Subepithelial Microvasculature in Large Airways Observed by High-Magnification Bronchovideoscope

Abstract

The bronchial vasculature serves important functions and is modified in a variety of pulmonary and airway diseases. The remarkable ability of the bronchial vasculature to undergo remodeling has implications for disease pathogenesis. However, there is very little information on normal bronchial circulation. The aim of this study was to obtain information on bronchial microvessels in large airways using a high-magnification bronchovideoscope. Recently, we developed a high-magnification bronchovideoscope (XBF-200HM3 [side-viewing type]) in cooperation with Olympus Medical Systems. This bronchovideoscope can provide information on the bronchial mucosa with a maximum magnification of 110 times. Between August 2000 and July 2004, 26 patients without abnormalities in the large airways were enrolled into this study. Patients underwent conventional bronchoscopy and subsequent bronchoscopy with the high-magnification bronchovideoscope. After the bronchoscopic examination, we calculated the vessel area ratios and hemoglobin indexes of images made with the high-magnification bronchovideoscope by using appropriate software. In addition, we compared the findings obtained with the high-magnification bronchovideoscope of the 26 subjects with microscopic findings of autopsied tracheas of two patients without abnormalities. Many ramifying subepithelial microvessels of large airways were mainly observed in intercartilage and membranous portions, whereas only a few microvessels were seen in cartilage portions. Histologically, these subepithelial microvessels were thought to be distributed within approximately 800 and 500 microm beneath the surface of the intercartilage portions and membranous portions, respectively. Vessel area ratios of the intercartilage portions were significantly higher than those of the cartilage and membranous portions. The hemoglobin indexes of the intercartilage portions were significantly higher than those of the cartilage and membranous portions, and these indexes were also significantly higher in the membranous portion than in the cartilage portion. A dense concentration of subepithelial microvessels was mainly observed in the intercartilage portion, indicating an increase in submucosal circulation. This high-magnification bronchovideoscope is a useful tool for observing and evaluating the subepithelial microvessels in large airways.