Small airways disease: expiratory computed tomography comes of age

Effect of ventilation technique and airway diameter on bronchial lumen to pulmonary artery diameter ratios in clinically normal beagle dogs

In dogs, a mean broncho-arterial ratio of 1.45 ± 0.21 has been previously defined as normal. These values were obtained in dogs under general inhalational anesthesia using a single breath-hold technique. The purpose of the study was to determine whether ventilation technique and bronchial diameter have an effect on broncho-arterial ratios. Four healthy Beagle dogs were scanned twice, each time with positive-pressure inspiration and end expiration. For each ventilation technique, broncho-arterial ratios were grouped into those obtained from small or large bronchi using the median diameter of the bronchi as the cutoff value. Mean broncho-arterial ratios obtained using positive-pressure inspiration (1.24 ± 0.23) were statistically greater than those obtained at end expiration (1.11 ± 0.20) P = 0.005. There was a strong positive correlation between bronchial diameter and broncho-arterial ratios for both ventilation techniques (positive-pressure inspiration rs = .786, P < 0.0005 and end expiration rs = .709, P < 0.0005). Mean broncho-arterial ratio for the large bronchi obtained applying positive-pressure inspiration was 1.39 cm ± 0.20 and during end expiration was 1.22 cm ± 0.20. Mean broncho-arterial ratio for the small bronchi obtained during positive-pressure inspiration was 1.08 cm ± 0.13 and during end expiration was 1.01 cm ± 0.13. There was a statistically significant difference between these groups (F = 248.60, P = 0.005). Findings indicated that reference values obtained using positive-pressure inspiration or from the larger bronchi may not be applicable to dogs scanned during end expiration or to the smaller bronchi.

[Imaging techniques in the examination of the distal airways: asthma and COPD]

Imaging techniques are highly useful diagnostic tools to study small airway diseases. Despite their differences, from a clinical pathological perspective, these diseases show similar radiological manifestations. High-resolution computed tomography (CT) is the technique of choice to study diffuse diseases and those of the small airways; the slices obtained in expiratory high-resolution CT scan should form part of the study protocol of small airway diseases. Based on the findings of high-resolution CT, small airway diseases can be divided into two large groups: (a) those presenting direct morphological signs of bronchiolar involvement, and (b) those showing indirect signs of bronchiolar involvement (air trapping/mosaic pattern). High-resolution CT is highly useful to study the complications of asthma (allergic bronchopulmonary aspergillosis) and to evaluate clinically similar processes, such as hypersensitivity pneumonitis. In asthmatic patients, multi-detector CT (MDTC) allows clinical symptoms, thickening of the airway wall and the degree of airflow obstruction to be directly correlated. MDTC is also useful for quantitative evaluation of the degree of air trapping in patients with emphysema. Magnetic resonance imaging after inhalation of distinct gases, such as (3)He and xenon-129 and dual-energy CT are also useful imaging techniques in the direct or indirect evaluation of the degree of airflow obstruction (air trapping).

Biomass exposure and the high resolution computed tomographic and spirometric findings

BACKGROUND

The adverse health effects of biomass fuel exposure (BFE) is complex and widespread. According to our knowledge, the interstitial lung disease due to BFE is not clear in literature.

OBJECTIVE

In this descriptive crossectional study, the main objective was to assess the effects of BFE on the respiratory system.

METHODS

Patient group was included non-smoker 21 woman and the control group was included non-smoker 22 woman. High resolution computed tomographic (HRCT) examinations were made with supin and prone positions in two groups. The spirometric measurements, including the diffusion capacity at rest for carbon monoxide, single breath (DLCO), were also made.

RESULTS

It was found that BFE caused obstructive and restrictive spirometric impairments. The prevalence of the fibrotic bands, peribronchovascular thickenings, nodular radio opacities, and curvilinear densities in the high resolution computed tomographic examinations were 7, 5, 7, and 16 times higher in the exposure group than the control group, respectively. There was a significant positive correlation between the forced vital capacity (FVC), forced expiratory volume first second (FEV(1)), FEV(1)/FVC, forced expiratory flow during middle half of forced vital capacity (FEF25-75), DLCO and the volumetric densities of the HRCT slices with deep expiration in prone position.

CONCLUSIONS

We think that, the findings due to BFE, pose a special situation and it can be named "biomass lung".

