An alternative bronchoscopic transparenchymal nodule access by “invisible tunnel” technique under electromagnetic navigation without the transbronchial access tool

Abstract

Background

The diagnosis of peripheral pulmonary lesions (PPL) is still challenging. We describe a novel method for sampling PPL without bronchial signs by creating invisible tunnel under electromagnetic navigation without the transbronchial access tool (TABT).

Methods

During electromagnetic navigation, we adjust the angle of the edge extended working channel catheter based on the real-time position of the lesion in relation to the locating guide rather than preset route. A biopsy brush or biopsy forceps is used to punch a hole in the bronchial wall. A locating guide is then re-inserted to real-time navigate through the lung parenchyma to the lesion. Safety and feasibility of this method was analyzed.

Results

A total of 32 patients who underwent electromagnetic navigation bronchoscopy were retrieved. The mean size of the lesion is 23.1 mm. The mean operative time of all patients was 12.4 min. Ten of the patients did not have a direct airway to the lesion, thus creating an invisible tunnel. For them, the length of the tunnel from the bronchial wall POE to the lesion was 11–30 mm, with a mean length of 16.9 mm and a mean operation time of 14.1 min. Adequate samples were obtained from 32 patients (100%), and the diagnostic yield was 87.5% (28/32). Diagnostic yield of with create the invisible tunnel TBAT was 90% (9/10), and one patient undergone pneumothorax after operation.

Conclusions

This method is feasible and safe as a novel approach sampling pulmonary lesions without bronchial signs, and it further improves current tunnel technique.

Introduction

Clinical practice has shown an increase in the detection of peripheral pulmonary lesions (PPL), but their diagnosis is still challenging [1]. The emerging bronchoscopy technique offers a more accurate approach to the localization of lung lesions [2]. Several studies have demonstrated that the biopsy yield of bronchoscopy is related to the size of the lesion, distance from the hilum, and radial endobronchial ultrasound (R-EBUS), and the positive of bronchial signs [3, 4]. Bronchoscopic transparenchymal nodule access (BTPNA), also known as the tunnel technique, establishes a "tunnel" from the bronchial wall to the lesions through a transparenchymal approach, which is better for approaching lesions without bronchus sign [5]. There are currently two available methods of BTPNA under electromagnetic navigation.

The first is combined with the larger Archimedes platform (Broncus Medical, Inc, San Jose, California, USA), which calculates a suitable point of entry (POE) locations with a straight line, vessel-free access to the lesion, as well as bronchoscopy paths for guiding the bronchoscope to the POE locations [6]. Within the visualization of the bronchoscope, the puncture needle creates a POE in the airway wall, which is dilated by a balloon catheter [5]. The sheath with blunt stylet, then guided by electromagnetic navigation through the parenchymal tissue, advanced in a straight tunnel to the lesion, and the position was confirmed under fluoroscopy [5]. It can theoretically reach even very peripheral lesions so long as a tunnel is long enough. However, a longer tunnel means more damage to the lung parenchyma during positioning, and it may sometimes be difficult to avoid large vessels. Two patients (17%) participating in BTPNA in the Herth et al. study were unable to complete the operation due to the inability to establish an avascular route [5]. In addition, setting POE in the central airway often exacerbates the risk of infection and fistulae.

Another is to create an “invisible tunnel” with the transbronchial access tool (TBAT), which is part of the CrossCountry/Super Dimension system (Medtronic, Minneapolis, Minnesota, USA) [7]. According to a virtual navigation pathway generated by the SuperDimension system, a guidewire needle punctures the bronchial wall creating an entry point, and a cone-shaped dilator catheter is advanced over the guidewire toward the target lesion through the edge extended working channel (EWC) catheter [2]. However, it may not be helpful when the lesion is in the superior segment in an extreme posteromedial location or apical posterior segment of the upper lobe [8]. The EWC catheter would straighten as soon as the TBAT was deployed, thus deflecting the catheter enough to miss the entry point [8]. Three patients (21%) participating in TBAT in the Bowling et al. study were unable to complete the operation due to missing the entry point [7].

In this article, we report an alternative method that establishes an "invisible tunnel” based on electromagnetic navigation without TBAT. This method adjusts the angle of the EWC catheter based on the real-time position of the lesion in relation to the locating guide (LG) rather than a preset virtual pathway. A biopsy brush or biopsy forceps is used to punch a hole in the bronchial wall. A locating catheter is then inserted in a fixed EWC catheter to real-time navigate through the lung parenchyma to the lesion.

Methods

Study design and participants

A single-center retrospective study was conducted on patients who underwent electromagnetic navigation bronchoscopy in The First Hospital of Zhejiang University from June 2021 to January 2022. Inclusion criteria included: (a) patients > 18 years of age and (b) chest CT showed a peripheral lung lesion requiring sampling; Exclusion criteria included: (a) patients in poor general condition and unable to bronchoscopy under heavy sedation or general anesthesia; (b) uncorrectable coagulopathy or bleeding; and (c) any other severe or life-threatening comorbidity. The study was conducted in accordance with the Declaration of Helsinki (as revised in 2013). This study was approved by the Ethics Committee of the First Affiliated Hospital of Zhejiang University School of Medicine (No. 2022–710).

