脈動血氧飽和度測定法之評估假體系統建立

Abstract

為替代以人體進行高風險且代價高昂的臨床試驗用於評估脈動血氧飽和度測定法準確性的程序，本研究首創以雙腔室封閉流動系統概念建置一簡便且成本合理的光機電系統，並搭配主要攜氧功能的血紅蛋白作為模擬不同脈動血氧飽和度關鍵配方而構成假體系統。首先以重複性量測與調控量測條件參數的方式，得以瞭解欲模仿對象之人體光學特性與適當量測條件，接著建置假體系統表現與人體相仿靜態/脈動光學訊號，假體系統的建置分為四大子系統：（1）模擬血液光學特性的血紅蛋白溶液（2）模擬周邊靜態組織光學特性的衰光濾鏡（3）模擬脈動波形特性的凸輪元件（4）模擬脈動心律的自動化機電裝置，確立假體系統具備模仿人體的能力後，透過搭載不同衰光濾鏡組於假體系統以模擬不同人體的靜態光學特性差異，並瞭解其個體差異對於量測R-Ratio值的影響。結果顯示固定量測距離25 mm與LEDs驅動電流52 mA時，能達最佳量測重複性，且以0.15 mM血紅蛋白溶液填入假體系統，搭載紅光/近紅外光波段透光度分別為2.01%T/ 1.26%T的濾鏡組合與最大/最小軸徑10/13mm凸輪，可使25×20×5 mm檢測槽產生規律性等效光學路徑0.5mm的脈動變化，且可調控自動化機電裝置中的馬達轉速為85 rpm時，等同人體心律數85 bpm，上述組件參數皆能調控而模擬各不同人體，因此，當假體系統分別搭載不同衰光濾鏡組作為代表不同人體，揭露了具不同靜態光學特性的人體間具有不同%SpO2－R Curve，此說明若測定儀採用的經驗校正曲線未適用於患者時發生量測不準確的原因，然而，若施予與市售測定儀相同功能之動態補光進行量測，可顯著觀察作為代表不同人體的兩假體系統之%SpO2－R Curve其斜率與截距逐漸調整至一致等現象。故本研究所建置的評估假體系統具潛力做為模擬不同血氧飽和度狀況之仿真系統，且可藉由衰光濾鏡、凸輪尺寸等組件參數的調整模擬各不同人體之動態光學訊號。

For providing an alternative of the high risk and costly clinical trials to assess the accuracy of pulse oximetry. A simple and cost-effective optical mechatronics system was established with a two-chamber closed flow system which was filled in the main oxygen-carrying function of hemoglobin to simulate various peripheral oxygen saturation and constitute a phantom system. First of all, repeated measurement and regulation of measurement parameters was carried out to investigate the imitated optical characteristics of human and appropriate measurement conditions, and then built the phantom system performing static/ pulsating optical signal similar to human. The phantom system was divided into four subsystems: (1) hemoglobin solutions for simulating the optical properties of blood, (2) neutral density filters for simulating the static properties of the static peripheral tissue, (3) a cam element that simulated pulsatile waveform profiles of blood, (4) an automated mechatronics devices for regulating pulsating rhythm. After confirming the ability of the phantom system to mimic the human, the difference of the static optical signal of human was simulated by carrying various groups of combined neutral density filters and the effect on the R-Ratio value was investigated. The results showed that the fixed measurement distance of 25 mm and the LED driving current 52 mA, it can achieve the best repeatability as well as 0.15 mM hemoglobin solution filled into the phantom system, equipped with red/ near infrared light transmittance are 2.01 %T/ 1.26 %T filters, and a 25×20×5 mm detection chamber combination with a cam in radius of 10 mm base circle producing regular equivalent optical path 0.5 mm pulsation alterations, and it can regulate the motor speed in the mechatronics device to 85 rpm, the equivalent of the human heartbeats of 85 bpm. The above-mentioned parameters can be regulated to simulate various human, therefore, when the phantom system were equipped with different groups of combined neutral density filters as a representative of different human, demonstrated different static optical characteristics of human with different %SpO2-R curves, this result showed the reasons of inaccurate due to an empirical calibration curve used in the commercial instrument inapplicable to the patients’ characteristics. Furthermore, when the dynamically light-compensated technology with the same function as the commercial instrument was applied, the % SpO2-R curves representative as two human can be found as a phenomenon in which the slope and intercept were gradually adjusted to the same. Hence, the proposed phantom system has the potential to simulate the various peripheral oxygen saturation, and can simulate the different dynamic optical properties of human by adjustments of combined neutral density filters, cam size and profile as well other component parameters.