Department of Medicine and Geriatrics, Kwong Wah Hospital, 25 Waterloo Road, Kowloon, Hong Kong.
Hong Kong Med J. 2009 Dec;15(6):440-6.
To explore the correlation and concordance between end-tidal carbon dioxide and arterial carbon dioxide partial pressure, and confirm the experience of the general consensus among service environments.
A prospective cross-sectional analysis.
Two respiratory service units in Hong Kong.
Two hundred respiratory patients were recruited, in whom 219 sets of observations were recorded. Patients deemed to require arterial blood gas determination also had their end-tidal carbon dioxide partial pressure measured at that time, using two LifeSense LS1-9R Capnometers.
The agreement of end-tidal carbon dioxide partial pressure and arterial carbon dioxide partial pressure was studied by correlation coefficients, mean and standard deviation of their difference, and the Bland-Altman plot.
Overall, the correlation was low and insignificant (r=0.1185, P=0.0801). The mean of the difference was 7.2 torr (95% confidence interval, 5.5-8.9) and significant (P<0.001). The limits of agreement by Bland-Altman analysis were -18.1 to 32.5 torr, which were too large to be acceptable. In the sub-group on room air, the mean difference was reduced to 2.26 torr, the correlation between end-tidal carbon dioxide partial pressure and arterial carbon dioxide partial pressure was 0.2194 (P=0.0068), though statistically significant, the extent of correlation was still low.
End-tidal carbon dioxide partial pressure did not show significant correlation or concordance with arterial carbon dioxide partial pressure, especially when supplemental oxygen was used. End-tidal carbon dioxide partial pressure currently cannot replace arterial blood gas measurement as a tool for monitoring arterial carbon dioxide partial pressure. Possible reasons for the discrepancy with previous studies include small sample size in previous studies, lack of research facilities in service settings, and publication bias against negative studies.
探讨呼气末二氧化碳与动脉血二氧化碳分压的相关性和一致性，并确认服务环境中的普遍共识经验。
前瞻性的横断面分析。
香港的两个呼吸服务单位。
共招募了 200 名呼吸科患者，其中记录了 219 组观察结果。需要进行动脉血气测定的患者也同时使用两个 LifeSense LS1-9R Capnometers 测量其呼气末二氧化碳分压。
通过相关系数、差值的均值和标准差以及 Bland-Altman 图研究呼气末二氧化碳分压与动脉血二氧化碳分压的一致性。
总体而言，相关性较低且无统计学意义（r=0.1185，P=0.0801）。差值的均值为 7.2 torr（95%置信区间，5.5-8.9）且有统计学意义（P<0.001）。 Bland-Altman 分析的一致性界限为-18.1 至 32.5 torr，太大而无法接受。在空气组亚组中，差值的均值降低至 2.26 torr，呼气末二氧化碳分压与动脉血二氧化碳分压之间的相关性为 0.2194（P=0.0068），虽然有统计学意义，但相关性的程度仍然较低。
呼气末二氧化碳分压与动脉血二氧化碳分压之间没有显著的相关性或一致性，尤其是在使用补充氧气时。呼气末二氧化碳分压目前不能替代动脉血气测量作为监测动脉血二氧化碳分压的工具。与之前的研究存在差异的可能原因包括之前研究的样本量较小、服务环境中缺乏研究设施以及对负面研究的发表偏倚。
