Background: The smaller airways, < 2 mm in diameter, offer little resistance in normal lungs, but become the major site of obstruction in chronic obstructive pulmonary disease (COPD).
Objective: To examine bronchiolar remodeling and alveolar destruction in COPD using micro-computed tomography (micro-CT).
Methods: Micro-CT was used to measure the number and cross-sectional lumen area of terminal bronchioles (TB) and alveolar mean linear intercept (Lm) in 4 lungs removed from patients with very severe (GOLD-4) COPD and 4 unused donor lungs that served as controls. These lungs were inflated with air to a transpulmonary pressure (P(L)) of 30 cm H(2)O and held at P(L) 10 cm H(2)O while they were frozen solid in liquid nitrogen vapor. A high resolution CT scan was performed on the frozen specimen prior to cutting it into 2-cm thick transverse slices. Representative core samples of lung tissue 2 cm long and 1 cm in diameter cut from each slice were fixed at -80 degrees C in a 1% solution of gluteraldehyde in pure acetone, post-fixed in osmium, critically point dried, and examined by micro-CT.
Results: A 10-fold reduction in terminal bronchiolar number and a 100-fold reduction in their minimal cross-sectional lumen area were measured in both emphysematous and non-emphysematous regions of the COPD lungs.
Conclusions: The centrilobular emphysematous phenotype of COPD is associated with narrowing and obliteration of the terminal bronchioles that begins prior to the onset of emphysematous destruction.