The purpose of the study was to investigate the accuracy of mainstream EtCO₂ measurements on the Y-piece (filtered) side of the heat and moisture exchanger filter (HMEF) in adult critically ill patients, compared to that on the patient (unfiltered) side of HMEF. We conducted a prospective observational method comparison study between July 2019 and December 2019. Critically ill adult patients receiving mechanical ventilation with HMEF were included. We performed a noninferiority comparison of the accuracy of EtCO₂ measurements on the two sides of HMEF. The accuracy was measured by the absolute difference between PaCO₂ and EtCO₂. We set the non-inferiority margin at + 1 mmHg in accuracy difference between the two sides of HMEF. We also assessed the agreement between PaCO₂ and EtCO₂ using Bland–Altman analysis. Among thirty-seven patients, the accuracy difference was − 0.14 mmHg (two-sided 90% CI − 0.58 to 0.29), and the upper limit of the CI did not exceed the predefined margin of + 1 mmHg, establishing non-inferiority of EtCO₂ on the Y-piece side of HMEF (P for non-inferiority < 0.001). In the Bland–Altman analyses, 95% limits of agreement between PaCO₂ and EtCO₂ were similar on both sides of HMEF (Y-piece side, − 8.67 to + 10.65 mmHg; patient side, − 8.93 to + 10.67 mmHg). The accuracy of mainstream EtCO₂ measurements on the Y-piece side of HMEF was noninferior to that on the patient side in critically ill adults. Mechanically ventilated adult patients could be accurately monitored with mainstream EtCO₂ on the Y-piece side of the HMEF unless their tidal volume was extremely low.

本研究的目的是调查成人危重患者热湿交换过滤器 (HMEF) Y 形件（过滤）侧主流 EtCO ₂测量值与患者（未过滤）侧测量值的准确性HMEF。我们在 2019 年 7 月至 2019 年 12 月之间进行了一项前瞻性观察方法比较研究。纳入了接受 HMEF 机械通气的危重成年患者。我们对 HMEF 两侧的 EtCO ₂测量精度进行了非劣效性比较。准确度通过PaCO ₂和EtCO ₂之间的绝对差来测量。我们将 HMEF 两侧准确度差异的非劣效裕度设置为 + 1 mmHg。我们还使用 Bland-Altman 分析评估了 PaCO ₂和 EtCO ₂之间的一致性。在 37 名患者中，准确度差异为 − 0.14 mmHg（双侧 90% CI − 0.58 至 0.29），CI 上限未超过 + 1 mmHg 的预定界限，证明 EtCO 的非劣效性₂在 HMEF 的 Y 形件一侧（ P表示非劣效性 < 0.001）。在 Bland-Altman 分析中，HMEF 两侧的 PaCO ₂和 EtCO ₂之间的 95% 一致性限度相似（Y 形件侧，− 8.67 至 + 10.65 mmHg；患者侧，− 8.93 至 + 10.67 mmHg）。在危重成人中，HMEF Y 形件侧主流 EtCO ₂测量的准确性不低于患者侧。 机械通气成年患者可以通过 HMEF Y 形件侧的主流 EtCO ₂进行准确监测，除非他们的潮气量极低。