title: Defibrillation success during different phases of the mechanical chest compression cycle.
abstract: Animal studies indicate higher termination of VF/VT (TOF) rates after shocks delivered during the decompression phase of the compression cycle for manual and mechanical CPR. We investigated TOF for shocks delivered in different compression cycle phases during load distributing band (LDB) mechanical CPR in the CIRC trial.
  
  
  
  Shocks were retrospectively categorized as delivered during the compression, decompression, or relaxation phase of LDB compressions using transthoracic impedance data. Shocks delivered when the LDB device was paused, were used as controls. The first shock and the first up-to-three shocks (first shocks plus shocks two and three if given) from patients with initial VF/VT and LDB CPR prior to shock were grouped according to compression cycle phase. TOF rates for these groups versus the control group were analyzed using logistic regression for first shocks and the general estimating equations (GEE) model for the up-to-three shocks. Adjustments were made for bystander CPR, witnessed arrest, defibrillator shock energy and transthoracic impedance.
  
  
  
  Among 244 first shocks and 685 up-to-three shocks TOF success rates were lower (p<0.05 and p<0.02) for shocks given during the compression phase (72% and 71% respectively) than for control shocks given during compression pauses (86% and 82% respectively). Decompression and relaxation phase shocks had TOF rates not different from the controls.
  
  
  
  Shocks delivered in the compression phase of LDB chest compressions had lower TOF rates than shocks delivered while pausing the LDB device. More research is needed to see how defibrillation during chest compressions affect ROSC and survival.
authors.affiliation: University of Oslo, Institute of Clinical Medicine, University of Oslo, Oslo, Norway; Norwegian National Advisory Unit on Prehospital Emergency Medicine, Oslo University Hospital, Oslo, Norway. Electronic address: mikkelts@studmed.uio.no.
authors.forename: Mikkel T
authors.initials: MT
authors.lastname: Steinberg
authors.affiliation: University of Oslo, Institute of Clinical Medicine, University of Oslo, Oslo, Norway; Norwegian National Advisory Unit on Prehospital Emergency Medicine, Oslo University Hospital, Oslo, Norway.
authors.forename: Jan-Aage
authors.initials: JA
authors.lastname: Olsen
authors.affiliation: Oslo Centre for Biostatistics and Epidemiology, Research Support Services, Oslo University Hospital, Ullevål, Oslo, Norway.
authors.forename: Cathrine
authors.initials: C
authors.lastname: Brunborg
authors.affiliation: Houston Fire Department and the Baylor College of Medicine, Houston, TX, United States.
authors.forename: David
authors.initials: D
authors.lastname: Persse
authors.affiliation: Department of Emergency Medicine, Medical University of Vienna, Vienna, Austria.
authors.forename: Fritz
authors.initials: F
authors.lastname: Sterz
authors.affiliation: Hillsborough County Fire Rescue, Tampa, FL, United States.
authors.forename: Michael
authors.initials: M
authors.lastname: Lozano
authors.affiliation: Gold Cross Ambulance Service, Appleton Neenah-Menasha and Grand Chute Fire Departments, WI, United States; Theda Clark Regional Medical Center, Neenah, WI, United States.
authors.forename: Mark
authors.initials: M
authors.lastname: Westfall
authors.affiliation: Hillsborough County Fire Rescue, Tampa, FL, United States.
authors.forename: David T
authors.initials: DT
authors.lastname: Travis
authors.affiliation: Department of Emergency Medicine, Medical College of Wisconsin, Milwaukee, WI, United States.
authors.forename: E Brooke
authors.initials: EB
authors.lastname: Lerner
authors.affiliation: Norwegian National Advisory Unit on Prehospital Emergency Medicine, Oslo University Hospital, Oslo, Norway.
authors.forename: Lars
authors.initials: L
authors.lastname: Wik
mesh_terms: D016887:Cardiopulmonary Resuscitation / Q000379:methods*; D016022:Case-Control Studies; D047548:Defibrillators; D004554:Electric Countershock / Q000379:methods*; D004562:Electrocardiography; D006323:Heart Arrest / Q000628:therapy*; D006336:Heart Massage / Q000379:methods*; D006801:Humans; D012189:Retrospective Studies; D013997:Time Factors
keywords: Cardiac arrest; Defibrillation; Mechanical chest compressions