Do you experience shortness of breath or difficulty breathing after routine activities? Along with a high-pitched wheezing sound often? It could be tracheal stenosis!

This article will help you understand what tracheal stenosis is, its symptoms, and the diagnosis, followed by treatment options, with a focus on stenting as a management approach. Let us get started!

What is Tracheal Stenosis?

Abnormal narrowing of the trachea due to an injury or a birth defect, leading to difficulty breathing, is known as tracheal stenosis (TS). The upper airway includes the trachea, larynx, epiglottis, and subglottis¹. The trachea, commonly known as the windpipe, is a tube-shaped structure made up of C-shaped rings of cartilage that help keep it open, so air can travel from the nose down into the lungs. If the trachea becomes narrowed, this airflow is obstructed, making it difficult to breathe normally.

There are two types of TS:

1. Congenital TS is present at birth and is very rare. It can be life-threatening and usually needs emergency care as soon as it is diagnosed.
2. Acquired TS develops later in life, often due to an injury, trauma, or infection is more common, especially in adults

Causes of TS

Congenital TS is caused by the formation of complete tracheal rings instead of the usual c-shaped ones. These o-shaped rings are narrower and can make it difficult to breathe normally. If symptoms get worse over time, a surgical procedure called slide tracheoplasty is often needed to widen the airway 

In the case of acquired TS, multiple factors lead to disease development. They may be:

1. Prolonged intubation
2. Autoimmune diseases such as rheumatoid arthritis, systemic lupus erythematosus, and others can lead to laryngotracheal stenosis 
3. Infectious diseases such as tuberculosis, bacterial tracheitis, etc
4. Direct injury to the trachea by trauma, inhalation of gases, or radiation therapy
5. A benign or malignant tumour pressing on the windpipe

Symptoms and diagnosis

A person with TS may experience any of the following symptoms:

1. Dyspnea or shortness of breath, leading to difficulty breathing
2. Chest congestion
3. Stridor or noisy breathing, which can be mistaken for wheezing
4. Asthma, which does not get better upon treatment
5. Recurring respiratory infections, including pneumonia
6. Cyanosis, blue colouration near the mouth or nose

If you have any of the above symptoms and they persist over time, consult with your healthcare provider at the earliest.

TS can be diagnosed by using different tests in the following categories:

1. Pulmonary function tests- These are the first set of tests performed to learn how well the lungs are working
2. Imaging- To help diagnose TS, doctors often start with a routine chest X-ray to check the lungs and windpipe. In some cases, more detailed imaging, like a CT scan of the neck and chest, or an MRI, may be recommended for a clearer view of the airway
3. Endoscopy techniques- Bronchoscopy and laryngoscopy are conducted to determine lesions and the degree of narrowing in the windpipe
4. Blood test- To determine if there is any infection or inflammation
5. Biopsy- This is performed to check for any abnormal or malignant growths in the airway, especially if there's a concern about an underlying cause

Management of TS

While different treatments are available for TS, there is no standard guideline for proper management. Treatment depends on the location, severity, and nature of the condition. Mild cases of TS can often be treated with minimally invasive procedures such as balloon dilation and laser surgery. These techniques usually provide short-term relief, lasting from 6 months to one year. More severe cases usually require a combination of treatments, including surgery. To provide long-term relief, doctors may use stents to keep the airway open or perform open surgeries. Open surgery may involve either removing the narrowed section of the trachea and reconnecting the healthy ends (tracheal resection with reanastomosis) or reshaping the airway through tracheoplasty. Inoperable cases generally use the Montgomery T-tube or adjunctive treatments¹. Surgery is the most effective way to treat benign tracheal stenosis, but for many patients with severe disease, pneumonia, or poor overall health, undergoing surgery or general anaesthesia may not be a safe option. A tracheal stent is both a minimally invasive approach and a long-term treatment. Let us now dive in and understand the use of tracheal stents in managing TS. 

Stents- What are they?

Stents are tube-like devices with a hollow centre, inserted into the trachea to relieve narrowing or blockage, support healing, and provide reinforcement against external pressure. The most common reason for placing a stent is to treat airway obstruction, followed by structural defects in the airway wall or to help control bleeding.. Stents are generally used when more conservative treatment options have not been successful, and their placement requires specialist training and experience. Stents can be life-changing for people with TS, making each breath feel noticeably easier.

Stents are made of different materials, including silicone, nitinol, stainless steel, or hybrid materials. The ideal properties of a stent are:²

1. Stable
2. Strong 
3. Biocompatible
4. Resistant to migration
5. Easily deployed and removed

The type and material of the stent used depend on the severity of the condition and anatomy. 

