Ambulance telephone triage using 'NHS Pathways' to identify adult cardiac arrest

Background UK ambulance services are called to 30 000 cardiac arrests (CAs) annually where resuscitation is attempted. Correct identification by the ambulance service trebles survival by facilitating bystander-cardiopulmonary resuscitation (CPR) and immediate ambulance dispatch. Identification of CA by telephone is challenging and involves algorithms to identify key features. 'NHS Pathways' is now used for triage by six of 12 UK ambulance services, covering a population of 20 million. With the significant improvements in survival when CA is accurately identified, it is vital that 'NHS Pathways' is able to identify CA correctly. Methods All '999' emergency calls to South Central Ambulance Service (SCAS) over a 12-month period screened by NHS Pathways v9.04 were identified. All actual or presumed CAs identified by the emergency call taker were cross-referenced with the ambulance crew's Patient Report Form to identify all confirmed CAs. Results A total of 469 400 emergency (999) calls were received by SCAS. Of the 3119 CA identified by ambulance crew, 753 were not initially classified as CA by NHS Pathways (24.1%). Overall, sensitivity=0.759 (95% CI 0.743 to 0.773); specificity=0.986 (95% CI 0.9858 to 0.98647); and positive predictive value=26.80% (95% CI 25.88 to 27.73%). Conclusions NHS Pathways accurately identifies 75.9% of adult CAs. The remainder represents approximately 7500 treatable CAs in the UK annually where the diagnosis is missed, with significant implications for patient outcome. Further work is required to improve this first link in the chain of survival.