Sex differences in central airway luminal area among people with interstitial lung disease

Background: Interstitial lung disease (ILD) encompasses several pulmonary disorders associated with scarring and fibrosis of pulmonary tissue. People with idiopathic pulmonary fibrosis, a subset of ILD, have greater central airway luminal area compared to age- and sex-matched healthy controls when evaluated using microcomputed tomography, a process examining the luminal area of ex-vivo lung tissue. In this study we aimed to confirm these findings using a different method of airway assessment, three-dimensional (3D) reconstruction of computed tomography (CT) scans. Moreover, in health, males have larger central airways than height-matched females, but it remains unknown if there are sex differences in airway area among people with ILD. We hypothesized that sex differences observed in healthy people would persist among people with ILD. Methods: A cohort of 399 patients with lung CT scans were screened, of which 19 people (7 females) with ILD were included in analyses after exclusions. People with ILD were matched based on sex, age, and height to 19 healthy controls. We assessed cross-sectional luminal area at the midpoint of seven conducting airways (trachea, left and right main bronchus, intermediate bronchus, left and right upper lobe, and left lower lobe). Results from pulmonary function tests were also abstracted, as available. To examine sex differences, we compared airway luminal area, normalized to participant height, between males and females with ILD. Sex differences were analyzed using a univariate ANOVA test. Results: People with ILD had a preserved ratio of forced expiratory volume in the first second to forced vital capacity (101 ±12%predicted) and decreased diffusing capacity for carbon monoxide (55 ±23%predicted). People with ILD had airways that were between 19.6%-45.0% larger than controls (p<0.05). Composite physiologic index, a marker of ILD severity, was not different between sexes (p=0.07). Males with ILD had significantly larger, luminal areas than females in two central airways - right main bronchus (1.46±0.41 vs. 1.07±0.22 mm 2 /cm, p=0.04) and left upper lobe (0.54±0.10 vs. 0.43±0.08 mm 2 /cm, p=0.02). However, luminal area of other central airways, including: trachea (2.15±0.57 vs. 1.65±0.32 mm 2 /cm, p=0.051), bronchus intermediate (0.77±0.23 vs. 0.61±0.13 mm 2 /cm, p=0.12), right upper lobe (0.47±0.15 vs. 0.40±0.06 mm 2 /cm, p=0.26), left main bronchus (0.93±0.33 vs. 0.69±0.16 mm 2 /cm, p=0.09), and left lower lobe (0.41±0.13 vs. 0.40±0.08 mm 2 /cm, p=0.79) were not different between sexes in people with ILD. Conclusion: Sex differences observed in healthy people are potentially preserved in ILD, but a more robust sample is required to fully elucidate these findings. Illuminating any sex differences in ILD pathophysiology may provide knowledge to treat and improve clinical outcomes in ILD. Funding: National Heart, Lung, and Blood Institute (F32HL154320 to JWS; 5R35HL139854 to MJJ). This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.