Comparison of the Thin Convex Probe Endobronchial Ultrasound Bronchoscope to Standard Endobronchial Ultrasound and Flexible Bronchoscope—A Cadaveric Study

US Respiratory & Pulmonary Diseases, 2017;2(1): Epub ahead of print

Abstract:

Background: Convex Probe Endobronchial Ultrasound (CP-EBUS) with transbronchial needle aspiration (TBNA) is used to sample mediastinal and hilar lymph nodes and is considered a gold standard for mediastinal staging of lung cancer. Current technology is limited in ability to sample lesions located away from the mediastinum. The aim of this study was to evaluate the range of a new Thin Convex Probe EBUS prototype in a cadaveric model and compare its accessibility into distal airways to that of a standard flexible and CP-EBUS bronchoscope using a cadaveric model. Methods: Three separate bronchoscopes were used and compared: standard bronchoscope (Olympus BF-H190), linear CP-EBUS bronchoscope (Olympus BF-UC180F), and the Thin CP-EBUS bronchoscope. (Olympus BF-Y0055). Each bronchoscope was inserted sequentially into a male and female cadaver. The number of bronchial generation accessible was recorded and compared using fluoroscopy. A polymer was created and inserted into various airways to simulate lesions, which were then localized and sampled. Results: The TCP-EBUS prototype demonstrated improved accessibility of distal airways when compared to CP-EBUS bronchoscope. In the male and female cadaver the TCP-EBUS bronchoscope accessed an additional generation and in most instances accessed the same distal airways as a standard bronchoscope. Conclusion: The Thin Convex Probe-EBUS bronchoscope can extend further into the distal airways than the traditional CP-EBUS bronchoscope and can achieve a reach similar to a standard bronchoscope, thus allowing the potential to bring real-time biopsy capability to areas of the lung that currently cannot be reached by standard Convex Probe-EBUS.
Keywords: Endobronchial ultrasound, convex probe, thin convex probe, bronchoscopy, cadaver
Disclosure: Nichole T Tanner is currently receiving grant funding and consulting fees from Olympus America, Inc. and Cook Inc. Alexander Chen is currently receiving research funding and consulting fees from Olympus America, Inc. Gerard A Silvestri and Nicholas J Pastis are currently receiving grant funding from Olympus America, Inc. Sean P Callahan and Thierry Bacro have no conflict of interest or source funding to declare. The abstract was presented at Advancements in Lung Cancer Diagnostics and Treatment Session; American College of Chest Physicians Chest Annual Meeting 2016; Chest. 2016;150(4_S):979A.

Compliance with Ethics: All procedures were performed under the guidance of the institutional review board of the Medical University of South Carolina (Pro#37817).


Authorship: All named authors meet the International Committee of Medical Journal Editors (ICMJE) criteria for authorship of this manuscript, take responsibility for the integrity of the work as a whole, and have given final approval to the version to be published.

Received: October 17, 2016 Accepted December 13, 2016
Correspondence: Sean P Callahan, Medical University of South Carolina, 96 Jonathan Lucas Street, CSB 816, MSC 630, Charleston, South Carolina 29425, US. E: callahse@musc.edu
Support: The study was supported by a grant from Olympus America, Inc.
Open Access: This article is published under the Creative Commons Attribution Noncommercial License, which permits any noncommercial use, distribution, adaptation, and reproduction provided the original author(s) and source are given appropriate credit.

Assessment of peripheral pulmonary nodules and mediastinal lymph nodes is critical in the diagnosis and staging of lung cancer, which is the leading cause of cancer death worldwide.1,2 Endobronchial ultrasound (EBUS) continues to evolve, allowing clinicians the ability to evaluate peripheral and central pulmonary lesions as well as various layers of bronchi. Current EBUS bronchoscopes are larger and less maneuverable than a standard bronchoscope, which limits their ability to access certain regions of the lung.

