title: Retrospective evaluation of current-based impedance compensation defibrillation in out-of-hospital cardiac arrest.
abstract: OBJECTIVE
  Transthoracic impedance (TTI) is a principal parameter that influences the intracardiac current flow and defibrillation outcome. In this study, we retrospectively evaluated the performance of current-based impedance compensation defibrillation in out-of-hospital cardiac arrest (OHCA) patients.
  
  
  METHODS
  ECG recordings, along with TTI measurements were collected from multiple emergency medical services (EMSs) in the USA. All the EMSs in this study used automated external defibrillators (AEDs) which employing rectilinear biphasic (RLB) waveform. The distribution and change of TTI between successive shocks, the influence of preceding shock results on the subsequent shock outcome, and the performance of current-based impedance compensation defibrillation was evaluated.
  
  
  RESULTS
  A total of 1166 shocks from 594 OHCA victims were examined in this study. The average TTI for the 1st shock was 134.8 Ω and a significant decrease in TTI was observed for the 2nd (p<0.001) and 3rd (p=0.033) sequential escalating shock. But TTI did not change after the 3rd shock. A higher success rate was observed for shocks with preceding defibrillation success. The success rate remained unchanged over the whole spectrum of TTI.
  
  
  CONCLUSIONS
  The average TTI was relatively higher in this OHCA population treated with RLB defibrillation as compared with previously reported data. TTI was significantly decreased after 1st and 2nd successive escalating shock but kept constant after the 3rd shock. Preceding shock success was a better predictor of subsequent defibrillation outcome other than TTI. Current-based impedance compensation defibrillation resulted in equivalent success rate for high impedance patients when compared with those of low impedance.
authors.affiliation: School of Biomedical Engineering and Medical Imaging, Third Military Medical University, Chongqing, China.
authors.forename: Bihua
authors.initials: B
authors.lastname: Chen
authors.forename: Changlin
authors.initials: C
authors.lastname: Yin
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Ristagno
authors.forename: Weilun
authors.initials: W
authors.lastname: Quan
authors.forename: Qing
authors.initials: Q
authors.lastname: Tan
authors.forename: Gary
authors.initials: G
authors.lastname: Freeman
authors.forename: Yongqin
authors.initials: Y
authors.lastname: Li
mesh_terms: D000328:Adult; D002307:Cardiography, Impedance / Q000379:methods*; D047548:Defibrillators; D004554:Electric Countershock / Q000379:methods*; D004562:Electrocardiography; D005260:Female; D006801:Humans; D008297:Male; D058687:Out-of-Hospital Cardiac Arrest / Q000628:therapy*; D012189:Retrospective Studies; D016896:Treatment Outcome; D014693:Ventricular Fibrillation / Q000628:therapy*