title: Population density, automated external defibrillator use, and survival in rural cardiac arrest.
abstract: OBJECTIVE
  To determine whether population density is an independent predictor of survival from out-of-hospital cardiac arrest managed by basic life support (BLS) services using automated external defibrillators (AEDs).
  
  
  METHODS
  A retrospective, observational study in Kentucky of 34 BLS services covering 22 counties during the years 1992 to 1994 who used AEDs to treat patients who had out-of-hospital cardiac arrests.
  
  
  RESULTS
  Of 311 patients who had out-of-hospital cardiac arrests, 110 (35%) were defibrillated, 46 (15%) were resuscitated to hospital admission, and 19 (6%) survived to hospital discharge. Univariate predictors for survival to hospital discharge were emergency medical services response interval (from call receipt to ambulance arrival) < 8 minutes, defibrillation by the AED, initial rhythm of ventricular fibrillation or ventricular tachycardia (VF/VT), and population density > 100/square mile (sq mi) for the BLS service area (p < 0.001). A forced logistic regression model of survival to hospital discharge, using these 4 factors plus the presence of a witnessed arrest or bystander CPR, demonstrated that population density > 100/sq mi was highly significant (OR 9.4, 95% CI: 1.7 to 51.4, p < 0.01). Stepwise logistic regression models with combinations of these 6 factors found that survival to hospital discharge was best predicted by an initial rhythm of VF/VT (p = 0.004) and population density > 100/sq mi (p = 0.011).
  
  
  CONCLUSIONS
  Population density is strongly associated with survival from out-of-hospital cardiac arrest. BLS services within areas with population densities < or = 100/sq mi sustained little benefit from the addition of AEDs to their treatment of patients who had out-of-hospital cardiac arrests.
authors.affiliation: Department of Emergency Medicine, University of Kentucky Medical Center, Lexington 40536-0084, USA. jsstap01@pop.uky.edu
authors.forename: J S
authors.initials: JS
authors.lastname: Stapczynski
authors.forename: J E
authors.initials: JE
authors.lastname: Svenson
authors.forename: C K
authors.initials: CK
authors.lastname: Stone
mesh_terms: D000368:Aged; D004554:Electric Countershock; D005260:Female; D006323:Heart Arrest / Q000401:mortality* / Q000628:therapy; D006801:Humans; D007629:Kentucky / Q000453:epidemiology; D008020:Life Support Care; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D011156:Population Density; D012189:Retrospective Studies; D012423:Rural Health; D016019:Survival Analysis