title: Effects of BMI on static lung volumes in patients with airway obstruction.
abstract: BACKGROUND
  Both chronic airway obstruction and obesity are increasing in prevalence but the effect of their combination on pulmonary function parameters across the range of airway obstruction is unknown.
  
  
  METHODS
  We studied the impact of increasing BMI on static lung volumes and airway function in a cohort of 2,265 subjects from a large pulmonary function laboratory database who were 40 to 80 years of age and met GOLD (Global Initiative for Chronic Obstructive Lung Disease) spirometric criteria for COPD (postbronchodilator FEV₁/FVC < 0.7). We also evaluated the influence of severity of airway obstruction (by GOLD criteria) on these relationships.
  
  
  RESULTS
  With increasing BMI in the group as a whole, functional residual capacity, residual volume, expiratory reserve volume, and specific airway resistance (sRaw) decreased exponentially (all P < .001); total lung capacity (TLC) decreased linearly (P < .001); and inspiratory capacity (IC) and IC/TLC increased linearly (P < .001). However, vital capacity was not influenced significantly. The effects of increasing BMI on FEV₁/FVC and sRaw were greatest in GOLD stage III/IV (P < .05), whereas increasing BMI had greater effects on IC in GOLD stage I (P < .001).
  
  
  CONCLUSIONS
  With increasing BMI, subjects with airway obstruction had consistent reductions in lung hyperinflation, with significant improvements in IC and the FEV₁/FVC ratio; this effect was greatest in patients with the most severe airway obstruction. These results have important implications for the clinical assessment of patients with combined obesity and airway obstruction.
authors.affiliation: Department of Medicine, Queen's University and Kingston General Hospital, Kingston, ON, Canada. Electronic address: odonnell@queensu.ca.
authors.forename: Denis E
authors.initials: DE
authors.lastname: O'Donnell
authors.affiliation: Department of Medicine, Queen's University and Kingston General Hospital, Kingston, ON, Canada.
authors.forename: Athavudh
authors.initials: A
authors.lastname: Deesomchok
authors.affiliation: Department of Community Health and Epidemiology, Queen's University, Kingston, ON, Canada.
authors.forename: Yuk-Miu
authors.initials: YM
authors.lastname: Lam
authors.affiliation: Department of Medicine, Queen's University and Kingston General Hospital, Kingston, ON, Canada.
authors.forename: Jordan A
authors.initials: JA
authors.lastname: Guenette
authors.affiliation: Department of Medicine, Queen's University and Kingston General Hospital, Kingston, ON, Canada.
authors.forename: Naparat
authors.initials: N
authors.lastname: Amornputtisathaporn
authors.affiliation: Department of Medicine, Queen's University and Kingston General Hospital, Kingston, ON, Canada.
authors.forename: Lutz
authors.initials: L
authors.lastname: Forkert
authors.affiliation: Department of Medicine, Queen's University and Kingston General Hospital, Kingston, ON, Canada.
authors.forename: Katherine A
authors.initials: KA
authors.lastname: Webb
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000403:Airway Resistance; D015992:Body Mass Index; D005105:Expiratory Reserve Volume; D005260:Female; D005652:Functional Residual Capacity; D006801:Humans; D008176:Lung Volume Measurements; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000150:complications / Q000503:physiopathology*; D010993:Plethysmography, Whole Body; D011653:Pulmonary Diffusing Capacity; D029424:Pulmonary Disease, Chronic Obstructive / Q000150:complications / Q000503:physiopathology*; D013147:Spirometry; D014109:Total Lung Capacity