Atelectatic bronchus refers to a bronchus that appears narrowed or collapsed, without an obvious cause, when visualized by bronchoscopy. This phenomenon is different from the commonly observed generalized collapse of the membranous portion of the tracheobronchial tree during expiratory phase of respiration in patients with severe obstructive airways disease. An isolated atelectatic or collapsed bronchus is frequently encountered during bronchoscopy. This finding is usually observed in the segmental and subsegmental bronchi. Bronchial atelec-tasis can be partial or complete. In many circumstances, such atelectases are nonpathologic and represent physiologic collapse or narrowing of bronchi during end-expiratory phase of breathing. The main factors that contribute to this occurrence during bronchoscopy include hypoventilation from sedation and diminished lung volumes in supine posture. The physiologic atelectasis is easily reversed by instructing the patient to inhale deeply. This maneuver, described as "dynamic" bronchoscopy, leads to the opening of the bronchus to its maximal diameter and enables the bronchoscopist to insert the bronchoscope farther into the airways.
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