Introduction

Chest compressions during CPR induce oscillations in capnography (E_TCO₂) waveforms. Studies suggest E_TCO₂ oscillation characteristics are associated with intrathoracic airflow dependent on airway patency. Oscillations can be quantified by the Airway Opening Index (AOI). We sought to evaluate multiple methods of computing AOI and their association with return of spontaneous circulation (ROSC).

Methods

We conducted a retrospective study of 307 out-of-hospital cardiac arrest (OHCA) cases in Seattle, WA during 2019. E_TCO₂ and chest impedance waveforms were annotated for the presence of intubation and CPR. We developed four methods for computing AOI based on peak E_TCO₂ and the oscillations in E_TCO₂ during chest compressions (ΔE_TCO₂). We examined the feasibility of automating ΔE_TCO₂ and AOI calculation and evaluated differences in AOI across the methods using nonparametric testing (α = 0.05).

Results

Median [interquartile range] AOI across all cases using Methods 1–4 was 28.0 % [17.9–45.5 %], 20.6 % [13.0–36.6 %], 18.3 % [11.4–30.4 %], and 22.4 % [12.8–38.5 %], respectively (p < 0.001). Cases with ROSC had a higher median AOI than those without ROSC across all methods, though not statistically significant. Cases with ROSC had a significantly higher median [interquartile range] ΔE_TCO₂ of 7.3 mmHg [4.5–13.6 mmHg] compared to those without ROSC (4.8 mmHg [2.6–9.1 mmHg], p < 0.001).

Conclusion

We calculated AOI using four proposed methods resulting in significantly different AOI. Additionally, AOI and ΔE_TCO₂ were larger in cases achieving ROSC. Further investigation is required to characterize AOI’s ability to predict OHCA outcomes, and whether this information can improve resuscitation care.

中文翻译：

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调查心肺复苏期间的气道开放指数

介绍

CPR 期间的胸部按压会引起二氧化碳图 (E _T CO ₂ ) 波形的振荡。研究表明 E _T CO ₂振荡特征与依赖于气道通畅的胸腔内气流有关。振荡可以通过气道开放指数 (AOI) 进行量化。我们试图评估计算 AOI 的多种方法及其与自主循环恢复 (ROSC) 的关系。

方法

我们在 2019 年对华盛顿州西雅图市的 307 例院外心脏骤停 (OHCA) 病例进行了一项回顾性研究。对 E _T CO ₂和胸部阻抗波形进行了注释，以确定是否存在插管和 CPR。我们开发了四种基于峰值 E _T CO ₂和胸外按压期间E _T CO ₂的振荡(ΔE _T CO ₂ ) 计算 AOI 的方法。_{我们检查了 ΔE T} CO ₂和 AOI 计算自动化的可行性，并使用非参数测试评估了不同方法的 AOI 差异 (α = 0.05)。

结果

使用方法 1-4 的所有病例的中位数 [四分位距] AOI 为 28.0 % [17.9-45.5 %]、20.6 % [13.0-36.6 %]、18.3 % [11.4-30.4 %] 和 22.4 % [12.8-38.5 % ]，分别 ( p  < 0.001)。在所有方法中，有 ROSC 的病例的 AOI 中值都高于没有 ROSC 的病例，尽管没有统计学意义。与没有 ROSC 的病例相比（4.8 mmHg [2.6–9.1 mmHg]，p  < 0.001） ，具有 ROSC 的病例的中位数 [四分位距] ΔE _T CO _{2显着更高，为 7.3 mmHg [4.5–13.6 mmHg]。}

结论

我们使用四种建议的方法计算 AOI，从而产生显着不同的 AOI。此外，在达到 ROSC 的情况下，AOI 和 ΔE _T CO ₂更大。需要进一步调查来描述 AOI 预测 OHCA 结果的能力，以及这些信息是否可以改善复苏护理。