Distribution of emphysema in heavy smokers: impact on pulmonary function

Respir Med. 2010 Jan;104(1):76-82. doi: 10.1016/j.rmed.2009.08.004. Epub 2009 Sep 6.


Purpose: To investigate impact of distribution of computed tomography (CT) emphysema on severity of airflow limitation and gas exchange impairment in current and former heavy smokers participating in a lung cancer screening trial.

Materials and methods: In total 875 current and former heavy smokers underwent baseline low-dose CT (30 mAs) in our center and spirometry and diffusion capacity testing on the same day as part of the Dutch-Belgian Lung Cancer Screening Trial (NELSON). Emphysema was quantified for 872 subjects as the number of voxels with an apparent lowered X-ray attenuation coefficient. Voxels attenuated <-950 HU were categorized as representing severe emphysema (ES950), while voxels attenuated between -910 HU and -950 HU represented moderate emphysema (ES910). Impact of distribution on severity of pulmonary function impairment was investigated with logistic regression, adjusted for total amount of emphysema.

Results: For ES910 an apical distribution was associated with more airflow obstruction and gas exchange impairment than a basal distribution (both p<0.01). The FEV(1)/FVC ratio was 1.6% (95% CI 0.42% to 2.8%) lower for apical predominance than for basal predominance, for Tlco/V(A) the difference was 0.12% (95% CI 0.076-0.15%). Distribution of ES950 had no impact on FEV(1)/FVC ratio, while an apical distribution was associated with a 0.076% (95% CI 0.038-0.11%) lower Tlco/V(A) (p<0.001).

Conclusion: In a heavy smoking population, an apical distribution is associated with more severe gas exchange impairment than a basal distribution; for moderate emphysema it is also associated with a lower FEV(1)/FVC ratio. However, differences are small, and likely clinically irrelevant.

Publication types

  • Randomized Controlled Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aged
  • Female
  • Forced Expiratory Volume / physiology
  • Humans
  • Logistic Models
  • Lung Neoplasms / diagnostic imaging
  • Male
  • Mass Screening
  • Middle Aged
  • Pulmonary Disease, Chronic Obstructive / diagnostic imaging
  • Pulmonary Disease, Chronic Obstructive / physiopathology*
  • Pulmonary Emphysema / diagnostic imaging
  • Pulmonary Emphysema / physiopathology*
  • Smoking / adverse effects
  • Smoking / physiopathology*
  • Spirometry
  • Tomography, X-Ray Computed
  • Vital Capacity / physiology*