Accurate staging is mandatory for the management of patients with lung cancer. In particular, mediastinal lymph node staging is initiated by radiologic examinations such as chest computed tomography (CT) and positron emission tomography scan. In addition, invasive mediastinal staging is required for tissue sampling. Mediastinoscopy is still considered the gold standard for invasive mediastinal staging in patients with lung cancer.1 Complications related to mediastinoscopy are extremely low when done by experienced surgeons (morbidity, 1.5%; mortality, 0.4%).2 However, there are possibilities of major complications including bleeding from major vessels (0.1%–0.2%), tracheobronchial injury, and esophageal trauma.2
Recently, a new bronchoscopic ultrasound technology has emerged as an alternative method for surgical mediastinal staging. The convex probe endobronchial ultrasound (CP-EBUS) developed in 2002 in collaboration with Olympus Medical Systems, allows real-time EBUS-guided transbronchial needle aspiration (EBUS-TBNA) of mediastinal and hilar lymph nodes.3 EBUS-TBNA has been shown to be a minimally invasive modality for mediastinal staging in patients with lung cancer with a high diagnostic yield with a reported pooled sensitivity of 85% to 100% and pooled specificity of 100%.4–9 The CP-EBUS is a special type of bronchoscope with an ultrasound probe on the tip of a flexible bronchoscope. A dedicated transbronchial needle is used for EBUS-TBNA. Training is mandatory for performing a successful and safe EBUS-TBNA. This article explains the detailed techniques of EBUS-TBNA necessary for bronchoscopists to master this innovative procedure.
The CP-EBUS is commercially available by Olympus (BF-UC160F-OL8/BF-UC180F; Olympus Medical Systems, Tokyo, Japan) and PENTAX (EB-1970UK; PENTAX Europe, Hamburg, Germany). Currently, there is no clinical data to support the efficacy of the PENTAX EBUS scope for mediastinal staging. Therefore, this article will focus on procedures using the Olympus system. The ultrasound images are processed using an ultrasound scanner. The CP-EBUS can be attached to the dedicated ultrasound scanner (EU-C60, Olympus) and the ultrasound scanner (ProSound Alpha5; ALOKA, Tokyo, Japan). EBUS-TBNA is performed under real-time ultrasound guidance using dedicated TBNA needles. The 22-gauge and 21-gauge TBNA needle (NA-201SX-4022/NA-201SX-4021, Olympus) is dedicated for the CP-EBUS.
Ultrasound Processor (EU-C60/EU-ME1)
Patient information can be registered in the ultrasound scanner (Name, Medical Record Number, etc.). The scanning range can be changed from 2 to 9 cm depending on the target. We recommend using the 4-cm range (the default setting), as mediastinal and hilar lymph nodes as well as the major vascular structures are best visualized at 4 cm. The gain can be changed for optimal imaging and should be adjusted so that lymph nodes can be easily distinguished from vessels.
Convex Probe Endobronchial Ultrasound (BF-UC160F-OL8/BF-UC180F)
The CP-EBUS should be sterilized according to institutional and manufacture standards. The dedicated cover is used to protect the attachment to the processor. After taking the cover off, the CP-EBUS is connected to the ultrasound processor.
Attachment of the Balloon
For optimal ultrasound imaging, the latex balloon should be attached to the tip of the CP-EBUS and inflated with normal saline. A 20-mL syringe filled with saline is connected to a stopcock and an extension tube. This is connected to the balloon channel located in front of the working channel after removal of air. The balloon is then attached to the ultrasound probe by using the dedicated balloon applicator forceps. Only 0.3 to 0.5 mL of saline is necessary to inflate the balloon during the procedure. In patients with Latex allergy, the procedure can be performed without the balloon, but ultrasound imaging may not be ideal. Deformity of the airway may lead to poor ultrasound imaging without the balloon. During EBUS-TBNA, penetration of the needle through the airway may push the airway away from the probe, which will result in loss of ultrasound imaging.
