Continuing Education Activity

Tracheal abnormalities requiring reconstruction are rare but can affect patients of all ages. Tracheal stenosis makes up 1% of all laryngotracheal stenoses, but mortality can range from 20 to 30% and reach as high as 70% when present within the first month of life. Tracheal anomalies are typically divided into two categories: congenital and acquired. Congenital lesions are present at birth and frequently present in conjunction with other abnormalities. Concomitant cardiopulmonary abnormalities are present in up to 50% of patients. This activity outlines the approach to the diagnosis and management of tracheal stenosis. Throughout the activity, the role of the multidisciplinary team will be highlighted in both evaluation and management of patients requiring tracheal reconstruction.

Objectives:

• Review the complex nature of tracheal abnormalities.
• Describe the relevant anatomy pertinent to tracheal surgery.
• Outline a stepwise approach for managing tracheal stenosis.
• Summarize the approaches to tracheal reconstruction and how to manage complications.

Introduction

Tracheal abnormalities requiring reconstruction are rare but can affect patients of all ages. Tracheal stenosis makes up 1% of all laryngotracheal stenoses, but mortality can range from 20 to 30% and reach as high as 70% when present within the first month of life. Tracheal anomalies are typically divided into two categories: congenital and acquired. Congenital lesions are present at birth and frequently present in conjunction with other abnormalities. Concomitant cardiopulmonary abnormalities are present in up to 50% of patients.[1] Acquired tracheal stenosis can result from a variety of insults and is often multifactorial; however, it is most frequently a result of prolonged intubation, leading to pressure-induced necrosis injury of the tracheal mucosa. Poiseuille's law states that airflow is directly proportional to the radius to the fourth power, highlighting the potential detriment of even a small decrease in tracheal lumen diameter. The pediatric population is at increased risk of clinically significant tracheal airway compromise due to the small caliber of the trachea in the early years. The diameter of the trachea from 0 to 2 years of age ranges from 4 to 7 mm and does not reach 1 cm in diameter until around 8 years of age.[2] As a result, children are less able to tolerate stenotic lesions of the airway and more frequently require surgical management.

Congenital tracheal stenosis can arise from embryologic malformations resulting in a wide variety of abnormalities. These are often associated with underlying genetic mutations or syndromes. Some of these include:

• Tracheomalacia
• Complete tracheal rings
• Tracheal cartilaginous sleeve
• Tracheoesophageal fistula
• Tracheal agenesis
• External vascular compression (rings and slings)

Acquired lesions can occur in pediatric and adult populations. These are often iatrogenic, but the differential must remain broad and may include:

• Intubation trauma and high cuff pressure (pressure-induced ischemic necrosis)
• Complications of tracheostomy tubes (granulation tissue, suprastomal granuloma, A-frame deformity)
• Inflammatory or infectious conditions and their sequelae
• Blunt or penetrating trauma
• Inhalational injury
• Neoplasms, both benign and malignant

After diagnosing tracheal stenosis, it is important to grade it appropriately. Typically, tracheal stenosis is divided into the long segment (LSTS) or short segment (SSTS) lesions. SSTS typically spans fewer than 5 tracheal rings, and LSTS is typically defined as a lesion that spans over 50 to 75% of the airway, but these definitions can vary based on patient age and size. Also, it is important to know if the stenotic segment is intrathoracic or extrathoracic (above sternal notch), as this will greatly alter surgical approaches and anesthetic considerations. Intrathoracic stenoses often require a sternotomy and extracorporeal membrane oxygenation (ECMO) or cardiopulmonary bypass (CPB). Aside from length, the caliber of the luminal stenosis must be quantified. The original Cotton-Meyer grading scale initially introduced for grading subglottic stenosis is used to grade tracheal stenosis, and is based on the percentage of airway lumen narrowing.[3]

• Grade I: 0 to 50%
• Grade II: 51 to 70%
• Grade III: 71 to 99%
• Grade IV: no detectable lumen

Anatomy and Physiology

The trachea begins at the caudal aspect of the cricoid cartilage and extends to the carina. During organogenesis, the laryngotracheal structures form from the laryngotracheal bud emanating from the foregut immediately caudal to the fourth branchial arch. The development of the tracheoesophageal septum ensues and is crucial in separating these structures. As mentioned, newborn tracheal diameter ranges from 4 to 7 mm, and the adult diameter ranges from 12 to 25 mm. The length of a newborn trachea is approximately 4 cm and ranges from 11 to 13 cm in adults.

