title: A counterbalanced cross-over study of the effects of visual, auditory and no feedback on performance measures in a simulated cardiopulmonary resuscitation.
abstract: BACKGROUND
  Previous research has demonstrated that trained rescuers have difficulties achieving and maintaining the correct depth and rate of chest compressions during both in and out of hospital cardiopulmonary resuscitation (CPR). Feedback on rate and depth mitigate decline in performance quality but not completely with the residual performance decline attributed to rescuer fatigue. The purpose of this study was to examine the effects of feedback (none, auditory only and visual only) on the quality of CPR and rescuer fatigue.
  
  
  METHODS
  Fifteen female volunteers performed 10 minutes of 30:2 CPR in each of three feedback conditions: none, auditory only, and visual only. Visual feedback was displayed continuously in graphic form. Auditory feedback was error correcting and provided by a voice assisted CPR manikin. CPR quality measures were collected using SkillReporter® software. Blood lactate (mmol/dl) and perceived exertion served as indices of fatigue. One-way and two way repeated measures analyses of variance were used with alpha set a priori at 0.05.
  
  
  RESULTS
  Visual feedback yielded a greater percentage of correct compressions (78.1 ± 8.2%) than did auditory (65.4 ± 7.6%) or no feedback (44.5 ± 8.1%). Compression rate with auditory feedback (87.9 ± 0.5 compressions per minute) was less than it was with both visual and no feedback (p < 0.05). CPR performed with no feedback (39.2 ± 0.5 mm) yielded a shallower average depth of compression and a lower percentage (55 ± 8.9%) of compressions within the accepted 38-50 mm range than did auditory or visual feedback (p < 0.05). The duty cycle for auditory feedback (39.4 ± 1.6%) was less than it was with no feedback (p < 0.05). Auditory feedback produced lower lactate concentrations than did visual feedback (p < 0.05) but there were no differences in perceived exertion.
  
  
  CONCLUSIONS
  In this study feedback mitigated the negative effects of fatigue on CPR performance and visual feedback yielded better CPR performance than did no feedback or auditory feedback. The perfect confounding of sensory modality and periodicity of feedback (visual feedback provided continuously and auditory feedback provided to correct error) leaves unanswered the question of optimal form and timing of feedback.
authors.affiliation: College of Nursing, University of Texas at Arlington, Arlington, Texas, USA.
authors.forename: Carolyn L
authors.initials: CL
authors.lastname: Cason
authors.affiliation: Department of Kinesiology, University of Texas at Arlington, Arlington, Texas, USA.
authors.forename: Cynthia
authors.initials: C
authors.lastname: Trowbridge
authors.affiliation: College of Nursing, University of Texas at Arlington, Arlington, Texas, USA.
authors.forename: Susan M
authors.initials: SM
authors.lastname: Baxley
authors.affiliation: Department of Kinesiology, University of Texas at Arlington, Arlington, Texas, USA.
authors.forename: Mark D
authors.initials: MD
authors.lastname: Ricard