title: Analysis of longitudinal changes in dyspnea of patients with chronic obstructive pulmonary disease: an observational study.
abstract: BACKGROUND
  Guidelines recommend that symptoms as well as lung function should be monitored for the management of patients with chronic obstructive pulmonary disease (COPD). However, limited data are available regarding the longitudinal change in dyspnea, and it remains unknown which of relevant measurements might be used for following dyspnea.
  
  
  METHODS
  We previously consecutively recruited 137 male outpatients with moderate to very severe COPD, and followed them every 6 months for 5 years. We then reviewed and reanalyzed the data focusing on the relationships between the change in dyspnea and the changes in other clinical measurements of lung function, exercise tolerance tests and psychological status. Dyspnea with activities of daily living was assessed with the Oxygen Cost Diagram (OCD) and modified Medical Research Council dyspnea scale (mMRC), and two dimensions of disease-specific health status questionnaires of the Chronic Respiratory Disease Questionnaire (CRQ) and the St. George's Respiratory Questionnaire (SGRQ) were also used. Dyspnea at the end of exercise tolerance tests was measured using the Borg scale.
  
  
  RESULTS
  The mMRC, CRQ dyspnea and SGRQ activity significantly worsened over time (p < 0.001), but the OCD did not (p = 0.097). Multiple regression analyses revealed that the changes in the OCD, mMRC, CRQ dyspnea and SGRQ activity were significantly correlated to changes in forced expiratory volume in one second (FEV1) (correlation of determination (r²) = 0.05-0.19), diffusing capacity for carbon monoxide (r² = 0.04-0.08) and psychological status evaluated by Hospital Anxiety and Depression Scale (r² = 0.14-0.17), although these correlations were weak. Peak Borg score decreased rather significantly, but was unrelated to changes in clinical measurements.
  
  
  CONCLUSIONS
  Dyspnea worsened over time in patients with COPD. However, as different dyspnea measurements showed different evaluative characteristics, it is important to follow dyspnea using appropriate measurements. Progressive dyspnea was related not only to progressive airflow limitation, but also to various factors such as worsening of diffusing capacity or psychological status. Changes in peak dyspnea at the end of exercise may evaluate different aspects from other dyspnea measurements.
authors.affiliation: Department of Respiratory Care and Sleep Control Medicine, Graduate School of Medicine, Kyoto University, Kyoto, Japan. ogato@kuhp.kyoto-u.ac.jp
authors.forename: Toru
authors.initials: T
authors.lastname: Oga
authors.forename: Mitsuhiro
authors.initials: M
authors.lastname: Tsukino
authors.forename: Takashi
authors.initials: T
authors.lastname: Hajiro
authors.forename: Akihiko
authors.initials: A
authors.lastname: Ikeda
authors.forename: Koichi
authors.initials: K
authors.lastname: Nishimura
mesh_terms: D000203:Activities of Daily Living; D000368:Aged; D018450:Disease Progression; D004417:Dyspnea / Q000175:diagnosis / Q000209:etiology* / Q000503:physiopathology / Q000523:psychology; D005080:Exercise Test; D017079:Exercise Tolerance; D005541:Forced Expiratory Volume; D006801:Humans; D016014:Linear Models; D008137:Longitudinal Studies; D008168:Lung / Q000503:physiopathology*; D008297:Male; D011237:Predictive Value of Tests; D011653:Pulmonary Diffusing Capacity; D029424:Pulmonary Disease, Chronic Obstructive / Q000150:complications* / Q000175:diagnosis / Q000503:physiopathology / Q000523:psychology; D011788:Quality of Life; D012720:Severity of Illness Index; D013147:Spirometry; D011795:Surveys and Questionnaires; D013997:Time Factors; D014797:Vital Capacity