The trachea is composed of stacked c-shaped cartilaginous rings, and this rigid structure is key to preventing collapse. The membranous posterior wall contains the trachealis muscle, and the creation of this incomplete ring structure allows the trachea to expand during the dynamic respiratory process. There are typically 16 to 20 cartilaginous rings along the trachea that grow with the patient early in life.

When considering reconstruction, it is important to understand the blood supply to the trachea. Arterial supply is provided by branches from the inferior thyroid and bronchial arteries, which enter the lateral sidewall bilaterally. During reconstruction, it is crucial to preserve this lateral vascular supply.

Another key element in tracheal reconstructive surgery is a clear understanding of nearby structures and their intimate relationships with the airway. In the cervical region, the esophagus parallels the posterior wall of the trachea. The recurrent laryngeal nerves run in the tracheoesophageal groove bilaterally before entering the larynx and must be identified and preserved. The thyroid gland spans the cervical trachea and is intimately attached anteriorly via Berry’s ligament. In the thoracic cavity, the trachea is surrounded by multiple mediastinal structures, particularly the lungs and vascular structures entering and leaving the heart. This fact emphasizes the necessity of a multidisciplinary approach when managing distal or LSTS reconstructions, which will be discussed later.[4][5]

Indications

In general, symptomatic patients meet indications for surgical reconstruction. When considering tracheal stenosis repair, knowing the Cotton-Myer grade and determining if it is a SSTS or LSTS are critical. These patients have three options for treatment: observation and conservative management, endoscopic surgical repair, and open surgical repair.[6] General indications include the following:

Conservative Observation

• Poor surgical candidate
• Ventilator dependent due to pulmonary disease
• Asymptomatic mild disease
• The pediatric patient still growing

Endoscopic Repair

• Symptomatic mild to moderate disease
• Thin scar band or web
• A stenotic segment of fewer than 1 or 2 tracheal rings
• Adjunctive procedures following open repair

Open Repair

• SSTS and LSTS
• Failed endoscopic repair
• Complete tracheal rings
• Concomitant cardiopulmonary abnormalities requiring repair

Contraindications

There are many relative contraindications to consider. First and foremost, the overall health and prognosis of the patient must be considered, as a perfectly reconstructed tracheal lumen may still require a tracheostomy tube and ventilatory support in certain circumstances. The goals of the patient, the family, and the surgical team must be aligned, and expectations must be clearly communicated and understood.

Fitness to undergo surgery must be considered, and if questionable, could be a reason to continue observation over reconstruction. Laryngeal stenoses must be addressed before embarking on tracheal reconstruction or perhaps concomitantly in select patients.  Severe pulmonary dysfunction must be ruled out, and airway inflammation from underlying pulmonology or gastroenterology conditions must be addressed preoperatively to ensure a favorable environment for healing. Conditions resulting in poor wound healing, such as active infection, diabetes, previous irradiation, steroid use, or underlying inflammatory conditions may also preclude surgical intervention.[7]

Equipment

The following equipment is required:

• Laryngoscopy/bronchoscopy set
• Suspension laryngoscopy set
• Microlaryngeal instrument set
• Endoscopes and tower
• Airway LASER (typically CO2)
• Endoscopic airway balloons (size should be 2 mm larger than age-appropriate endotracheal tube)
• Head and neck soft tissue set
• Tracheotomy set

Personnel

These patients (pediatric patients in particular) frequently have multiple comorbidities, and it is important to have a full multi-disciplinary team in place both pre- and post-operatively. This team will involve specialists in otolaryngology, cardiothoracic (CT) surgery, pulmonology, gastroenterology, critical care, anesthesiology, speech and language pathology, and care coordination.

