Filtered electrocardiogram combined with end-tidal carbon dioxide for the identification of patients’ cardiac arrest status during uninterrupted chest compressions in cardiopulmonary resuscitation

Comprehensive Summary

Wu et al. examined whether a strategy combining filtered electrocardiogram and end-tidal carbon dioxide (fEEt) could identify cardiac arrest status during uninterrupted chest compressions. The authors conducted a single-center prospective observational study involving 51 adult cardiac arrest patients, yielding 575 analyzed segments. The fEEt strategy classified cardiac arrest status as return of spontaneous circulation (ROSC), shockable rhythm, pulseless electrical activity (PEA), or asystole during ongoing compressions. These classifications were compared with traditional clinical assessments performed during compression interruptions, which served as the reference standard. The fEEt strategy demonstrated good agreement in identifying ROSC (κ=0.695) and shockable rhythms (κ=0.704), with moderate agreement for PEA (κ=0.535) and asystole (κ=0.574). When PEA and asystole were combined as non-shockable rhythms requiring continued compressions, the fEEt strategy showed good overall agreement (κ=0.656) with traditional assessments.

Outcomes and Implications

High-quality chest compressions are the cornerstone of cardiac arrest resuscitation, yet current practice requires periodic interruptions to assess rhythm and check for pulses, reducing coronary and cerebral perfusion pressure and worsening outcomes. Contemporary guidelines emphasize minimizing "hands-off" time, but clinicians still need to determine arrest status to guide management decisions: ROSC requires stopping compressions, shockable rhythms require defibrillation, and non-shockable rhythms require continued compressions. The fEEt strategy addresses this dilemma by combining filtered ECG (to remove compression artifacts) with end-tidal CO2 monitoring to identify cardiac arrest status during ongoing compressions. This study demonstrates proof-of-concept that fEEt can reasonably identify ROSC and shockable rhythms (kappa ~0.70) without compression interruptions, performing substantially better than end-tidal CO2 alone. The moderate agreement for distinguishing PEA from asystole (kappa ~0.55) is less impressive but may be clinically acceptable since both require the same management: continued compressions. The more clinically relevant finding is that fEEt showed good agreement (kappa 0.656) when identifying non-shockable rhythms requiring continued compressions versus conditions requiring different interventions. However, several important limitations temper enthusiasm for immediate clinical adoption. The single-center study of 51 patients provides preliminary evidence but requires validation in larger, diverse populations. Most critically, the study provides no data on whether using fEEt to guide resuscitation improves patient outcomes compared to current practice. The moderate-to-good agreement levels mean 30-45% disagreement with clinical assessment in some categories, which could lead to inappropriate management decisions. For example, falsely identifying ROSC could lead to premature cessation of compressions in a patient without pulses, while falsely identifying a shockable rhythm could delay defibrillation. The study doesn't address practical implementation questions such as whether fEEt can be calculated in real-time, what equipment or software is required, or whether it integrates with existing defibrillator/monitors. For emergency clinicians, this technology represents a promising approach to reducing compression interruptions while maintaining situational awareness during resuscitation. However, it should be viewed as an adjunct to clinical judgment rather than a replacement for periodic assessment. Before widespread adoption, fEEt requires validation in multicenter trials demonstrating improved patient outcomes, refinement to improve accuracy in distinguishing PEA from asystole, and development of user-friendly technology that integrates seamlessly into resuscitation workflows. Future research should also examine optimal strategies for responding to fEEt readings that conflict with clinical suspicion and whether this technology is cost-effective given the substantial resources already devoted to cardiac arrest care.