Dunning M, Woehlck H J
Medical College of Wisconsin, Milwaukee, USA.
J Clin Monit. 1997 Nov;13(6):357-62. doi: 10.1023/a:1007450826769.
The passage of volatile anesthetic agents through accidentally dried CO2 absorbents in anesthesia circuits can result in the chemical breakdown of anesthetics with production of greater than 10000 ppm carbon monoxide (CO). This study was designed to evaluate a portable CO monitor in the presence of volatile anesthetic agents.
Two portable CO monitors employing electrochemical sensors were tested to determine the effects of anesthetic agents, gas sample flow rates, and high CO concentrations on their electrochemical sensor. The portable CO monitors were exposed to gas mixtures of 0 to 500 ppm CO in either 70% nitrous oxide, 1 MAC concentrations of contemporary volatile anesthetics, or reacted isoflurane or desflurane (containing CO and CHF3) in oxygen. The CO measurements from the electrochemical sensors were compared to simultaneously obtained samples measured by gas chromatography (GC). Data were analyzed by linear regression.
Overall correlation between the portable CO monitors and the GC resulted in an r2 value >0.98 for all anesthetic agents. Sequestered samples produced an exponential decay of measured CO with time, whereas stable measurements were maintained during continuous flow across the sensor. Increasing flow rates resulted in higher CO readings. Exposing the CO sensor to 3000 and 19000 ppm CO resulted in maximum reported concentrations of approximately 1250 ppm, with a prolonged recovery.
Decrease in measured concentration of the sequestered samples suggests destruction of the sample by the sensor, whereas a diffusion limitation is suggested by the dependency of measured value upon flow. Any value over 500 ppm must be assumed to represent dangerous concentrations of CO because of the non-linear response of these monitors at very high CO concentrations. These portable electrochemical CO monitors are adequate to measure CO concentrations up to 500 ppm in the presence of typical clinical concentrations of anesthetics.
挥发性麻醉剂通过麻醉回路中意外干燥的二氧化碳吸收剂时，可导致麻醉剂发生化学分解，产生超过10000 ppm的一氧化碳（CO）。本研究旨在评估在挥发性麻醉剂存在的情况下便携式CO监测仪的性能。
对两台采用电化学传感器的便携式CO监测仪进行测试，以确定麻醉剂、气体样本流速和高CO浓度对其电化学传感器的影响。将便携式CO监测仪暴露于含0至500 ppm CO的气体混合物中，该气体混合物分别为70%氧化亚氮、1 MAC浓度的当代挥发性麻醉剂，或在氧气中与异氟烷或地氟烷反应后的产物（含有CO和CHF3）。将电化学传感器测得的CO值与同时用气相色谱法（GC）测得的样本进行比较。数据采用线性回归分析。
对于所有麻醉剂，便携式CO监测仪与GC之间的总体相关性导致r2值>0.98。隔离样本中测得的CO随时间呈指数衰减，而在传感器持续流动过程中测量值保持稳定。流速增加导致CO读数升高。将CO传感器暴露于3000和19000 ppm CO中，报告的最大浓度约为1250 ppm，恢复时间延长。
隔离样本测量浓度的降低表明传感器对样本有破坏作用，而测量值对流速的依赖性表明存在扩散限制。由于这些监测仪在非常高的CO浓度下呈非线性响应，任何超过500 ppm的值都必须被视为代表危险的CO浓度。这些便携式电化学CO监测仪足以在典型临床麻醉剂浓度存在的情况下测量高达500 ppm的CO浓度。
