A new computed tomography (CT) imaging study published in the American Journal of Respiratory and Critical Care Medicine found early changes in small airways linked to idiopathic pulmonary fibrosis (IPF).
IPF lung samples with microscopic parenchymal fibrosis had terminal bronchioles with increased wall thicknesses (P <.05) and dilated airway lumens (P <.001), compared to control lungs. These changes can lead to the formation of honeycomb cysts, a major sign of IPF.
In lung samples that did not show microscopic parenchymal fibrosis, IPF samples showed decreased numbers of terminal (P <.01) and transitional (P <.001) bronchioles, as well as an increase in the wall area of the terminal bronchioles compared to control lungs. While there was a reduction in microscopic bronchioles seen during microCT scanning, clinical CT scans showed an increase in the total number of visible airways compared to controls (P <.01). These clinical CT scans indicated that the higher number of visible airways was due to increases in the wall thickness (P <.05) and lumen area (P <.05) of the airways which resulted in more visible airways with lumens larger than 2 mm.
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The study’s authors stated, “This study has important implications for the current thinking on how the lung tissue is remodeled in IPF, and highlights small airways as a potential target to modify IPF outcomes.”
For the study, explanted lungs from 8 IPF patients and 8 donor controls were analyzed. The lungs were inflated with air before being frozen for imaging. Clinical CT scans were used to assess the number and characteristics of large airways while microCT was used for stereological assessment of the small airways. Unbiased, systematic uniform random sampling was used to select 8 samples per lung for microCT analysis.
Stereological assessments included quantification of the number of small airways along with calculation of the areas of the airway walls and lumens. MicroCT was also used to measure the volume fraction of tissue, alveolar surface area, and septal wall thickness to determine the amount of parenchymal fibrosis.
Ikezoe K, Hackett T-L, Peterson S, et al. Small airway reduction and fibrosis is an early pathologic feature of idiopathic pulmonary fibrosis. Am J Respir Crit Care Med. Published online August 3, 2021. doi:10.1164/rccm.202103-0585OC