1. Department of Respiratory Medicine; Hitachinaka General Hospital; Hitachi, Ltd.; Hitachinaka-shi Ibaraki Japan
2. Hitachinaka Medical Education and Research Centre; University of Tsukuba Hospital; Hitachinaka-shi Ibaraki Japan
3. Department of Pulmonology; Graduate School of Comprehensive Human Sciences; University of Tsukuba; Tsukuba Ibaraki Japan
4. Department of Respiratory Medicine; National Hospital Organization; Ibarakihigashi National Hospital; Tokai-mura Naga-gun Ibaraki Japan