The Research Of Portable Continuous Blood Pressure Measurement Device Based On Pulse Wave Transit Time

Blood pressure is an important physiological parameter which can reflect the physiological state of the human vascular system and is an important diagnostic criterion for diseases such as hypertension.Several BP measurement methods available can only measure the blood pressure intermittently,such as the oscillometric method generally adopted by the commercial blood pressure gauge.Since the blood pressure is variable,by people’s physical condition,mood,movement,and most people have the changing rule with highest blood pressure in the morning and afternoon during a day,while the lowest blood pressure in the midnight.That’s why some patient with hypertension missed diagnosis.Therefore,the research of continuous blood pressure is meaningful.The common method of continuous blood pressure measurement is based on pulse wave transit time,which related blood pressure to the velocity of blood transit in the vessel.In order to track monitoring the blood pressure of the persons who work in the specific environment simply,fast and with high specificity,the paper designs a device integrated a blood pressure calibration module and a continuous blood pressure measurement module.The blood pressure calibration module is based on oscillometric method and will be used in the calibration process as a criterion.The continuous blood pressure measurement module is based on the pulse wave transit time,which is obtained by calculating the time intervel between the peak point of ECG and the photoplethysmography in a cardiac cycle.In this paper,the difference threshold method is improved for the peak detection of the ECG,PPG and the oscillatory wave.In the end,a system verification experiment is designed,including ithe verification experiment of the blood pressure calibration module and the continuous blood pressure measurement experiment.The experimental results show that the average error of the calibration module is-1.1± 3.21 mmHg,which meets the requirements of the design indicators with the accuracy of ± 8mmhg.The average error of systolic blood pressure during continuous blood pressure calibration was 0.00085± 5.458 mmHg,while the average error of diastolic blood pressure calibration was 0.00042± 4.376 mmHg.In the continuous blood pressure mearsurement experiment,the mean absolute error of systolic blood pressure is about 2.228 ± 5.757 mmHg,while diastolic blood pressure is about 1.355± 4.55 mmHg,meeting the requirements of design index of the average error less than 8mmHg.