Bronchopleural fistula secondary to smoke inhalation injury: a case report

Abstract

Background

Bronchopleural fistula is a rare and severe condition characterized by an abnormal connection between the bronchial tree and pleural space, often leading to significant morbidity and mortality. Although typically resulting from surgical procedures, trauma, or pulmonary infections, bronchopleural fistula caused by smoke inhalation injury is exceptionally uncommon. Smoke inhalation can lead to extensive thermal and chemical damage to the respiratory tract, increasing the risk of infection and necrotic tissue changes that can complicate recovery.

Case presentation

We report a case of a 23-year-old white American male with a history of polysubstance use, who suffered extensive burn injuries and smoke inhalation following a propane explosion. Initial bronchoscopy revealed airway inflammation, erythema, and carbonaceous deposits. Despite treatment with antibiotics, the patient was readmitted with a persistent cough, productive foul-smelling sputum, and fever. Imaging and subsequent bronchoscopy revealed a right-sided bronchopleural fistula complicated by hydropneumothorax and empyema. Surgical intervention, including right lower lobectomy and intrapleural antibiotic therapy, was successful, leading to patient recovery and discharge with no recurrence at 1-month follow-up.

Conclusion

This case highlights a rare etiology of bronchopleural fistula due to smoke inhalation injury, emphasizing the need for prompt diagnosis and a multidisciplinary approach to manage this severe complication. Early imaging, bronchoscopic evaluation, appropriate antibiotic therapy, and surgical intervention are crucial for improved outcomes in bronchopleural fistula secondary to inhalation injuries.

Introduction

Bronchopleural fistula (BPF) is a serious and potentially life-threatening condition characterized by abnormal communication between the bronchial tree and the pleural space. It often results in persistent air leaks and respiratory complications such as pneumonia, pneumothorax, or empyema. While surgical procedures are the leading cause of BPF development [1], other causes may include pulmonary infections, trauma, or neoadjuvant therapy [2]; cases secondary to smoke inhalation and/or burn injury are exceedingly rare.

Smoke inhalation injury increases mortality by 24 times in fire-related injuries and is highlighted to be one of the most important risk factors for improving morbidity and mortality [3]. Smoke inhalation can cause direct thermal and chemical injury to the respiratory tract, leading to tissue necrosis and inflammation. In rare instances, these injuries can progress to BPF, posing significant challenges in diagnosis and management. The in-hospital mortality rate of patients with BPF ranges from 18% to 50% [4]. Therefore, prompt diagnosis and management are necessary, and diagnostic workups may range from clinical evaluation to imaging, such as a chest computed tomography (CT) scan, or direct visualization of the fistula through bronchoscopy.

This case report discusses a rare presentation of BPF secondary to smoke inhalation, highlighting the clinical course, diagnostic challenges, and therapeutic approach.

Case presentation

A young 23-year-old white American man, with a history of substance use disorder, was admitted to the hospital as a level 1 trauma activation for severe burns. The patient was camping and using a propane heater in his sleeping tent, when he lit a cigarette which resulted in an explosion. He sustained significant burns all over his body and he underwent rapid sequence intubation in the emergency room. A tracheostomy had to eventually be performed 4 days after admission, and he was decannulated after 21 days. His initial bronchoscopy on the day of admission showed inhalational injury with erythema of the distal trachea and large airways, in addition to injured mucosa over the right mainstem and right lower lobe, indicating friable bronchial mucosa; carbonaceous phlegm was also visualized in the right upper and left upper lobe. He was treated with cefepime for pneumonia.

Following his discharge, he was transferred to a rehabilitation unit, but he was admitted to the hospital again for a persistent cough for 1 week, which was productive with copious foul-smelling sputum and bad taste, associated with 2 days of mild fever. A chest X-ray performed at this time revealed an air–fluid level in the right lung concerning cavitary pneumonia. Subsequent CT imaging (Fig. 1) showed a small- to moderate-sized loculated complex concerning a right hydropneumothorax with pleural thickening, and showed two areas that appeared to be directed toward the cavity; raising concern for bronchopleural fistula in the superior segment of the right lower lobe. He was treated with vancomycin, cefepime, and metronidazole to cover for possible necrotizing pneumonia.