In the pediatric population, in particular, these patients should be managed through a multidisciplinary aerodigestive clinic. This allows for collaboration and care coordination amongst physicians and other medical personnel, thus allowing expeditious care and minimization of risks and complications.[8]

Preparation

Prior to any airway reconstruction, the nature and severity of the stenosis are confirmed with a formal airway evaluation, including direct laryngoscopy and bronchoscopy by the Otolaryngologist. This is typically performed in conjunction with gastroenterology and pulmonology, with esophagogastroduodenoscopy and flexible bronchoscopy/bronchoalveolar lavage as indicated, to ensure the health of the shared aerodigestive tract. 

If reconstruction is considered following formal airway evaluation and the patient’s clinical condition allows it, imaging is usually performed to help plan the surgical procedure and confirm findings. A high-resolution CT (HRCT) scan with contrast of the neck and chest will help define the stenotic segment as well as define any cardiopulmonary abnormalities that need to be addressed. CT angiogram and MRI are sometimes helpful depending on the nature and etiology of the pathology.

With recent advances in 3-D printing and rapid prototyping, many institutions are also beginning to utilize this technology both in preoperative planning and intraoperative repair. Patient-specific 3-D models can be designed and printed rather quickly and cost-effectively from HRCT scans. In theory, this allows surgical teams to define the stenosis better, manipulate it preoperatively to test concepts and techniques, and improve confidence intraoperatively. There are also reports of patient-specific bioresorbable implants being utilized to address difficult tracheobronchial stenoses with good preliminary data.[9] Ultimately, many believe that 3-D printing will allow for patient-specific bioprinted grafts.[10]

Technique or Treatment

As outlined above, preoperative assessment and classification of the stenosis is key in selecting the appropriate repair technique. Lesions amenable to endoscopic repair and those requiring open repair confined to the extrathoracic trachea are often amenable to repair by a trained Otolaryngologist alone. When lesions become intrathoracic or concomitant cardiopulmonary abnormalities need repair, a transthoracic approach with sternotomy is often required. This requires enlisting CT surgery, and these procedures are often done using extracorporeal membrane oxygenation (ECMO) or cardiopulmonary bypass (CPB). The general steps are outlined below.

Endoscopic Repair [11]

• Clear communication between the surgeon and the anesthesiologist is paramount. During endoscopic balloon inflation, there will likely be desaturation events for which one must be prepared. Also, electrocautery or laser manipulation greatly increases airway fire risk, and all precautions must be absolutely followed.
• Preoperative IV steroids are encouraged, but prophylactic antibiotics are generally not required. Topical anesthesia using 4% lidocaine allows for improved anesthesia throughout the case and is generally recommended.
• Suspension laryngoscopy is performed, and adequate exposure is confirmed. 4 mm endoscopes are typically adequate for most patients but may be adjusted for small children.
• Identify the stenosis and determine whether radial incisions are appropriate before balloon dilation.
• If indicated, use cold steel instruments or an appropriate laser to make radial incisions through the stenosis.
• Insert an appropriately sized airway balloon into the airway, ensuring half of the balloon is distal and half is proximal to the stenosis.
• Communicate with anesthesia and once the patient is stable, inflate the balloon for the predetermined time.
• Deflate and inspect the stenosis and repeat dilation if indicated.
• Topical steroids can be administered with pledget or injection on the site of dilation to prevent restenosis.
• Hemostasis is achieved with topical agents (oxymetazoline, epinephrine)

Tracheal Resection and Reanastomosis [12]

• This is performed for SSTS and can often be done under general anesthesia with endotracheal tube intubation. If the lesion is distal or other cardiac repairs are being performed, ECMO or CPB are recommended.
• Preoperative IV steroids and antibiotics are encouraged.
• Exposure of the stenotic segment of the trachea is performed, ensuring the preservation of vital surrounding structures.
  • Extrathoracic lesions can be managed via a transcervical incision and approach.
  • Intrathoracic lesions often require a sternotomy.
• After exposure and identification of the stenotic segment to be resected, endoscopic visualization of the planned site of resection is confirmed.
• Prolene sutures are secured below the stenosis to ensure distal control of the airway following resection.
• A vertical tracheotomy along the stenosis is performed, and visual inspection allows for confirmation of resection feasibility.
• Resection of the stenosis proceeds, using caution to avoid injury to surrounding structures.
• Following resection, releasing techniques are performed as indicated to achieve a tension-free closure. These include anterior and posterior blunt dissection (avoiding disruption of laterally based vascular supply) and supra- and infra-hyoid releasing maneuvers.
• The distal and proximal stumps are then reanastomosed in an interrupted fashion, beginning posteriorly and finishing anteriorly.
• Closure of the wound is performed. Depending on patient cooperation, the tension of the closure, the patient may remain intubated and sedated during the immediate postoperative process to ensure adequate healing.