Preparation of the Needle
Before the procedure, the dedicated TBNA needle and the VacLok syringe (Merit Medical Systems, UT USA) should be set for continuous negative pressure, so that it is ready for use. To avoid damaging of the channel of the bronchoscope, always confirm that the sheath adjuster knob and the needle safety lock are pulled all the way back. Make sure to feel the “click” of the needle when it is pulled all the way back inside of the sheath. The Vaclok syringe can be set to create negative pressure from 5 mL to 20 mL. We use the Vaclok syringe on 20 mL, but for some cases with hypervascular lymph nodes, TBNA is performed without suction to avoid blood contamination.
EBUS-TBNA can be performed on an outpatient basis under local anesthesia with mild conscious sedation. Midazolam (Versed; Roche Pharmaceuticals, Nutley, NJ USA) and Fentanyl (Fentanyl Citrate Injection; Baxter, Deerfield, IL USA) are given to the patient intravenously before the start of the examination. The bronchoscope is usually inserted orally, and a 2-mL bolus dose of 1% lidocaine is splayed from the larynx to the airway through the instrument channel during the procedure. Electrocardiogram, pulse oximetry, and blood pressure monitoring are required without the presence of an anesthesiologist.
Although EBUS-TBNA can be performed in an ambulatory setting under conscious sedation, some physicians prefer the use of the endotracheal tube or rigid bronchoscopy under general anesthesia. Because the EBUS-TBNA scope is larger than a regular bronchoscope, an endotracheal tube larger or equal to size 8 is required. Cough reflex is minimal under general anesthesia, which may be an advantage during the procedure.10 The limitation of the endotracheal tube is that we are limited to perform EBUS in patients who will tolerate a size 8 or larger endotracheal tube. Biopsy of the upper paratracheal lymph nodes require higher endotracheal tube placement. The use of the laryngeal mask airway has also been shown to be useful during EBUS-TBNA.10 The EBUS-TBNA scope fits easily within a #4 laryngeal mask airway.10
Insertion of the Bronchoscope
The operator must be aware of the fact that the optical system of the CP-EBUS provides an 80 degrees field of view at a 35 degrees forward oblique angle. Therefore, to obtain a straight view, the bronchoscope needs to be slightly flexed down. One should also note that the ultrasound probe attached on the tip of the bronchoscope is not visible without the inflation of the balloon. Thus, the tip should not be accidentally forced onto the airway, which may cause trauma. The endobronchial images obtained by CP-EBUS are not as clear as the conventional flexible bronchovideoscope image. Therefore, the authors prefer to examine the tracheobronchial tree using the conventional bronchovideoscope before EBUS-TBNA to look for any endobronchial abnormalities that may be difficult to detect with the EBUS scope.
After achieving local anesthesia and conscious sedation, the CP-EBUS is inserted orally into the trachea. The bronchoscope should be passed through the vocal cords by visualization of the anterior angle of the glottis. Do not force the scope into the glottis, because the tip is not visible and may cause dislocation of the cartilage. Once the bronchoscope is inside the airway, the tip should be slightly flexed down to obtain a straight view. Because of the size of the CP-EBUS, one is limited to endoscopic inspection of the airway. For the left side, the bifurcation of the upper and lower lobe bronchi, and for the right side, the bifurcation of the middle and lower lobe bronchus is the limit.
Visualization of Lymph Nodes
Once the bronchoscope is introduced into the airway until the desired position is reached for EBUS imaging, the balloon is inflated with saline to provide an ultrasonic transparent fluid coupling medium to achieve a maximum contact with the tissue of interest. For optimal imaging, ∼0.5 mL of saline is needed for mediastinal lymph nodes and 0.3 mL for hilar lymph nodes.