Procedure

Lesions marking

All patients were admitted for suspected lung cancer, and preoperative thoracic high-resolution CT was refined. Import the patient's resulting images into the SuperDimension navigation system 7.0 (Medtronic; Inc.) for virtual 3D model construction and route creation. Mark the lesion with a green sphere and determine the approximate virtual route before the procedure.

Fast navigation

An electromagnetic field is generated around the chest of a patient with tracheal intubation under general anesthesia to reconstruct a 3D real-time image of the bronchial airways. Transnasal bronchoscopy (Olympus^™, OD 4.2 mm, ID 2.8 mm) is recommended over transoral bronchoscopy because it is more conducive to catheter fixation. A navigation catheter (combining a 180° or 90° angle EWC catheter and a LG catheter) is inserted into the bronchoscope's working channel to reach the peripheral airway near the lesion or the lesion that the bronchoscope cannot reach.

Actual POE and accurate navigation

For the lesions without bronchial sign, POE and tunnel are required to reach the lesion. Unlike the previous method [5, 9] the actual POE into the airway wall in our method depends on the real-time position of the lesion in relation to the navigation catheter (EWC/LG). When the green sphere appears semi-floating, the navigation catheter and the lesion are at the same level. The navigation catheter is adjusted until its tip points towards the center of the sphere, which is the actual POE.

Secure the EWC catheter and after R-EBUS has confirmed the absence of blood vessels, gently puncture the terminal bronchial wall with a brush or biopsy forceps to create a POE. Afterward, biopsy forceps or brushes are withdrawn from the EWC catheter. The LG is inserted for blunt separation, slightly adjusting the depth and angle to navigate to the lesion in real time (Fig. 1) and reconfirmed with R-EBUS (combined with X-ray fluoroscopy or cone–beam CT-guided positioning if conditions permit) (Fig. 2).

Fig. 1

ENB image before (a) and after (b) establishing invisible tunnel

Fig. 2

R-EBUS image of peripheral pulmonary lesion after successful invisible tunnel technique without TBAT

Sampling the lesion

Target the lesion and extend the biopsy forceps or brush into the EWC catheter for brushing or biopsy. The operation was terminated if a rapid on-site examination (ROSE) demonstrated a diagnostic result. Non-diagnostic ROSE requires re-positioning and sampling. The choice of biopsy tool depends on a number of different factors, including the proximity of the lesion to blood vessels and the pleural surface.

Data collection

The following data were retrieved from the hospital electronic medical record system and the super dimension system: patient’s demographics, lesion characteristics (maximum diameter, location, and imaging), lesion access time, biopsy yield, diagnostic yield, and adverse events. Lesion arrival time is defined as the time between the completion of registration and the first targeting of the lesion.

The biopsy yield was defined as the number of subjects who obtained sufficient samples divided by the percentage of subjects who attempted this method. A diagnosis is positive if a specific diagnosis (e.g., cancer, tuberculosis, and fungus) is obtained from the sample. In addition, patients with a non-specific diagnosis (e.g., inflammation) are followed up for at least 6 months. Lesions that regress or remained unchanged during follow-up are also considered to have a positive diagnosis.

Statistical analysis

Continuous variables are summarized as mean, standard deviation, and other relevant statistical summaries. If the results were not normally distributed, the median and quartiles were reported. Changes in continuous variables were assessed using paired or unpaired Student's t tests, as appropriate. Ratios were expressed as percentages, and CIs for proportions were calculated using the exact binomial distribution.

Results

Basic characteristics of patients

A total of 32 patients who underwent electromagnetic navigation bronchoscopy were retrieved. The mean age of them 58 years. Fifteen (47%) of them reconfirmed the location with r-EBUS during the precede. The mean size of the lesion is 23.1 mm in long axis diameter. The mean operative time of all patients was 12.4 min. Ten of the patients did not have a direct airway to the lesion, thus creating an invisible tunnel. For them, the length of the tunnel from the bronchial wall POE to the lesion was 11–30 mm, with a mean length of 16.9 mm and a mean operation time of 14.1 min. The mean distance from the POE location to the pleura was 29.4 mm. The basic characteristics of patients are shown in Tables 1 and 2.

