Airway Fistulas in Adults

Introduction

Fistula formation in the airway may be broadly defined as any defect that allows pathologic communication between the respiratory tract and an adjacent structure. The type of airway fistula is determined by which section of the tracheobronchial tree and which adjacent structure is involved. For example, a tracheoesophageal fistula (TEF) is a communication between the trachea and the esophagus, whereas a bronchopleural fistula (BPF) is a communication between a lobar or segmental bronchus and the pleural space. The cause of a fistula may be iatrogenic, traumatic, or secondary to a medical disorder. The fistula size, location, and the effects on ventilation are important in determining the morbidity for the patient, the options for therapeutic intervention, and the challenges the fistula may present to anesthesiology or intensive care providers. Table 45.1 provides an overview of the major airway fistula types in adults.

Table 45.1

Characteristics of Acquired Airway Fistulas in Adults

	Tracheoesophageal Fistula (TEF)	Bronchopleural Fistula (BPF)	Alveolopleural Fistula (APF)
Description	Pathologic communication between the trachea and the esophagus	Pathologic communication between a lobar or segmental bronchus and the pleural space	Pathologic communication between the distal respiratory tree and the pleural space
Etiology	Malignancy Blunt or penetrating trauma Mediastinal infection Previous surgery Corrosive fluid ingestion Poisons and inhalation burns Iatrogenic Esophageal stent injury EGD injury TEE probe injury Tracheal tube injury	Pulmonary surgery Pneumonectomy Lobectomy Segmentectomy Chest trauma Pulmonary infection Treatment of malignancy Chemoradiation Radiofrequency ablation Microwave ablation	Pulmonary surgery Lung volume reduction Segmentectomy Wedge resection Chest trauma Pulmonary infection Spontaneous pneumothorax Mechanical ventilator trauma
Sequelae	Cough after ingestion (Ono’s sign) Poor nutrition Airway soilage Pneumonia Pulmonary sepsis	Persistent air leak Atelectasis Pneumothorax Tension pneumothorax Subcutaneous emphysema Pneumonia Empyema	Persistent air leak Atelectasis Pneumothorax Tension pneumothorax Subcutaneous emphysema Pneumonia Empyema
Management	Minimize aspiration Acid suppression therapy Treat pulmonary infection Pulmonary toilet Esophageal stenting Esophageal diversion Surgical repair	Chest tube thoracostomy Nutritional support Treat pulmonary infection Pulmonary toilet Optimize ventilation Bronchoscopic intervention Surgical repair	Chest tube thoracostomy Heimlich valve Blood patch pleurodesis Chemical pleurodesis Bronchoscopic intervention Surgical repair

EGD , Esophagogastroduodenoscopy; TEE , transesophageal echocardiography.

A large fistula of the central airways (such as TEF of the trachea or a BPF of a mainstem bronchus) that causes significant respiratory distress can be a devastating condition and frequently requires surgical intervention to prevent the development of pulmonary sepsis, which can be catastrophic. All types of airway fistulas warrant the utmost level of preoperative planning for even the most seasoned anesthesiologist. Thorough physical examination, reviewing the computed tomography (CT) scan, and bronchoscopic evaluation to localize the defect are essential in planning the anesthetic management. Airway techniques, such as jet ventilation or placement of a left- or right-sided double-lumen tube (DLT), may be necessary to avoid further injury to a central defect, preserve oxygenation and ventilation, and isolate the defect site for surgical repair.

In its own category of airway fistula is an alveolopleural or alveolar-parenchymal-pleural fistula (APF) of the distal tracheobronchial tree (beyond a segmental bronchus), which allows air to leak into the pleural space. The etiology and treatment of an APF is distinct from a BPF or tracheal fistula. If an APF does not readily heal it may lead to a persistent air leak (PAL), a condition where air continues to enter the pleural space from the lung parenchyma for an extended period, in particular if the patient is placed on positive pressure ventilation. A postoperative PAL is typically defined as one that lasts 4 postoperative days or beyond the expected postoperative hospital stay. ^, Whereas a PAL may lead to a prolonged hospital stay and increased mortality, the usual course is less ominous than that of a large central airway fistula, especially if the etiology of the APF is postsurgical. Most patients with a PAL after lung resection can be safely discharged home under conservative management, and a chest tube connected to a one-way (Heimlich) valve for later removal at a follow-up clinic visit. ^, However, some patients with an APF may need to undergo a surgical or endoscopic procedure to seal or isolate the defect to expedite the healing process.

A bronchopleural-cutaneous fistula (BPCF) describes a special condition occurring when a communication exists between the respiratory tree, the pleural space, and the subcutaneous area of the chest wall. Respired gases enter into the pleural space and then into the subcutaneous tissue to cause diffuse subcutaneous emphysema. This may occur when penetrating trauma to the chest wall injures a bronchus or other airway. For a BPCF, percutaneous chest tube placement will incompletely evacuate the pleural space to reinflate the lung because of continued filling via the airway fistula during spontaneous or mechanical ventilation.

