OBJECTIVE: To analyze the risk factors for secondary hypoxemia in emergency traumatic pneumothorax (TP) patients following transthoracic drainage to provide a scientific basis for clinical prevention and treatment. METHODS: This single-center retrospective study included 130 TP patients who underwent chest drainage between January 2021 and May 2024 at West China Hospital, Sichuan University. Patient demographics and clinical data were collected via the electronic medical record system. Univariate and multivariate logistic regression analyses were performed to identify independent risk factors for secondary hypoxemia. A predictive model was developed based on multifactorial logistic regression analysis and presented as a Nomogram to assess its discrimination, calibration and clinical utility. RESULTS: Advanced age, high body mass index (BMI), history of smoking, use of conventional drains, and prolonged lung reopening time were identified as independent risk factors for secondary hypoxemia. The constructed Nomogram model demonstrated strong discrimination (AUC=0.92) and calibration (Hosmer-Lemeshow test, P=0.515). Decision curve analysis (DCA) confirmed its clinical application. CONCLUSION: This study identifies key risk factors for secondary hypoxemia in TP patients after transthoracic drainage and presents a validated predictive model to support clinical decision-making. These findings may help clinicians recognize high-risk patients, implement preventive measures, and reduce hypoxemia incidence, ultimately improving patient outcomes.