Bronchiolar disorders

Bronchiolar abnormalities are relatively common and occur in a variety of clinical settings. Various histopathologic patterns of bronchiolar injury have been described and have led to confusing nomenclature with redundant and overlapping terms. Some histopathologic patterns of bronchiolar disease may be relatively unique to a specific clinical context but others are nonspecific with respect to either etiology or pathogenesis. Herein, we present a scheme separating (1) those disorders in which the bronchiolar disease is the predominant abnormality (primary bronchiolar disorders) from (2) parenchymal disorders with prominent bronchiolar involvement and (3) bronchiolar involvement in large airway diseases. Primary bronchiolar disorders include constrictive bronchiolitis (obliterative bronchiolitis, bronchiolitis obliterans), acute bronchiolitis, diffuse panbronchiolitis, respiratory bronchiolitis, mineral dust airway disease, follicular bronchiolitis, and a few other rare variants. Prominent bronchiolar involvement may be seen in several interstitial lung diseases, including hypersensitivity pneumonitis, respiratory bronchiolitis-associated interstitial lung disease, cryptogenic organizing pneumonia (idiopathic bronchiolitis obliterans organizing pneumonia), and pulmonary Langerhans' cell histiocytosis. Large airway diseases that commonly involve bronchioles include bronchiectasis, asthma, and chronic obstructive pulmonary disease. The clinical relevance of a bronchiolar lesion is best determined by identifying the underlying histopathologic pattern and assessing the correlative clinico-physiologic-radiologic context.

Small airways diseases: detection and insights with computed tomography

Diseases affecting the small airways are difficult to detect by traditional diagnostic tests. Widespread involvement is needed before symptoms and abnormalities on pulmonary function testing or chest radiography become apparent. Obstruction of the bronchioles may be detected indirectly by computed tomography (CT) because regional under-ventilation results in reduced perfusion which in turn is shown as a mosaic attenuation pattern of the lung parenchyma. When there is inflammation of the bronchioles with accompanying exudate, the airways may become directly visible on CT, for example in cases of diffuse panbronchiolitis. Quantification of the various morphological features of small airways disease is possible from CT images and this increased precision has aided investigations of structure/function relationships. An understanding of the pathology and microscopic distribution of disease in relation to the airways allows some prediction of the likely computed tomography appearances in this wide spectrum of conditions, and thus helps to refine the differential diagnosis.

Airflow obstruction in bronchiectasis: correlation between computed tomography features and pulmonary function tests

BACKGROUND

An obstructive defect is usual in bronchiectasis, but the pathophysiological basis of airflow obstruction remains uncertain. High resolution computed tomographic (CT) scanning now allows quantitation of static morphological abnormalities, as well as dynamic changes shown on expiratory CT scans. The aim of this study was to determine which static and dynamic structural abnormalities on the CT scan are associated with airflow obstruction in bronchiectasis.

METHODS

The inspiratory and expiratory features on the CT scan of 100 patients with bronchiectasis undergoing concurrent lung function tests were scored semi-quantitatively by three observers.

RESULTS

On univariate analysis the extent and severity of bronchiectasis, the severity of bronchial wall thickening, and the extent of decreased attenuation on the expiratory CT scan correlated strongly with the severity of airflow obstruction; the closest relationship was seen between decreased forced expiratory volume in one second (FEV(1)) and the extent of decreased attenuation on the expiratory CT scan (R(s) = -0.55, p<0. 00005). On multivariate analysis bronchial wall thickness and decreased attenuation were consistently the strongest independent determinants of airflow obstruction. The extent of decreased attenuation was positively associated with the severity of bronchial wall thickness, but was not independently linked to gas transfer levels. Endobronchial secretions seen on CT scanning had no functional significance; the severity of bronchial dilatation was negatively associated with airflow obstruction after adjustment for other morphological features.

CONCLUSIONS

These findings indicate that airflow obstruction in bronchiectasis is primarily linked to evidence of intrinsic disease of small and medium airways on CT scanning and not to bronchiectatic abnormalities in large airways, emphysema, or retained endobronchial secretions.

Imaging the airways. Hemoptysis, bronchiectasis, and small airways disease

Advances in technology have increased the contribution of radiology in understanding and evaluating diseases of the airways. In patients with hemoptysis, CT is now established as a complementary technique to bronchoscopy, or as an alternative to bronchoscopy in selected cases. The introduction of high-resolution CT has improved the detection and assessment of bronchiectasis and small airways disease, allowed better correlation between pathologic changes and radiologic appearances, and provided new insights into possible links between small airways disease and bronchial disease.

Airway obstruction in pediatric patients. From croup to BOOP

Causes for airways obstruction in infants and children vary considerably from those encountered in adult populations. The recent dissemination of rapid CT scan (helical and electron beam) has changed the diagnostic imaging approach in children with suspected airways obstruction. Fast CT scan not only detects the location of obstruction with high sensitivity but also frequently provides clues to specific pathologic diagnoses.