The tip of the CP-EBUS is flexed and gently pressed onto the airway. A two-screen display is used to provide endoscopic image of the airway and the corresponding ultrasound image underlying the tip of the bronchoscope simultaneously. By moving the tip of the CP-EBUS in small motion, the lesion of interest is localized. The tip of the bronchoscope should be carefully adjusted so that the maximum diameter of the lymph node is visualized in the center of the ultrasound image. Ultrasonically visible vascular landmarks are used to identify the specific lymph node stations according to the new International Association for the Study of Lung Cancer lymph node map (Figs. 1A, 2A).11 The Doppler mode is used to confirm and identify surrounding vessels as well as the blood flow within lymph nodes. The lymph node station, size, number, and the ultrasound characteristics of each lymph node can be recorded. Lymph nodes >1 cm in short axis, round shaped, distinct margins without the presence of central hilar structures or with the presence of coagulation necrosis sign are suspicious for malignancy and need to be biopsied.12 It is important to check the location and the size of lymph node on chest CT before the start of the EBUS-TBNA procedure (Figs. 1, 2).
Matters That Require Attention for EBUS-TBNA
Before anything, the operator needs to understand and remind themselves that the exit of the channel of the CP-EBUS is at 20 degrees with respect to the outer covering of the insertion tube.
Confirm that the needle is set and ready for EBUS-TBNA. The internal stylet should be slightly pulled out. The sheath adjuster knob should be pulled up completely and locked. The needle must be back all the way into the sheath and the safety lock secured.
The assistant and the operator should double check to verify that the needle is properly set before inserting the needle into the channel of the bronchoscope. The outer sheath of the dedicated needle is first advanced out from the channel. This must be confirmed by endoscopic images before advancing the needle. Always make sure that the sheath is visible before the needle is pushed out. If not done properly, this will result in the damage of the bronchoscope.13 Always keep the endoscopic images clear during the procedure. Always confirm proper positioning of the sheath as well as the needle inside of the lymph node during EBUS-TBNA.
Fastening the Needle
Once confirming that the needle is in the proper position (knobs secured), the dedicated TBNA needle is fastened to the working channel of the bronchoscope (Fig. 3B). The assistant should assist the operator so that the needle does not kink during this process (Fig. 3A). The tip of the bronchoscope should not be flexed to avoid damage of the channel.
Identifying the Puncture Site
Once the needle is fastened to the bronchoscope, the tip of the flexible part of the bronchoscope becomes a bit stiff. Reidentify the lesion of interest with the CP-EBUS. The bronchoscopic image of the airway should be simultaneously visualized to localize the insertion point of the needle. The tip should repeatedly be flexed up for contact for ultrasound image and down away from the airway for endoscopic visualization. Decide the point of entry using small landmarks on the airway (Figs. 1B, 2B).
Adjusting the Sheath
The tip of the bronchoscope is straightened to allow the sheath to easily come out of the channel. The sheath adjuster knob is loosened, and the length of the sheath is adjusted so that the sheath can be visualized on endoscopic image (Fig. 3C). The sheath should be adjusted by endoscopic images (Fig. 3D). The sheath should not be pushed out too far, as it will make the procedure difficult.
The tip of the bronchoscope is flexed up for contact, and the lymph node is visualized again on ultrasound image. The sheath should be visualized on the endoscopic image, and the bronchoscope should be adjusted so that the sheath is wedged in between the cartilaginous ring. After the needle adjuster is unlocked, you are ready for EBUS-TBNA (Fig. 3E). There will be resistance during penetration. Secure the needle with your fingers and advance the needle slowly (Fig. 3F). You should always have visual of the needle on the ultrasound image (Fig. 3I). The assistant should secure the bronchoscope by the patient's mouth and give a little push at the same time the operator pushes the needle out. In case a cartilage ring is encountered during TBNA, the bronchoscope is moved a little bit up or down so that the needle will go through the intercartilage space. After penetration, the internal stylet is used to clear out the internal lumen, which may become clogged with bronchial membrane (Fig. 3G). This little move is very important and has increased the yield of EBUS-TBNA significantly. The internal sheath is then removed, and negative pressure is applied with the Vaclok syringe on demand (Fig. 3H). In cases where significant blood contamination is seen within the aspirated material, EBUS-TBNA may be repeated without suction to achieve a better quality sample. The needle is moved back and forth within the lymph node (10–20 times). The Vaclok syringe is then detached from the end of the needle while the needle is still inside of the lymph node. Pull the needle back into the outer sheath until you hear the click on the needle. Lock the needle and pull the outer sheath back into the channel of the bronchoscope. Retrieve the needle for collection of the specimen.
