Gehring H, Nahm W, Hufker D, Schmitz A, Ocklitz E, Mertins W, Schmucker P
Klinik für Anaesthesiologie, Medizinische Universität zu Lübeck.
Anaesthesist. 1998 Jan;47(1):39-44. doi: 10.1007/s001010050520.
When looking for the possible cause of distortions in values measured for the determination of breath ethanol concentration (BEC) in artificially respirated patients, consideration must be given to the humidity and temperature of the gas examined. In the present study, the effects of humidified and warmed and of dry and cold air on the accuracy of a newly developed BEC measuring device, as compared to a reference model and to a conventional system, were examined in a lung model.
A temperature-regulated pediatric incubator was used containing a 10 I gas reservoir and a breath humidifier with temperature regulated water bath. This setup provided constant temperature and humidity in the gas examined during measurement period. In the 'expiration' the air was directed from the breath humidifier through a measuring unit via a 'mouthpiece' into the reference system (Alcotest 7110, Dräger Inc., Lübeck) and then out. The measuring unit consisted of sensors for the temperature and relative humidity, and of a connector for the three sample extraction systems (PES). PES I was the conventional system with a 100-cm gas-sample pipe (Alcomed 3010), PES II the newly developed system (AlcoMed 3011, both from Envitec, Wismar) with a 10-cm gas-sample pipe, and PES III with a 20-cm heated gas-sample pipe. During 'inspiration' 2 l of air was fed into the system to rinse the measuring unit and to fill the reservoir. 61 measurements were performed with dry and cold air, and 71 with humidified and warmed air, in the course of which the ethanol concentration was increased from 0 to 1.5/1000. Data were evaluated using regression analysis and the Bland & Altman method.
The constancy of the values set for temperature, relative humidity and absolute humidity in the lung model was given for all measurements. In the dry and cold air, the results from all three test systems coincided almost perfectly with the reference values. The measured BEC in the humidified and warmed air using sample-extraction systems II and III corresponded to a high degree with the reference, while in the case of PES I, only a moderate linear correlation was achieved. The temperature and humidity of the expired gas during artificial respiration influence the gas samples extracted for the purposes of BEC measurement. Newly developed sample-extraction systems II and III coincide with the reference system, even under respiration-simulated gas conditions.
在寻找人工呼吸患者呼出气体乙醇浓度（BEC）测定值出现偏差的可能原因时，必须考虑被测气体的湿度和温度。在本研究中，在肺模型中研究了加湿加温空气和干燥冷空气对一种新开发的BEC测量装置准确性的影响，并与参考模型和传统系统进行了比较。
使用一个温度可控的儿科培养箱，其中有一个10升的储气罐和一个带有温度调节水浴的呼吸加湿器。该装置在测量期间为被测气体提供恒定的温度和湿度。在“呼气”过程中，空气从呼吸加湿器通过一个测量单元，经“吹嘴”进入参考系统（Alcotest 7110，德尔格公司，吕贝克），然后排出。测量单元包括温度和相对湿度传感器，以及用于三个样品提取系统（PES）的连接器。PES I是传统系统，带有一根100厘米的气体采样管（Alcomed 3010），PES II是新开发的系统（AlcoMed 3011，均来自Envitec，维斯马），带有一根10厘米的气体采样管，PES III带有一根20厘米的加热气体采样管。在“吸气”过程中，向系统中注入2升空气，以冲洗测量单元并填充储气罐。使用干燥冷空气进行了61次测量，使用加湿加温空气进行了71次测量，在此过程中乙醇浓度从0增加到1.5/1000。数据采用回归分析和布兰德-奥特曼方法进行评估。
所有测量中肺模型设定的温度、相对湿度和绝对湿度值均保持恒定。在干燥冷空气中，所有三个测试系统的结果与参考值几乎完全一致。使用样品提取系统II和III在加湿加温空气中测得的BEC与参考值高度吻合，而对于PES I，仅实现了中等程度的线性相关。人工呼吸期间呼出气体的温度和湿度会影响为BEC测量而提取的气体样本。新开发的样品提取系统II和III即使在模拟呼吸气体条件下也与参考系统一致。
