title: Suppression of the cardiopulmonary resuscitation artefacts using the instantaneous chest compression rate extracted from the thoracic impedance.
abstract: OBJECTIVE
  To demonstrate that the instantaneous chest compression rate can be accurately estimated from the transthoracic impedance (TTI), and that this estimated rate can be used in a method to suppress cardiopulmonary resuscitation (CPR) artefacts.
  
  
  METHODS
  A database of 372 records, 87 shockable and 285 non-shockable, from out-of-hospital cardiac arrest episodes, corrupted by CPR artefacts, was analysed. Each record contained the ECG and TTI obtained from the defibrillation pads and the compression depth (CD) obtained from a sternal CPR pad. The chest compression rates estimated using TTI and CD were compared. The CPR artefacts were then filtered using the instantaneous chest compression rates estimated from the TTI or CD signals. The filtering results were assessed in terms of the sensitivity and specificity of the shock advice algorithm of a commercial automated external defibrillator.
  
  
  RESULTS
  The correlation between the mean chest compression rates estimated using TTI or CD was r=0.98 (95% confidence interval, 0.97-0.98). The sensitivity and specificity after filtering using CD were 95.4% (88.4-98.6%) and 87.0% (82.6-90.5%), respectively. The sensitivity and specificity after filtering using TTI were 95.4% (88.4-98.6%) and 86.3% (81.8-89.9%), respectively.
  
  
  CONCLUSIONS
  The instantaneous chest compression rate can be accurately estimated from TTI. The sensitivity and specificity after filtering are similar to those obtained using the CD signal. Our CPR suppression method based exclusively on signals acquired through the defibrillation pads is as accurate as methods based on signals obtained from CPR feedback devices.
authors.affiliation: Electronics and Telecommunications Department, University of the Basque Country, Alameda Urquijo S/N, 48013 Bilbao, Spain. elisabete.aramendi@ehu.es
authors.forename: E
authors.initials: E
authors.lastname: Aramendi
authors.forename: U
authors.initials: U
authors.lastname: Ayala
authors.forename: U
authors.initials: U
authors.lastname: Irusta
authors.forename: E
authors.initials: E
authors.lastname: Alonso
authors.forename: T
authors.initials: T
authors.lastname: Eftestøl
authors.forename: J
authors.initials: J
authors.lastname: Kramer-Johansen
mesh_terms: D016477:Artifacts; D002307:Cardiography, Impedance; D016887:Cardiopulmonary Resuscitation; D047548:Defibrillators; D004562:Electrocardiography; D006801:Humans; D058687:Out-of-Hospital Cardiac Arrest / Q000503:physiopathology / Q000628:therapy*