Short summary

Response time for emergency medical service vehicles such as ambulances and helicopters is one of the usually proposed key performance indicators in emergency medical services systems. It is beyond doubt that short response time is pivotal in critical conditions such as out-of-hospital cardiac arrest and trauma. However, using light and sirens and moving fast in ambulances is dangerous for patients and personnel and may be detrimental to public safety. Each year, several serious and fatal accide

Rationale

Response time for emergency medical service (EMS) units such as ambulances, rapid response cars and helicopters is a key performance indicator and is frequently used in the political debate on EMS coverage and performance. Short response time is considered pivotal in critical conditions such as out-of-hospital cardiac arrest [1] and major trauma [2]. Studies have shown reduced response time association with improved outcome [3, 4], and the opposite has been described as well [5-7]. Using lights and sirens for rapid EMS response may put conveyed patients, prehospital personnel, and public at potential risk [8] and each year, several serious and fatal accidents occur [9-13].

In Scandinavia, the use of criteria-based dispatch [14, 15] is the standard procedure and widely used. The type of EMS response and urgency is decided within the Emergency Medical Dispatch Center (EMDC) by a specialist call-taker, usually a nurse or emergency medical technician. To achieve short response time, EMS vehicles utilize lights and sirens, and crews are allowed to be non-compliant with traffic rules [16], posing a risk for accidents. Less severe conditions may be managed according to national and international guidelines despite longer response time, suggesting the consideration of additional levels of response beyond the current practice guidelines.

Apart from specific conditions such as out-of-hospital cardiac arrest and trauma [1, 2], there is lack of scientific evidence, other than best practice, to justify the shortest possible response time is related to improved patient outcomes [17]. Several confounders may affect patient outcomes, including crowding in the receiving hospital and a shortage of personnel. Similarly, prolonged on-scene times as the result of time-consuming complex medical procedures, may affect the time to final treatment in the hospital. Thus, the intention to describe several factors influencing time to an event such as mortality remains paramount.

With the access to a complete database of all ambulance and helicopter missions in Denmark and the unique Danish Civilian Registration Register [18], we have the ability to merge data on response time and data on on-scene time, transport time to a hospital; interventions on the mission; length of hospital stay; days spent in the intensive care unit including ventilator days, SAPS II/III [19], serious adverse events, and mortality.

Description of the cohort

The nationwide observational registry-based study will use data obtained retrospectively from electronic medical records. Patient identification, stratification within the Danish Index for Acute Medical Assistance, time stamps and critical prehospital interventions will be collected from the Danish national prehospital medical record system. Data regarding mortality will be collected from Danish Civil Registration Register [18]. For diagnoses, Danish National Patient Register [27] will be searched. For intensive care data, Danish Intensive Care Database will be consulted. The study cohort comprises all patients treated by ambulance and/or helicopter in Denmark from 2016-2022. Ambulance missions will be stratified according to mission carried out with or without lights and sirens. Patients will be excluded if they are unidentified or if data is insufficient. Non-emergency transport missions will be excluded.

Data and biological material

To elucidate the possible association between criteria-based dispatch category and ambulance and helicopter on-scene time; transport time to a hospital and critical interventions, illness severity and mortality, we will analyze data on all ambulance missions and helicopter missions in Denmark from 2016-2022.

Collaborating researchers and departments

Department of Intensive Care, Rigshospitalet

• Anders Perner

Department of Emergency Medicine, Odense University Hospitaltal

• Annmarie Touborg Lassen

Prehospital Division, Oslo University Hospital

• Marius Rehn

Department of Anesthesiology and Intensive Care Medicine, Sygehus Lillebælt

• Anne Craverio Brøchner

RKKP Danish Region's Quality Development Programme

• Helle Collatz Christensen

Publications associated with the project

Ambulance and helicopter response time. Association with patient outcome and illness severity: Protocol of a systematic literature review and meta-analysis. Accepted for publication in Acta Anaesthesiologica Scandinavica on 27 September 2023. In production as per 6 October 2023.