Retraction Note: BMC Pulm Med 19, 207 (2019) https://doi.org/10.1186/s12890-019-0956-x

The Editor has retracted this article [1] because the authors have been unable to provide documents confirming that ethics approval was obtained in advance of the study. Additionally, discrepancies in study design and recruitment dates were noted between the trial registry [2] and the article.

Authors Chuncheng Zhang, Jing Yue, Mingyue Li, Wei Jiang, Yu Pan, Zhimin Song, Cailian Shi, Weixuan Fan and Zhenxiang Pan all agree to this retraction.