Strategies To Improve Survival Outcomes Of Out- Of-Hospital Cardiac Arrest (OHCA): A Simulation Study

The published Pan-Asian Resuscitation Outcomes (PAROS) study identified several modifiable factors that improve OHCA survival.1 These include shorter ambulance response time, bystander cardiopulmonary resuscitation (CPR), and pre-hospital defibrillation performed by automated external defibrillator (AED). This study aimed to identify a strategy that maximizes improvements in survival upon hospital discharge or 30-days post OHCA in Singapore for a one-time investment of $10, $20, or $30 million put toward one of the following strategies 1) reducing response time via purchase of more ambulances 2) increased CPR training; 3) greater investment in AEDs. We first determined the number of additional ambulances, CPR trainings, and AEDs that could be purchased with a given budget. We then simulated the changes in ambulance response time, and likelihood of 1) CPR and 2) AED usage as a function of their increased availability. We then combined this information with odds ratios for increasing survival to hospital discharge of each factor estimated from PAROS Singapore 2010-2015 data to determine the increase in survival probability from each investment strategy. Odds ratios for ambulance response time (for each additional minute), bystander CPR and bystander defibrillation were 0.87 (95% CI: 0.82-0.94, p<0.001), 1.38 (95% CI: 1.11-1.71, p=0.003), 3.13 (95% CI: 2.06-4.63, p<0.001). Survival at baseline was 4.03% (95% CI: 3.96%-4.10%). Predictive survival for the three strategies given a budget of $10M were 4.25% (95% CI: 4.18%-4.33%), 4.09% (95% CI: 4.03%-4.16%), and 4.84% (95% CI: 4.73%-4.95%) for ambulance, CPR and AED investments, respectively. Increasing the budget to $30M improved survival to 4.40%, 4.22%, and 6.47% which represents 7, 4, and 50 additional lives saved for three strategies respectively. Investment into either of three strategies given a budget of 10M slightly improved survival. When the budget was increased to 20M and 30M, survival was further improved. Increasing number of AEDs achieved the highest survival.