Chang Kuo-Chen, Orr Joe, Hsu Wei-Chih, Yu Lu, Tsou Mei-Yung, Westenskow Dwayne R, Ting Chien-Kun
Department of Anesthesiology, Taipei Veterans General Hospital, 3F, No. 201, Sec. 2, Shipai Rd., Beitou District, Taipei City, 11217, Taiwan, ROC.
Department of Anesthesiology and Biomedical Engineering, University of Utah, Salt Lake, UT, USA.
J Clin Monit Comput. 2016 Apr;30(2):169-73. doi: 10.1007/s10877-015-9696-5. Epub 2015 Apr 21.
Esophagogastroduodenoscopy procedures are typically performed under conscious sedation. Drug-induced respiratory depression is a major cause of serious adverse effects during sedation. Capnographic monitoring of respiratory activity improves patient safety during procedural sedation. This bench study compares the performance of the nasal cannulas and oral bite blocks used to monitor exhaled CO2 during sedation. We used a spontaneously breathing mechanical lung to evaluated four CO2 sampling nasal cannulas and three CO2 sampling bite blocks. We placed pneumatic resistors in the mouth of the manikin to simulate different levels of mouth opening. We compared CO2 measurements taken from the sampling device to CO2 measurements taken directly from the trachea. The end tidal CO2 concentration (PETCO2) measured through the bite blocks and nasal cannulas was always lower than the corresponding PETCO2 measured at the trachea. The difference became larger as the amount of oxygen delivered through the devices increased. The difference was larger during normal ventilation than during hypoventilation. The difference became larger as the amount of oral breathing increased. The two nasal cannulas without oral cups failed to provide sufficient CO2 for breath detection when the mouth was fully open and oxygen was delivered at 10 L/min. Our simulation found that respiratory rate can be accurately monitored during the procedure using a CO2 sampling bite block or a nasal cannula with oral cup. The accuracy of PETCO2 measurements depends on the device used, the amount of supplement oxygen, the amount of oral breathing and the patient's minute ventilation.
食管胃十二指肠镜检查通常在清醒镇静下进行。药物引起的呼吸抑制是镇静期间严重不良反应的主要原因。呼吸活动的二氧化碳波形图监测可提高操作镇静期间的患者安全性。这项实验台研究比较了在镇静期间用于监测呼出二氧化碳的鼻插管和口腔咬块的性能。我们使用自主呼吸机械肺来评估四种二氧化碳采样鼻插管和三种二氧化碳采样咬块。我们在人体模型口中放置气动电阻器以模拟不同程度的张口。我们将从采样设备获取的二氧化碳测量值与直接从气管获取的二氧化碳测量值进行比较。通过咬块和鼻插管测得的呼气末二氧化碳浓度（PETCO2）始终低于在气管处测得的相应PETCO2。随着通过设备输送的氧气量增加，差异变得更大。正常通气时的差异大于通气不足时的差异。随着口腔呼吸量增加，差异变得更大。当嘴巴完全张开且以10L/分钟的速度输送氧气时，两个没有口腔杯的鼻插管无法提供足够的二氧化碳用于呼吸检测。我们的模拟发现，在手术过程中使用二氧化碳采样咬块或带口腔杯的鼻插管可以准确监测呼吸频率。PETCO2测量的准确性取决于所使用的设备、补充氧气的量、口腔呼吸的量和患者的分钟通气量。
