[1
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Department of Respiratory Medicine, Shengjing Hospital of China Medical University,
No. 36 Sanhao Street, Heping District, Shenyang City, China.
[2
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Department of Respiratory Medicine, Shengjing Hospital of China Medical University,
No. 36 Sanhao Street, Heping District, Shenyang City, China. Electronic address: lzhaoli@163.com.