THE SIGNIFICANCE OF PULMONARY VASCULAR CHANGES IN EMPHYSEMA

Summary Observations on the morphology of vascular changes in emphysema and related conditions are presented, with particular emphasis on those in the pulmonary and bronchial arteries. These observations indicate that the sclerosis of the small arteries in emphysema results from organization of thrombi, this thrombosis being precipitated by the cause of the inflammation of the adjoining air passages producing some degree of damage to the arterial wall. In early generalized emphysema pulmonary arterial sclerosis is found predominantly in the small arteries adjoining terminal and respiratory bronchioles; in these early lesions inflammatory damage is largely confined to these bronchioles. It is emphasized that sclerosis of the smaller pulmonary arteries is not directly proportional to the degree of inflammatory damage to bronchioles. The relation between the two, particularly in early or mild cases, varies within wide limits. It is pointed out that the significance of pulmonary arterial sclerosis as one factor in the genesis of pulmonary hypertension has not yet been accurately assessed, since morphological studies of this subject have been limited and the widespread complete arterial obliteration that occurs in chronic inflammatory disease of the lungs has not been adequately recognized. Observations on the bronchial arteries in emphysema and on the development of anastomoses between these vessels and pulmonary arteries indicate that these last develop from the minute vessels in organizing tissue in inflammatory areas. Where a “demand” for nutriment continues, the vessels enlarge. Such vessels are bronchial in origin; and where the wall of a pulmonary vessel has been involved, an anastomosis arises. The vascular changes observed in emphysema are not of great ætiological importance but are the incidental concomitant of earlier general connective tissue changes in the region. As happens in all parts of the body, the vessels are necessarily involved in any connective tissue disturbance. At the same time sclerosis and particularly obliteration will limit the nutrition of tissues depending on them. The vascular phenomena therefore are important in that, by their presence, they support the hypothesis propounded, as the result of observations of the bronchioles and related structures, that emphysema is intimately related to and develops as the result of previous damage to and chronic inflammatory changes in the bronchioles and proximate pulmonary tissues.