Modeling the impact of ventilations on the capnogram in out-of-hospital cardiac arrest

Abstract

Aim Current resuscitation guidelines recommend waveform capnography as an indirect indicator of perfusion during cardiopulmonary resuscitation (CPR). Chest compressions (CCs) and ventilations during CPR have opposing effects on the exhaled carbon dioxide (CO 2) concentration, which need to be better characterized. The purpose of this study was to model the impact of ventilations in the exhaled CO 2 measured from capnograms collected during outof-hospital cardiac arrest (OHCA) resuscitation. Methods We retrospectively analyzed OHCA monitor-defibrillator files with concurrent capnogram, compression depth, transthoracic impedance and ECG signals. Segments with CC pauses, two or more ventilations, and with no pulse-generating rhythm were selected. Thus, only ventilations should have caused the decrease in CO 2 concentration. The variation in the exhaled CO 2 concentration with each ventilation was modeled with an exponential decay function using non-linear-least-squares curve fitting. Results Out of the original 1002 OHCA dataset (one per patient), 377 episodes had the required signals, and 196 segments from 96 patients met the inclusion criteria. Airway type was endotracheal tube in 64.8% of the segments, supraglottic King LT-D™ in 30.1%, and unknown in 5.1%. Median (IQR) decay factor of the exhaled CO 2 concentration was 10.0% (7.8 − 12.9) with R 2 = 0.98(0.95 − 0.99). Differences in decay factor with airway type were not statistically significant (p = 0.17). From these results, we propose a model for estimating the contribution of CCs to the end-tidal CO 2 level between consecutive ventilations and for estimating the end-tidal CO 2 variation as a function of ventilation rate.

European Resuscitation Council Guidelines 2021: Adult advanced life support

“…End-tidal CO 2 is most reliable when the patient's trachea is intubated, but it can also be used with a SGA or bag mask. 311 The aims of monitoring waveform capnography during CPR include: 21,310 Confirming correct tracheal tube placement (see airway section).…”

Erweiterte lebensrettende Maßnahmen für Erwachsene

“…Im typischen Kapnogramm spiegelt das am Ende der Plateauphase gemessene etCO 2 das alveoläre pCO 2 am besten wider. Endtidales CO 2 ist beim intubierten Patienten am zuverlässigsten, kann aber auch mit einer SGA- oder bei der Maskenbeatmung verwendet werden [ 338 ].…”

Surgical nurses’ knowledge levels about hemodynamic monitoring

“…ETCO2 is the partial carbon dioxide pressure at the end of expiratory and measured by a capnograph device. Parameters provided by respiratory gas monitoring, such as respiratory gas flow, are required to monitor the saturation level of the patient (21,22). In a study that retrospectively investigated the differences in arterialend-tidal carbon dioxide in 799 pediatric patients undergoing general anesthesia with ventilation, it was determined that the decrease in PaCO2 was strongly related to the decrease in the PaCO2-ETCO2 difference (23).…”