The Tilt Test System Based On Continuous Noninvasive Measurement Of Beat-to-beat Blood Pressure

Tilt table test is the important and effective method for evaluating the baroreflex sensitivity and cardiovascular regulation capability. It has become an accepted tool for assessment of patients presenting syncopal symptoms in the clinical medicine and aeromedicine. It can only perform the intermittent blood pressure in the conventional tilt table, and the research mainly obtained in the supine or tilting position, during the head up tilt table testing due to the drawbacks of conventional apparatus. In the aeromedicine domain, the capability of the new high-performance agile aircraft to reach a high speed in less than a second make it highly desirable to be able to study immediate rapid and transient cardiovascular response to stimulated gravitational stress.Based on the obvious need in the clinical aviation medicine, we designed a new type tilt test system that is able to not only measure the continuous blood pressure by PWTT but also obtain physiological signals of the dynamic course during the tilt table rotation. Using the system, we described the dynamic regulation course and obtained the physiological parameters describing the transient state.The head blood pressure not only reflects the blood supply for brain, but also relates to the capability of cardiovascular regulation. It is very important to measure the head blood pressure continuously. Our study established the method for detecting the head blood pressure, and analyzed the dynamic course of autonomic nerve system regulation during the bed rotating.Main results of the research:1). Designed the tilt test system to measure the continuous beat-to-beat blood pressure by PWTT. The system could detect several physiological signals, such as respiration, ECG, PCG, pulse wave, cuff pressure, korotkoff's sound, aorta area impedance and bed angle etc.2). Designed the new type manual tilt table with cushion and angle sensor, which provided high-quality signals during rotating with mild vibration.3). Programmed the signal analysis procedure and calculated the PWTT, ICT, LVET, korotkoff's sound delay time using the characteristic marker of the measured physiological signals.4) Presented the measurement scheme that obtained the intermittent blood pressure measurements (such as SBP, DBP, MAP) by the combination of oscillometric method and Korotkoff's sound waveform method, and proved the feasibility by compare the Korotkoff's sound waveform method with auscultatory method.5). Presented the method that marked the ejection point from aorta area impedance. According to the principle of impedance rheogram, we designed the aorta area impedance measurement system that can obtain the ECG and aorta area impedance at same time by four electrodes. Our research verified the ejection marker from aorta area impedance by comparing the LVET calculated by two different methods.6). Detected the blood pressure of heart level by PWTT calculated from beginning point of aorta area impedance to the beginning point of the pulse wave of brachial artery with calibrating by Korotkoff's sound delay time. We analyzed the error of PWTT obtained from the peak point of ECG's R wave peak point.7). Detected the head blood pressure by the PWTT from the beginning point of carotid artery to the beginning point of temporal artery, and calibrated the PWTT by hydrostatics method and Korotkoff's sound delay time.8).using the new tilt test system, we completed the 75°head-up tilt test, and analyzed the change and physiological causes of intermettent blood pressure, HRV and BPV. We observed and analyzed the trends of heart rate, blood pressure of heart level, head blood pressure during the dynamic course.9). Presented the parameters of transient state. Rotation of the tilt table is step stimulation to the cardiovascular regulation system, while the change of heart rate, blood pressure of heart level and head blood pressure are the step response. We put forward the heart rate rise time, head blood pressure regulation time and head blood pressure recover level to representing the instant regulation capability of cardiovascular system.In conclusion, our research accomplished the continuous beat to beat blood pressure of heart level, head blood pressure by noninvasive method. We observed and analyzed the change trend of blood pressure and heart rate, and presented the instant state physiological parameters which reflect health state. We will propose more experiment, and present effective parameters of cardiovascular system regulation capability.