Introduction: New South Wales Ambulance is the sole provider of emergency medical services in NSW, Australia. The service responds to over 900,000 incidents annually, with around 1% being cardiac arrest cases. Dispatchers used the Medical Priority Dispatch System version 12.1 to triage calls. Each year, over 87,000 calls are coded as cardiac arrest, unconscious, not alert or ineffective breathing. More than 8,600 of these are coded as cardiac arrest.
Methods: Over a two-month period, all calls that were coded as cardiac arrest, unconscious, ineffective breathing or not alert were reviewed. Electronic case sheets from 5,818 incidents were reviewed to determine whether the patient was in cardiac arrest. Paramedic-witnessed arrests were excluded.
The cases analysed were cross-tabulated to compare the identification of cardiac arrest (MPDS Protocol 09) against the confirmed finding of cardiac arrest. A 2x2 table was generated to summarise the results.
Results: Call-takers in NSW, Australia correctly identified 92.2% of cardiac arrest cases at the time of the emergency call. Of all calls that were coded as cardiac arrest at the time of the emergency call, 74.5% of patients were in cardiac arrest when the paramedics arrived. In addition, NSW call-takers demonstrated a very high specificity (95.4%) and negative predictive value (98.8%).
Internationally, identification of cardiac arrest during the emergency call ranges from 41-97%, with no difference between protocol-based and criteria-based triage systems. NSW Ambulance is at the upper end of this range. However, presence of cardiac arrest in those cases that were coded as cardiac arrest is around the middle of the range from published studies.
Conclusions: NSW Ambulance call-takers have a high sensitivity for identification of cardiac arrest. This high performance will optimise other NSW Ambulance programs such as tasking lay responders and the Early Access to Defibrillation program.

4 - Accuracy in the identification of cardiac arrest by Emergency Medical Dispatchers in New South Wales (NSW), Australia