Almost all North American cities have first responder programs. To date there is no published documentation of the roles first responders play, nor of the frequency and type of interventions they perform. Many urban stakeholders question the utility and safety of routinely dispatching large vehicles emergently to calls that may not require their services. Real world data on first responder interventions will help emergency medical services (EMS) directors and planners determine manpower requirements, assess training needs, and optimize dispatch protocols to reduce the rate of inappropriate “code 3” (lights and siren) responses.

Our objectives were to determine how often first responders arrive first on scene, to estimate the time interval between first response and EMS response, and to examine the frequency and type of interventions performed by first responders.

In a prospective observational study, trained observers were assigned to fire department first responder (FDFR) units. These observers recorded on-scene times for FDFR and EMS units, and documented the performance of first responder interventions.

FDFRs arrived first on scene in 49% of code 3 calls. They performed critical interventions in 18% of calls attended and 36% of calls where they arrived first. Oxygen administration was the most frequent critical intervention, yet occult hypoxemia was common and compliance with oxygen administration protocols was poor.

First responders perform critical interventions during a minority of code 3 calls, even when “critical” is defined generously. Many “lights and siren” dispatches are unnecessary. Future research should attempt to identify dispatch criteria that more accurately predict the need for first responder intervention. First responder training and continuous quality improvement (CQI) should focus on interventions that are performed with some regularity, particularly oxygen administration.