Endobronchial Ultrasound via the Fiberoptic Bronchoscope

Abstract

Flexible fiberoptic bronchoscopy (FFB), introduced by Ikeda in the late 1960s, dramatically improved the potential for diagnosing lung lesions. 1 Since that time, FFB has been utilized for numerous therapeutic and diagnostic indications. One of the most important uses of FFB is to obtain tissue to evaluate suspicious mediastinal and parenchymal lung lesions by transbronchial biopsy or transbronchial needle aspiration (TBNA). 2-5 Although the FFB allows the operator to place biopsy forceps or needles in close proximity to paratracheal or parabronchial lesions, the yield of these procedures depends on several factors, including the expertise of the bronchoscopist, size of the lesion, rapid cytopathological interpretation, and ability to adequately localize the abnormality by imaging techniques such as chest radiographs, computed tomography (CT) scanning, and fluoroscopy. It is therefore not surprising that the reported diagnostic yield of these procedures is quite variable. For example, in assessing suspicious mediastinal lesions, TBNA has been reported to have a diagnostic yield ranging from 38 to 90%. 6,7 Accordingly, methods to improve the overall diagnostic yield and accuracy of these procedures is appropriate.The use of ultrasound imaging to visualize the lung and mediastinum by a transcutaneous or transesophageal approach has been proposed as a potential adjunct to methods such as fluoroscopy and CT scanning. 8-12 These techniques are of limited value, however, due to anatomic constraints and the inability to image across the air interface of the lung. Recent studies have shown that endobronchial ultrasound via the FFB using miniature ultrasound probes is feasible and of practical value in the guidance of bronchoscopic biopsies. 7,[13][14][15] This chapter will review the current technology, hardware, and techniques employed to perform endobronchial ultrasound. The results of recent studies and the benefits of and problems with this new technology as well as potential future applications will be discussed. BRONCHOSCOPY WITHOUT ULTRASOUND GUIDANCEIn 1949 Schieppati used rigid bronchoscopy to sample mediastinal lymph nodes with a rigid needle. 16 Because of the limitations of the rigid needle, new methods were sought to improve the ability to reach all mediastinal nodal stations. In 1983, Wang and Terry introduced a 21-gauge flexible needle that could be used with the FFB. 17 This greatly enhanced the ability of the bronchoscopist to sample mediastinal lymph nodes. With the flexible needle, the bronchoscopist can readily biopsy paratracheal and parabronchial lymph nodes that are not within the reach of rigid needles. Furthermore, the procedure can be performed without overnight hospitalization or general anesthesia. Despite the added capabilities of the flexible needle, the reported sensitivity of mediastinal TBNA varies widely from center to center. It is likely that the low sensitivity of TBNA at some centers reflects a poor understanding of the anatomic relationships of the mediastinal structures, a lack of...