Children with severe asthma have substantial structural airway changes on computed tomography

Abstract

BackgroundIn adults with severe asthma(SA) airway wall thickening, bronchiectasis and low attenuation regions(LAR) have been described on chest computed tomography(CT) scans. The extent to which these structural abnormalities are present in children with SA is largely unknown.AimTo study the presence and extent of airway abnormalities on chest CT of children with SA.Methods161 in-and expiratory CT scans, either spirometer-controlled or technician-controlled, obtained in 131 children with SA (mean age 11.0±3.8 years) were collected retrospectively. Inspiratory scans were analysed manually using a semi-quantitative score and automatically using LungQ (v2.1.0.1, Thirona B.V., The Netherlands). LungQ segments the airway tree, identifies the generation for each airway-artery (AA)-pair, and measures the following AA-dimensions: outer airway wall diameter(Aout), adjacent artery diameter(A) and airway wall thickness(Awt). Bronchiectasis was defined as Aout/A ≥1.1, airway wall thickening as Awt/A ≥0.14. LAR, reflecting small airways disease(SAD) was measured automatically on in- and expiratory scans and manually on expiratory scans. Functional SAD was defined as FEF25–75and/or FEF75z-scores<-1.645. Results are shown as median and interquartile range.ResultsBronchiectasis was present on 95.8% and airway wall thickening on all CT's using the automated method. Bronchiectasis was present on 28% and airway wall thickening on 88.8% of the CT's using the manual semi-quantitative analysis. The percentage of AA-pairs defined as bronchiectasis was 24.62% (12.7–39.3%) and airway wall thickening was 41.7% (24.0–79.8%) per CT using the automated method. LAR was observed on all CT's using the automatic analysis and on 82.9% using the manual semi-quantitative analysis. Patients with LAR or functional SAD had more thickened airways than patients without.ConclusionDespite a large discrepancy between the automated and the manual semi-quantitative analysis, bronchiectasis and airway wall thickening are present on most CT scans of children with SA. SAD is related to airway wall thickening.

A new approach to computed tomography measurement of airway remodelling in paediatric asthma

“…The findings of van den B osch et al . [ 15 ] showed much higher central airway remodelling than expected. The most surprising finding was the high prevalence and extent of bronchiectasis.…”

“…In this issue of ERJ Open Research , van den B osch et al . [ 15 ] report use of a novel measure of airway remodelling on chest CT that normalises the bronchial outer diameter (B out ) to the companion artery lumen diameter (A) at equivalent segmental generation (giving the B out /A ratio). Because the entire airway and vascular trees are automatically segmented on an inspiratory chest CT scan, this calculation can be efficiently performed for all visible bronchus–artery (BA) pairs.…”

“…van den B osch et al . [ 15 ] used the BA analysis to evaluate airway remodelling in a retrospective study of paediatric patients with a diagnosis of severe asthma in 161 CT scans obtained in 131 patients over the years 2007–2019. Inclusion criteria were chest CT scan with severe asthma diagnosis between the ages of 4 and 18 years and a reconstructed slice thickness of ≤1.5 mm.…”

“…Other imaging studies found a more modest prevalence for bronchiectasis of 20–30% in children with severe asthma [ 16 ], which was similar to the prevalence found by van den B osch et al . [ 15 ] using manual semi-quantitative scoring. Similarly high degrees of airway remodelling were found for the bronchial wall thickness to artery lumen ratio (B wt /A ≥0.14 as the cut-off).…”

“…These data from van den B osch et al . [ 15 ] are among the first to purport a normalised airway measure of central airway remodelling, which is robust to data acquired using multiple scanners and protocols. Moreover, the findings in the current work are consistent with patterns of air trapping in children with severe asthma that suggest airway and parenchymal remodelling may be occurring much earlier in these patients than previously thought.…”