title: Air trapping on computed tomography images of healthy individuals: effects of respiration and body mass index.
abstract: OBJECTIVE
  To evaluate the relationships of changes in the lung area during respiration and of individual body mass index (BMI) to air trapping on expiratory computed tomography (CT) in young non-smoking adults of either gender.
  
  
  METHODS
  The volunteers were 10 women and 10 men (mean age 25.7 years) who were healthy lifelong non-smokers. We obtained both end-inspiratory and end-expiratory CT images at three levels: the upper, middle and lower lung. The ratio of cross-sectional lung area upon expiration to cross-sectional lung area upon inspiration (lung area ratio) was determined for each lung at each of the three levels. In cases showing air trapping, we calculated the percentage of area of air in relation to the total lung area in each section. BMI was calculated for each participant.
  
  
  RESULTS
  Air trapping was present in dependent areas of the lungs of 6 women and 5 men. The mean percentage of area of air trapped was statistically greater for men (9.8+/-9.2%) than for women (4.9+/-5.2%). The mean lung area ratio was 0.52+/-0 14 among volunteers with air trapping (66 sections) and 0.69+/-0.12 among those without air trapping (54 sections) (p < 0.001). At each lung level, the mean lung area ratio was greater in individuals with air trapping than in those without. Mean BMI was also greater in these people (p = 0.009).
  
  
  CONCLUSIONS
  Change in the respiratory lung area and BMI contribute to development of air trapping.
authors.affiliation: Department of Radiology, Akita University School of Medicine, Japan. hashi@med.akita-u.ac.jp
authors.forename: M
authors.initials: M
authors.lastname: Hashimoto
authors.forename: E
authors.initials: E
authors.lastname: Tate
authors.forename: J
authors.initials: J
authors.lastname: Watarai
authors.forename: M
authors.initials: M
authors.lastname: Sasaki
mesh_terms: D000328:Adult; D000388:Air; D015992:Body Mass Index; D045853:Exhalation / Q000502:physiology*; D005260:Female; D006801:Humans; D001239:Inhalation / Q000502:physiology*; D008168:Lung / Q000033:anatomy & histology* / Q000000981:diagnostic imaging; D008297:Male; D012737:Sex Factors; D014057:Tomography, X-Ray Computed