title: Chest compression fraction: A time dependent variable of survival in shockable out-of-hospital cardiac arrest.
abstract: BACKGROUND
  The role of chest compression fraction (CCF) in resuscitation of shockable out-of-hospital cardiac arrest (OHCA) is uncertain. We evaluated the relationship between CCF and clinical outcomes in a secondary analysis of the Resuscitation Outcomes Consortium PRIMED trial.
  
  
  METHODS
  We included patients presenting in a shockable rhythm who suffered OHCA prior to EMS arrival. Multivariable logistic regression was used to determine the relationship between CCF and survival to hospital discharge, return of spontaneous circulation (ROSC), and neurologically intact survival. We also performed a secondary analysis restricted to patients without ROSC in the first 10 min of EMS resuscitation.
  
  
  RESULTS
  Among the 2011 patients, median (IQR) age was 65 (54, 75) years, 78.2% were male, and mean (SD) CCF was 0.71 (0.14). Compared to the reference group (CCF<0.60), the odds ratio (OR) for survival was 0.49 (95% CI: 0.36, 0.68) for CCF 0.60-0.79 and 0.30 (95% CI: 0.20, 0.44) for CCF≥0.80. Results were similar for outcomes of ROSC and neurologically intact survival. Conversely, when restricted to the cohort who did not achieve ROSC during the first 10 min (n=1633), compared to the reference group (CCF<0.60), the OR for survival was 0.79 (95% CI: 0.53, 1.18) for CCF 0.60-0.79 and OR 0.88 (95% CI: 0.56, 1.36) for CCF≥0.80.
  
  
  CONCLUSIONS
  In this study of OHCA patients presenting in a shockable rhythm, CCF was paradoxically associated with lower odds of survival. CCF is a complex measure and taken by itself may not be a consistent predictor of good clinical outcomes.
authors.affiliation: University of Toronto, Toronto, ON, Canada. Electronic address: Sheldon.Cheskes@sunnybrook.ca.
authors.forename: Sheldon
authors.initials: S
authors.lastname: Cheskes
authors.affiliation: University of Washington, Seattle, WA, United States.
authors.forename: Robert H
authors.initials: RH
authors.lastname: Schmicker
authors.affiliation: University of Washington, Seattle, WA, United States.
authors.forename: Tom
authors.initials: T
authors.lastname: Rea
authors.affiliation: University of Washington, Seattle, WA, United States.
authors.forename: Judy
authors.initials: J
authors.lastname: Powell
authors.affiliation: University of Toronto, Toronto, ON, Canada.
authors.forename: Ian R
authors.initials: IR
authors.lastname: Drennan
authors.affiliation: University of Washington, Seattle, WA, United States.
authors.forename: Peter
authors.initials: P
authors.lastname: Kudenchuk
authors.affiliation: University of Ottawa, Ottawa, ON, Canada.
authors.forename: Christian
authors.initials: C
authors.lastname: Vaillancourt
authors.affiliation: Oregon Health and Science University, Portland, OR, United States.
authors.forename: William
authors.initials: W
authors.lastname: Conway
authors.affiliation: University of Ottawa, Ottawa, ON, Canada.
authors.forename: Ian
authors.initials: I
authors.lastname: Stiell
authors.affiliation: St. Paul's Hospital, Vancouver, BC, Canada.
authors.forename: Dion
authors.initials: D
authors.lastname: Stub
authors.affiliation: University of California/San Diego, San Diego, CA, United States.
authors.forename: Dan
authors.initials: D
authors.lastname: Davis
authors.affiliation: University of British Columbia, Vancouver, BC, Canada.
authors.forename: Noah
authors.initials: N
authors.lastname: Alexander
authors.affiliation: University of British Columbia, Vancouver, BC, Canada.
authors.forename: Jim
authors.initials: J
authors.lastname: Christenson
mesh_terms: D000368:Aged; D016887:Cardiopulmonary Resuscitation / Q000379:methods*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D058687:Out-of-Hospital Cardiac Arrest / Q000401:mortality* / Q000628:therapy*; D015996:Survival Rate; D013909:Thorax; D013997:Time Factors
keywords: Cardiopulmonary resuscitation; Heart arrest; Resuscitation; Survival