Yamamori Shinji, Takasaki Yuji, Ozaki Makoto, Iseki Hiroshi
Faculty of Advanced Techno-Surgery, Institute of Advanced Biomedical Engineering & Science, Tokyo Women's Medical University, 8-1 Kawada-cho, Shinjuku-ku, Tokyo, Japan.
J Clin Monit Comput. 2008 Jun;22(3):209-20. doi: 10.1007/s10877-008-9126-z. Epub 2008 May 28.
Capnogram is often distorted due to aspiration of expired gas when a sidestream capnometer is used for non-intubated, spontaneously breathing condition. The purpose of this study was to make a flow-through capnometer without aspiration and to check if this capnometer precisely detected apnea during obstructive sleep apnea (OSA).
(1) Flow-through capnometer The capnometer consisted of a flow-through etCO(2) sensor, cap-ONE, and an accompanying capnometer. The size of cap-ONE was small enough to be fitted under the nose where gas expired from the nose and the mouth passed through. Thus, the expired gas to be measured is directly blown into the cap-ONE. (2) The cap-ONE using a spontaneously breathing model Capnograms obtained by the cap-ONE and sidestream capnometers during nasal and oral breathing under normal and reduced ventilation were compared with a reference capnogram. (3) Clinical study with OSA patients With nineteen OSA patients capnograms during apnea events diagnosed as OSA by polysomnography were examined using the cap-ONE. (4) Simulation study with an OSA model Apnea in which inspiratory flow was zero and small expiratory flows repeated was produced. Capnograms and apnea detection were compared between the cap-ONE and sidestream capnometers.
In the spontaneouly breathing model capnograms and etCO(2) of the cap-ONE during nasal and oral breathing were almost identical with the reference capnogram but those of sidetream capnometers during oral breathing were significantly reduced. In the clinical study 41% of total OSA events showed capnograms with prolonged and elevated phase with small ripples. In a simulation study reduction of CO(2) tension during no-inspiration was small and apnea was successfully detected with the cap-ONE. However, with sidestream capnometers the reduction of CO(2) tension was large and apnea was not detected.
We concluded that the cap-ONE can record capnograms with minimum distortion and detect apnea reliably during OSA.
在使用旁流式二氧化碳监测仪对未插管的自主呼吸患者进行监测时，由于呼出气体的抽吸，二氧化碳波形图常常会失真。本研究的目的是制作一种无抽吸的流通式二氧化碳监测仪，并检查该监测仪在阻塞性睡眠呼吸暂停（OSA）期间能否准确检测到呼吸暂停。
（1）流通式二氧化碳监测仪 该监测仪由一个流通式呼气末二氧化碳（etCO₂）传感器Cap-ONE及配套的二氧化碳监测仪组成。Cap-ONE的尺寸小到足以安装在鼻子下方，使从鼻子和嘴巴呼出的气体能够通过。因此，待测的呼出气体被直接吹入Cap-ONE中。（2）使用自主呼吸模型的Cap-ONE 将Cap-ONE和旁流式二氧化碳监测仪在正常通气和通气减少情况下，经鼻和经口呼吸时获得的二氧化碳波形图与参考二氧化碳波形图进行比较。（3）OSA患者的临床研究 对19例OSA患者，使用Cap-ONE检查经多导睡眠图诊断为OSA的呼吸暂停事件期间的二氧化碳波形图。（4）OSA模型的模拟研究 产生吸气流量为零且有小的呼气流量重复出现的呼吸暂停。比较Cap-ONE和旁流式二氧化碳监测仪之间的二氧化碳波形图及呼吸暂停检测情况。
在自主呼吸模型中，Cap-ONE在经鼻和经口呼吸时的二氧化碳波形图和etCO₂与参考二氧化碳波形图几乎相同，但旁流式二氧化碳监测仪在经口呼吸时的二氧化碳波形图明显降低。在临床研究中，41%的总OSA事件显示二氧化碳波形图有延长和升高阶段且有小波动。在模拟研究中，无吸气时二氧化碳张力的降低很小，Cap-ONE成功检测到呼吸暂停。然而，旁流式二氧化碳监测仪的二氧化碳张力降低很大，未检测到呼吸暂停。
我们得出结论，Cap-ONE能够以最小的失真记录二氧化碳波形图，并在OSA期间可靠地检测到呼吸暂停。
