Respirology. 2012 Jan;17(1):79-86.

Airway dimensions and pulmonary function in chronic obstructive pulmonary disease and bronchial asthma.

Kurashima K, Hoshi T, Takayanagi N, Takaku Y, Kagiyama N, Ohta C, Fujimura M, Sugita Y.

Department of Respiratory Medicine, Saitama Cardiovascular and Respiratory Center, Kumagaya City, Kanazawa, Japan. kurashima.kazuyoshi@pref.saitama.lg.jp

 

Abstract

BACKGROUND AND OBJECTIVE:

COPD and bronchial asthma are chronic airway diseases with a different pathogenesis. Comparisons of differences in airway calibre by bronchial generation between these diseases and their importance to pulmonary function have not been fully studied. We investigated airway calibre and wall thickness in relation to pulmonary function in patients with asthma, COPD, asthma plus emphysema and normal subjects using CT.

METHODS:

Sixty-three asthmatic patients, 46 COPD, 23 patients with asthma plus emphysema and 61 control subjects were studied cross-sectionally. We used a software with curved multiplanar reconstruction to measure airway dimensions from 3rd- to 6th-generation bronchi of the right lower posterior bronchus.

RESULTS:

Patients with COPD had increased wall thickness, but the airway was not narrow from the 3rd-(subsegmental) to 6th-generation bronchi. Mean bronchial inner diameter (Di) of 3rd- to 6th-generation bronchi in patients with asthma or asthma plus emphysema was smaller than that of COPD patients and normal subjects. Airway luminal area (Ai) of 5th-generation bronchi most closely correlated with pulmonary function in patients with stable asthma. Although Di was similar in patients with asthma and asthma plus emphysema, the Ai of 6th-generation bronchi correlated significantly with pulmonary function in patients with asthma plus emphysema.

CONCLUSIONS:

Airway calibre in asthma may be smaller than in COPD. Airflow limitations correlated more closely with peripheral Ai in patients with asthma plus emphysema than in patients with asthma alone.

Respirology © 2011 Asian Pacific Society of Respirology.

PMID: 21883679

 

Supplements:

Asthma and chronic obstructive pulmonary disease (COPD) are most common obstructive airway diseases and they are often overlapped. However, differential diagnosis is sometimes difficult, particularly for asthma with airway remodeling. The present study focused on the airway dimensions of these diseases and their relation to lung function. Reduced airway inner diameter compared to adjusted artery and thick airway wall are useful markers to detect presence of asthma by CT examination. These changes could be observed throughout airway, but 4th or 5th generation airways are most easily recognized. Recognition of asthma and CT-diagnosed emphysema in patients with chronic airflow limitation are important because they predict different prognosis (Kurashima K et al. BMJ open 2013, Nov 4;3(11):e003541). The present study showed that relationships between airway luminal area at given bronchial generation and pulmonary function are different in asthma and in mixture of asthma and emphysema. These facts suggest that the therapeutic targets for pure asthma and a mixture of asthma and emphysema should be different.

Kazuyoshi Kurashima-1Figure 1. Bronchial trees are automatically traced peripheral points to the trachea (upper panel). Longitudinal image of the right lower posterior bronchus is shown (lower panel). At any point of airway exactly perpendicular view to airway axis can be made and it can be used to study airway wall and inner diameter (upper panel).

 

Kazuyoshi Kurashima-2

Figure 2. Short axis images of normal and asthma airways are shown. Note the differences of relative diameters of bronchi to their accompanying arteries. Asthma airway is not always narrow and thick, but reduced airway diameter and thick airway wall are useful CT findings to detect presence of asthma.

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