Effect of Body Position on Chest Compression Quality During CPR in an Obesity Simulation Model: A Randomized Crossover Trial

Objectives Obesity may impair the effectiveness of cardiopulmonary resuscitation (CPR) through biomechanical constraints; however, its impact on chest compression quality and the role of simple ergonomic modifications remain unclear. This study aimed to evaluate the effect of simulated obesity and body position on CPR performance.Methods This prospective randomized crossover simulation trial included 60 paramedics. Each participant performed 2-min chest compression sessions under three conditions: standard manikin, obesity-simulation manikin, and obesity-simulation manikin with the paramedic elevated on a 10 cm pad. Primary outcomes were compression depth, rate, and complete chest recoil. The secondary outcome was perceived exertion. Data were analyzed using linear mixed-effects models. The trial was prospectively registered (ACTRN12625000658415).Results Compression depth was significantly lower in both obesity-simulation conditions than in the standard condition, with adjusted mean differences of 17.83 mm (95% CI 15.95–19.71) and 18.44 mm (95% CI 16.58–20.30), respectively (both p < 0.001). The median percentage of compressions with adequate depth was 98.0% in the standard condition and 0.0% in both obesity-simulation conditions (both p < 0.001). Compression rate differed only modestly across conditions. Mean compression force and the Borg Rating of Perceived Exertion were significantly higher in obesity-simulation scenarios (both p < 0.001). No significant differences were observed between the two obesity-simulation conditions (difference 0.61 mm, 95% CI −1.25 to 2.47; p = 0.523), indicating that elevation of the paramedic did not improve CPR performance.Conclusions Simulated obesity markedly impairs chest compression quality despite increased paramedics’ effort, likely due to biomechanical constraints. The 10 cm elevation of the paramedic did not improve compression effectiveness. These findings highlight the need for targeted strategies and further prospective clinical studies to optimize CPR in patients with obesity.