Although the features of each fistula type are unique, an understanding of the pathophysiology of each is essential for the astute thoracic anesthesiology provider. The preoperative assessment of a challenging airway fistula includes ascertaining not only the characteristics of the airway fistula, but also other coexisting patient factors, a clear procedural plan, and the assurance of the availability of support staff and equipment. Communication with the surgeon or other proceduralist before initiation of the procedure often guides airway management planning and helps avoid pitfalls during the procedure. Patients must also be informed when significant difficulties are foreseen with oxygenation and ventilation or when there is a possible need for postoperative ventilatory support. The prudent approach is to have multiple backup modalities available, which may include extracorporal membrane oxygenation (ECMO) for the highest risk cases. The following case presentation highlights a management paradigm for a real patient with a central airway fistula.

Case Presentation

A 64-year-old former 20 pack-year smoker underwent a successful spinal surgery to repair a traumatic back injury sustained during a snowmobile accident, but he was experiencing anorexia, mild dysphagia, and persistent nausea during the recovery period. He was referred for an esophagogastroduodenoscopy (EGD), which demonstrated Barrett’s mucosa in the lower third of the esophagus and a fungating, partially obstructive mass at the gastroesophageal junction. Biopsies of the mass and further imaging confirmed a diagnosis of esophageal adenocarcinoma stage uT3N1M0. He was treated with several weeks of radiation therapy (50 Gray), neoadjuvant chemotherapy (carboplatin and paclitaxel), and nutritional support with tumor response and symptomatic improvement. He subsequently underwent a minimally invasive Ivor Lewis esophagectomy and laparoscopic jejunostomy from which he recovered well and was discharged home on the sixth postoperative day. However, at two weeks postprocedure, the patient returned to the hospital with fever, productive cough, and dyspnea. He had bilateral diffuse rales on physical exam. A CT scan of the chest showed bilateral basal predominant groundglass opacities and patchy consolidations, as well as defects in the proximal left mainstem bronchus and the esophagus that appeared to communicate ( Fig. 45.1 A). The patient was scheduled for an urgent EGD and flexible bronchoscopy for further assessment and treatment.

• Fig. 45.1, ( A ) Axial computed tomography (CT) image showing a fistula in the proximal left mainstem bronchus. There are bilateral pulmonary infiltrates from soiling of the airway. ( B ) Fiberoptic bronchoscopy at the level of the carina 2 days after CT imaging. The enlarging fistula is visualized in the membranous portion of the posterior left mainstem bronchus.

Case Management

Preoperative Assessment and Planning

The general preoperative assessment of a patient with a known or suspected airway fistula should be thorough, but it should focus on respiratory status, hemodynamics, airway assessment, and comorbidities that are likely to be significant factors in the induction and maintenance of the general anesthetic. Relevant comorbidities include major organ system dysfunction, morbid obesity, infectious processes, metabolic or hematologic derangements from oncologic treatment or ongoing pathologic process, and the presence of injuries from a recent trauma or surgery. In this case, the patient was hemodynamically stable when assessed for surgery but had persistent fever, cough, and dyspnea suggesting the presence of pulmonary infection. The airway assessment was reassuring, he was of average body habitus, and he had no other major organ system dysfunction outside of the gastrointestinal (GI) tract before presentation. No significant metabolic or hematologic derangements were present. The CT scan suggested an anastomotic leak and soilage of the lungs bilaterally secondary to a suspected central fistula.

Impact of an airway fistula on the ability to ventilate with positive-pressure ventilation (PPV) is difficult to predict as the actual size of the fistula is only one factor to consider, along with its shape, location, and other patient-specific factors, such as lung compliance. Maintenance of spontaneous ventilation is advantageous when suitable for the patient or the planned procedure. Ventilation is especially compromised in the setting of a large fistula and noncompliant lung parenchyma, which favors respired air passing through the low-resistance fistula into dead space rather than participating in alveolar gas exchange. With a clinically significant airway fistula, the patient may experience dyspnea and a sense of air hunger in response to respiratory acidosis and ineffective respiratory mechanics because of the loss of the driving negative intrapleural pressure. If a chest drainage system is in place during preoperative assessment, it can provide additional useful information about the size of the air leak by observing the air leak chamber ( Box 45.1 ). Patients with marked respiratory distress or grade 4 air leaks are unlikely to tolerate a standard anesthetic induction or PPV via a single-lumen endotracheal tube that does not isolate the airway defect. The patient in this case was only mildly dyspneic with a small-appearing (<8 mm) fistula based on CT imaging.

