Article Text
Abstract
Background Predefibrillation end-tidal CO2 (ETCO2) may predict defibrillation success and could guide defibrillation timing in ventricular fibrillation (VF) cardiac arrest. This relationship has only been studied using advanced airways. Our aim was to evaluate this relationship using both basic (bag–valve–mask (BVM)) and advanced airways (supraglottic airways and endotracheal tubes).
Methods Prehospital patient records and defibrillator files were abstracted for patients with out-of-hospital cardiac arrest in Ontario, Canada, with initial VF cardiac rhythms between 1 January 2018, and 31 December 2019. Analyses assessed the relationship between each predefibrillation ETCO2 reading and defibrillation outcomes at the subsequent 2 min pulse check (ie, VF, asystole, pulseless electrical activity (PEA) or return of spontaneous circulation (ROSC)), accounting for airway types used during resuscitation. Multivariable logistic regression evaluated the association between the first documented predefibrillation ETCO2 and postshock VF termination or ROSC.
Results Of 269 cases abstracted, 153 had predefibrillation ETCO2 measurements and were included in the study. Among these cases, 904 shocks were delivered and 44.4% (n=401) had predefibrillation ETCO2 measured. The first ETCO2 reading was more often from BVM (n=134) than advanced airways (n=19). ETCO2 readings were lower when measured through BVM versus advanced airways (30.5 mm Hg (4.06 kPa) (±14.4 mm Hg (1.92 kPa)) vs 42.1 mm Hg (5.61 kPa) (±22.5 mm Hg (3.00 kPa)), adjANOVA p<0.01). Of all shocks with ETCO2 reading (n=401), no difference in preshock ETCO2 was found for subsequent shocks that resulted in persistent VF (32.2 mm Hg (4.29 kPa) (±15.8 mm Hg (2.11 kPa))), PEA (32.8 mm Hg (4.37 kPa) (±17.1 mm Hg (2.30 kPa))), asystole (32.4 mm Hg (4.32 kPa) (±20.6 mm Hg (2.75 kPa))) or ROSC (32.5 mm Hg (4.33 kPa) (±15.3 mm Hg (2.04 kPa))), analysis of variance p=0.99. In the multivariate analysis using the initial predefibrillation ETCO2, there was no association with VF termination on the subsequent shock (adjusted OR (adjOR) 0.99, 95% CI 0.97 to 1.02, p=0.57) or ROSC (adjOR 1.00, 95% CI 0.97 to 1.03, p=0.94) when evaluated as a continuous or categorical variable.
Conclusion Predefibrillation ETCO2 measurement is not associated with VF termination or ROSC when basic and advanced airways are included in the analysis. The role of predefibrillation ETCO2 requires careful consideration of the type of airway used during resuscitation.
- resuscitation
- airway
Data availability statement
Data may be obtained from a third party and are not publicly available.
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Data availability statement
Data may be obtained from a third party and are not publicly available.
Footnotes
Handling editor Edward Carlton
Contributors All authors were responsible for the conceptualisation, planning, writing and editing of the manuscript. JLK, LT and SC obtained the dataset and assisted in its preparation for abstraction. JLK was responsible for the data abstraction. JLK and IRD were responsible for the statistical analyses. IRD and SC were responsible for project supervision. JLK is responsible for the overall content of the study as guarantor.
Funding SC received investigator-initiated grant funding from Zoll Medical for AED on the Fly, Improving Community Response to Cardiac Arrest and Monitoring Ventilation during out of Hospital Cardiac Arrest research studies. SC received speaker’s honorarium for educational events on cardiopulmonary resuscitation quality from Zoll Medical. SC sits on the advisory board of Drone Delivery Canada.
Competing interests None declared.
Patient and public involvement Patients and/or the public were not involved in the design, conduct, reporting or dissemination plans of this research.
Provenance and peer review Not commissioned; externally peer reviewed.
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