Ruiz de Gauna Sofía, Gutiérrez Jose Julio, Ruiz Jesus, Leturiondo Mikel, Azcarate Izaskun, González-Otero Digna María, Corcuera Carlos, Russell James Knox, Daya Mohamud Ramzan
University of the Basque Country, UPV/EHU, Bilbao, Bizkaia, Spain.
University of the Basque Country, UPV/EHU, Bilbao, Bizkaia, Spain.
Resuscitation. 2020 Nov;156:215-222. doi: 10.1016/j.resuscitation.2020.06.007. Epub 2020 Jul 1.
Ventilation rate is a confounding factor for interpretation of end-tidal carbon dioxide (ETCO) during cardiopulmonary resuscitation (CPR). The aim of our study was to model the effect of ventilation rate on ETCO during manual CPR in adult out-of-hospital cardiac arrest (OHCA).
We conducted a retrospective analysis of OHCA monitor-defibrillator files with concurrent capnogram, compression depth, transthoracic impedance and ECG. We annotated pairs of capnogram segments presenting differences in average ventilation rate and average ETCO value but with other influencing factors (e.g. compression rate and depth) presenting similar values within the pair. ETCO variation as a function of ventilation rate was adjusted through curve fitting using non-linear least squares as a measure of goodness of fit.
A total of 141 pairs of segments from 102 patients were annotated. Each pair provided a single data point for curve fitting. The best goodness of fit yielded a coefficient of determination R of 0.93. Our model described that ETCO decays exponentially with increasing ventilation rate. The model showed no differences attributable to the airway type (endotracheal tube or supraglottic King-LT-D).
Capnogram interpretation during CPR is challenging since many factors influence ETCO. For adequate interpretation, we need to know the effect of each factor on ETCO. Our model allows quantifying the effect of ventilation rate on ETCO variation. Our findings could contribute to better interpretation of ETCO during CPR.
通气频率是心肺复苏（CPR）期间呼气末二氧化碳（ETCO）解读的一个混杂因素。我们研究的目的是建立成人院外心脏骤停（OHCA）手动CPR期间通气频率对ETCO影响的模型。
我们对伴有同步二氧化碳图、按压深度、经胸阻抗和心电图的OHCA监测除颤器文件进行了回顾性分析。我们标注了二氧化碳图片段对，这些片段对的平均通气频率和平均ETCO值存在差异，但其他影响因素（如按压频率和深度）在片段对内呈现相似的值。通过使用非线性最小二乘法进行曲线拟合来调整ETCO随通气频率的变化，以此作为拟合优度的度量。
共标注了来自102例患者的141对片段。每对片段为曲线拟合提供一个数据点。最佳拟合优度产生的决定系数R为0.93。我们的模型表明，ETCO随通气频率增加呈指数衰减。该模型显示气道类型（气管内导管或声门上King-LT-D）无差异。
CPR期间二氧化碳图解读具有挑战性，因为许多因素会影响ETCO。为了进行充分解读，我们需要了解每个因素对ETCO的影响。我们的模型能够量化通气频率对ETCO变化的影响。我们的研究结果有助于更好地解读CPR期间的ETCO。
