Retrospective Study Using Computed Tomography to Compare Sufficient Chest Compression Depth for Cardiopulmonary Resuscitation in Obese Patients.

Background This study aimed to investigate the relationship between body mass index (BMI) and sufficient chest compression depth (CCD) in obese patients by a mathematical model. Methods and Results This retrospective analysis was performed with chest computed tomography images conducted between 2006 and 2018. We classified the selected individuals into underweight (<18.5), normal weight (>= 18.5, <25), overweight (>= 25, <30), and obese (>= 30) groups according to BMI (kg/m(2)). We defined heart compression fraction (HCF) as and estimated under-HCF (the value of HCF <20%), and over-HCF (the residual depth <2 cm after simulation with chest compression depth 5 and 6 cm). We compared these outcomes between BMI groups. Of 30 342 individuals, 8856 were selected and classified into 4 BMI groups from a database. We randomly selected 100 individuals in each group and analyzed a total of 400 individuals' cases. Higher BMI groups had a significantly decreased HCF with both 5 and 6 cm depth (P<0.001). The proportion of under-HCF with both depths increased according to BMI group, whereas the proportion of over-HCF decreased except for the 5 cm depth (P<0.001). The adjusted odds ratio of under-HCF, according to BMI group after adjustment of age and sex, was 7.325 (95% CI, 3.412-15.726; P<0.001), with 5 cm and 10.517 (95% CI, 2.353-47.001; P=0.002) with 6 cm depth, respectively. Conclusions The recommended chest compression depth of 5 to 6 cm in the current international guideline is unlikely to provide sufficient ejection fraction during cardiopulmonary resuscitation in obese patients.