Intraprocedural CT guided Navigation with Ventilatory Strategy for Atelectasis (ICNVA): a modified electromagnetic navigation bronchoscopy

doi:10.21203/rs.3.rs-3898037/v1

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Intraprocedural CT guided Navigation with Ventilatory Strategy for Atelectasis (ICNVA): a modified electromagnetic navigation bronchoscopy

https://doi.org/10.21203/rs.3.rs-3898037/v1

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Background: CT-body divergence limits the accuracy of electromagnetic navigation bronchoscopy (ENB) in peripheral lung lesions diagnosis. We developed intraprocedural CT guided Navigation with Ventilatory Strategy for Atelectasis (ICNVA) ENB for patients with peripheral lung lesions.

Methods: Retrospective observational study in which ten consecutive patients with pulmonary lesions (without bronchial direct connection) underwent ICNVA-ENB was conducted. We collected three sets of CT data: preENB CT, post-anesthesia intubation CT, and postENB CT.

To evaluated the accuracy of ICNVA-ENB, we measured the distance between the ENB probe and the actual lesion location, but also recorded the results of rapid on-site evaluation (ROSE), and postoperative pathology. To evaluate the impact of CT-body divergence induced by atelectasis, we calculated the mutual position distance of target lesions in preENB CT, post-anesthesia intubation CT and postENB CT. Furthermore, ENB operation time, operative complications were recorded.

Results: Our analysis revealed that the distance between the navigation probe with the actual location of lesion center is 4–10 (5.90±1.73) mm. The ROSE results were consistent with the postoperative pathological diagnosis in 9 out of 10 patients (90%). The ICNVA-ENB atelectasis CT-body divergence was smaller than traditional ENB ((12.10±3.67)mm vs (6.60±2.59)mm, p＜0.01). The ENB operation time was 20-53(29.30±10.14) minutes and one patient developed slight intrapulmonary hemorrhage.

Conclusions: ICNVA-ENB can reduce the CT-body divergence and appears to be safe and accurate for patients with peripheral lung lesions.

electromagnetic navigation bronchoscopy (ENB)

atelectasis

CT-body divergence

intraprocedural CT

ventilatory strategy

Electromagnetic Navigation Bronchoscopy(ENB) is a commonly used technique in respiratory interventional therapy and diagnosis. It has shown an accuracy of 70–83% in diagnosing peripheral lung lesions [1]. However, there are limitations to its accuracy due to CT-body divergence, which is caused by atelectasis and CT data mismatch [2].

Atelectasis is one of the main factors contributing to CT-body divergence and is frequently observed in ENB procedures. General anesthesia, endotracheal intubation, and bronchoscopy operation are associated with the development of atelectasis. The I-LOCATE trial revealed that the incidence of atelectasis is as high as 89% in patients who underwent anesthesia tracheoscopy, leading to a deviation in the location of the target lesion [2].

To minimize the impact of atelectasis, some research teams, such as Salahuddin et al.[3] and Michael A. Pritchett et al [4, 5], have explored ventilation strategies to prevent atelectasis during anesthetic bronchoscopy. However, there is limited research on the topic, and no consensus has been reached regarding the optimal ventilation strategies. The accuracy of the proposed strategies is also limited, indicating a need for further improvement in this area.

Another important reason for CT-body divergence in the context of ENB is CT data mismatch. Currently, all research studies utilize preoperative CT data for navigation path planning in ENB. These scans are typically taken when patients are conscious and in a deep inspiration state. However, during ENB procedures, patients are under anesthesia and mechanical ventilation, which can result in a different distribution of lung volumes. As a result, there may be inevitable differences in the actual lung volume compared to the pre-procedural CT data, leading to CT-body divergence.

To address this issue, we propose using CT data obtained after general anesthesia and bronchoscope implantation for navigation path planning. By considering the patient's condition during ENB, such as being under anesthesia and mechanical ventilation, we can account for the differences in lung volume distribution. Additionally, we implement a new ventilation strategy that helps maintain the pulmonary region in a static and inflation state during ENB. This strategy eliminates atelectasis and reduces the deviation distance between the actual target lesion location and the navigation target. By incorporating these measures, we aim to minimize CT-body divergence and improve the accuracy of ENB procedures.

We call this method as ICNVA-ENB which meaning intraprocedural CT guided Navigation with Ventilatory Strategy for Atelectasis. The purpose of this study is to evaluate the safety and effectiveness of ICNVA-ENB. We present this article in accordance with the STROBE reporting checklist.

Study setting and subjects

This retrospective observational study was conducted in Department of Thoracic Surgery, The First Affiliated Hospital, Jiangxi Medical College, Nanchang University. It adhered to the guidelines of the Declaration of Helsinki and was approved by the Ethics Committee of The First Affiliated Hospital, Jiangxi Medical College, Nanchang University (approval number: 2023028).

