title: The relationship between chest compression fraction and outcome from ventricular fibrillation arrests in prolonged resuscitations.
abstract: BACKGROUND
  Guidelines direct rescuers to minimize CPR interruptions during resuscitation. There is little evidence that evaluates the relationship of increasing CPR fraction among patients with relatively high fractions or prolonged resuscitation.
  
  
  METHODS
  We conducted an observational study of persons who suffered out-of-hospital ventricular fibrillation arrest and required >5 min of emergency medical services (EMS) CPR for persistent pulselessness. We determined the association between hands-on CPR fraction and outcomes of spontaneous circulation, survival to hospital discharge, and neurologically favorable survival. Analyses were stratified by median hands-on CPR and were conducted for those who required 5, 10, and 20 min of EMS CPR for persistent pulselessness.
  
  
  RESULTS
  Of 414 potentially eligible patients, 323 (78%) required >5 min of EMS CPR, 234 (56%) required >10 min of EMS CPR, and 153 (37%) required EMS CPR for >20 min. The median CPR fraction was 81%. We did not observe a significant association for the outcomes of hospital survival and neurologically favorable survival for the 5-min and 10-min groups. When restricted to patients who required >20 min of EMS CPR, the half who received a higher hands-on CPR fraction were more likely to achieve spontaneous circulation (40% versus 18%, p=0.004), survival to hospital discharge (20% versus 8%, p=0.03), and neurologically favorable survival (20% versus 7%, p=0.02).
  
  
  CONCLUSIONS
  Over one-third required 20 min of persistent EMS CPR. The EMS was able to achieve a high hands-on CPR fraction in the context of advanced therapies. Those who required the most prolonged EMS CPR appeared to benefit from greater hands-on CPR fraction.
authors.affiliation: Harborview Medical Center and the University of Washington, United States. Electronic address: rea123@u.washington.edu.
authors.forename: Thomas
authors.initials: T
authors.lastname: Rea
authors.affiliation: Harborview Medical Center and the University of Washington, United States.
authors.forename: Michele
authors.initials: M
authors.lastname: Olsufka
authors.affiliation: Harborview Medical Center and the University of Washington, United States.
authors.forename: Lihua
authors.initials: L
authors.lastname: Yin
authors.affiliation: Harborview Medical Center and the University of Washington, United States.
authors.forename: Charles
authors.initials: C
authors.lastname: Maynard
authors.affiliation: Harborview Medical Center and the University of Washington, United States.
authors.forename: Leonard
authors.initials: L
authors.lastname: Cobb
mesh_terms: D000328:Adult; D000368:Aged; D016887:Cardiopulmonary Resuscitation / Q000379:methods*; D004632:Emergency Medical Services; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D058687:Out-of-Hospital Cardiac Arrest / Q000401:mortality / Q000628:therapy*; D015996:Survival Rate; D013997:Time Factors; D016896:Treatment Outcome; D014693:Ventricular Fibrillation / Q000401:mortality / Q000628:therapy*
keywords: CPR; Heart arrest; Ventricular fibrillation