Repeated self-directed CPR testing enhances compression depth: Evidence from a large retrospective cohort

Background High-quality chest compressions are critical to survival after cardiac arrest, yet CPR skills decline after conventional training. Low-dose, high-frequency (LDHF) training may sustain competence, but large-scale longitudinal evidence from self-directed stations remains limited. Methods We conducted a single-center retrospective cohort study of healthcare professionals completing at least two manikin-based CPR assessments between June 2023 and April 2026. Automated testing was performed using a self-directed manikin-based simulation station without real-time feedback. Mixed-effects models assessed associations of interval and test-day number with compression depth, rate, recoil, and guideline compliance. Sensitivity analyses modeled test-day number categorically and adjusted depth models for age and recorded sex. Results Among 2,558 participants (6,232 tests), mean depth increased from 49.8 ± 9.2 mm on test day 1 to 52.5 ± 7.6 mm on test day 2 and remained within guideline targets thereafter; rate and recoil were stable. Interval had a negligible association with depth (0.027 mm per 30 days, p = .027) that was attenuated after demographic adjustment ( p = .101). Per 30 days, interval was weakly associated with depth compliance, but not rate or combined compliance. Later test-day number was associated with higher depth (1.59 mm per test day, p < .001), with consistent categorical and adjusted findings. Conclusion Later test-day number was consistently associated with higher depth, whereas interval explained little variation. Although the observational design cannot establish station effectiveness or an optimal refresher interval, this study provides one of the largest longitudinal descriptions of repeated self-directed CPR assessment in certified healthcare professionals.