title: Dynamic hyperinflation with bronchoconstriction: differences between obese and nonobese women with asthma.
abstract: BACKGROUND
  Symptoms and respiratory function tests may be difficult to assess and interpret in obese patients with asthma, particularly if the asthma is severe. It is unclear whether the dynamic changes that occur during bronchoconstriction differ between obese versus nonobese patients with asthma.
  
  
  OBJECTIVE
  To explore whether the changes in airway caliber and lung volumes that occur with acute bronchoconstriction are different in obese and nonobese patients with asthma and whether any differences contribute to the quality and intensity of symptoms.
  
  
  METHODS
  Thirty female patients with asthma were studied. Spirometry, lung volume measurements, and dyspnea scores were obtained before and immediately after bronchoconstriction induced by methacholine, aiming to provoke a reduction in FEV1 of 30%.
  
  
  RESULTS
  Body mass index was independently associated with changes in lung volume after adjustment for baseline airway caliber and hyperresponsiveness. Increases in functional residual capacity and decreases in inspiratory capacity were significantly greater in obese participants (P < 0.001 and P = 0.003, respectively).
  
  
  CONCLUSIONS
  Changes in respiratory function, notably dynamic hyperinflation, are greater in obese individuals with bronchoconstriction. This may potentially alter the perception and assessment of asthma severity in obese patients with asthma.
authors.affiliation: Respiratory Research Unit, Department of Medical and Surgical Sciences, Dunedin School of Medicine, University of Otago, Dunedin, New Zealand.
authors.forename: Tim J T
authors.initials: TJ
authors.lastname: Sutherland
authors.forename: Jan O
authors.initials: JO
authors.lastname: Cowan
authors.forename: D Robin
authors.initials: DR
authors.lastname: Taylor
mesh_terms: D000328:Adult; D001249:Asthma / Q000150:complications / Q000503:physiopathology*; D015992:Body Mass Index; D016084:Bronchoconstriction / Q000502:physiology*; D005260:Female; D005541:Forced Expiratory Volume / Q000502:physiology; D006801:Humans; D008875:Middle Aged; D009765:Obesity / Q000150:complications* / Q000503:physiopathology; D011379:Prognosis; D011656:Pulmonary Emphysema / Q000209:etiology / Q000503:physiopathology*; D012720:Severity of Illness Index