Ambulance clinicians exposure to out-of-hospital cardiac arrest over 14 years in London, UK: a retrospective observational study

• EMS clinicians in London attend OHCA on average 4 times per year, once every 63 days. • The rate of exposure to cardiac arrest is declining in London. • Specialist clinicians have a very high rate of exposure to these incidents. • Staff attend children in cardiac arrest only once every 5 years on average. • Traumatic cardiac arrests are attended on average once every 3.7 years. We aimed to describe the exposure to out-of-hospital cardiac arrest (OHCA) amongst ambulance clinicians in London, UK over a 14-year period. We undertook a retrospective, observational study using routinely collected data. Staff employed in full time, clinical roles between 2010 and 2023, were matched to attendances at OHCA incidents where resuscitation was attempted. Rates of staff attendance at OHCA incidents were calculated. 8,340 clinicians with eligible periods of employment were included in our analysis. We identified 61,862 OHCA incidents where resuscitation was attempted and matched 61,412 of these to at least one clinician included in the analysis. The median rate of OHCA attendance amongst full-time ambulance clinicians was 4.00 (95% CI 3.23 to 4.77) incidents per year and the rate of exposure decreased over time. Critical care paramedics had the highest rate of exposure with a median rate of 55.00 incidents per year. OHCAs involving children, and those of a traumatic aetiology, were attended rarely - on average once every 5.06 and 3.68 years respectively. Full-time ambulance clinicians in London attend OHCA incidents on average 4 times a year, and the rate of exposure is declining. Certain patient groups are attended much more infrequently. The low rate of exposure may present challenges for training and skill retention.