title: A different rescuer changing strategy between 30:2 cardiopulmonary resuscitation and hands-only cardiopulmonary resuscitation that considers rescuer factors: a randomised cross-over simulation study with a time-dependent analysis.
abstract: OBJECTIVE
  To compare the time-dependent changes in the quality of chest compressions in 30:2 cardiopulmonary resuscitation (CPR) and hands-only cardiopulmonary resuscitation (HO-CPR) and to evaluate how individual rescuer factors affect the quality of chest compressions over time for both CPR techniques.
  
  
  METHODS
  Total 1028 adult hospital and university workers participated in CPR training programs including sessions of 30:2 CPR and HO-CPR. Tests of both CPR methods were performed in a random order using a manikin with Skill-Reporter™. Data were collected from 863 subjects. The time-dependent changes in chest compressions quality and the effects of individual rescuer factors (age, gender, body mass index (BMI), prior CPR training and experience) were analysed using the general linear model for a repeated-measures procedure.
  
  
  RESULTS
  In HO-CPR, the mean proportion of correct compressions depth (MPCD) decreased significantly throughout the time sectors following 20-40s (74.4-50.4% in 100-120 s) compared to 30:2 CPR (83.4-76.3% in 100-120 s) (p<0.0001). A significant decline of MPCD (MPCD<70%) was initially observed at 40-60s in HO-CPR, however, this pattern was not observed in 30:2 CPR. Individual rescuer factors minimally affected the time-dependent change in MPCD during 30:2 CPR. For HO-CPR, all rescuer factors except for male or obese/overweight (BMI≥25) were associated with a significant declines of MPCD, and these decline were usually observed from 40 to 60s.
  
  
  CONCLUSIONS
  Switching rescuers at an interval of 2-min is reasonable for 30:2 CPR. However, for HO-CPR switching rescuers every 1-min may be preferable except when rescuers are male or obese/overweight (BMI≥25).
authors.affiliation: Department of Emergency Medicine, Konkuk University Medical Center, Konkuk University School of Medicine, Seoul, Republic of Korea.
authors.forename: Dae Young
authors.initials: DY
authors.lastname: Hong
authors.forename: Sang O
authors.initials: SO
authors.lastname: Park
authors.forename: Kyeong Ryong
authors.initials: KR
authors.lastname: Lee
authors.forename: Kwang Je
authors.initials: KJ
authors.lastname: Baek
authors.forename: Dong Hyuk
authors.initials: DH
authors.lastname: Shin
mesh_terms: D000328:Adult; D016887:Cardiopulmonary Resuscitation / Q000379:methods*; D018592:Cross-Over Studies; D005260:Female; D006323:Heart Arrest / Q000628:therapy*; D006801:Humans; D016014:Linear Models; D008297:Male; D008348:Manikins; D008875:Middle Aged; D012307:Risk Factors; D016896:Treatment Outcome