Bronchiolitis and chronic lung disease

Abstract

A plea is made for the re-examination of the natural history of non-specific chronic lung disease from the viewpoint of bronchiolar pathology.

This entails first an appreciation of the normal structure and function of the bronchial tree in general, and of the small bronchioles in particular.

Summarising previous work, it is concluded that in the commoner form of respiratory tract inflammation, the bronchiolar element, acute bronchiolitis, is the significant lesion and warrants closer attention than has been given it in the past.

Permanent damage following acute bronchiolitis is extremely common, the most important sequel being bronchiolar obliteration. Some degree of diffuse bronchiolar damage, including obliteration, has been demonstrated in all adult lungs examined.

Non-specific chronic lung disease is divided into three main morphological forms: bronchiectasis, emphysema and pulmonary fibrosis. In all three forms bronchiolar damage and obliteration is extreme. Bronchiolar obliteration is regarded as the essential lesion in the pathogenesis of these conditions, the severity of the chronic lung disease being satisfyingly related to the operation of factors acting to produce long-standing bronchiolar obstruction and, therefore, obliteration.

The operation of other factors determines which of the three morphological forms will predominate, and clinically, which diagnosis will be made. In this manner the natural history of chronic lung disease can be examined as a whole, stressing the essential unity of its three morphological forms.