Noninvasive System for Continuous Blood Pressure Monitoring under Low Cuff Pressure

• Main Authors: Lu Kun Chih, 陸坤池
• Other Authors: Shyu Liang Yu
• Format: Others
• Language: zh-TW
• Published: 2000
• Online Access: http://ndltd.ncl.edu.tw/handle/58836153262376776450

碩士 === 中原大學 === 醫學工程學系 === 88 === Most of the noninvasive blood pressure measurement devices could only measure the blood pressure discretely. In addition, the pressure of the cuff always makes patients feel uncomfortable when using the ausculatory and oscillometric methods. Thus, it’s not suitable to obtain blood pressure measurement for a long time using traditional methods. The purpose of the study is to develop a noninvasive blood pressure measurement system that has a low-pressure cuff and could monitor the blood pressure pulse for a long period of time without any pumping device. A custom-made low-pressure cuff is applied to patient’s wrists in order to obtain the blood pressure waveform. This cuff is operated in the pressure of 40 mmHg. A fixed-point DSP (TMS320C50, Texas Instruments, Inc.) is used to process the signal and executes all the necessary calculation which includes heart rate, systolic blood pressure, diastolic blood pressure, and a DC potential for feedback to the subtraction circuit. After processing, the results are displayed on a 128*64 dots matrix LCD. The proposed system is capable of storing the above information in the internal SRAM for more then 6 hours. In addition, stored information can be transmitted to a personal computer through an RS-232 interface for further off-line analysis. In order to test the accuracy and flexibility of this system, 20 patients were recruited for the evaluation study from the Tri-services General Hospital (TSGH). Patients have been anesthetized and invasive blood pressure signal was obtained using an artery catheter. These invasive blood pressure signals are fed in to the proposed system and the results are compared with the artery blood pressure. The results indicate that the range of average errors is less than 3 mmHg and the average maximum error is 5.9 ±1.3 mmHg. This error of the proposed system is close to the standard established by the AAMI. Additionally, the Pearson correlation coefficients between these two measurements are as high as 0.95. The results indicate that the proposed system can provide a good correlation when compare with an invasive blood pressure measurement device. After resulting the technical difficulty of the low-pressure cuff, the proposed system can be a valuable tool for long-term blood pressure monitoring.