title: Strong corruption of electrocardiograms caused by cardiopulmonary resuscitation reduces efficiency of two-channel methods for removing motion artefacts in non-shockable rhythms.
abstract: OBJECTIVE
  Cardiopulmonary resuscitation (CPR) artefact removal methods provide satisfactory results when the rhythm is shockable but fail on non-shockable rhythms. We investigated the influence of the corruption level on the performance of four different two-channel methods for CPR artefact removal.
  
  
  METHODS
  395 artefact-free ECGs and 13 pure CPR artefacts with corresponding blood pressure readings as a reference channel were selected. Using a simplified additive data model we generated CPR-corrupted signals at different signal-to-noise ratio (SNR) levels from -10 to +10 dB. The algorithms were optimized on learning data with respect to SNR improvement and then applied to testing data. Sensitivity and specificity were derived from the shock/no-shock advice of an automated external defibrillator before CPR corruption and after artefact removal.
  
  
  RESULTS
  Sensitivity for the filtered data (>95%) was significantly superior to that for the unfiltered data (76%), p<0.001. However, specificity was similar for the filtered and unfiltered data (<90% vs 89.3%). For large artefacts (-10 dB) specificity decreased below 70%. No important difference in the performance of the four algorithms was found.
  
  
  CONCLUSIONS
  Using a simplified data model we showed that, when the ECG rhythm is non-shockable, two-channel methods could not reduce CPR artefacts without affecting the rhythm analysis for shock recommendation. The reason could be poor reconstruction when the artefacts are large. However, poor reconstruction was not a hindrance to re-identifying shockable rhythms. Future investigations should both include the refinement of filter methods and also focus on reducing motion artefacts already at the recording stage.
authors.affiliation: Faculty of Mathematics, University of Vienna, Vienna, Austria. tobias.werther@univie.ac.at
authors.forename: Tobias
authors.initials: T
authors.lastname: Werther
authors.forename: Andreas
authors.initials: A
authors.lastname: Klotz
authors.forename: Marcus
authors.initials: M
authors.lastname: Granegger
authors.forename: Michael
authors.initials: M
authors.lastname: Baubin
authors.forename: Hans G
authors.initials: HG
authors.lastname: Feichtinger
authors.forename: Anton
authors.initials: A
authors.lastname: Amann
authors.forename: Hermann
authors.initials: H
authors.lastname: Gilly
mesh_terms: D000465:Algorithms; D000818:Animals; D016477:Artifacts; D016887:Cardiopulmonary Resuscitation / Q000009:adverse effects* / Q000379:methods; D017097:Electric Impedance; D004562:Electrocardiography / Q000295:instrumentation*; D004632:Emergency Medical Services / Q000379:methods; D006323:Heart Arrest / Q000175:diagnosis / Q000628:therapy*; D006801:Humans; D008962:Models, Theoretical; D009068:Movement; D012680:Sensitivity and Specificity