How likely is the patient to be in cardiac arrest? Caller breathing descriptors in ambulance calls that were dispatched as cardiac arrest

Background: In emergency ambulance calls, callers use a variety of ways to describe patients’ breathing, or the absence thereof. Call-takers have the task of interpreting these descriptions, and for unconscious patients, determining if they fit with the dispatch system's requirements for a cardiac arrest. We aimed to categorise the breathing descriptions callers use and determine the likelihood of patients being in cardiac arrest for different breathing description categories. Method: Using call audio and ambulance dispatch data from St John Western Australia (Jan-Jun 2021) for cases dispatched as out-of-hospital cardiac arrest (OHCA) during initial “case entry” questioning, we created a schema of breathing descriptors and coded calls for their occurrence. For each descriptor we determined the percentage of cases confirmed by Emergency Medical Services (EMS) as being in arrest (true positive cases) on arrival at the scene. Results: Of 375 cases dispatched as OHCA, 85.3% (320) were true positives. Callers used a wide range of descriptors, across 23 categories. Descriptors with a high percentage of true positive cases were Dead, NOT breathing, Blue/Purple and Unsure. Some descriptors, notably Barely, Gasp and Laboured were less commonly OHCA, but still had over 50% true positives. Conclusion: Patients who are dispatched as OHCA by call-takers have a diverse range of caller descriptors for their breathing status. While descriptor categories varied in the percentage of EMS-confirmed OHCAs, none had a low percentage. We recommend exposing call-takers to the broad range of breathing descriptors which can be applied to their role in identifying OHCA and addressing caller perceptions of patient signs of life.