title: The effect of body weight on distal airway function and airway inflammation.
abstract: Obesity is a global health problem that adversely influences the respiratory system. We assessed the effects of body mass index (BMI) on distal airway function and airway inflammation.
  
  
  
  Impulse oscillometry (IOS) as a measure of distal airway function, together with spirometry, were assessed in adults with a range of different BMIs. Airway inflammation was assessed with the fraction of exhaled nitric oxide (FeNO) and participants exhaled at various exhalation flows to determine alveolar and bronchial NO.
  
  
  
  In total 34 subjects were enrolled in the study; 19 subjects had a normal BMI (18.50-24.99), whilst 15 subjects were overweight (BMI 25.00-29.99), or obese (BMI ≥30). All subjects had normal spirometry. However, IOS measures of airway resistance (R) at 5Hz, 20Hz and frequency dependence (R5-20) were elevated in overweight/obese individuals, compared to subjects with a normal BMI (median (interquartile range)); 5Hz: 0.41 (0.37, 0.45) vs. 0.32 (0.30, 0.37)kPa/l/s; 20Hz: 0.34 (0.30, 0.37) vs. 0.30 (0.26, 0.33)kPa/l/s; R5-20: 0.06 (0.04, 0.11) vs. 0.03 (0.01, 0.05)kPa/l/s; p<0.05), whereas airway reactance at 20Hz was decreased in overweight/obese individuals (20Hz: 0.07 (0.03, 0.09) vs. 0.10 (0.07, 0.13)kPa/l/s, p=0.009; 5Hz: -0.12 (-0.15, -0.10) vs. -0.10 (-0.13, -0.09)kPa/l/s, p=0.07). In contrast, within-breath IOS measures (a sign of expiratory flow limitation) and FeNO inflammatory measures, did not differ between groups (p>0.05).
  
  
  
  Being overweight has significant effects on distal and central airway function as determined by IOS, which is not detected by spirometry. Obesity does not influence airway inflammation as measured by FeNO. IOS is a reliable technique to identify airway abnormalities in the presence of normal spirometry in overweight people.
authors.affiliation: National Heart and Lung Institute, Imperial College, Dovehouse Street, London SW3 6LY, United Kingdom. Electronic address: kim.vande.kant@mumc.nl.
authors.forename: Kim D G
authors.initials: KD
authors.lastname: van de Kant
authors.affiliation: National Heart and Lung Institute, Imperial College, Dovehouse Street, London SW3 6LY, United Kingdom. Electronic address: p.paredi@imperial.ac.uk.
authors.forename: Paolo
authors.initials: P
authors.lastname: Paredi
authors.affiliation: National Heart and Lung Institute, Imperial College, Dovehouse Street, London SW3 6LY, United Kingdom. Electronic address: sally.meah@imperial.ac.uk.
authors.forename: Sally
authors.initials: S
authors.lastname: Meah
authors.affiliation: National Heart and Lung Institute, Imperial College, Dovehouse Street, London SW3 6LY, United Kingdom. Electronic address: h.kalsi09@imperial.ac.uk.
authors.forename: Harpal S
authors.initials: HS
authors.lastname: Kalsi
authors.affiliation: National Heart and Lung Institute, Imperial College, Dovehouse Street, London SW3 6LY, United Kingdom. Electronic address: p.j.barnes@imperial.ac.uk.
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Barnes
authors.affiliation: National Heart and Lung Institute, Imperial College, Dovehouse Street, London SW3 6LY, United Kingdom. Electronic address: o.usmani@imperial.ac.uk.
authors.forename: Omar S
authors.initials: OS
authors.lastname: Usmani
mesh_terms: D000328:Adult; D000368:Aged; D000403:Airway Resistance / Q000502:physiology*; D001835:Body Weight / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009569:Nitric Oxide / Q000032:analysis; D009765:Obesity / Q000503:physiopathology*; D012129:Respiratory Function Tests; D013147:Spirometry; D055815:Young Adult
chemical_list: D009569:Nitric Oxide
keywords: Body mass index; Fraction of exhaled nitric oxide; Impulse oscillometry; Lung function