Fig. 4

The comparison of PDV between patients with and without smoking history, and the correlation between the smoking index and PDV in patients with smoking history. a The median PDV of patients with smoking history was higher than that of never smokers (900 ml vs. 830 ml; P = 0.030). b The smoking index showed a positive correlation with PDV in patients with smoking history, and the correlation coefficient (rho) was 0.221. PDV pleural drainage volume