Convex probe endobronchial ultrasound (CP-EBUS) with transbronchial needle aspiration (TBNA) is used to sample mediastinal and hilar lymph nodes and is considered a first-line test for mediastinal staging of lung cancer.3 It is an effective, safe, and minimally invasive procedure, which can also diagnose sarcoidosis and lymphoma.4,5 While CP-EBUS provides access to mediastinal nodes and centrally located pulmonary lesions, it is limited in its ability to sample lesions located more distal to the central airways. A 35° forward oblique direction of view, the diameter of the scope, and the inability to flex the scope at an acute angle make it particularly difficult for the CP-EBUS bronchoscope to navigate into the upper lobes and the narrow right middle lobe (RML) orifice.6 An alternative to the CP-EBUS is radial EBUS (r-EBUS), which can reach the periphery of the lung; however, lack of ‘real-time’ ultrasound during needle puncture is a limiting factor.

These limitations led to the development of the thin CP-EBUS (TCP-EBUS) (OLYMPUS MEDICAL SYSTEMS CORP, Tokyo, Japan) to perform real-time

EBUS-TBNA at and around segmental bronchi. The TCP-EBUS scope has a more favorable forward oblique direction of view (20°), a smaller diameter distal tip, and greater range of angulation than traditional CP-EBUS. This technology was previously tested in a porcine model and demonstrated improved accessibility to peripheral bronchi and capability of sampling segmental lymph nodes.7 A recent study assessed the effectiveness of performing both an airway inspection and TBNA of mediastinal, hilar and proximal parenchymal lymph nodes using a similar hybrid thin EBUS model. In this randomized, controlled human trial, a modified CP-EBUS bronchoscope with smaller diameter distal tip, wider angle of flexion and better direction of view, could provide better visualization of lung segments and allow for fewer bronchoscopes when performing a myriad of procedures.8

We undertook this study to further evaluate the TCP-EBUS prototype in a cadaveric model to objectively document the endobronchial territory it can access and compare it to that of the current CP-EBUS and standard sized diagnostic flexible bronchoscope.

Methods

Two cadavers of differing sizes, one male and female, embalmed with Carolina Perfect Solution® (Carolina Biological Supply Co., Burlington, NC) were secured through the Medical University of South Carolina (MUSC) Center for Anatomical Studies and Education and were used for the purposes of this experiment. Cricothyrotomy with 8 mm endotracheal tube placement was performed on both to access the airways. Bag mask ventilation was then used to re-inflate the lungs. A standard flexible bronchoscope was introduced and therapeutic suction of secretions performed.

Three separate bronchoscopes were used for this experiment: standard bronchoscope (BF-H190, OLYMPUS MEDICAL SYSTEMS CORP, Tokyo, Japan), linear CP-EBUS bronchoscope (BF-UC180F OLYMPUS MEDICAL SYSTEMS CORP, Tokyo, Japan), and the TCP-EBUS bronchoscope (BF-Y0055, OLYMPUS MEDICAL SYSTEMS CORP, Tokyo, Japan). The TCP-EBUS bronchoscope has a 5.9 mm distal tip, 5.7 mm insertion tube, 170° angle of flexion and 20° direction of view as compared to that of the CP-EBUS bronchoscope (6.9 mm, 6.3 mm, 120° and 35°) and standard flexible bronchoscope (5.5 mm, 5.1 mm, 210° and 0°), respectively (see Table 1).Figure 1 shows the CP-EBUS bronchoscope next to the TCP-EBUS bronchoscope. Each of the three bronchoscopes (without needles in the working channel) was then inserted sequentially into the following locations: left upper lobe (LUL), left lower lobe (LLL), right upper lobe (RUL), right middle lobe (RML), and right lower lobe (RLL). The number of bronchial generations accessible starting with the carina as the first was recorded. Fluoroscopy was performed at the most distal generation. The cadavers and fluoroscopy arm were kept stationary without change in position throughout the entire procedure.

