b'CARES 2023 Annual ReportFigure 11 presents a bivariate analysis of survival to hospital discharge rate by EMS response time (measured from call receipt at the dispatch center to arrival of the ambulance on scene) for all OHCA patients as well as three subsets: bystander witnessed, bystander witnessed VF/VT (Utstein), and unwitnessed cases. Patients with a witnessed VF/VT arrest experienced a significant decrease in survival with increasing EMS response time. In contrast, response time had minimal impact on survival among unwitnessed arrests.45.3%40.2% 38.5%40%34.7% 34.2%31.2%30% 29.6%24.2% 25.4% 25.7%Survival Rate (%)22.9% 23.6%20.1% 21.2%20% 18.1% 17.4%15.8% 14.5% 14.1%12.9% 13.3% 13.4%12.0% 11.0% 11.1%9.8% 9.8% 9.2% 8.6% 8.8% 8.2%10% 7.9% 7.3%5.4% 5.1% 5.4% 4.6% 4.9% 4.7% 4.5% 4.6%4.0% 3.9% 3.8%0%3 3:01 -4 4:01 -5 5:01 -6 6:01 -7 7:01 -8 8:01 -9 9:01 -10 10:01 -11 11:01 -12 12Response Time Interval (minutes)All Bystander Witnessed Bystander Witnessed VF/VT UnwitnessedFigure 11. Survival rate by EMS response time and arrest witness status.Figure 12 illustrates the interdependence between the links in the chain of survival, by highlighting how rapid 911 response and bystander CPR (bCPR) work in tandem to improve patient survival. Bystander CPR helps provide critical and timely intervention while 911 vehicles are en route to the scene. By comparing the same patient subgroups in Figure 11 and Figure 12, one can observe how survival is elevated when bystander CPR is performed.50% 48.7%43.4% 42.0%40% 39.0%36.3% 35.5%31.6% 32.8%30% 26.9% 27.1%26.0% 24.9%Survival Rate (%)22.9% 20.9% 21.2%19.9%20% 18.1% 15.8% 17.2% 17.2% 16.1%15.1% 14.1%12.7% 11.5% 11.6% 11.0% 10.6% 11.1% 10.2% 12.7%9.7%10% 11.0% 9.0%10.0% 9.2% 8.2% 8.2% 7.7% 7.6%5.6% 6.7% 6.6% 5.9%0%3 3:01 -4 4:01 -5 5:01 -6 6:01 -7 7:01 -8 8:01 -9 9:01 -10 10:01 -11 11:01 -12 12Response Time Interval (minutes)All with bCPR Bystander Witnessed with bCPR Bystander Witnessed VF/VT with bCPR All without bCPRFigure 12. Survival rate by EMS response time and arrest witness status, among patients who received bystander CPR.36 37'