NEW YORK, (Reuters Health) – Quantitative and morphological analyses of the vascular bed in bronchial biopsy specimens from 20 asthmatic and 20 nonasthmatic patients have revealed significant differences.
The bronchial lamina propria of asthmatics contains a greater number of vessels occupying a larger percentage of vascular area than nonasthmatics, Dr. Gastone Salvato of General Hospital, Merano, Italy reports in the journal Thorax for December.
A correlation between the number of vessels and disease severity was clearly evident in this study. Patients with severe asthma had a greater number of vessels but not a larger vascular area than patients with mild or moderate asthma. ["This suggests that the inflammatory process underlying severe asthma induces growth of new vessels which, however, remain so small that they do not significantly enlarge the vascular area," Dr. Salvato writes.
"Asthmatic capillaries and venules had edematous walls and thickening of the subendothelial basement membrane," the researcher reports, "often with fibrohyalinosis of the walls." Intense intravascular eosinophil recruitment, activation, and lysis, commonly seen in asthmatics, "are possible factors in the severity of vascular wall changes," Dr. Salvato says.
To Dr. Salvato's knowledge, an additional finding of muscular formations protruding into the arterial lumen in four asthmatics and one nonasthmatic has not been reported before. These structures "presumably help to regulate distribution of blood to the tissues to enable them to adapt functionally," he writes. This "hypothetical regulatory activity" may be impaired in asthmatics, according to the researcher.