A barium polymer was created using 5% (by weight) barium sulfate in powder form added to an aqueous solution of 10% (by weight) bovine skin gelatin (Sigma-Aldrich, St. Louis, MO) and 2% agar (Sigma-Aldrich, St. Louis, MO) and heated to 90°C during mixing and was maintained as a solution at 45–50°C prior to injection. Approximately 3 ml of the polymer was then instilled into cadavers in a third-generation airway using a therapeutic bronchoscope (Olympus BF-1TH190) and Guide Sheath (Olympus K-203). The airways chosen to place the polymer were based on locations that are difficult to reach with conventional CP-EBUS. The barium polymer was placed in the anterior segment of the RUL (RB3) in the male cadaver and lateral basal segment of LLL (LB9), anterior segment of RUL (RB3), medial segment of RML (RB5) and medial basal segment of RLL (RB7) in the female cadaver. The TCP- EBUS bronchoscope was then inserted into the airways and used to observe the lesion endobronchially, as well as assess it via ultrasound if possible. A 22-gauge Olympus Vizishot needle was deployed into the lesion to observe access with EBUS. The purpose of placing the polymer in the airway to was to view it endobronchially. Assessing sample obtained from the polymer was beyond the scope of this study.

The institutional review board at the Medical University of South Carolina approved this study (Pro# 37817).

References:
1. Gould MK, Donington J, Lynch WR, et al., Evaluation of individuals with pulmonary nodules: when is it lung cancer? Diagnosis and management of lung cancer, 3rd ed: American College of Chest Physicians evidence-based clinical practice guidelines,Chest, 2013;143:e93S–120S.
2. Ferlay J, Soerjomataram I, Dikshit R, et al., Cancer incidence and mortality worldwide: sources, methods and major patterns in GLOBOCAN 2012, Int J Cancer, 2015;136:E359–386.
3. 3. Silvestri GA, Gonzalez AV, Jantz MA, et al., Methods for staging non-small cell lung cancer: Diagnosis and management of lung cancer, 3rd ed: American College of Chest Physicians evidencebased clinical practice guidelines, Chest, 2013;143:e211S–250S.
4. Gupta D, Dadhwal DS, Agarwal R, et al., Endobronchial ultrasoundguided transbronchial needle aspiration vs conventional transbronchial needle aspiration in the diagnosis of sarcoidosis, Chest, 2014;146:547–56.
5. Grosu HB, Iliesiu M, Caraway NP, et al., Endobronchial Ultrasound Guided Transbronchial Needle Aspiration Accurately Diagnoses and Subtypes Lymphoma, Ann Am Thorac Soc, 2015;12(9):1336–44.
6. Kang HJ, Hwangbo B, Technical aspects of endobronchial ultrasound-guided transbronchial needle aspiration, Tuberc Respir Dis (Seoul), 2013;75:135–9.
7. Wada H, Hirohashi K, Nakajima T, et al., Assessment of the new thin convex probe endobronchial ultrasound bronchoscope and the dedicated aspiration needle: a preliminary study in the porcine lung,J Bronchology Interv Pulmonol, 2015;22:20–7.
8. Yarmus L, Akulian J, Ortiz R, et al., A randomized controlled trial evaluating airway inspection effectiveness during endobronchial ultrasound bronchoscopy,J Thorac Dis, 2015;7:1825–2.
9. Memoli JS, El-Bayoumi E, Pastis NJ, et al., Using endobronchial ultrasound features to predict lymph node metastasis in patients with lung cancer, Chest, 2011;140:1550–6.
10. Ost DE, Ernst A, Lei X, et al., Diagnostic Yield and Complications of Bronchoscopy for Peripheral Lung Lesions: Results of the AQuIRE Registry, Am J Respir Crit Care Med, 2016 Jan 1;193(1):68–77.
11. Rivera MP, Mehta AC, Wahidi MM, Establishing the diagnosis of lung cancer: Diagnosis and management of lung cancer, 3rd ed: American College of Chest Physicians evidence-based clinical practice guidelines,Chest, 2013;143:e142S–165S.
12. Silvestri GA, Vachani A, Whitney D, et al., A Bronchial Genomic Classifier for the Diagnostic Evaluation of Lung Cancer, N Engl J Med, 2015;373:243–51.
Keywords: Endobronchial ultrasound, convex probe, thin convex probe, bronchoscopy, cadaver