Communications Engineering Department, University of the Basque Country UPV/EHU, Alameda Urquijo S/N, 48013 Bilbao, Spain.
Communications Engineering Department, University of the Basque Country UPV/EHU, Alameda Urquijo S/N, 48013 Bilbao, Spain.
Resuscitation. 2015 Mar;88:28-34. doi: 10.1016/j.resuscitation.2014.11.027. Epub 2014 Dec 15.
To determine the accuracy and reliability of the thoracic impedance (TI) signal to assess cardiopulmonary resuscitation (CPR) quality metrics.
A dataset of 63 out-of-hospital cardiac arrest episodes containing the compression depth (CD), capnography and TI signals was used. We developed a chest compression (CC) and ventilation detector based on the TI signal. TI shows fluctuations due to CCs and ventilations. A decision algorithm classified the local maxima as CCs or ventilations. Seven CPR quality metrics were computed: mean CC-rate, fraction of minutes with inadequate CC-rate, chest compression fraction, mean ventilation rate, fraction of minutes with hyperventilation, instantaneous CC-rate and instantaneous ventilation rate. The CD and capnography signals were accepted as the gold standard for CC and ventilation detection respectively. The accuracy of the detector was evaluated in terms of sensitivity and positive predictive value (PPV). Distributions for each metric computed from the TI and from the gold standard were calculated and tested for normality using one sample Kolmogorov-Smirnov test. For normal and not normal distributions, two sample t-test and Mann-Whitney U test respectively were applied to test for equal means and medians respectively. Bland-Altman plots were represented for each metric to analyze the level of agreement between values obtained from the TI and gold standard.
The CC/ventilation detector had a median sensitivity/PPV of 97.2%/97.7% for CCs and 92.2%/81.0% for ventilations respectively. Distributions for all the metrics showed equal means or medians, and agreements >95% between metrics and gold standard was achieved for most of the episodes in the test set, except for the instantaneous ventilation rate.
With our data, the TI can be reliably used to measure all the CPR quality metrics proposed in this study, except for the instantaneous ventilation rate.
确定胸腔阻抗（TI）信号评估心肺复苏（CPR）质量指标的准确性和可靠性。
使用包含压缩深度（CD）、呼气末二氧化碳（capnography）和 TI 信号的 63 例院外心脏骤停事件数据集。我们基于 TI 信号开发了一种胸外按压（CC）和通气检测器。TI 信号因 CC 和通气而出现波动。决策算法将局部最大值分类为 CC 或通气。计算了 7 项 CPR 质量指标：平均 CC 率、分钟内不足 CC 率的分数、CC 分数、平均通气率、分钟内过度通气的分数、瞬时 CC 率和瞬时通气率。CD 和 capnography 信号分别被接受为 CC 和通气检测的金标准。检测器的准确性通过灵敏度和阳性预测值（PPV）进行评估。从 TI 和金标准计算的每个指标的分布，并使用单样本 Kolmogorov-Smirnov 检验进行正态性检验。对于正态和非正态分布，分别应用两样本 t 检验和 Mann-Whitney U 检验，以测试均值和中位数是否相等。为每个指标绘制 Bland-Altman 图，以分析从 TI 和金标准获得的值之间的一致性水平。
CC/通气检测器对 CC 的中位灵敏度/PPV 分别为 97.2%/97.7%，对通气的灵敏度/PPV 分别为 92.2%/81.0%。所有指标的分布均具有相等的均值或中位数，并且在测试集中的大多数事件中，除了瞬时通气率外，指标与金标准之间的一致性超过 95%。
根据我们的数据，TI 可可靠地用于测量本研究提出的所有 CPR 质量指标，除了瞬时通气率。
