Objectives: Our aim was to report the effect of the emergency call processing in the dispatching centre on survival from out-of-hospital ventricular fibrillation (VF).
Methods: This retrospective cohort study was conducted in Helsinki Emergency Medical Services. All consecutive cases with out-of-hospital bystander witnessed VF of cardiac origin between 1 January 1997 and 31 December 2002 were included. Data were collected prospectively. Call processing times, call numbers per dispatcher and telephone guided cardiopulmonary resuscitation (CPR) were studied. Discharge alive from hospital was used as primary end point.
Results: The study population consisted of 373 cases. Cardiac arrest (CA) was recognised in 296 cases (79.4%) by the dispatcher. Survival to discharge was 37.2% (110/296) if CA was recognised and 28.6% (22/77) if it was not recognised (p=0.1550). When the dispatcher handled <4 VF calls during the study period survival to discharge was 22.1% (17/77) compared to 38.2% (50/131) and 39.4% (65/165) when the call volume was 4-9 or >9 (p=0.0227). The mean time to dispatch a first responding unit (FRU) was 77.1+/-44.3 s. Survival to discharge was 39.4% (65/165) when the FRU dispatching time was <60s and 32.2% (67/208) when dispatching took > or =60 s (p=0.1496). The mean time to CA recognition was 170.2+/-130.1 s. Spontaneous circulation was achieved more rapidly when the time was <150 s (p=0.0426), but there was no difference in survival to discharge. Telephone guided CPR instructions were given in 123 cases (35.5%). Survival to discharge was 43.1% (53/123) when CPR instructions were given and 31.7% (72/223) when they were not given (p=0.0453).
Conclusions: We showed that low CA call numbers per dispatcher is associated with a decreased probability of survival. Giving telephone guided CPR instructions should be promoted as they influence the outcome. Further studies are needed to determine optimal call processing times.