| Arterial blood pressure is an important physiological parameter for the assessment of cardiovascular haemodynamic function in basic medical research as well as in clinical application. Blood pressure can fluctuate distinctly with individual biorhythm, emotion and any other kinds of internal and external stimulations Therefore, the blood pressure of every single measurement or continual measurement comes out discrepantly. By measuring the blood pressure in every cardiac cycle, continuous measurement is proved to be more effective than the two measurement mentioned before. Yet, the existing continuous blood pressure measure approaches are not suitable for long-term continuous blood pressure measurement due to their complicated apparatus and specific position for the high precision sensors.This dissertation investigates a new noninvasive continuous blood pressure measurement by Photoplethysmograph pulse wave and a new concept about normalizing the Photoplethysmograph pulse wave. Based on this concept, a new approach is developed to calculate cardiovascular parameters and diastolic pressure, which is applied to this novel blood pressure measure system. It is the first blood pressure measure system in China that has been used to measure blood pressure continuously without invasion in zero-g environment. Compared with the results of Korotkoff-Sound method, the results from this novel measure system showed that the system meet the AAMI requirements very well and has the potential to used in basic research and clinical application.The main tasks and results of this dissertation are summarized as following1. Extraction of cardiovascular parameters by normalized Photoplethysmograph pulse wave.This dissertation investigates the relation between Photoplethysmograph pulse wave and blood pressure waveform by considering the formation mechanism and propagation process of pulse wave. Although the amplitude of Photoplethysmograph pulse wave can't represent arterial blood pressure directly; it reflects the change of arterial blood pressure faithfully. The dissertation also investigates the relation between arterial blood pressure and cardiovascular parameters by looking into the single elastic cavity model and two elastic cavity model of Human Cardiovascular System. Besides that, this dissertation develops a new concept about normalizing the Photoplethysmograph pulse wave. By applying this concept, it resolved the problem that the amplitudes of Photoplethysmograph pulse wave were too discrete to reflect the change of cardiovascular parameters. Based on this concept, the dissertation also develops a calculating method of cardiovascular parameters.2. Calculating of the systolic pressure and diastolic pressure by analyzing the pulse wave propagation time and normalized Photoplethysmograph pulse wave.The theory of calculating systolic pressure by analyzing the pulse transit time, and the method of calculating the systolic pressure by deriving the equation of pulse transit time and systolic pressure and calibrating parameters of the equation by experiment is provide. The method to calculate diastolic pressure by using Photoplethysmograph pulse wave is analyzed in this paper. Cardiovascular parameters are obtained in calibration experiment and diastolic pressure is figured out continuously by using systolic pressure and cardiovascular parameters.3. Signal processing of pulse wave by wavelet transformation.The Photoplethysmograph signal is a kind of faint physiological signal and very vulnerable to be interfered by noise. Meanwhile, the shape of the pulse wave changes greatly from person to person because of the variability of individual artery elastic and blood content in the finger capillary vessels. This dissertation investigates the spectrum of pulse wave and the source of noise, and develops a method of reducing the noise and identifying the characteristic points of pulse wave by mallat arithmetic. Compared with the wave before signal processing by wavelet transform, there was no significant difference between the two waveforms.4. Developing of continuous noninvasive blood pressure measure apparatus.In order to provide effective medical supervision and protection for the astronauts in simulation experiments on ground and in manned spacecrafts, China astronaut training center requested for a new apparatus that can meet the requirements as below. First, it can measure noninvasive blood pressure, oxyhemoglobin saturation as well as stroke volume continuously. Second, it can analyze and displaying ECG, pulse wave signals and other physiological indexes in real time. Finally, the apparatus must be small and have the good performance in low power consumption. Based on these requirements, this dissertation develops a new cardiac function monitor by Photoplethysmograph pulse wave. This monitor is the first apparatus that can be used to measure noninvasive continuous blood pressure under zero-gravity environment. |
