1. Division of Respiratory Medicine, University of Tsukuba Hospital, University of Tsukuba, Tsukuba, Ibaraki 305‑8576, Japan
2. Division of Respiratory Medicine, Mito Medical Center, University of Tsukuba‑Mito Kyodo General Hospital, Mito, Ibaraki 310‑0015, Japan
3. Division of Cardiology, Mito Medical Center, University of Tsukuba‑Mito Kyodo General Hospital, Mito, Ibaraki 310‑0015, Japan