ABSTRACT
Endobronchial ultrasound (EBUS) has become an essential tool in lung cancer staging and the diagnosis of centrally located pulmonary lesions. Vigilance during EBUS-guided biopsy is crucial. The disappearance of a previously visualised lesion should raise suspicion of a developing pneumothorax. We present our experience with an intra-procedural pneumothorax following EBUS-guided biopsy and discuss the procedural considerations relevant to its prompt recognition and management.
KEY WORDS: Endobronchial ultrasound, lung cancer, pneumothorax
INTRODUCTION
Endobronchial ultrasound (EBUS) is an established and indispensable modality for staging of lung cancer and the diagnosis of centrally located pulmonary lesions.[1] EBUS-guided transbronchial needle aspiration (EBUS-TBNA) and newer techniques, such as the EBUS-guided cryobiopsy (EBUS-Cryo), are generally considered safe. The reported incidence of pneumothorax or pneumomediastinum is less than 1%.[2,3,4] Despite its favourable safety profile, rare complications can occur and may pose diagnostic and management challenges. Recently, we encountered an instructive case that underscores critical procedural and safety considerations during EBUS-guided interventions.
CASE HISTORY
A 52-year-old woman presented with right orbital swelling of 2 weeks’ duration. Magnetic resonance imaging of the brain revealed multiple cerebral lesions suspicious for metastases. A subsequent computed tomography scan of the chest demonstrated a right upper lobe lesion measuring 2.5 × 1.8 cm. The lesion is in close proximity to the right upper paratracheal region. The patient underwent EBUS-TBNA under general anaesthesia. EBUS-TBNA was performed using the Olympus BF-UC-190F scope with a 22-gauge VIziShot 2 TBNA needle. Cryobiopsy was performed with a flexible 1.1 mm cryoprobe. Three EBUS-TBNA passes were attempted. On-site macroscopic evaluation of the specimens indicated that they were suboptimal. Hence, EBUS-Cryo was explored as an alternative to improve specimen yield. An electrocautery knife was used to create a tract for the cryoprobe insertion [Figure 1a]. Following this, the EBUS bronchoscope was withdrawn for cleaning. Upon reintroducing the EBUS scope for EBUS-Cryo, the right upper paratracheal lesion was no longer clearly visualised [Figure 1b]. A decision was made to perform a transbronchial biopsy of the lung lesion guided by radial EBUS and fluoroscopy [Figure 1c]. Four cryobiopsy samples were successfully obtained, confirming a diagnosis of lung adenocarcinoma positive for epidermal growth factor receptor (EGFR) exon 19 deletion. The post-procedure chest radiograph demonstrated a right-sided pneumothorax and subcutaneous emphysema [Figure 1d], necessitating an urgent chest tube insertion. The patient was discharged home after full lung re-expansion on day 2.
Figure 1.
(a) Right lung mass seen on EBUS after an electrocautery knife was used to create a track for cryoprobe insertion. (b) Right lung mass not seen on endobronchial ultrasound upon reinsertion of the EBUS. (c) A cryoprobe is seen in the right lung lesion on a fluoroscopy image with a subtle right-sided pneumothorax. (d) A large right-sided pneumothorax seen on the chest radiograph post-procedure. EBUS: Endobronchial ultrasound
DISCUSSION
A retrospective review of the procedure raised several questions regarding the poor visualisation of the lesion. Several possibilities were being considered, including technical factors such as suboptimal inflation of the EBUS balloon (leading to inadequate acoustic coupling), inaccurate positioning of the EBUS bronchoscope or it could be caused by an underlying iatrogenic pneumothorax. However, the bronchoscopist repeatedly adjusted the EBUS balloon inflation to confirm optimal contact and also has rechecked the correct anatomical positioning of the EBUS scope. These effectively rule out technical factors related to scope placement and balloon inflation as the cause of poor lesion visualisation.