Fig. 1

Computed tomography image of the chest showing two areas with abnormal connection between the lung and the pleural cavity (yellow arrow) and a hydropneumothorax

Bronchoscopy was performed (Fig. 2) which showed copious amounts of yellow–green mucus in the trachea. The superior segment of the right lower lobe was hypertrophic and significantly inflamed, and the scope could not be passed beyond the segmental bronchi level. Copious secretions and mucus were coming from the superior segment of the right lower lobe, which is likely where the fistula was. Broncho-alveolar lavage from bronchoscopy revealed gram-negative rods and gram-positive cocci in chains and clusters on Gram stain, with cultures resulting positive for pan-susceptible Streptococcus constellatus and anaerobic gram-negative rods (Prevotella buccae). A chest tube was placed for his hydropneumothorax, which expressed purulent fluid raising concern for empyema. There was evidence of an air leak on the chest tube further confirming the finding of a bronchopleural fistula.

Fig. 2

Bronchoscopy images showing inflamed mucosa and copious amount of purulent material in the superior segment of right lower lobe

Thoracic surgery was consulted for repair of the fistula and a possible resection of the right lower lobe, which was planned after the infection resolved. Another apical chest tube was placed for pleural antibiotic irrigation with intrapleural vancomycin for Streptococcus constellatus for at least 1 week, in addition to systemic metronidazole for anaerobic coverage. After 7 days of intrapleural vancomycin treatment, right thoracotomy was performed by thoracic surgery. The surgery revealed a thick-walled abscess around the right lower lobe in the intra- and extra-pleural space, and lobectomy of the right lower lobe was performed with removal of the abscess cavity. Intrapleural vancomycin was discontinued after achieving source control, and treatment with systemic metronidazole and ceftriaxone was continued to complete 4 weeks. His chest tubes were removed, and he was discharged home with outpatient physical and occupational therapy. He continued to do well on 1-month follow-up.

Discussion

Bronchopleural fistula, a sinus tract that runs between the bronchus and the pleural space, can be caused by lung neoplasm, lung trauma, necrotizing pneumonia/empyema, and consequences from medical procedures, including radiation, thoracocentesis, lung biopsy, or chest tube drainage [5]. This case represents a very uncommon etiology of bronchopleural fistula, that is, smoke inhalation injury in a patient affected by a gas explosion.

Several mechanisms may be involved in the development of BPF. Ablation of visceral pleura and adjacent lung tissue leads to dehydration of the lung tissue, reducing the elastic properties of the tissue. This reduces the capability of the lung tissue to close the puncture or heal during an active repair process, resulting in a permanent fistula formation. In addition, the necrotic or ablated viscera may be complicated by the development of necrotizing pneumonia, causing the disintegrating zone to connect with the bronchus and visceral pleura, thereby resulting in a fistula. A fistula may also develop due to the necrotic and/or diseased tissue being expelled into the pleural cavity or expectorated out [6]. The development of pneumothorax in such cases is a common complication. Other possible etiologies include complications after pneumonectomy or lobectomy [7].

A bronchopleural fistula may be diagnosed on the basis of clinical findings. However, radiological modalities provide the best picture of the diagnostic features, which may include a steady rise of intrapleural air space, the appearance of a new air–fluid level, tension pneumothorax, or a drop in air–fluid level of more than 2 cm if the chest tube is not placed. Another tool for diagnosis includes fiberoptic bronchoscopy, which allows direct visualization of the fistula [8]. In certain cases, such as this case, the fistula may be too distal to be directly visualized through a bronchoscope. In such cases, an amalgamation of different features, such as the suspicion of a connection between the cavities on imaging and evidence of an air leak in the chest tube, help in the formation of a diagnosis.

