title: Longitudinal changes in lung hyperinflation in COPD.
abstract: OBJECTIVE
  COPD is characterized by an accelerated and progressive decline in forced expiratory volume in 1 second (FEV1) and lung hyperinflation. Although lung hyperinflation is the hallmark of COPD, data on the longitudinal changes in lung hyperinflation and any association with the decline in FEV1are lacking. The aim of this study was to evaluate the longitudinal changes in lung hyperinflation and to investigate its relationship with FEV1decline.
  
  
  METHODS
  We conducted a prospective cohort study and studied 176 COPD patients with annual lung volume measurements over a period of 5 years or more. We used a random coefficient model to calculate the annual changes in lung volumes and to evaluate the factors associated with changes in lung hyperinflation. Additionally, the relationship between the change in lung hyperinflation and FEV1was assessed.
  
  
  RESULTS
  Residual volume (RV), inspiratory capacity (IC), and total lung capacity (TLC) declined at a mean rate of 39.5, 49.6, and 63.8 mL/year, respectively. While IC/TLC declined at 0.70%/year, RV/TLC also declined at 0.35%/year. Changes in both IC/TLC and RV/TLC varied significantly. Frequent exacerbations led to an increase in RV/TLC and faster decline in IC/TLC over time. RV/TLC declined in 59.7% and increased in 40.3% of the patients. A significant negative correlation was found between the rates of change in FEV1and RV/TLC, and the rate of decline in FEV1was greater in patients with an increase in RV/TLC than in those with a decline in RV/TLC (54.2 vs 10.7 mL/year,P<0.001).
  
  
  CONCLUSIONS
  The rate of change in lung hyperinflation varied greatly among COPD patients. Progression of hyperinflation was associated with frequent exacerbations and a faster decline in FEV1.
authors.affiliation: Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, Seoul National University Hospital, Seoul.
authors.forename: Jimyung
authors.initials: J
authors.lastname: Park
authors.affiliation: Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, Seoul National University Hospital, Seoul.
authors.forename: Chang-Hoon
authors.initials: CH
authors.lastname: Lee
authors.affiliation: Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, Seoul National University Bundang Hospital, Seongnam-Si, South Korea.
authors.forename: Yeon Joo
authors.initials: YJ
authors.lastname: Lee
authors.affiliation: Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, Seoul National University Bundang Hospital, Seongnam-Si, South Korea.
authors.forename: Jong Sun
authors.initials: JS
authors.lastname: Park
authors.affiliation: Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, Seoul National University Bundang Hospital, Seongnam-Si, South Korea.
authors.forename: Young-Jae
authors.initials: YJ
authors.lastname: Cho
authors.affiliation: Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, Seoul National University Bundang Hospital, Seongnam-Si, South Korea.
authors.forename: Jae Ho
authors.initials: JH
authors.lastname: Lee
authors.affiliation: Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, Seoul National University Bundang Hospital, Seongnam-Si, South Korea.
authors.forename: Choon-Taek
authors.initials: CT
authors.lastname: Lee
authors.affiliation: Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, Seoul National University Bundang Hospital, Seongnam-Si, South Korea.
authors.forename: Ho Il
authors.initials: HI
authors.lastname: Yoon
mesh_terms: D000368:Aged; D018450:Disease Progression; D005260:Female; D005541:Forced Expiratory Volume; D006801:Humans; D007320:Inspiratory Capacity; D008137:Longitudinal Studies; D008168:Lung / Q000503:physiopathology*; D008176:Lung Volume Measurements; D008297:Male; D008875:Middle Aged; D011379:Prognosis; D011446:Prospective Studies; D029424:Pulmonary Disease, Chronic Obstructive / Q000175:diagnosis / Q000503:physiopathology*; D012115:Residual Volume; D013997:Time Factors; D014109:Total Lung Capacity
keywords: chronic obstructive; cohort studies; forced expiratory volume; lung volume measurements; pulmonary disease