The diagnostic accuracy attained with the use of transbronchial fine needle aspiration biopsy, aspiration of bronchial secretion, bronchial washing, brush biopsy and forceps biopsy via a flexible fiberoptic bronchoscope was compared in patients with carcinoma of the lung. In endoscopic visible tumours the sensitivity of forceps biopsy was higher than that of the other methods. When forceps biopsy was combined with bronchial washing the overall diagnostic accuracy was significantly higher than that of any of the single methods, while no appreciable increase was obtained by adding additional methods. Selective brush biopsy from every segment bronchus has been established as a method in the search for occult bronchial carcinoma. The extent of respiratory mucosal damage and wound healing after brush biopsy was therefore studied in rabbits. Large differences in the extension and depth of the damage was observed. The basement membrane was often penetrated. Regeneration started during the first day after brush biopsy and a normal ciliated epithelium was restored within three weeks. To determine if the bronchoscope itself damaged the respiratory epithelium, bronchial mucosa was studied in the pig after examination with a flexible fiberoptic bronchoscope. The columnar epithelial cells were torn off in areas where the bronchoscope had rubbed against the airway wall but the basement membrane was not damaged. Since the function of the respiratory epithelium is to remove inhaled particles from the airways, mucociliary clearance was studied in man after fiberoptic bronchoscopy. The study suggests that the tracheobronchial clearance system has a large reserve for mechanical trauma. Mucociliary clearance can however be decreased after fiberoptic bronchoscopy in some patients. An increasing number of patients with impaired cardiopulmonary function are today subjected to examination with flexible fiberoptic broncoscopy. The haemodynamic effects of fiberoptic bronchoscopy performed under topical anaesthesia were therefore studied in patients with restrictive lung disease. The procedure induced marked haemodynamic changes during passage of the larynx and during suctioning. A slight fall in arterial oxygen tension was observed during bronchial suctioning and in the post-bronchoscopic period. Three of ten patients developed ST-T-segment changes during bronchial suctioning. / <p>S. 1-48: sammanfattning, s. 49-126: 5 uppsatser</p> / digitalisering@umu.se