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Relationship between CT air trapping criteria and lung function in small airway impairment quantification.

ABSTRACT: Small airways are regarded as the elective anatomic site of obstruction in most chronic airway diseases. Expiratory computed tomography (CT) is increasingly used to assess obstruction at this level but there is no consensus regarding the best quantification method. We aimed to evaluate software-assisted CT quantification of air trapping for assessing small airway obstruction and determine which CT criteria better predict small airway obstruction on single breath nitrogen test (SBNT).Eighty-nine healthy volunteers age from 60 to 90 years old, underwent spirometrically-gated inspiratory (I) and expiratory (E) CT and pulmonary function tests (PFTs) using SBNT, performed on the same day. Air trapping was estimated using dedicated software measuring on inspiratory and expiratory CT low attenuation area (LAA) lung proportion and mean lung density (MLD). CT indexes were compared to SBNT results using the Spearman correlation coefficient and hierarchical dendrogram analysis. In addition, receiver operating characteristic (ROC) curve analysis was performed to determine the optimal CT air-trapping criterion.43 of 89 subjects (48,3%) had dN2 value above the threshold defining small airway obstruction (i.e. 2.5%?N2/l). Expiratory to inspiratory MLD ratio (r = 0.40) and LAA for the range -850 -1024 HU (r = 0.29) and for the range -850 -910 HU (r = 0.37) were positively correlated with SBNT results. E/I MLD was the most suitable criterion for its expression. Expiratory to inspiratory MLD ratio (E/I MLD) showed the highest AUC value (0.733) for small airway obstruction assessment.Among all CT criteria, all correlating with small airway obstruction on SBNT, E/I MLD was the most suitable criterion for its expression in asymptomatic subjects with mild small airway obstructionRegistered at Clinicaltrials.gov, identifier: NCT01230879.

SUBMITTER: Bommart S

PROVIDER: S-EPMC4015710 | biostudies-literature | 2014 Feb

REPOSITORIES: biostudies-literature

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Relationship between CT air trapping criteria and lung function in small airway impairment quantification.

Bommart Sébastien S Marin Grégory G Bourdin Arnaud A Molinari Nicolas N Klein François F Hayot Maurice M Vachier Isabelle I Chanez Pascal P Mercier Jacques J Vernhet-Kovacsik Hélène H

BMC pulmonary medicine 20140228

<h4>Background</h4>Small airways are regarded as the elective anatomic site of obstruction in most chronic airway diseases. Expiratory computed tomography (CT) is increasingly used to assess obstruction at this level but there is no consensus regarding the best quantification method. We aimed to evaluate software-assisted CT quantification of air trapping for assessing small airway obstruction and determine which CT criteria better predict small airway obstruction on single breath nitrogen test ...[more]

PMID: 24581147

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Project description:ObjectivesQuantitative computed tomography (QCT) offers some promising markers to quantify cystic fibrosis (CF)-lung disease. Air trapping may precede irreversible bronchiectasis; therefore, the temporal interdependencies of functional and structural lung disease need to be further investigated. We aim to quantify airway dimensions and air trapping on chest CT of school-age children with mild CF-lung disease over two years.MethodsFully-automatic software analyzed 144 serial spirometer-controlled chest CT scans of 36 children (median 12.1 (10.2-13.8) years) with mild CF-lung disease (median ppFEV1 98.5 (90.8-103.3) %) at baseline, 3, 12 and 24 months. The airway wall percentage (WP5-10), bronchiectasis index (BEI), as well as severe air trapping (A3) were calculated for the total lung and separately for all lobes. Mixed linear models were calculated, considering the lobar distribution of WP5-10, BEI and A3 cross-sectionally and longitudinally.ResultsWP5-10 remained stable (P = 0.248), and BEI changed from 0.41 (0.28-0.7) to 0.54 (0.36-0.88) (P = 0.156) and A3 from 2.26% to 4.35% (P = 0.086) showing variability over two years. ppFEV1 was also stable (P = 0.276). A robust mixed linear model showed a cross-sectional, regional association between WP5-10 and A3 at each timepoint (P < 0.001). Further, BEI showed no cross-sectional, but another mixed model showed short-term longitudinal interdependencies with air trapping (P = 0.003).ConclusionsRobust linear/beta mixed models can still reveal interdependencies in medical data with high variability that remain hidden with simpler statistical methods. We could demonstrate cross-sectional, regional interdependencies between wall thickening and air trapping. Further, we show short-term regional interdependencies between air trapping and an increase in bronchiectasis. The data indicate that regional air trapping may precede the development of bronchiectasis. Quantitative CT may capture subtle disease progression and identify regional and temporal interdependencies of distinct manifestations of CF-lung disease.

Project description:BackgroundAlthough ambient air pollution has been linked to reduced lung function in healthy children, longitudinal analyses of pollution effects in asthmatic patients are lacking.ObjectiveWe sought to investigate pollution effects in a longitudinal asthma study and effect modification by controller medications.MethodsWe examined associations of lung function and methacholine responsiveness (PC20) with ozone, carbon monoxide (CO), nitrogen dioxide, and sulfur dioxide concentrations in 1003 asthmatic children participating in a 4-year clinical trial. We further investigated whether budesonide and nedocromil modified pollution effects. Daily pollutant concentrations were linked to ZIP/postal code of residence. Linear mixed models tested associations of within-subject pollutant concentrations with FEV1 and forced vital capacity (FVC) percent predicted, FEV1/FVC ratio, and PC20, adjusting for seasonality and confounders.ResultsSame-day and 1-week average CO concentrations were negatively associated with postbronchodilator percent predicted FEV1 (change per interquartile range, -0.33 [95% CI, -0.49 to -0.16] and -0.41 [95% CI, -0.62 to -0.21], respectively) and FVC (-0.19 [95% CI, -0.25 to -0.07] and -0.25 [95% CI, -0.43 to -0.07], respectively). Longer-term 4-month CO averages were negatively associated with prebronchodilator percent predicted FEV1 and FVC (-0.36 [95% CI, -0.62 to -0.10] and -0.21 [95% CI, -0.42 to -0.01], respectively). Four-month averaged CO and ozone concentrations were negatively associated with FEV1/FVC ratio (P < .05). Increased 4-month average nitrogen dioxide concentrations were associated with reduced postbronchodilator FEV1 and FVC percent predicted. Long-term exposures to sulfur dioxide were associated with reduced PC20 (percent change per interquartile range, -6% [95% CI, -11% to -1.5%]). Treatment augmented the negative short-term CO effect on PC20.ConclusionsAir pollution adversely influences lung function and PC20 in asthmatic children. Treatment with controller medications might not protect but rather worsens the effects of CO on PC20. This clinical trial design evaluates modification of pollution effects by treatment without confounding by indication.

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Relationship between CT air trapping criteria and lung function in small airway impairment quantification.

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Relationship between CT air trapping criteria and lung function in small airway impairment quantification.

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