Elsevier

Academic Radiology

Volume 21, Issue 8, August 2014, Pages 986-993
Academic Radiology

Original Investigation
Longitudinal Changes in Airway Remodeling and Air Trapping in Severe Asthma

https://doi.org/10.1016/j.acra.2014.05.001Get rights and content

Rationale and Objectives

Previous cross-sectional studies have demonstrated that airway wall thickness and air trapping are greater in subjects with severe asthma than in those with mild-to-moderate asthma. However, a better understanding of how airway remodeling and lung density change over time is needed. This study aimed to evaluate predictors of airway wall remodeling and change in lung function and lung density over time in severe asthma.

Materials and methods

Phenotypic characterization and quantitative multidetector-row computed tomography (MDCT) of the chest were performed at baseline and ∼2.6 years later in 38 participants with asthma (severe n = 24 and mild-to-moderate n = 14) and nine normal controls from the Severe Asthma Research Program.

Results

Subjects with severe asthma had a significant decline in postbronchodilator forced expiratory volume in 1 second percent (FEV1%) predicted over time (P < .001). Airway wall thickness measured by MDCT was increased at multiple airway generations in severe asthma compared to mild-to-moderate asthma (wall area percent [WA%]: P < .05) and normals (P < .05) at baseline and year 2. Over time, there was an increase in WA% and wall thickness percent (WT%) in all subjects (P = .030 and .009, respectively) with no change in emphysema-like lung or air trapping. Baseline prebronchodilator FEV1% inversely correlated with WA% and WT% (both P < .05). In a multivariable regression model, baseline WA%, race, and health care utilization were predictors of subsequent airway remodeling.

Conclusions

Severe asthma subjects have a greater decline in lung function over time than normal subjects or those with mild-to-moderate asthma. MDCT provides a noninvasive measure of airway wall thickness that may predict subsequent airway remodeling.

Section snippets

Materials and Methods

Forty-seven subjects from the SARP cohort were followed longitudinally with MDCT imaging at full inspiration after maximal bronchodilation at least 1 year apart at two sites (St. Louis, MO and Madison, WI) after institutional review board approval (ID#201206102). Informed consent was obtained in writing after the nature of the procedure had been fully explained. All subjects underwent detailed characterization at baseline and at follow-up as previously described (13). Pulmonary function testing

Participant Characteristics

Forty-seven subjects from the SARP cohort underwent volumetric MDCT at full inspiration and expiration after maximal bronchodilation and again 2.6 ± 1.1 years later (range, 1.2–5.5 years). The cohort included 9 normal subjects, 14 mild-to-moderate asthma subjects, and 24 severe asthma subjects. Subjects with asthma had greater atopy than normal individuals and those with severe asthma had greater health care utilization than those with mild-to-moderate asthma (Table 1). At baseline,

Discussion

Subjects with severe asthma have evidence of airway wall thickening detectable by multiple modalities. Qualitative analysis of high-resolution CT (HRCT) scans in severe asthma subjects reveals abnormalities in 80% of subjects (20). Airway WT measured by quantitative MDCT, represented by WA% and WT%, is increased in subjects with severe asthma compared to mild-to-moderate asthma and control subjects and correlates with both degree of airflow obstruction and pathologic measures of remodeling (21)

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    • Cited by (0)

    C.A.W. and A.S. are co-first authors.

    The research is supported by grants from the National Institutes of Health National Heart, Lung, and Blood Institute (grant numbers: HL69149, HL64368, HL69349, HL69170, HL-69155, HL69174, HL69130, HL69167, HL69116, HL69174); The Hartwell Foundation (S.B.F.) and M01RR00036.

    Conflicts of Interest: All author's Universities have received grant monies from National Institutes of Health to conduct the Severe Asthma Research Program (SARP). No additional potential conflicts exist with companies/organizations whose product or services are pertinent to this article.

    Information on the trial registration (NCT01716494 and NCT01760915) can be obtained at: http//:www.clinicaltrials.gov.

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