based on Fourier transform theory, the first peak frequency F1, the second peak F2and the phase shift time Ï„ between two peaks were proposed to assessing atherosclerosis with ages. And the characteristic parameters(F1, F2and Ï„) of138subjects in the frequency domain were calculated, their correlations with age were discussed, the results indicate that the new parameters can be as simply non-invasive evaluation for atherosclerosis. On the other hand, the radial, carotid, femoral and dorsalis pedis artery physical layout in body and their power spectrum characteristics were analyzed and discussed, and we intensified to learn frequency domain features of peripheral arterial pressure signal.Fifthly, on the basis of study frequency domain features of peripheral artery pressure wave signal, we presented a new method based on the spectrum characteristic of the radial arterial waveform, the method which was the Butterworth band-pass filtering unwanted frequency components and reconstructing after filtering data for detection the key points c and e in the wave to calculating the pulse transit time PTT. The previous two methods were examined using SPSS software by correlation and the Bland-Altman analysis; the results show that the calculating PTT values of two ways are the basic consistent. However, comparison to the superimposed radial wave method, the PTT value of the frequency domain reconstruction method is large, and it can be as a method for computing the PTT.Sixthly, because the multi-resolution wavelet transform has been successfully applied to detection and evaluation of QRS characteristic points in the ECG signal, we learned from the previous studies, and presented this approach for detection of c and e key points in the radial arterial wave signal. We Selected some good multiresolution wavelet coefficients of the critical layers to reconstruct a new wave, and detected the key characteristic points of c and e in it for calculating the PTT value.Finally, we selected the superimposed radial wave method as a reference standard, respectively compared with the frequency domain reconstruction method and multi-resolution wavelet coefficients reconstruction method in calculating PTT value of the24young subjects. The test results show that the multi-resolution wavelet coefficients reconstruction algorithm is independently correlated with the superimposed radial wave method(R=0.910, P<0.001), and superior to the frequency domain band-pass filtering reconstruction method(R=0.689, P<0.001).