Chest
Volume 125, Issue 4, April 2004, Pages 1352-1358
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Clinical Investigations
ASTHMA
Bronchial Dilatation in Asthma: Relation to Clinical and Sputum Indices

https://doi.org/10.1378/chest.125.4.1352Get rights and content

Background

Investigations using high-resolution CT (HRCT) show that bronchial dilatation (BD) is found in many patients with asthma. However, the pathogenesis and pathophysiologic relevance of BD in asthma are poorly understood. A balance between matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs) may control the remodeling of extracellular matrix, and excess MMPs have been associated with destruction or dilatation of airways in patients with bronchiectasis.

Objectives

To study the prevalence of BD as assessed by HRCT according to standard subjective criteria in 37 patients with stable asthma and 10 healthy control subjects, and to examine the relation of BD in asthmatic patients to clinical characteristics and sputum indices, including MMP-9 and TIMP-1 levels.

Results

At least one dilated bronchus was present in 23 asthmatic subjects (62%) and 2 control subjects (20%) [p = 0.030]. The ratio of dilated bronchi to all eligible bronchi in each subject (individual BD%) was higher in the asthmatic patients than in the control subjects (11.4 ± 16.1% vs 1.3 ± 3.0%, p = 0.011) [mean ± SD]. Asthmatic patients with (n = 23) and those without BD (n = 14) were similar with regard to age, duration and severity of asthma, atopy, pulmonary function, sputum eosinophil or neutrophil count, and sputum levels of MMP-9 or TIMP-1 and their molar ratio. Individual BD% of asthmatic patients was also unrelated to these clinical and sputum variables. When analysis was confined to the 23 patients with BD, however, individual BD% correlated with the severity score of asthma (r = 0.49, p = 0.023). The results of follow-up HRCT obtained from 19 patients suggested that BD was a fixed rather than transient phenomenon.

Conclusion

BD is more prevalent in asthmatic patients than in normal subjects and might be associated with the severity of asthma. Cellular inflammation or possible imbalance between MMP-9 and TIMP-1 was not demonstrated in this study to be related to BD in asthma.

Section snippets

Subjects

We studied 37 adult patients with asthma treated at the outpatient asthma clinic of Kyoto University Hospital. Asthma was diagnosed according to the American Thoracic Society criteria.24 All patients had stable disease for at least 2 months before study entry and were receiving short-acting inhaled β2-agonists as needed. Thirty-six patients (97%) were treated with inhaled corticosteroids (702 ± 273 μg/d as expressed in equivalent dose of beclomethasone dipropionate) [mean ± SD]. Fifteen

Comparison of Asthmatic Patients and Control Subjects

The characteristics of the asthmatic and control subjects are shown in Table 1. Age and sex did not differ between the two groups. The asthmatic patients had more obstructive airways than the control subjects, as demonstrated by lower FEV1/FVC and FEF25–75% values. The two indices used to evaluate the prevalence of BD were both significantly higher in the asthmatic patients than in the control subjects (Table 1, Fig 1). Figure 2 shows representative CT images obtained from a control subject and

Discussion

As reported by others, we showed that BD on HRCT was more common in asthmatic patients than in healthy control subjects. Individual BD% correlated with the severity of asthma in patients with at least one or more dilated bronchi. Contrary to our hypothesis, however, the prevalence of BD was not related to the sputum level of MMP-9 or the MMP-9/TIMP-1 molar ratio.

Several authors have examined the prevalence of BD on HRCT in asthmatic patients and healthy subjects.347 They used the same

References (37)

  • F Paganin et al.

    Chest radiography and high resolution computed tomography of the lungs in asthma

    Am Rev Respir Dis

    (1992)
  • F Paganin et al.

    Computed tomography of the lungs in asthma: influence of disease severity and etiology

    Am J Respir Crit Care Med

    (1996)
  • CS Park et al.

    Airway obstruction in asthmatic and healthy individuals: inspiratory and expiratory thin section CT findings

    Radiology

    (1997)
  • N Awadh et al.

    Airway wall thickness in patients with near fatal asthma and control groups: assessment with high resolution computed tomographic scanning

    Thorax

    (1998)
  • A Niimi et al.

    Airway wall thickness in asthma assessed by computed tomography: relation to clinical indices

    Am J Respir Crit Care Med

    (2000)
  • SA Little et al.

    High resolution computed tomographic assessment of airway wall thickness in chronic asthma: reproducibility and relationship with lung function and severity

    Thorax

    (2002)
  • E Harmanci et al.

    High-resolution computed tomography findings are correlated with disease severity in asthma

    Respiration

    (2002)
  • G Murphy et al.

    The matrix metalloproteinases and their inhibitor

    Am J Respir Cell Mol Biol

    (1992)
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    This work was supported by AstraZeneca Asthma Research Award 2000 (Japanese Society of Allergology and Japan Allergy Foundation).

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