Abstract
BACKGROUND AND AIM: Unsuccessful defibrillation shocks adversely affect survival from out-of-hospital cardiac arrest (OHCA). Ventricular fibrillation (VF) waveform analysis is the tool-of-choice for the non-invasive prediction of shock success, but surrogate markers of perfusion like end-tidal CO(2) (EtCO(2)) could improve the prediction. The aim of this study was to evaluate EtCO(2) as predictor of shock success, both individually and in combination with VF-waveform analysis. MATERIALS AND METHODS: In total 514 shocks from 214 OHCA patients (75 first shocks) were analysed. For each shock three predictors of defibrillation success were automatically calculated from the device files: two VF-waveform features, amplitude spectrum area (AMSA) and fuzzy entropy (FuzzyEn), and the median EtCO(2) (MEtCO(2)) in the minute before the shock. Sensitivity, specificity, receiver operating characteristic (ROC) curves and area under the curve (AUC) were calculated, for each predictor individually and for the combination of MEtCO(2) and VF-waveform predictors. Separate analyses were done for first shocks and all shocks. RESULTS: MEtCO(2) in first shocks was significantly higher for successful than for unsuccessful shocks (31mmHg/25mmHg, p<0.05), but differences were not significant for all shocks (32mmHg/29mmHg, p>0.05). MEtCO(2) predicted shock success with an AUC of 0.66 for first shocks, but was not a predictor for all shocks (AUC 0.54). AMSA and FuzzyEn presented AUCs of 0.76 and 0.77 for first shocks, and 0.75 and 0.75 for all shocks. For first shocks, adding MEtCO(2) improved the AUC of AMSA and FuzzyEn to 0.79 and 0.83, respectively. CONCLUSIONS: MEtCO(2) predicted defibrillation success only for first shocks. Adding MEtCO(2) to VF-waveform analysis in first shocks improved prediction of shock success. VF-waveform features and MEtCO(2) were automatically calculated from the device files, so these methods could be introduced in current defibrillators adding only new software.