title: Effects of rescuer position on the kinematics of cardiopulmonary resuscitation (CPR) and the force of delivered compressions.
abstract: BACKGROUND
  Depending on the clinical setting, rescuers may provide CPR from a kneeling (if the patient is on the ground) or standing (if the patient is in a bed) position. The rescuer position may affect workload, and hence rate of fatigue and quality of CPR.
  
  
  OBJECTIVE
  This study evaluates how three common rescuer positions affect the kinematics of CPR and the force of delivered compressions.
  
  
  METHODS
  Subjects were 18 health care providers experienced in CPR. Each participant performed CPR from three different positions: kneeling beside the Resusci Anne manikin placed on the floor (F); standing beside the manikin placed on a Table 63 cm in height (H), and standing beside the manikin placed on a Table 37 cm in height (L). The compression to ventilation ratio was 15:2. CPR duration was 5 min for each position, with a rest period of 50 min in-between. The order of position was randomised. The manikin was equipped with a six-axial force load cell to collect 3D compression forces at a sampling rate of 1000 Hz. An eight-camera Motion Analysis Digital System was adopted to collect 3D trajectory information. Data were compared using crossover-design analysis of variance (p<0.05 was regarded as statistically significant). Ratings of Perceived Exertion (RPE) were measured by modified Borg scale.
  
  
  RESULTS
  Significant differences were observed in the head, shoulder, lower trunk, hip and knee angles between the three methods. Lower trunk flexion angle (degrees) for H, L, and F were -14.52+/-1.13, -28.83+/-1.75, and 14.39+/-1.14, respectively. Hip flexion angle for H, L, and F were -16.21+/-3.30, -42.59+/-4.75, and -47.39+/-4.36, respectively. However, compression force (N) in H, L, and F were 455.8+/-17.6, 455.7+/-14.0, 461.5+/-13.5, respectively (p>0.05). Compression depths (mm) were: 43.5+/-3.4, 42.0+/-5.4, 44+/-5.2, respectively (p>0.05). Compression frequencies (times/min) were: 117.9+/-12.4, 116.6+/-13.4, 108.8+/-11.7, respectively (p>0.05). No differences were found between the three positions for RPE.
  
  
  CONCLUSIONS
  In this study, while the kinematics of CPR differed significantly with varying rescuer position, these differences did not affect the compression force, depth and frequency as performed by experienced providers.
authors: Department of Emergency Medicine, National Cheng Kung University, Tainan 70403, Taiwan. chich@mail.ncku.edu.tw
authors: Chih-Hsien
authors: CH
authors: Chi
authors: Jui-Yi
authors: JY
authors: Tsou
authors: Fong-Chin
authors: FC
authors: Su
mesh_terms: D001696:Biomechanical Phenomena; D016887:Cardiopulmonary Resuscitation / Q000592:standards*; D019245:Compressive Strength; D018592:Cross-Over Studies; D004634:Emergency Medical Technicians; D006801:Humans; D008348:Manikins; D011187:Posture