Big things come in small packages—Clinical use of endobronchial ultrasound

Abstract

Endobronchial ultrasound (EBUS) revolutionized bronchoscopy. It first became available for clinical use in 1999 as a mechanical radial probe and was initially used to define airway wall anatomy, but was supplanted by convex probe EBUS bronchoscopes in 2002–now the preferred initial approach for evaluation of mediastinal pathology. Radial EBUS has since proven invaluable for evaluating the peripheral lung and aiding biopsy guidance despite the limitations in ultrasound (US) propagation through air filled structures. Centrally, airways pass through the mediastinum in direct contact with the esophagus, heart, great vessels, and lymph nodes, making the mediastinum amenable to direct US imaging. However, beyond the lung hila, the airways are largely surrounded by air, generally preventing production of usable US images by halting penetration and reverberation of sound waves. The tissue mass that makes up the terminal airway walls, however, does propagate ultrasound waves before encountering reflective air. The ratio of tissue to air varies according to anatomic location and physiologic/disease state; identifying patterns in the varying ratio of tissue to air within the lungs allows the ability to distinguish normal from abnormal lung. This presentation will describe the clinical use of EBUS in modern bronchoscopy.