A Pilot Study of the Feasibility of Confocal Endomicroscopy for Examination of the Human Airway

Background Traditional methods of evaluating human airway histology, such as surgical biopsy or endobronchial biopsy, are limited by the risks associated with these tissue-sampling procedures. Objective The purpose of this study was to develop and evaluate the first confocal endomicroscope for real-time, in vivo imaging of human respiratory mucosa in a clinical setting. Methods A confocal endomicroscope prototype was designed using Pentax bronchoscope parts (EB1970K). Airways of adult patients (N=5) undergoing rigid bronchoscopy for various clinical indications were imaged with the confocal endomicroscope after intravenous administration of fluorescein sodium. The device was introduced into the airways through the rigid bronchoscope. Images were collected from the trachea, primary and secondary carinae, and any endobronchial mass. The images were compared with those obtained from histologic sections from conventional endobronchial biopsies. Results Confocal endomicroscopy provided real-time images of the cellular and subcellular structures of the respiratory mucosa and submucosa in vivo. The pseudostratified columnar epithelium (including columnar cells and goblet cells) could be visualized. Images obtained at increasing depth showed the lamina propria and microvasculature. Longitudinal folds in the mucosa enabled imaging in cross-section, showing alignment of epithelial cells along the basement membrane and cilia on the surface of the cells. Below the epithelium, the smooth muscle could be identified. In images from a patient with an endobronchial adenocarcinoma, confocal imaging could distinguish between a normal airway epithelium and malignant tissue. Conclusions Confocal endomicroscopy is a feasible method for analyzing human airway wall architecture and endobronchial abnormalities in histologic detail in vivo.