The impact of using time critical intervention‐based dispatch thresholds on lowering lights and siren use to EMS 911 incidents

Abstract Objectives Emergency Medical Services (EMS) has historically utilized lights and sirens (L&S) to respond to 911 incidents. L&S are used in 86% of scene responses nationally; however, time critical interventions (TCIs) occur in less than 7% of these incidents. Responses with L&S are associated with increased risk of crashes and injuries. Our objective was to determine the impact of TCI‐based dispatch thresholds on L&S use, dispatch accuracy, and response times. Methods We performed a before‐after retrospective evaluation of TCI‐based dispatch methodology at a suburban EMS system. We categorized all EMS interventions as TCI or not, and we determined a TCI threshold above which we would use L&S. We then assigned response priorities to each call nature based on the proportion of TCIs within them. We compared historical results with those from the 6 months following implementation in terms of L&S use, dispatch accuracy, and response times. Results There were 13,879 responses in the “before” group and 14,117 in the “after” group. The rate of L&S use decreased from 56.2% in the before group to 27.6% in the after group, while TCIs were performed in 6.9% of responses in the before group and 7.6% in the after group. Accuracy increased from 48.8% to 75.1% and median response time increased by 0.1 min from 8.3 to 8.4 min. Conclusion Using TCI‐based dispatch thresholds, we decreased L&S use and increased accuracy with minimal increased response time. Our results support the use of this methodology to determine EMS response modes.