Structural characterization of bronchial mucosal biopsies from healthy volunteers: a light and electron microscopical study.

Bronchial mucosal biopsies were collected by flexible fibreoptic bronchoscopy (FFB) from normal healthy volunteers. The volunteers were not receiving any medication and had been free from respiratory infection for at least five weeks prior to the bronchoscopy. Biopsies with a minimum of 115 microns of undamaged perpendicularly sectioned epithelium were investigated by light and transmission electron microscopy. The height of the epithelium varied between 22-62.5 microns, with a median value of 41.5 microns. The volume density of the various epithelial cells in relation to the total epithelium was 61% for the ciliated and non-ciliated, non-secretory luminal cells, 6% for the goblet cells and 32% for the basal cells. The width of the lamina reticularis of the basement membrane ranged between 3-17.5 microns, with a median value of 8.5 microns. Blood vessels occupied 2.8% of the subepithelial tissue. Only a few inflammatory cells were seen in the connective tissue, volume density occupied by lymphocytes and polymorphonuclear granulocytes, 0.6% and 0.2% respectively. This study shows that structural damage is a common finding in biopsies collected by FFB. Mechanical damage of bronchial biopsies caused by the forceps should be considered before alterations in the epithelium are attributed to pulmonary disease.