Aussedat B, Thomé-Duret V, Reach G, Lemmonier F, Klein J C, Hu Y, Wilson G S
INSERM U 341, Department of Diabetology, Hôtel-Dieu, Paris, France.
Biosens Bioelectron. 1997;12(11):1061-71. doi: 10.1016/s0956-5663(97)00083-3.
A crucial step in developing a glucose monitoring system using a subcutaneous implanted glucose sensor is the transformation of the sensor signal (a current) into an estimation of a blood glucose concentration. We have developed an Electronic Control Unit (ECU) able to recognize, before and after a glucose load, that the sensor current presents a plateau, thus triggering an alarm asking for blood glucose determination. The system, fed with these results, subsequently transforms the current into an estimation of glucose concentration by linear extrapolation based on the sensor sensitivity and the background current computed from the two sets of current and glycaemia values (two-point calibration). In addition, the system is able to trigger an alarm when this estimation decreases below a threshold that can be set by the user. This system was evaluated in experiments performed in 12 normal rats. The quality of the calibration was assessed by comparing, by error grid analysis, the data displayed on the liquid-crystal display of the ECU to concomitant plasma glucose concentration determined at frequent intervals, 65 +/- 6 and 26 +/- 5% of the values were in zones A (good) and B (acceptable estimation) of the grid, respectively. The system was set to trigger an alarm when the estimation of glucose concentration decreased below 70 mg/dl. Following an insulin administration, the alarm was triggered when the system displayed a 64 +/- 2 mg/dl glucose concentration. The concomitant plasma glucose concentration was 59 +/- 5 mg/dl (NS). In conclusion, this work validates experimentally the new, user-friendly method for calibrating the glucose sensor integrated into the ECU, based on an automatic detection of plateaus. The quality of the sensor calibration performed with this procedure is compatible with the appropriate functioning of this continuous glucose monitoring system, which was demonstrated by its ability to detect mild hypoglycaemia following insulin injection.
使用皮下植入式葡萄糖传感器开发葡萄糖监测系统的关键步骤是将传感器信号（电流）转换为血糖浓度估计值。我们开发了一种电子控制单元（ECU），它能够在葡萄糖负荷前后识别出传感器电流呈现出平稳状态，从而触发警报，要求进行血糖测定。该系统根据这些结果，随后通过基于传感器灵敏度以及从两组电流和血糖值计算得出的背景电流进行线性外推（两点校准），将电流转换为葡萄糖浓度估计值。此外，当该估计值降至用户可设定的阈值以下时，系统能够触发警报。该系统在12只正常大鼠身上进行的实验中进行了评估。通过误差网格分析比较ECU液晶显示屏上显示的数据与频繁测定的血浆葡萄糖浓度，评估校准质量，分别有65±6%和26±5%的值位于网格的A区（良好）和B区（可接受估计）。当葡萄糖浓度估计值降至70mg/dl以下时，系统设置为触发警报。注射胰岛素后，当系统显示葡萄糖浓度为64±2mg/dl时触发警报。同时测定的血浆葡萄糖浓度为59±5mg/dl（无显著性差异）。总之，这项工作通过实验验证了基于自动检测平稳状态的、用于校准集成在ECU中的葡萄糖传感器的新型用户友好方法。用该程序进行的传感器校准质量与该连续葡萄糖监测系统的正常运行相兼容，这通过其检测胰岛素注射后轻度低血糖的能力得到了证明。