 Slide Tracheoplasty [6]

• This procedure has become the standard of care for LSTS and distal lesions. It allows for expansion of the stenotic segment while allowing for maximal tracheal preservation. Due to the nature and location of lesions managed with slide tracheoplasty, these are frequently performed via a sternotomy for adequate exposure. This also means that these patients generally require ECMO or CPB for the duration of the procedure.
• It is important to mention the clinical implications of a tracheal bronchus (bronchus suis). This is a rare (<1%) developmental abnormality identified by a bronchus coming off the trachea above the carina and often supplying the entire right upper lobe (1). This abnormality tethers the trachea and inhibits the surgeon’s ability to slide the cut tracheal ends into apposition, usually preventing a successful slide tracheoplasty.
• Preoperative IV steroids and antibiotics are encouraged.
• Exposure is more complicated, often requiring sternotomy, which is performed in conjunction with CT surgery.
• Following adequate stenosis (often via sternotomy), the stenosis site is confirmed endoscopically.
• The center of the stenotic segment is incised horizontally, and supra- and infra-hyoid releasing maneuvers are performed.
• After adequate release, the posterior wall of the proximal segment and anterior wall of the distal segment are incised vertically along the length of the stenosis.
• The two segments are overlapped, ensuring the proximal segment is anterior.
• Closure proceeds in an interrupted fashion, achieving a water-tight and tension-free anastomosis.
• Following a leak test, the chest is closed with the assistance of the CT surgeons.
• Postoperative care centers around avoiding neck extension. This can be achieved with sedation/paralysis for a prolonged period of time or chin-to-chest sutures.

Complications

Tracheal reconstruction is often successful, but complication rates can approach 40%.[1] Early identification and management of complications is key to long-term success. Aside from the expected complications of the surgery, specific complications regarding tracheal reconstruction can be separated into the following categories:[13]

Anastomotic

• Granulation tissue
• Restenosis or stricture
• Tracheomalacia
• Leak
• Dehiscence

Fistulas

• Tracheoinnominate
• Tracheoesophageal
• Tracheocutaneous

Miscellaneous

• Recurrent laryngeal nerve injury
• Dysphagia/aspiration
• Mediastinitis
• Pneumomediastinum
• Pneumothorax
• Prolonged ventilatory requirement
• Death

Clinical Significance

Tracheal stenosis is a rare complication resulting from either failed embryologic development or insults to the tracheal lumen. The most common cause is prolonged intubation and high cuff pressure with resultant stenosis. Mortality rates for severe tracheal stenosis are high, particularly in the pediatric population, and must be identified and treated early. Appropriate classification and grading will allow surgeons and care teams to appropriately triage and treat patients successfully. The reconstructive plan must match the goals of care, and communication between the care team and the patient is essential. Surgical reconstruction through endoscopic or open approaches is generally successful. However, despite advances in surgical technique, complications are still prevalent and must be managed appropriately and expeditiously to prevent unwanted outcomes.

Enhancing Healthcare Team Outcomes

Tracheal stenosis requiring reconstruction is a rare anomaly that requires a dedicated multidisciplinary team in order to achieve success for the patient. While the surgeons (Otolaryngology, Cardiothoracic) are ultimately responsible for the surgical reconstruction, their success is dependent upon a team. These patients require an extensive workup preoperatively, and their clinical status must be optimized prior to undergoing surgery. Also, postoperative care is extensive. Critical care physicians, pulmonologists, gastroenterologists, anesthesiologists, speech and language pathologists, nursing support, and care coordinators must work tirelessly to ensure the safety and well-being of the patient. Communication is key and this is why these patients should be managed exclusively through a multidisciplinary aerodigestive clinic where all of these services are available.[8]