- 期刊
Portable Impedance Cardiography System for Real-Time Noninvasive Cardiac Output Measurement
可攜式即時心輸入量測系統
摘要
量測左心室體積改變的許多方法中，阻抗式心輸出量測(ICG)是唯一已知的非侵入式方法。本研究提議發展一套可攜式ICG系統以長期連續監測心血管活力，此系統結合數位訊號處理單晶片的運算能力以達成及時監測的功能。本系統除了利用數位訊號處理單晶片以外，與其他系統之主要不同為硬體線路之頻寬，此頻寬之改進是依據作者先前之研究，選擇較佳之頻寬能使訊號具有更好之可信度及可靠度。同時，所完成之系統相當輕便能做為可攜式監測系統。測試結果顯示本系統能在如Valsava及握拳等生理挑戰測試中有效的監測心搏量與心輸出。同時，實驗結果也顯示本系統與Fick方法所量測的心輸出無明顯的差異，而且相關係數高達0.91。以上結果顯示本系統是一有效且可靠的裝置能用來監控病人的心血管活力，並能提供動態的心血管功能資訊。本系統目前並未利用數位訊號處理單晶片的全部能力，往後若能將自適性濾波器及小波等更先進的訊號處理方式實現於系統中，將能更進一步增強訊號偵測的能力，同時提高本系統的可靠性。
並列摘要
Impedance cardiography (ICG) is the only known method that can observe the continuous left ventricular volume changes non-invasively and conveniently. This paper proposes to develop a portable ICG system for long-term continuous cardiac activity monitoring using the impedance technique. This ICG system combines the advance analog amplifier with the calculation power of digital signal processing chip to achieve real-time monitoring. One of the major differences between the proposed system and the existing systems is in the bandwidth of dZ/dt circuit. Using proper bandwidth can significantly increase the reliability and validity of ICG signal. Additionally, the proposed system is light weight and suitable for a portable monitoring system. The results demonstrate that the proposed ICG system is capable of tracking the dynamic changes of SV and CO during physiological challenges such as Valsava maneuver and the hand grip task. On the other hand, the results also show that there is no difference between CO obtained by the proposed ICG system and the Fick method. Additionally, the correlation coefficient is 0.91. The results indicate that the proposed system is a valid and reliable tool for patient monitoring and it is capable of assessing the dynamic cardiac activity information. Due to the simplicities of the current signal processing and events detection methods, the CPU is idled for substantial amount of time. Thus, in the future, more advanced techniques such as adaptive filtering and wavelet analysis can be implemented for event detection to increase the accuracy and reliability.