# Out-of-Hospital Cardiac Arrest Ambulance Delay Zones and AED Placement in a Southern Brazilian City

## TL;DR

This study identifies areas in a Brazilian city with long ambulance response times for cardiac arrests and suggests optimal AED locations to improve survival.

## Contribution

The study proposes strategic AED placement to reduce response times and improve OHCA outcomes in a medium-sized city.

## Key findings

- 77% of OHCA patients died despite bystander CPR and defibrillation in 31% of cases.
- Ambulance response times exceeded 5 minutes in most cases, especially during peak hours.
- Strategic AED placement could cover 76% of OHCA cases with a 320-second travel time versus 709 seconds for ambulances.

## Abstract

Out-of-hospital cardiac arrests (OHCAs) have high mortality rates, worsened by limited access to automated external defibrillators (AEDs). This study analyzed OHCA response times, identified areas with prolonged ambulance travel times, and proposed optimal AED locations in a medium-sized city in southern Brazil. Data from 278 non-traumatic OHCA cases (2019–2022) in patients over 18 years old, with ambulance response times under 20 min, were included. Spatial survival analysis assessed the probability of exceeding the recommended 5-min (300 s) ambulance response time. The maximal covering location problem identified 100 strategic AED sites within a 150-s reach for bystanders. AED and ambulance travel times were compared using the Wilcoxon test (p < 0.01). Defibrillation occurred in 89 cases (31.01%), and bystander CPR was performed in 149 cases (51.92%). Despite these efforts, 77% of patients died. The median ambulance response time was 11.63 min, exceeding 5 min in most cases, particularly at peak times like 11 a.m. AED placement in selected locations could cover 76% of OHCA occurrences, with a mean AED travel time of 320 s compared to 709 s for ambulances. Strategic AED placement could enhance early defibrillation and improve survival outcomes.