The sequence of events and a thorough review of the procedure indicate that the electrocautery knife was the most likely cause of the pneumothorax. While EBUS-TBNA, transbronchial lung cryobiopsy, and positive pressure ventilation were considered, they are deemed less probable contributors. This is supported by the rapid disappearance of the lesion after the use of the electrocautery knife. The time lapse from the use of the electrocautery knife to the reinsertion of the scope after cleaning was 1 minute and 20 seconds. Furthermore, a retrospective review of the chest radiograph obtained during the transbronchial lung cryobiopsy identified a subtle pneumothorax, suggesting the complication occurred earlier in the procedure.
The principles of ultrasound physics provide an explanation for the lesion’s disappearance during the procedure. Ultrasound imaging relies on the transmission and reflection of sound waves as they pass through a medium of different acoustic impedances.[5] The presence of air in the pleural space creates a physical barrier between the ultrasound probe and the lesion. Because air has a very high acoustic impedance mismatch with soft tissue and the lowest propagation velocity among bodily media, it reflects the majority of the ultrasound waves at the tissue-air interface.[6] Consequently, when ultrasound waves encounter an air interface, transmission beyond that point is almost entirely attenuated, resulting in loss of visualisation of deeper structures.
During a transbronchial lung biopsy, fluoroscopy can be used for a preliminary assessment of pneumothorax. Although pneumothorax can occasionally be seen on fluoroscopy, it lacks sensitivity compared to conventional chest radiography[7] and is not the primary diagnostic method for delineating pneumothorax. Furthermore, as seen in our case [Figure 1c], a subtle pneumothorax can be missed when the proceduralist’s attention is focused on the biopsy target.
In the context of mechanical ventilation, mechanical ventilation–related barotrauma is closely associated with elevated airway pressures and can be mitigated by avoiding unnecessary Positive end-expiratory pressure (PEEP).[8] When endotracheal intubation is required, the use of a larger internal-diameter tube reduces airway resistance, thereby helping to prevent the high peak inspiratory pressures that contribute to barotrauma.[9] Nevertheless, pneumothorax remains a potential complication. The onset of a significant pneumothorax typically activates ventilator alarms, such as those indicating high airway pressure, hypercapnia, or low exhaled tidal volume. However, the use of an EBUS bronchoscope within the airway increases airway resistance, frequently producing transient, artefactual elevations in airway pressure. These readings may obscure the early detection of a pneumothorax. Consequently, unless a tension pneumothorax develops − manifesting as a pronounced rise in peak airway pressure or signs of haemodynamic compromise − this complication may be overlooked intraoperatively.
This encounter underscores the critical importance of vigilance during EBUS-guided procedures, especially when using larger ancillary instruments such as the electrocautery knife or cryoprobe. A step by step approach to address this complication is presented in Table 1. In conclusion, a crucial procedural insight is that the sudden disappearance of a previously visualised lesion should immediately raise suspicion for a developing pneumothorax.
Table 1.
Step by step approach for diagnosis pneumothorax during EBUS
| Step | Action | Rationale/Goal |
|---|---|---|
| 1. Immediate Technical Confirmation | Immediately confirm optimal EBUS scope positioning (anatomical location). | To rule out scope misplacement or displacement. |
| Confirm optimal EBUS balloon coupling (adequate inflation). | To rule out inadequate acoustic coupling (technical error). | |
| 2. Rapid Bedside Assessment | Perform rapid transthoracic ultrasound (check for lung sliding/lung point). | Quickest way to rule out or detect a pneumothorax. |
| Briefly remove the EBUS scope to assess for a sudden drop in airway pressure (if on positive pressure ventilation). | To detect air leakage in a potential pneumothorax. | |
| 3. Imaging and Definitive Management | Maintain a low threshold for intra-procedural Chest X-ray (CXR). | Provides definitive visual confirmation of pneumothorax. |
| Manage confirmed pneumothorax according to established clinical guidelines. | To ensure patient safety and address the underlying complication. |
Key messages
The importance of vigilance during EBUS-guided biopsy, especially with the disappearance of a previously visualised lesion, should raise suspicion of a developing pneumothorax
Conflicts of interest
There are no conflicts of interest.
Funding Statement
Nil.
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