Prophylactic use of adequate antibiotics and mechanical ventilation is the first and foremost approach in treating bronchopleural fistulae to prevent necrotizing pneumonia in burn patients [9]. Invasive procedures for closing the fistula include the following [10]:

• 1. Blocking agents that use ethanol, fibrin glue, albumin-glutaraldehyde tissue adhesive, oxidized regenerated cellulose, ethyl-2-cyanoacrylate, and silver nitrate to stimulate granulation tissue formation that leads to scarring and permanent fistula closure.

• 2. Atrial septal defect/ventricular septal defect occluders which have double-disc mesh structures made of woven nickel-titanium alloy wire with self-expanding properties, with sizes ranging from 4 to 40 mm, to directly close the fistula.

• 3. Airway stents, of metal and silicon variants, can be used to close malignant fistulas. Silicon stents are classified as straight stents, used in the upper and middle trachea, and Y-shaped stents used in the lower trachea up to the carina. Metal stents provide good support and are resistant to fracture, but have United States Food and Drug Administration warnings due to associated complications.

• 4. Endobronchial valves, categorized as Zephyr endobronchial valves and intrabronchial valves, are designed for endoscopic lung decompression. They are one-way valves that restrict the dual flow of air into the diseased part of the lung, preventing the occurrence of obstructive pneumonia. However, the valve should be removed within 4–6 weeks to prevent granuloma formation.

• 5. Endobronchial Watanabe spigots, which are silicone bronchial plugs in the form of a socket with a studded surface and gripping ends, are placed in the airway with the assistance of bronchoscopy to prevent air from entering the diseased part of the lung [11].

In terms of medical management, patients with BPF benefit from pharmacological treatment. The most common agents in this case include beta-2 agonists and muscarinic antagonists. Albuterol, salmeterol, levalbuterol, or salbutamol counteract bronchospasms caused by inhaled smoke irritants, whereas muscarinic antagonists, such as atropine, scopolamine, tropicamide, and ipratropium, also increase mucociliary clearance of inhaled particles. Racemic epinephrine has a vasoconstrictive action, and thus can be used to treat airway edema caused by inhaled irritants. Other drugs include N-acetylcysteine, which has pulmonary antioxidant and mucolytic properties that prevent a cell from reactive oxygen species damage, and aerosolized heparin, which prevents inspissation of secretions, improves microcirculation by breaking the fibrin component of the bronchial cast, and has been found to reduce mortality. Bronchoalveolar lavage helps remove obstructing plugs, improving the oxygen supply of the lungs [12].

The definitive treatment of bronchopleural fistula is surgery, which includes pneumonectomy or lobectomy. However, lung resection should be taken into consideration before deciding on conservative therapy alone, as the fistula may require a long time to heal, and it is difficult to manage in patients requiring long-term positive pressure ventilation [13].

Fistulae can be complicated by pleural empyema, which is a new challenge to surgeons, as encountered in our case as well, as it may require urgent drainage. The literature on the use of intrapleural antibiotic irrigation in bronchopleural fistula and empyema is limited. It is treated with systemic antibiotics almost all the time, with or without surgery. However, it is important to note that smoke inhalation injury resulting in fistula formation is rare. Torbic et al. report the use of intrapleural antibiotics in post-pneumonectomy empyema patients [14], with the rationale that the ability of systemic antibiotics to reliably reach therapeutic levels in infected pleural fluid may be reduced due to changes in microcirculation [15]. Burn injuries may have a similar effect owing to the pleural ablation and lung tissue dehydration, thereby decreasing the effectivity of systemic antibiotics. This, in addition to the failure of first line antibiotic therapy prior to readmission in our case, made intrapleural antibiotics a plausible option.

Conclusion

Bronchopleural fistula has proven challenging to physicians, as the reported mortality of bronchopleural fistula can be as high as 71% [16]. Smoke inhalation and burn injury is an extremely rare cause of BPF, with no such cases reported previously in literature to the best of our knowledge. This case highlights the significance of considering BPF as a complication of burn injury to the lungs, even in cases where it may not be directly visualized through bronchoscopy. Prompt management, including the administration of appropriate antibiotics, chest tube placement, and lobectomy, can significantly improve the prognosis and mortality.