The study included patients with pulmonary nodules who required peripheral bronchoscopy with ENB and rapid on-site evaluation (ROSE) between May 1st to August 30th.

Prior to the procedure, all patients underwent a chest CT scan which revealed that their pulmonary lesions were located in the outer third of the lungs. All lesions have undergone over a year of follow-up and the lesions have increased in size or solid components. They rejected percutaneous biopsy or surgical resection for some reasons, like percutaneous biopsy failure, requirement of pathologic diagnosis, etc.

Patients with lesion diameter ≤ 6mm or > 3cm, lesions directly connected to the bronchial tree, pregnant patients, those with a history of bronchial asthma, severe pneumothorax, rib fractures, severe abdominal or thoracic aortic aneurysm, pleural effusions, ascites, or diaphragmatic paralysis were excluded from the study. Written informed consent was obtained from all patients.

Operating procedures (Fig. 1, 2)

ICNVA-ENB procedures

1) Patients received preoxygenation with the lowest oxygen concentration (it was usually 60%≤Fraction of inspiration O_2, FiO2 ≤ 80%) to keep blood oxygen saturation > 92%. This process last 5 minutes.

2) After deep general anesthesia with non-depolarizing muscle relaxants and tracheal intubating with an 8.5mm endotracheal tube, we implanted the bronchoscope (BF290, Olympus).

3) Performing increment-decrement ventilatory strategy to reverse atelectasis induced by anesthesia and intubation.

We selected the Pressure Controlled Ventilation (PCV) mode and set inspiratory pressure at 10-15cm H₂O and positive end-expiratory pressure (PEEP) at 5cm H₂O. Then we increased the PEEP by 5cm H₂O each time until it reached 35cm H₂O, and then decreased the PEEP by 5cm H₂O each time until it reached 5cm H₂O. Every PEEP changing sustain 5 complete respiratory processes.

4) Keeping the optimally lowest FiO2 level to maintain the blood oxygen saturation > 92%. And setting the PEEP at desired level (it was usually 6-8cm H₂O and 10-12cm H₂O when lesion located in upper/middle lobe and lower lobe respectively).

5) Maintaining patients in the end of inspiratory state to minimize lung movement during breathing by using adjustable pressure limiting (APL). We manually used the APL valve at the end of inspiration to maintain the PEEP at desired level (following a protective lung ventilation strategy, airway pressure ≤ 35cmH2O).

6) Performing CT scan (O-arm CT, Siemens Somatom Confidence 64 sliding gantry, Siemens Healthcare) with a layer of 1mm thickness. Then we restored patients at normal breathing state. Exporting the DICOM format file to Medtronic V7 ENB system for navigation path planning.

7) Patients were kept in breath hold state as step 5. Then following preset navigation path, we complete ENB operation when navigation probe reached the target lesions.

8) Reviewed CT to confirm that the location of navigation probe, and confirm whether there is pneumothorax, bleeding, etc.

Biopsy procedures

After successfully completing the ICNVA-ENB procedures and aligning the navigation catheter, our next step involved inserting and advancing a biopsy tool towards the targeted lesion. To ensure accurate positioning, a CT scan was performed on the patient to confirm the visibility of the biopsy tool within the lesion.

Following the CT scan, we utilized ROSE in all cases. ROSE involves a quick assessment of the obtained tissue samples by a pathologist during the procedure. This real-time evaluation helps in confirming the adequacy and quality of the collected samples, allowing for quick adjustments or additional biopsies if required.

Statistical analysis

The statistical analysis involved the calculation of several measures to evaluate the accuracy and effectiveness of the ENB procedure and the impact of the specific ventilatory strategy on atelectasis.

First, to assess the accuracy of ENB arrival, the distance between the navigation probe center and the target lesion center in the CT data after ENB operation was calculated. This distance served as the accuracy index.

Next, the time from endotracheal intubation completion to bronchoscope removal was recorded as the ENB operation time. Complications, ROSE results, and postoperative pathological results were also recorded.

In order to assess the impact of using preoperative CT data and intraoperative CT data on the success rate of electromagnetic navigation bronchoscopy (ENB), we compared the preoperative CT data, intraoperative CT data, and post-procedure CT data of the same patients. This comparison was conducted by aligning the pre-ENB-anesthesia CT scan pairs using the main carina as a reference point for translation. The physical three-dimensional (3-D) motion was then calculated, considering the X, Y, and Z directions of motion. Then compare the positions of target nodules marked in different CT data sets. The specific methodology was followed according to [6].

The quantitative data are expressed as a number, median, and range, while categorical variables are described as a number and percentage. All statistical analyses were performed using SPSS 20 software (IBM Corp., Armonk, NY, USA).

Result

The results of the study conducted between May 2023 and August 2023 on 10 lesions of 10 patients who underwent ICNVA-ENB are summarized in the following paragraphs.

