The ability of end-tidal carbon dioxide (ΔEtCO2) for predicting fluid responsiveness has been extensively studied with conflicting results. This meta-analysis aimed to explore the value of ΔEtCO2 for predicting fluid responsiveness during the passive leg raising (PLR) test in patients with mechanical ventilation. PubMed, Embase, and Cochrane Central Register of Controlled Trials were searched up to November 2021. The diagnostic odds ratio (DOR), sensitivity, and specificity were calculated. The summary receiver operating characteristic curve was estimated, and the area under the curve (AUROC) was calculated. Q test and I2 statistics were used for study heterogeneity and publication bias was assessed by Deeks’ funnel plot asymmetry test. We performed meta-regression analysis for heterogeneity exploration and sensitivity analysis for the publication bias. Overall, six studies including 298 patients were included in this review, of whom 149 (50%) were fluid responsive. The cutoff values of ΔEtCO2 in four studies was 5%, one was 5.8% and the other one was an absolute increase 2 mmHg. Heterogeneity between studies was assessed with an overall Q = 4.098, I2 = 51%, and P = 0.064. The pooled sensitivity and specificity for the overall population were 0.79 (95% CI 0.72–0.85) and 0.90 (95% CI 0.77–0.96), respectively. The DOR was 35 (95% CI 12–107). The pooled AUROC was 0.81 (95% CI 0.77–0.84). On meta-regression analysis, the number of patients was sources of heterogeneity. The sensitivity analysis showed that the pooled DOR ranged from 21 to 140 and the pooled AUC ranged from 0.92 to 0.96 when one study was omitted. Though the limited number of studies included and study heterogeneity, our meta-analysis confirmed that the ΔEtCO2 performed moderately in predicting fluid responsiveness during the PLR test in patients with mechanical ventilation.

中文翻译：

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呼气末二氧化碳变化对机械通气患者被动抬腿试验中液体反应性预测的价值：系统评价和荟萃分析

潮气末二氧化碳 (ΔEtCO2) 预测液体反应性的能力已被广泛研究，但结果相互矛盾。本荟萃分析旨在探讨 ΔEtCO2 对预测机械通气患者被动抬腿 (PLR) 测试期间液体反应性的价值。检索了截至 2021 年 11 月的 PubMed、Embase 和 Cochrane Central Register of Controlled Trials。计算了诊断优势比 (DOR)、敏感性和特异性。估计汇总接收器操作特征曲线，并计算曲线下面积（AUROC）。Q检验和I2统计用于研究异质性，发表偏倚通过Deeks漏斗图不对称检验评估。我们对异质性探索进行了元回归分析，对发表偏倚进行了敏感性分析。总体而言，本综述纳入了 6 项研究，包括 298 名患者，其中 149 人 (50%) 对液体有反应。四项研究中 ΔEtCO2 的截止值为 5%，一项为 5.8%，另一项为绝对增加 2 mmHg。研究之间的异质性通过总体 Q = 4.098、I2 = 51% 和 P = 0.064 进行评估。总体人群的汇总敏感性和特异性分别为 0.79（95% CI 0.72–0.85）和 0.90（95% CI 0.77–0.96）。DOR 为 35 (95% CI 12–107)。合并的 AUROC 为 0.81 (95% CI 0.77–0.84)。在元回归分析中，患者数量是异质性的来源。敏感性分析显示，合并的 DOR 范围为 21 至 140，合并的 AUC 范围为 0.92 至 0。96 当一项研究被省略时。尽管纳入和研究异质性的研究数量有限，但我们的荟萃分析证实，ΔEtCO2 在预测机械通气患者 PLR 测试期间的液体反应性方面表现适中。