Changes in Bystander CPR Patterns of Private and Public Locations Before and After COVID-19: An Interrupted Time-Series of a Multicentre Out-of-Hospital Cardiac Arrest Cohort

Background: The COVID-19 pandemic exerted competing pressures on bystander cardiopulmonary resuscitation (CPR)—infection control aversion to rescue breathing versus a shift in arrests toward the home—yet reported effects have been inconsistent and evidence by arrest location and CPR method is scarce. Methods: Using the Korean Cardiac Arrest Research Consortium multicentre registry (January 2016–June 2025; 21,182 adults with home or public out-of-hospital cardiac arrest), we performed an interrupted time-series analysis across pre-COVID-19, pandemic (February 2020–May 2023) and endemic periods. Results: Both settings shared rising pre-COVID-19 trends; at the February 2020 interruption, the bystander CPR rate trajectory changed asymmetrically (home −0.278 versus public −0.151 percentage points/month), with block-bootstrap counterfactual shortfalls by series end of −17.6 (home) and −12.5 (public) percentage points. After adjustment, the location interaction was marginal overall (p = 0.065) but significant in witnessed arrests (p = 0.046). Conventional CPR fell abruptly and uniformly (level-change odds ratio 0.22), while compression-only CPR rose above 97% with no recovery through the endemic period. Period-by-location interaction was non-significant for return of spontaneous circulation, survival and good neurological outcome. Conclusions: COVID-19 produced a robust, uniform shift in bystander CPR methods toward compression-only CPR and a more limited and suggestive location-asymmetric change in the bystander CPR rate (marginal overall, significant only in witnessed arrests), without differential effects on short-term outcomes.