Body mass index and pneumothorax risk after CT-guided pulmonary nodule localization: a nonlinear analysis using restricted cubic splines

Pneumothorax remains the most frequent complication of CT-guided pulmonary nodule localization, yet the role of body mass index (BMI) is poorly understood. We investigated the nonlinear relationship between BMI and pneumothorax risk using restricted cubic spline (RCS) analysis. In this retrospective cohort study, 175 patients undergoing CT-guided localization for solitary pulmonary nodules (≤ 20 mm) were analyzed. Multivariable logistic regression and RCS models adjusted for clinical/procedural confounders identified BMI threshold effects. Pneumothorax definition (per British Thoracic Society guidelines): (1) Visible visceral pleural line on CT; (2) Lung compression ≥ 10%. The overall pneumothorax rate was 34.3% (60/175). RCS revealed a nonlinear association (P for nonlinearity = 0.016) with an inflection point at BMI = 24.8 kg/m². Below this point, each 1-unit BMI increase was associated with reduced pneumothorax risk (OR: 0.66, 95% CI: 0.54–0.82; P < 0.001). Above it, the association was not significant (OR: 1.40, 95% CI: 0.97–2.02; P = 0.071). The mean nodule size was 8.9 ± 2.1 mm, and most nodules were located in the peripheral lung regions. This single-center retrospective analysis suggests a nonlinear relationship between BMI and pneumothorax risk, with the lowest risk observed near BMI = 24.8 kg/m². These findings highlight the potential for BMI-based risk stratification but require validation in larger, prospective studies.