title: 50% duty cycle may be inappropriate to achieve a sufficient chest compression depth when cardiopulmonary resuscitation is performed by female or light rescuers.
abstract: OBJECTIVE
  Current guidelines for cardiopulmonary resuscitation recommend chest compressions (CC) during 50% of the duty cycle (DC) in part because of the ease with which individuals may learn to achieve it with practice. However, no consideration has been given to a possible interaction between DC and depth of CC, which has been the subject of recent study. Our aim was to determine if 50% DC is inappropriate to achieve sufficient chest compression depth for female and light rescuers.
  
  
  METHODS
  Previously collected CC data, performed by senior medical students guided by metronome sounds with various down-stroke patterns and rates, were included in the analysis. Multiple linear regression analysis was performed to determine the association between average compression depth (ACD) with average compression rate (ACR), DC, and physical characteristics of the performers. Expected ACD was calculated for various settings.
  
  
  RESULTS
  DC, ACR, body weight, male sex, and self-assessed physical strength were significantly associated with ACD in multivariate analysis. Based on our calculations, with 50% of DC, only men with ACR of 140/min or faster or body weight over 74 kg with ACR of 120/min can achieve sufficient ACD.
  
  
  CONCLUSIONS
  A shorter DC is independently correlated with deeper CC during simulated cardiopulmonary resuscitation. The optimal DC recommended in current guidelines may be inappropriate for achieving sufficient CD, especially for female or lighter-weight rescuers.
authors.affiliation: Department of Emergency Medicine, CHA University School of Medicine, Seongnam, Korea.
authors.forename: Chang Jae
authors.initials: CJ
authors.lastname: Lee
authors.affiliation: Department of Emergency Medicine, CHA University School of Medicine, Seongnam, Korea.
authors.forename: Tae Nyoung
authors.initials: TN
authors.lastname: Chung
authors.affiliation: Department of Emergency Medicine, CHA University School of Medicine, Seongnam, Korea.
authors.forename: Jinkun
authors.initials: J
authors.lastname: Bae
authors.affiliation: Department of Emergency Medicine, CHA University School of Medicine, Seongnam, Korea.
authors.forename: Eui Chung
authors.initials: EC
authors.lastname: Kim
authors.affiliation: Department of Emergency Medicine, CHA University School of Medicine, Seongnam, Korea.
authors.forename: Sung Wook
authors.initials: SW
authors.lastname: Choi
authors.affiliation: Department of Emergency Medicine, CHA University School of Medicine, Seongnam, Korea.
authors.forename: Ok Jun
authors.initials: OJ
authors.lastname: Kim
keywords: Cardiopulmonary resuscitation; Clinical competence; Education; Heart arrest; Prognosis