• BOX 45.1

Cerfolio Classification of Air Leaks

The bubbling in the air leak chamber of a chest drainage system can provide information about the air flow through an airway fistula. Air leak only present with cough indicates a small fistula, whereas a continuous air leak indicates a large fistula.

Grade 1, FE: During forced expiration only (i.e., cough)

Grade 2, E: Expiratory only

Grade 3, I: Inspiratory only

Grade 4, C: Continuous bubbling in the air leak chamber

When planning airway management, the anesthesia provider must appreciate that PPV in the presence of a fistula communicating with the GI tract may result in insufflation of the esophagus and stomach, possibly exacerbating reflux of gastric secretions into the lungs. PPV via a fistula communicating with the pleural space may result in a tension pneumothorax with hemodynamic collapse if a functioning chest drainage tube is not in place. A short, large-bore (≥20 Fr) chest tube should be placed for a large airway fistula communicating with the pleural space to palliate the high-volume air leak, prevent tension pneumothorax, and facilitate safer conditions for administering an anesthetic ( Box 45.2 ). ^, For proximal tracheal fistulas, rapid sequence induction followed by intubation beyond the fistula site with fiberoptic bronchoscopic guidance is recommended to obviate ventilatory concerns. If possible, an awake fiberoptic intubation with placement of a single-lumen tube is the safest practice.

• BOX 45.2

The Fanning Equation

The Fanning equation describes turbulent gas flow in a tube as occurs via chest tube drainage. A shorter, larger-bore chest tube is more effective at evacuating the pleural cavity. Appropriate chest tube size selection is key to preventing tension pneumothorax development.

V = \frac{π^{2} r^{5} P}{f l}

$V = \frac{π^{2} r^{5} P}{f l}$

V is the flow
P is the pressure gradient
r is the radius
f is the friction factor
l is the length

Airway Fistula Repair

In the operating room, a rapid sequence induction was performed to avoid unnecessary mask ventilation, and the patient was intubated with a single-lumen endotracheal tube. The patient was mechanically ventilated with low tidal volumes, low peak inspiratory pressures, low respiratory rate to allow for a prolong expiratory period, and no positive end-expiratory pressure (PEEP) to reduce air flow through the fistula ( Box 45.3 ). ^, Bronchoscopic evaluation confirmed endotracheal tube placement above the carina and no further injury to the fistula site. The bronchial fistula measured 5 mm at this time, and the patient tolerated mechanical ventilation without difficulty. Esophagoscopy revealed partial necrosis of the gastric conduit with fistula formation at the site of anastomosis. A self-expanding metallic esophageal stent was placed to limit tracheobronchial soiling while planning for a definitive surgical repair. A chest tube thoracostomy was also performed to drain the pleural space, and the patient was placed on intravenous antibiotics.

• BOX 45.3

Mechanical Ventilation for Airway Fistulas

The volume of air leak through the fistula is proportional to the mean airway pressure, which is reduced with these strategies:

Spontaneous breathing (if possible)

Low tidal volumes

Low peak inspiratory pressure

Low respiratory rate

Short inspiratory time

Permissive hypercapnia

Low or no positive end-expiratory pressure

Two days later, the patient returned to the operating room for a flexible bronchoscopy, resection of the gastric conduit via a right thoracotomy, esophageal diversion by cervical esophagostomy, and repair of the airway fistula. The patient was notably tachypneic with increased work of breathing but was hemodynamically stable. An arterial line was placed for continuous hemodynamic monitoring. Large-bore peripheral venous access and central venous access via implanted port were present. He was intubated after rapid sequence induction with a single-lumen endotracheal tube with notable air leak with PPV. A flexible bronchoscopy now showed an enlarged left mainstem bronchus fistula, likely secondary to the esophageal anastomotic leak ( Fig. 45.1 B). A left-sided double-lumen tube was placed gently into position in the left mainstem bronchus with fiberoptic bronchoscopic guidance to avoid further injury to the fistula site and to allow for isolation of the defect for repair via a right thoracotomy. He was extubated at the end of the procedure and underwent postanesthesia care in the intensive care unit (ICU).

Repair of a bronchial fistula has long been a major challenge for thoracic surgeons because of the limited healing potential of the poorly vascularized tracheobronchial tree. In this case, the repair of the bronchial fistula was performed with polypropylene suture, then covered with pedicled intercostal muscle and pericardial fat pad to buttress the closure. Omentum is also sometimes used to buttress the closure and is recommended in the surgical literature. Unfortunately, the closure in this case did not heal, possibly because of the patient’s poorly controlled suppurative infection in the chest and compromised blood supply to the anastomosis. The patient made multiple return trips to the operating room to undergo custom silicone airway stenting, followed by a repeat attempt at surgical repair of the airway fistula when the pleural space was more thoroughly drained. However, the patient eventually succumbed to pulmonary sepsis within approximately one month of his return presentation to the hospital.

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