title: Effects of repetitive or intensified instructions in telephone assisted, bystander cardiopulmonary resuscitation: an investigator-blinded, 4-armed, randomized, factorial simulation trial.
abstract: BACKGROUND
  Compression depth is frequently suboptimal in cardiopulmonary resuscitation (CPR). We investigated effects of intensified wording and/or repetitive target depth instructions on compression depth in telephone-assisted, protocol driven, bystander CPR on a simulation manikin.
  
  
  METHODS
  Thirty-two volunteers performed 10 min of compression only-CPR in a prospective, investigator-blinded, 4-armed, factorial setting. Participants were randomized either to standard wording ("push down firmly 5 cm"), intensified wording ("it is very important to push down 5 cm every time") or standard or intensified wording repeated every 20s. Three dispatchers were randomized to give these instructions. Primary outcome was relative compression depth (absolute compression depth minus leaning depth). Secondary outcomes were absolute distance, hands-off times as well as BORG-scale and nine-hole peg test (NHPT), pulse rate and blood pressure to reflect physical exertion. We applied a random effects linear regression model.
  
  
  RESULTS
  Relative compression depth was 35 ± 10 mm (standard) versus 31 ± 11 mm (intensified wording) versus 25 ± 8 mm (repeated standard) and 31 ± 14 mm (repeated intensified wording). Adjusted for design, body mass index and female sex, intensified wording and repetition led to decreased compression depth of 13 (95%CI -25 to -1) mm (p=0.04) and 9 (95%CI -21 to 3) mm (p=0.13), respectively. Secondary outcomes regarding intensified wording showed significant differences for absolute distance (43 ± 2 versus 20 (95%CI 3-37) mm; p=0.01) and hands-off times (60 ± 40 versus 157 (95%CI 63-251) s; p=0.04).
  
  
  CONCLUSIONS
  In protocol driven, telephone-assisted, bystander CPR, intensified wording and/or repetitive target depth instruction will not improve compression depth compared to the standard instruction.
authors.affiliation: Department of Emergency Medicine, Medical University of Vienna, Austria.
authors.forename: R
authors.initials: R
authors.lastname: van Tulder
authors.affiliation: Department of Emergency Medicine, Medical University of Vienna, Austria.
authors.forename: D
authors.initials: D
authors.lastname: Roth
authors.affiliation: Department of General Anaesthesiology, Intensive Care and Pain Management, Austria.
authors.forename: M
authors.initials: M
authors.lastname: Krammel
authors.affiliation: Department of Emergency Medicine, Medical University of Vienna, Austria.
authors.forename: R
authors.initials: R
authors.lastname: Laggner
authors.affiliation: Department of Emergency Medicine, Medical University of Vienna, Austria.
authors.forename: B
authors.initials: B
authors.lastname: Heidinger
authors.affiliation: Department of Emergency Medicine, Medical University of Vienna, Austria.
authors.forename: C
authors.initials: C
authors.lastname: Kienbacher
authors.affiliation: NOTRUF NOE GmbH, Emergency Call and Coordination Centre, Lower Austria, Austria.
authors.forename: H
authors.initials: H
authors.lastname: Novosad
authors.affiliation: NOTRUF NOE GmbH, Emergency Call and Coordination Centre, Lower Austria, Austria.
authors.forename: C
authors.initials: C
authors.lastname: Chwojka
authors.affiliation: Department of Emergency Medicine, Medical University of Vienna, Austria. Electronic address: christof.havel@meduniwien.ac.at.
authors.forename: C
authors.initials: C
authors.lastname: Havel
authors.affiliation: Department of Emergency Medicine, Medical University of Vienna, Austria.
authors.forename: F
authors.initials: F
authors.lastname: Sterz
authors.affiliation: Department of Emergency Medicine, Medical University of Vienna, Austria.
authors.forename: W
authors.initials: W
authors.lastname: Schreiber
authors.affiliation: Department of Emergency Medicine, Medical University of Vienna, Austria.
authors.forename: H
authors.initials: H
authors.lastname: Herkner
mesh_terms: D000328:Adult; D016887:Cardiopulmonary Resuscitation / Q000379:methods*; D004311:Double-Blind Method; D004631:Emergency Medical Service Communication Systems; D005260:Female; D006801:Humans; D008297:Male; D058687:Out-of-Hospital Cardiac Arrest / Q000628:therapy*; D011446:Prospective Studies; D013689:Telephone
keywords: Cardiopulmonary resuscitation; Chest compression; Manikin; Out of hospital cardiac arrest; Telephone