Effects of modifiable prehospital factors on survival after out-of-hospital cardiac arrest in rural versus urban areas

BACKGROUND: The modifiable prehospital system factors, bystander cardiopulmonary resuscitation (CPR), emergency medical services (EMS), response time, and EMS physician attendance, may affect short- and long-term survival for both rural and urban out-of-hospital cardiac arrest (OHCA) patients. We studied how such factors influenced OHCA survival in a mixed urban/rural region with a high survival rate after OHCA. METHODS: We analyzed the association between modifiable prehospital factors and survival to different stages of care in 1138 medical OHCA patients from an Utstein template-based cardiac arrest registry, using Kaplan-Meier type survival curves, univariable and multivariable logistic regression and mortality hazard plots. RESULTS: We found a significantly higher probability for survival to hospital admission (OR: 1.84, 95% CI 1.43-2.36, p < 0.001), to hospital discharge (OR: 1.51, 95% CI 1.08-2.11, p = 0.017), and at 1 year (OR: 1.58, 95% CI 1.11-2.26, p = 0.012) in the urban group versus the rural group. In patients receiving bystander CPR before EMS arrival, the odds of survival to hospital discharge increased more than threefold (OR: 3.05, 95% CI 2.00-4.65, p < 0.001). However, bystander CPR was associated with increased patient survival to discharge only in urban areas (survival probability 0.26 with CPR vs. 0.08 without CPR, p < 0.001). EMS response time ≥ 10 min was associated with decreased survival (OR: 0.61, 95% CI 0.45-0.83, p = 0.002), however, only in urban areas (survival probability 0.15 ≥ 10 min vs. 0.25 < 10 min, p < 0.001). In patients with prehospital EMS physician attendance, no significant differences were found in survival to hospital discharge (OR: 1.37, 95% CI 0.87-2.16, p = 0.17). In rural areas, patients with EMS physician attendance had an overall better survival to hospital discharge (survival probability 0.17 with EMS physician vs. 0.05 without EMS physician, p = 0.019). Adjusted for modifiable factors, the survival differences remained. CONCLUSIONS: Overall, OHCA survival was higher in urban compared to rural areas, and the effect of bystander CPR, EMS response time and EMS physician attendance on survival differ between urban and rural areas. The effect of modifiable factors on survival was highest in the prehospital stage of care. In patients surviving to hospital admission, there was no significant difference in in-hospital mortality or in 1 year mortality between OHCA in rural versus urban areas.