title: Chest compression fraction determines survival in patients with out-of-hospital ventricular fibrillation.
abstract: BACKGROUND
  Quality cardiopulmonary resuscitation contributes to cardiac arrest survival. The proportion of time in which chest compressions are performed in each minute of cardiopulmonary resuscitation is an important modifiable aspect of quality cardiopulmonary resuscitation. We sought to estimate the effect of an increasing proportion of time spent performing chest compressions during cardiac arrest on survival to hospital discharge in patients with out-of-hospital ventricular fibrillation or pulseless ventricular tachycardia.
  
  
  RESULTS
  This is a prospective observational cohort study of adult patients from the Resuscitation Outcomes Consortium Cardiac Arrest Epistry with confirmed ventricular fibrillation or ventricular tachycardia, no defibrillation before emergency medical services arrival, electronically recorded cardiopulmonary resuscitation before the first shock, and a confirmed outcome. Patients were followed up to discharge from the hospital or death. Of the 506 cases, the mean age was 64 years, 80% were male, 71% were witnessed by a bystander, 51% received bystander cardiopulmonary resuscitation, 34% occurred in a public location, and 23% survived. After adjustment for age, gender, location, bystander cardiopulmonary resuscitation, bystander witness status, and response time, the odds ratios of surviving to hospital discharge in the 2 highest categories of chest compression fraction compared with the reference category were 3.01 (95% confidence interval 1.37 to 6.58) and 2.33 (95% confidence interval 0.96 to 5.63). The estimated adjusted linear effect on odds ratio of survival for a 10% change in chest compression fraction was 1.11 (95% confidence interval 1.01 to 1.21).
  
  
  CONCLUSIONS
  An increased chest compression fraction is independently predictive of better survival in patients who experience a prehospital ventricular fibrillation/tachycardia cardiac arrest.
authors.affiliation: MSc, Emergency and Health Services Commission of British Columbia, 302-2955 Virtual Way, Vancouver, British Columbia, Canada V5M 4X6.
authors.forename: Jim
authors.initials: J
authors.lastname: Christenson
authors.forename: Douglas
authors.initials: D
authors.lastname: Andrusiek
authors.forename: Siobhan
authors.initials: S
authors.lastname: Everson-Stewart
authors.forename: Peter
authors.initials: P
authors.lastname: Kudenchuk
authors.forename: David
authors.initials: D
authors.lastname: Hostler
authors.forename: Judy
authors.initials: J
authors.lastname: Powell
authors.forename: Clifton W
authors.initials: CW
authors.lastname: Callaway
authors.forename: Dan
authors.initials: D
authors.lastname: Bishop
authors.forename: Christian
authors.initials: C
authors.lastname: Vaillancourt
authors.forename: Dan
authors.initials: D
authors.lastname: Davis
authors.forename: Tom P
authors.initials: TP
authors.lastname: Aufderheide
authors.forename: Ahamed
authors.initials: A
authors.lastname: Idris
authors.forename: John A
authors.initials: JA
authors.lastname: Stouffer
authors.forename: Ian
authors.initials: I
authors.lastname: Stiell
authors.forename: Robert
authors.initials: R
authors.lastname: Berg
mesh_terms: D000368:Aged; D016887:Cardiopulmonary Resuscitation / Q000379:methods / Q000592:standards / Q000706:statistics & numerical data*; D015331:Cohort Studies; D016208:Databases, Factual; D004554:Electric Countershock / Q000706:statistics & numerical data; D004632:Emergency Medical Services / Q000706:statistics & numerical data*; D005260:Female; D006323:Heart Arrest / Q000401:mortality / Q000628:therapy; D006801:Humans; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D017180:Tachycardia, Ventricular / Q000401:mortality / Q000628:therapy; D014693:Ventricular Fibrillation / Q000401:mortality* / Q000628:therapy*