Processing the Specimen
It is extremely important to process the specimen in a proper way to achieve maximum results. Although the EBUS-TBNA procedure can be performed successfully by following the steps explained in this article, handling of the specimen may differ between centers. However, this would depend on the cytologist or the pathologist working together with you at your endoscopy suite and thus should follow your institutional standards.
It is very helpful to have a cytologist during the procedure for rapid on-site evaluation of the aspirates. If you do not have access to a rapid on-site cytologic evaluation, three passes should be performed for each lymph node for best results. If a core is seen within the aspirate, two passes should be adequate.14
At the Division of Thoracic Surgery, Toronto General Hospital, we use the internal stylet for pushing out the specimen (Fig. 4A). The first few drops are placed on the slide glass (Fig. 4B). The material is smeared onto glass slides (Fig. 4C), and smears are air-dried and immediately stained using Diff-Quik staining (Fig. 4E) for immediate interpretation by an on-site cytopathologist to confirm adequate cell material (Fig. 4F). Furthermore, the smeared samples are fixed with 95% ethanol and Papanicolaou stain is performed. The rest of the specimen is placed in a 50-mL conical filled with normal saline for cell block preparation. The remaining specimen within the needle is washed in this conical using a 20-mL syringe (Fig. 4D).
Although many centers have adopted this new modality for lymph node staging in lung cancer, little has been described concerning the actual procedure of EBUS-TBNA.15 There are many publications related to EBUS-TBNA for lung cancer staging with a high diagnostic yield and low morbidity, but the majority of the publication comes from specialized centers.4–6,16–18 The pooled sensitivity and specificity is reported to be 85%–100% and 100%, respectively.7–9 Systematic reviews on the use of EBUS-TBNA for lung cancer staging reported only one incidence of morbidity in a patient with pneumothorax (0.07% morbidity)7 with only minor issues of agitation, cough, and presence of blood at the puncture site.9 With the spread of this technology, it is not surprising that complications may occur.19–22 EBUS-TBNA requires training to achieve high diagnostic yield with low morbidity even for physician and surgeons who have experience in conventional bronchoscopy. The learning curve of EBUS-TBNA is different from among bronchoscopists, and continuous training program will be needed for impartiality.23 In addition, the diagnostic yield is affected by both test-related factors and patient-related factors such as lymph node size and location.24 Our report should be a great help for those just starting EBUS-TBNA and also for those who have already started EBUS-TBNA.
EBUS-TBNA has now been adopted in >1300 centers around the world. EBUS-TBNA is now an established modality for mediastinal staging in patients with enlarged lymph nodes on CT or abnormal positron emission tomography scan.7–8 By expanding the use of EBUS-TBNA in the assessment of mediastinal and hilar lymphadenopathy, other possibilities of the use of EBUS-TBNA includes (1) restaging in lung cancer patients,25,26 (2) diagnosis of intrapulmonary nodule,27 (3) selection of candidates for radical radiotherapy,28 (4) mediastinal staging for metastatic lung tumors,29 (5) diagnosis of lymphoma,30,31 and (6) diagnosis of sarcoidosis.32,33
Although we are still limited to the use of a needle, microsamples obtained by EBUS-TBNA have been shown to be useful for molecular analysis.34–36 Epidermal growth factor receptor gene mutation and ALK fusion gene are biomarkers important for molecular targeted therapy.37,38 To obtain adequate sample by a nonsurgical biopsy technique for diagnosis as well as for molecular analysis in lung cancer patient will become important, because many of these patients have advanced disease at the time of first presentation. The combination of EBUS-TBNA and novel approaches in molecular analysis and biomarker assessment holds promise for enhanced diagnosis and personalized management of lung cancer.
The authors thank Dr. Shigetoshi Yoshida for providing the bronchoscopic anatomy figures and Dr. William Geddie for assistance in rapid on-site cytologic evaluation.
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