Spatial Variation and Resuscitation Process Affecting Survival after Out-of-Hospital Cardiac Arrests (OHCA)

Abstract

Background: Ambulance response times and resuscitation efforts are critical predictors of the survival rate after out-of-hospital cardiac arrests (OHCA). On the other hand, rural-urban differences in the OHCA survival rates are an important public health issue.

Methods: We retrospectively reviewed the January 2011-December 2013 OHCA registry data of Kaohsiung City, Taiwan. With particular focus on geospatial variables, we aimed to unveil risk factors predicting the overall OHCA survival until hospital admission. Spatial analysis, network analysis, and the Kriging method by using geographic information systems were applied to analyze spatial variations and calculate the transport distance. Logistic regression was used to identify the risk factors for OHCA survival.

Results: Among the 4,957 patients, the overall OHCA survival to hospital admission was 16.5%. In the multivariate analysis, female sex (adjusted odds ratio:, AOR, 1.24 [1.06-1.45]), events in public areas (AOR: 1.30 [1.05-1.61]), exposure to automated external defibrillator (AED) shock (AOR: 1.70 [1.30-2.23]), use of laryngeal mask airway (LMA) (AOR: 1.35 [1.16-1.58]), non-trauma patients (AOR: 1.41 [1.04-1.90]), ambulance bypassed the closest hospital (AOR: 1.28 [1.07-1.53]), and OHCA within the high population density areas (AOR: 1.89 [1.55-2.32]) were positively associated with improved OHCA survival. By contrast, a prolonged total emergency medical services (EMS) time interval was negatively associated with OHCA survival (AOR: 0.98 [0.96-0.99]).

Conclusions: Resuscitative efforts, such as AED or LMA use, and a short total EMS time interval improved OHCA outcomes in emergency departments. The spatial heterogeneity of emergency medical resources between rural and urban areas might affect survival rate.

Fig 1. Flow chart of the study design.

Abbreviations: CPR: cardiopulmonary resuscitation; AED: automated external defibrillator; LMA: laryngeal mask airway.

Fig 2. Study areas, population densities, and distributions of out-of-hospital cardiac arrests (OHCA) cases and hospitals in Kaohsiung, 2011–2013.

Purple points indicate that patients with OHCA were transported to the closest emergency hospital while green points represent bypassing it.

Fig 3. Survival percentages of out-of-hospital cardiac arrests (OHCA) by district in areas with high (> = 5,000 persons/km²) and low (< 5,000 persons/km²) population densities of Kaohsiung City, 2011–2013.

Fig 4. Interpolation of the interval from the call to hospital admission by using the Kriging method.

Areas marked with red indicate a prolonged interval of an out-of-hospital cardiac arrest (OHCA) case from the call to hospital admission, while areas marked with green show a short interval (<30 min). Uncolored areas are locations without sufficient interpolation information (sparse OHCA event points).