Table 1 provides information on the characteristics of the patients and lesions. All 10 lesions were located in the outer third of the pulmonary region, none of them were visible endobronchially, and all were located beyond the segmental bronchus.

Table 1

Clinical data of patients
No.	Sex	Age	BMI	Merger of underlying diseases	lesions location	The longest diameter of the lesion (mm)	The shortest diameter of the lesion (mm)	The longest diameter of solid component (mm)
1	F	36	21.33	none	LS_1 + 2	7	7	0
2	F	44	24.45	none	RS₁	11	7	0
3	M	54	20.81	none	RS₂	9.7	8.2	1.2
4	M	60	23.14	diabetes mellitus	RS₂	8	6.5	0
5	F	81	17.11	hypertension	LS₃	15	10.4	5
6	F	33	20.31	none	RS₄	8	4	0
7	F	46	18.43	none	RS₁	8	5	3
8	F	25	20.96	none	LS_1 + 2	10	9	0
9	F	54	18.00	none	RS₆	4.1	3.1	0
10	F	34	20.55	none	LS_1 + 2	7	6	0
F = female, M = male, BMI = body mass index, LS = left segment, RS = right segment.

Based on the final CT data, the navigation probe successfully reached within 1cm outside the center of the target lesion in all cases. The average distance between the navigation probe and the actual location of the lesion center was 4–10 (5.90 ± 1.73) mm. The traditional ENB atelectasis CT-body divergence is 7–17 (12.10 ± 3.67) mm, and ICNVA-ENB atelectasis CT-body divergence is 4–12 (6.60 ± 2.59) mm. The difference is statistically significant.

The ENB operation time was 20–53(29.30 ± 10.14) minutes. Out of the 10 patients, one developed intrapulmonary hemorrhage, as observed by localized patchy shadows on CT imaging. No other complications were reported during the procedure. The results of ROSE showed that all lesions were malignant, and every patient then underwent video-assisted thoracic surgery. The ROSE results were consistent with the postoperative pathological diagnosis in 9 out of 10 patients (90%). (Table 2)

Table 2

ENB data of patients
NO.	probe-lesion distance (mm)	traditional ENB atelectasis CT-body divergence (mm)	ICNVA-ENB atelectasis CT-body divergence (mm)	ENB operation time(min)	ROSE	Postoperative pathological diagnosis	complication
1	10	8	5	26	malignant	MIA	none
2	6	7	6	23	malignant	MIA	none
3	4	12	10	22	malignant	AAH	none
4	7	15	12	40	malignant	AIS	none
5	6	13	6	26	malignant	MIA	none
6	4	17	7	53	malignant	AIS	intrapulmonary hemorrhage
7	6	15	7	32	malignant	AIS	none
9	5	16	5	20	malignant	MIA	none
9	6	8	4	28	malignant	MIA	none
10	5	10	4	23	malignant	AIS	none
AAH = Adenomatous atypical hyperplasia, AIS = adenocarcinoma in situ, MIA = microinvasive adenocarcinoma.

Over the past few decades, bronchoscopy technology has advanced significantly, but its diagnostic yield is still limited to around 70% [7–11]. Despite the introduction of various technologies such as ultrathin-bronchoscopy, radial-probe endobronchial ultrasound, electromagnetic navigation, and robotic-bronchoscopy, the diagnostic yield has not significantly improved.

One of the new bronchoscopy tools, electromagnetic navigation bronchoscopy (ENB), combines electromagnetic navigation, virtual bronchoscopy, and 3D CT imaging technology to achieve real-time navigation and precise positioning of lung lesions. However, this technology relies on CT data for virtual map reconstruction, which can result in deviations in the localization of lesions. This CT-body divergence may be one of the important reasons limiting the accuracy of navigation technology [12]. During the ENB process, patients often experience atelectasis due to factors like anesthesia, endotracheal intubation, bronchoscopy operation, and ventilation mode. Anesthesia is particularly significant in causing CT-body divergence, leading to deviations in the location of the target lesion. In I-LOCATE trial, the incidence of atelectasis is 89% in patients underwent anesthesia tracheoscopy [2]. Optimizing the ventilation mode may be a crucial factor in improving atelectasis.

Researchers have suggested various ventilation strategies to improve atelectasis during bronchoscopy. For example, the VESPA strategy [3] includes large-diameter tracheal intubation, lower inhaled oxygen concentration, and positive end-expiratory pressure (PEEP) of 8–10 cmH2O, while the LNVP strategy [4, 5] includes sustained inflation, higher PEEP, and peak pressure threshold. However, the accuracy of these strategies is limited, and further improvement is needed.