Types of stents

Metal stents

Early metal stents were made from bare metal wire, typically using materials like steel or tantalum. Today, a wider range of metals, along with their alloys, are used to improve flexibility, strength, X-ray visibility and compatibility with the airway. They may be self-expandable metal stents (SEMS) or fixed-diameter stents requiring balloon dilation. However, due to rising complications, the FDA has issued a warning for the use of metal stents in airway diseases.

Silicone stents

Silicone stents came after metal stents, which are made up of soft material and have the following properties:

1. Easily moldable
2. Greater mechanical strength
3. Stability at higher temperatures
4. Less expensive
5. Easily deployed and removed 

The above properties helped silicone stents become popular in tracheal stenting. The three most common silicone stents are the Montgomery T-tube, the tubular stent, and the Y-stent.²

Hybrid stents

These are also called covered metallic stents. These combine the benefits of both metal and silicone stents while reducing their limitations. Hybrid stents typically use a silicone or similar material as a covering membrane, which helps prevent tissue ingrowth and allows for easier adjustment or repositioning. Other commonly used materials include polyurethane and polytetrafluoroethylene (PTFE). Examples of hybrid stents are the Ultraflex stent, the Alveolus stent, and the Freitag stent. 

How is stenting done? The procedure

With different types of stents available, how we put them inside is equally important. Bronchoscopic and open approaches are generally preferred for stenting. Earlier, rigid bronchoscopy was performed, but with advances in imaging and instrumentation, flexible bronchoscopy is now preferred. The steps in bronchoscopy are as follows:³

1. General anaesthesia followed by flexible bronchoscopy to confirm the location and assess severity
2. Balloon dilatation for dilating the narrowed airway
3. Advancing the selected stent through the guidewire
4. Deployment of the stent after confirming the position
5. CT scan/ fluoroscopy/ chest radiograph to ensure proper placement

Tracheal stents can also be placed using open surgical techniques, although this is rarely done. However, such methods are currently being explored in more complex procedures such as tracheal transplantation, tracheobronchial replacement, or airway reconstruction.³

Complications associated with stenting

Although stenting is a commonly used approach to manage TS, it does have associated risks and complications. Potential complications resulting from a stenting procedure can be any of the following:²

1. Granulation tissue formation
2. Stent migration
3. Stent misplacement and dislodgement
4. Tumor ingrowth
5. Lower respiratory tract infection
6. Tracheoesophageal fistula
7. Stent fracture
8. Mucus plugs

Regular follow-up visits with the healthcare provider are necessary to monitor the stent and catch complications earlier. Taking prescribed medications as directed, along with making appropriate lifestyle changes and practising breathing exercises, can help extend the effectiveness of the stent and improve overall breathing. 

Recent advances 

With innovations and technological advancements, stenting has also seen progress in many areas. The following are some of the newest airway stents:

Biodegradable stents

These stents offer the benefits of both silicone stents and covered SEMS, but with fewer side effects. This is because they are made from materials that naturally break down over time, spending only a limited period in the airway, and causing minimal interference with the surrounding tissue.⁴ Biodegradable stents are generally made up of a material called polydioxanone, which safely degrades into harmless by-products within the body. 

Drug-eluting stents

These stents are made with a special coating that slowly releases the drug/medication directly into the surrounding airway tissue. Side effects such as granulation tissue formation and infection can be minimised, while in cases of tumours, they can act as localised chemotherapy.⁵ Radioactive stents are also popular for their potential to inhibit the growth of tumours. However, more research and clinical trials are needed to better understand appropriate radiation doses and overall effectiveness. 

3D- printed stents

3D printing technology has found its way into every field today, including medicine and healthcare. In TS, it has enabled customized patient-specific stents matching the complex anatomy of the trachea, which significantly reduces the risk of stent migration. The first reported use of a 3D-printed airway stent was in 2018, in a complex post-transplant case where conventional stents had failed.⁵ In addition to advances in stent design, techniques for placing stents are also evolving, supported by ongoing research and clinical trials. 

Summary

Tracheal stenosis is the narrowing of your windpipe that can interfere with normal breathing. While it can feel unsettling to receive this diagnosis, it’s important to remember that today’s medical advances offer a wide range of effective treatment options. Treatment options range from minimally invasive balloon dilation to more complex surgeries. Stenting is one of the most common treatments and is often a less invasive way to help keep the airway open. Each patient has a unique anatomy and condition of TS, and your healthcare provider can guide you to the best treatment possible. Consistent follow-ups after the stenting procedure and maintaining a healthy lifestyle can help you to enjoy a significantly improved quality of life.