Interpleural distance predicts persistent air leak after initial primary spontaneous pneumothorax

BACKGROUND: Initial surgical intervention for a first episode of primary spontaneous pneumothorax (PSP) is controversial. However, if air leak persists after initial drainage, surgical treatment is recommended. Therefore, we investigated risk factors for persistent air leak (PAL) in patients with a first episode of PSP. METHODS: We retrospectively analyzed 122 patients with a first episode of PSP between January 2011 and April 2019. PAL was defined as air leak lasting 72 hours or longer. Early admission was defined hospital admission within 24 hours of symptom onset. Three methods were used to estimate pneumothorax size on chest X-rays taken at admission: interpleural distance, apex-cupola distance, and Light index. RESULTS: Among 122 patients, 55 developed PAL (PAL group) and 67 did not (non-PAL group). The size of pneumothorax was significantly larger in the PAL group than in the non-PAL group in all three methods of assessment (P<0.001). Early hospital admission was significantly associated with PAL (P=0.026). Logistic regression analysis revealed that the odds ratio for PAL per unit increase in pneumothorax size evaluated with the interpleural distance was 1.304 (P<0.001). Multivariate logistic regression analysis showed that interpleural distance at the hilum and early admission (P<0.001, P=0.008, respectively) were independent predictors of PAL in patients with a first episode of PSP. CONCLUSIONS: In our study, we demonstrated that the interpleural distance at the hilum is a simple and effective predictor of PAL in patients with a first episode of PSP. Our data may help decision-making for initial surgical treatment in these patients.