In clinical practice, there are two common methods for lung recruitment: sustained inflation and stepwise. The stepwise method using slow-low pressure can achieve lung recruitment while reducing impact on the circulatory system [13, 14]. LNVP strategy uses sustained inflation, higher PEEP, and peak pressure threshold, but this setting violates the protective lung ventilation strategy and may lead to ventilator-related lung injury [4, 5, 15–17]. In our early cases, we followed the LNVP strategy and found that patients were prone to intraoperative bleeding and hypotension and decreased oxygenation index.

Therefore, we changed to choose stepwise method to improve atelectasis. We utilized an optimized ventilation strategy with individualized adjustments, lower initial PEEP values, individualized suction pressure, and a lower pressure peak threshold to reduce the risk of ventilator-related lung injury. In our study, we found that optimized ventilation strategy (ICNVA-ENB) reducing the CT-body divergence induced by atelectasis compared to traditional ENB strategy ((12.10 ± 3.67)mm vs (6.60 ± 2.59)mm p<0.01). Furthermore, there were no complications related to ventilator-induced lung injury. So far, this study firstly applies this optimized ventilation strategy to minimize atelectasis in ENB examination.

In addition to atelectasis, the mismatch between preoperative and intraoperative CT data, known as CT bias, is another factor affecting the accuracy of ENB. Traditional ENB plans navigation paths using preoperative CT data, which may not accurately reflect intraoperative lung volume changes and anatomical position shift due to sedation, mechanical ventilation, and bronchoscope placement[5, 12]. Therefore, the key to improve ENB accuracy should be how to match the navigation location with the actual lesion location, rather than simply solving atelectasis. So far, no research has proposed a solution to this point. Benefit from the intraoperative CT equipment in our center, we propose using CT data after bronchoscope placement under anesthesia to plan the navigation path, reducing CT bias.

Currently, the largest report on the accurate rate of ENB diagnosis is the NAVIGATE study, which has a diagnostic accuracy of 67.8%. In NAVIGATE study, the presence of bronchial direct connection to lesion is a key factor determining its diagnostic accuracy [18]. In comparison, we achieved a 100% arrival rate confirmed by CT and a 90% pathological diagnosis accuracy in our study.

However, there are still some shortcomings in this study, including the sample size is small and most of the lesions were located in the upper lobe. The operator’s experience may affect ENB accuracy. Further research is needed to validate our findings.

The ICNVA-ENB technique described in this passage is a novel approach that utilizes intraoperative CT data for path planning in electromagnetic navigational bronchoscopy (ENB). This technique also incorporates a modified ventilatory method to prevent atelectasis and reduce CT-body divergence. We report that the ICNVA-ENB technique significantly improves the accuracy of ENB arrival. This study suggests that this technology has higher accuracy compared to traditional ENB and has shown no significant complications in our early experience. ICNVA-ENB may be a safe and effective strategy for the diagnosis and treatment of pulmonary lesions, particularly in cases where there is no endobronchial connection to the lesion.

ENB (Electromagnetic navigation bronchoscopy), ICNVA(intraprocedural CT guided Navigation with Ventilatory Strategy for Atelectasis), ROSE(rapid on-site evaluation), Fi (fraction of inspiration), PCV (pressure controlled ventilation), PEEP(positive end-expiratory pressure), APL(adjustable pressure limiting), AAH(Adenomatous atypical hyperplasia), AIS(adenocarcinoma in situ), MIA(microinvasive adenocarcinoma), GGO(ground-glass opacity), BMI(body mass index)

Ethics approval and consent to participate

Approval was obtained from the ethics committee of The First Affiliated Hospital, Jiangxi Medical College, Nanchang University (approval number: 2023028). The procedures used in this study adhere to the tenets of the Declaration of Helsinki. Informed consent was obtained from all individual participants included in this study.

Consent for publication

Informed consent obtained from all the participants to publish the information/image(s) in an online open-access publication.

Availability of data and materials

All data generated or analysed during this study are included in this published article and its supplementary information files.

Competing interests

The authors declare no competing interests.

Funding

None.

Authors' contributions

Conception and design: Shaohua Dai. Administrative support: Jian Tang. Data analysis and interpretation, Manuscript writing: Guoqiu Xu, Zhiguo Chen. Provision of study materials or patients, Collection and assembly of data: All authors. All authors read and approved the final manuscript.

Acknowledgements

Not applicable.

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No competing interests reported.

7video.mp4
Video ICNVA-ENB procedure and result of one patient

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Intraprocedural CT guided Navigation with Ventilatory Strategy for Atelectasis (ICNVA): a modified electromagnetic navigation bronchoscopy

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Abstract

Figures

Introducing

Methods

Study setting and subjects

Operating procedures (Fig. 1, 2)

Biopsy procedures

Statistical analysis

Result

Discussion

Conclusions

Abbreviations

Declarations

References

Additional Declarations

Supplementary Files

Status:

Version 1