Obesity survival paradox in pneumonia supported with extracorporeal membrane oxygenation: Analysis of the national registry

Purpose: To investigate whether the obesity survival paradox, where obesity is associated with improved survival, exists for pneumonia supported with extracorporeal membrane oxygenation (ECMO). Materials and methods: Between January 2014 and December 2015, 223 patients with acute respiratory failure who underwent ECMO in 11 hospitals in South Korea were enrolled retrospectively, and data relating to pneumonia cases were analyzed. Patients were divided into groups according to their pre-treatment body mass index (BMI): obese (BMI ≥ 25 kg/m²) and non-obese (BMI < 25 kg/m²). The BMI cut-off was adopted from the World Health Organization for Asian populations. Results: In total, 84 patients had pneumonia: obese group, 26; non-obese group, 58 (mean BMI, 27.8 vs. 21.4, p < 0.001). Pre-ECMO parameters and rescue therapy did not differ between the groups. The rate of successful weaning from ECMO was not different between the groups (76.9% vs. 72.4%, p = 0.753), but survival-to-discharge (73.1% vs. 36.2%, p = 0.002) and 6-month survival (69.2% vs. 36.2%, p = 0.005) rates were higher in the obese group. After adjusting for age and the pre-treatment PaO₂/FiO₂ ratio, low BMI was significantly associated with 6-month mortality (odds ratio 3.28, 95% confidence interval: 1.06–11.03, p = 0.044). Conclusions: An obesity survival paradox exists in pneumonia supported with ECMO.