Purpose

This study evaluates agreement between carbon dioxide measured arterial (PaCO₂) and transcutaneous (PtcCO₂) over time, by repeated successive measures, taking into consideration the inherent variability of arterial measurements.

Methods and results

11 patients receiving LTOT, with severe to very severe COPD in a stable phase were studied. Repeated arterial blood samples were drawn and PtcCO₂ measured simultaneously at the ear lobe. Bland-Altman analysis was used to evaluate 95 % limits of agreement (LoA). 194 paired samples were analysed. Following correction for bias, the difference between PaCO₂ and PtCO₂ during dynamic conditions was 0.02 kPa and LoA 0.94 to -0.90 kPa while 29 % of PtCO₂ measurements were outside the range of variability for arterial measurements.

Conclusion

PtcCO₂ corrected for intra-patient bias provide reasonable description of PaCO₂ values within but not outside steady state conditions. Our results suggest that PtcCO₂ is a valuable method for monitoring in chronic rather than acute conditions when bias can be removed.

中文翻译：

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慢性阻塞性肺疾病患者多次连续测量二氧化碳之间的动脉和经皮变异性和一致性。

目的

本研究通过重复连续测量评估动脉 (PaCO ₂ ) 和经皮 (PtcCO ₂ )二氧化碳测量值随时间的一致性，同时考虑到动脉测量值的固有可变性。

方法和结果

研究了 11 名接受 LTOT 且处于稳定期的重度至极重度 COPD 患者。重复抽取动脉血样并同时在耳垂处测量PtcCO ₂。Bland-Altman 分析用于评估 95% 的一致性限制 (LoA)。分析了 194 个配对样本。校正偏差后，动态条件下PaCO ₂和 PtCO ₂之间的差异为 0.02 kPa，LoA 为 0.94 至 -0.90 kPa，而 29% 的 PtCO ₂测量值超出了动脉测量值的可变性范围。

结论

PtcCO ₂校正了患者内部偏差，提供了在稳态条件内但不在稳态条件外的 PaCO ₂值的合理描述。我们的结果表明，当可以消除偏差时，PtcCO ₂是一种在慢性而非急性条件下进行监测的有价值的方法。