Low-flow time and neurological outcomes in out-of-hospital cardiac arrest: implications for prehospital care quality and health outcomes.

backgroundOut-of-hospital cardiac arrest (OHCA) remains a significant public health challenge with high mortality and morbidity. Low-flow time (LFT) is an important determinant of outcomes, yet the specific temporal thresholds for functional recovery across different cardiac rhythms remain poorly defined in metropolitan Asian settings. This study aimed to identify the optimal LFT cut point for predicting survival and favorable neurological outcomes using a large-scale emergency medical services (EMS) registry.

methodsThis retrospective cohort study analyzed 4,933 adult non-traumatic OHCA cases from the Taoyuan City EMS registry between January 2021 and October 2025. The primary exposure was LFT, defined as the duration from the initiation of CPR to hospital handover or return of spontaneous circulation. Multivariable logistic regression was utilized to evaluate the independent association between LFT and survival to discharge. Optimal LFT thresholds were identified using Receiver Operating Characteristic (ROC) curves and the Youden Index, stratified by initial cardiac rhythm (shockable vs. non-shockable).

resultsThe overall survival rate to discharge was 22.8% (n = 1,123). A significant rhythm-specific divergence in the impact of LFT was observed. In the shockable rhythm group, LFT exceeding 27 minutes was independently associated with increased mortality (Adjusted Odds Ratio [AOR]: 2.25; 95% CI: 1.19-4.27; p = 0.013). The optimal LFT threshold for predicting survival to discharge was 27 minutes (AUC 0.58; Sensitivity 41%, Specificity 72%), while the threshold for favorable neurological outcome was 26 minutes. In contrast, LFT was not a significant independent predictor for the non-shockable rhythm group (AUC 0.52; p > 0.05), where outcomes were likely dominated by non-temporal factors.

conclusionAmong OHCA patients presenting with shockable rhythms, a low-flow time of approximately 27 minutes was associated with survival and favorable neurological outcomes. However, given the modest predictive performance of this threshold, it should be interpreted as a supportive reference rather than a definitive clinical cutoff. These findings highlight the potential value of incorporating rhythm-specific temporal information into prehospital decision-making, EMS resource allocation, and future evaluations of termination-of-resuscitation protocols.