1 Department of Respiratory Medicine, Tohoku University Graduate School of Medicine, 1-1 Seiryo-machi, Aoba-ku, Sendai, 980-8574, Japan.
2 Department of Respiratory Medicine, Tohoku University Graduate School of Medicine, 1-1 Seiryo-machi, Aoba-ku, Sendai, 980-8574, Japan. ichikawa@rm.med.tohoku.ac.jp.
3 Department of Respiratory Medicine, Sendai City Hospital, Sendai, Japan.
4 Department of Respiratory Medicine, Osaki Citizen Hospital, Osaki, Miyagi, Japan.