Effects of N-acetylcysteine (▒) and placebo (░) on vital capacity (VC) and diffusing capacity of the lung for carbon monoxide (DL,CO) depending on baseline composite physiological index (BL-CPI) being lower or higher than 50 points. #: p = 0.0031; ¶: p = 0.... Effects of N-acetylcysteine (▒) and placebo (░) on vital capacity (VC) and diffusing capacity of the lung for carbon monoxide (DL,CO) depending on baseline composite physiological index (BL-CPI) being lower or higher than 50 points. #: p = 0.0031; ¶: p = 0.0015; +: p = 0.067. Reproduced from [19] with permission from BioMed Central. U. Costabel Eur Respir Rev 2011;20:201-207 ©2011 by European Respiratory Society