Table 1 Characteristics of patients with available demographic data in all case

Table 2 Characteristics of patients with available demographic data in cases with the invisible tunnel

Feasibility and safety

Adequate histological sampling sufficient for a histological diagnosis was successfully achieved in all patients. In addition, histology of the biopsy and r-EBUS demonstrated the accuracy of localization. Among all the patients, nineteen patients were diagnosed with adenocarcinoma of the lung. Thirteen patients were diagnosed with chronic inflammation of the lung tissue (two of them with granulomatous inflammation), and 9 patients had lesions that regressed or remained unchanged during the subsequent 6-month follow-up. Of the remaining four patients, two patients did not complete the review and lost contact, while two patients developed enlarged lesions. In patients with invisible tunnels, the total diagnostic yield was 90% (9/10), with a malignant diagnosis yield of 60% (lung adenocarcinoma) and a benign diagnosis yield of 30% (one with granulomatous inflammation). One patient with invisible tunnel developed pneumothorax after the biopsy operation, and the remaining patients were not found to have any adverse events, such as bleeding, pneumothorax, and infection intraoperatively or postoperatively. The feasibility and safety of the procedure are shown in Tables 3 and 4

Table 3 Safety and feasibility of the procedure in all cases

Table 4 Safety and feasibility of the procedure in cases with the invisible tunnel

Discussion

The appearance of BTPNA has improved the diagnosis of peripheral pulmonary lesions of the bronchoscopic approach by breaking the limitations of previous techniques that were dependent on the airway leading to the lesion. We report the first case series on using ENB-guided BTPNA without TBAT for the biopsy of the pulmonary lesion (Schematic diagram of our method is shown in Fig. 3). Ten patients did not have a direct airway to the lesion and therefore an invisible tunnel was created using our method. The procedure was successfully performed in them, and a diagnosis was made. One complication, a pneumothorax, occurred and required minimal intervention.

Fig. 3

Procedure of invisible tunnel technology without TBAT

The highlight of BTPNA is to preset and successfully establish a suitable tunnel path to target the lesion. Traditional BTPNA sometimes makes it difficult to preset tunnels avoiding large vessels. TBAT combined with a finer OD (1.9 mm) EWC allows access to more peripheral bronchi, alleviating this problem. However, the stiff TBAT will stretch the EWC catheter to change the direction that hard to achieve the preset route. It occurs when the lesions are in a special location (in the superior segment in an extreme posteromedial location or apical posterior segment of the upper lobe) or if the virtual pathway to the target is at a severe angle.

The practical foundation for our method is reliable electromagnetic navigation technology and familiarity with the anatomical features of the bronchoscopic route of the lesion. There are two main differences from the previous BTPNA. First, we use biopsy forceps or biopsy brushes rather than TBAT to create POE. The soft metal wire of the biopsy forceps or biopsy brush does not affect the orientation of the fixed EWC catheter when creating POE. During initial operation, it is reasonable to assume that a puncture needle is safer than biopsy forceps or a biopsy brush. However, the biopsy needles used for ultrasonographic mediastinal lymph node puncture were not long enough to reach PPL. In addition, the biopsy needle has a small aperture that makes it difficult to insert an LG catheter for blunt dissection. Second, instead of relying on a preset virtual path, we establish the tunnel and POE based on the real-time position of the navigation catheter (EWC/LG) in relation to the lesion during ENB navigation, which requires an experienced and skillful operator. As previously reported, TBAT sets the POE in the bronchial wall 1–2 cm from the lesion. Based on real-time navigation, for specific lesions, we chose to punch a little further away from the lesion (approximately 2.5 cm), thus avoiding excessive bending of the EWC. TBAT utilizes a vertical puncture needle to establish the tunnel and therefore does not allow the actual POE to be offset from the virtual point.

Nevertheless, our method allows POE to be slightly offset to the right. On withdrawal of the biopsy forceps and biopsy brush and reinsertion of the LG for blunt separation, minor adjustments can be made to the orientation and depth to reach the lesion again based on the real-time ENB navigation. This also provides greater assurance of the accuracy of the final positioning. Moreover, performing ROSE improves the diagnostic rate, shortens the duration of the procedure, and reduces sampling, thus preventing complications that may occur due to prolongation of the procedure. Hemorrhage and pneumothorax are the main adverse events of this method. R-EBUS confirmed the absence of large blood vessels before creating a POE, while LG bluntly separates to build a tunnel, both reducing the risk of hemorrhage. One patient developed a pneumothorax after biopsy, which may be related to the location of the lesion close to the pleura.

In addition, we used biopsy forceps and biopsy brushes in the collection of the specimens and did not use lavage. In retrospect, considering that some cases were diagnosed as inflammatory lesion, we believe that lavage of the specimen and obtaining the result of next-generation sequencing (NGS) or general bacterial culture can help to improve the diagnostic yield and contribute to precise treatment.

Strengths and limitations

We report the first case series on using ENB-guided BTPNA without TBAT for the biopsy of the pulmonary lesion without bronchial signs, which improves to some extent on previous BTPNA. The patient inclusion criteria were relatively strict and the yield was sufficient to demonstrate the feasibility of the method. There are also some limitations of our method. It requires an experienced and skillful operator. In addition, this study is a small, single-center retrospective study and there may be selection bias.

Conclusions

Our method is feasible and safe as a novel approach to sampling pulmonary lesions without bronchial signs, and it improves current tunneling techniques. Innovative bronchoscopic techniques continue to evolve, allowing precise access to peripheral lung lesions and improving diagnosis yield, which deserves further study.