1. Division of Pulmonary, Allergy and Critical Care Medicine, Kangdong Sacred Heart Hospital, Seoul, Korea.
2. Division of Pulmonary, Allergy and Critical Care Medicine, Chuncheon Sacred Heart Hospital, Chuncheon, Korea.
3. Division of Pulmonary, Allergy and Critical Care Medicine, Hallym University Sacred Heart Hospital, Anyang, Korea.
4. Division of Pulmonary, Allergy and Critical Care Medicine, Kangnam Sacred Heart Hospital, Seoul, Korea.