Airway Stenosis - Importance of Minimally Invasive Procedures

Introduction

Lungs are the primary functional component of the respiratory unit. The exchange of the gasses takes place in the alveoli of the lung, but the transportation of gasses is done by the windpipe and airways. Therefore, any obstruction in the airways is associated with breathing problems and metabolic changes in the body. Narrowing of the airways or airway stenosis is the most common cause of obstruction in airway passage.

What Is Airway Stenosis?

Obstruction or narrowing of the airways is known as airway stenosis. In most cases, these obstructions occur in the upper respiratory tract. This is also known as laryngotracheal stenosis. This includes obstruction of the larynx, glottis, subglottic region, and trachea.

What Are the Causes Of Airway Stenosis?

Airway stenosis can be caused by several factors. These are:

• Neoplasms: Various malignant tumors like adenoid cystic carcinoma, squamous cell carcinoma, carcinoid, and mucoepidermoid carcinomas are responsible for obstruction of the airway passage.

• Benign Tumors: Benign tumors of the upper respiratory tract such as granular cell tumors, hamartomas, carcinoid tumors, hemangiomas, neurogenic tumors, and cartilaginous tumors or chondromas are responsible for airway obstruction.

• Abnormal Tissue: Fibrosis of the airway tract or presence of the scar tissue is associated with airway obstructions.

What Are the Types Of Airway Stenosis?

Based on the causative factors, airway stenosis can be classified into the following types:

1. Structural Stenosis: This type of stenosis is caused by structural obstructions. This is again divided into:

• Type 1 Stenosis: Type 1 stenosis is caused by the overgrowth of benign and malignant tumors.

• Type 2 Stenosis: This type of obstruction is caused due to external compression by various anatomical structures. The associated conditions are; enlarged lymph nodes, goiter, large vessels, or other mediastinal structures, including non-pulmonary tumors.

• Type 3 Stenosis: This type of stenosis is caused by structural alteration of the airways. The main causative factor for such alteration is surgical intervention, trauma, and transplantations due to pulmonary disorders.

• Type 4 Stenoses: This is mainly caused by anatomical changes in the windpipe. Factors like the presence of scar tissues due to surgery, intubation, trauma, and burn injury are associated with this.

2. Dynamic (Functional) Stenosis: This is associated with the morphologic changes of the cartilage of the windpipe. The most common factor is the abnormal softening of the cartilage. This is classified into two types:

• Type 1: In this type, a tent-shaped deformation of the cartilage is seen.

• Type 2: This is seen in emphysema cases where the posterior membrane becomes loose and bulged out.

Symptoms:

1. Shortness of breath.

2. Breathing difficulty and symptoms of leatheriness.

3. Persistent coughing and regular lung infections.

4. Difficulty in sleeping as patients experience episodes of breathing difficulty.

What Are the Minimally Invasive Procedures Used to Treat Airway Stenosis?

Airway stenosis can be treated with various procedures. Open surgical techniques are required to remove scar tissue that is more than one centimeter in size. Laryngotracheoplasty is a surgical procedure that is done for scar lysis and prevention of restenosis. In this procedure, the graft is placed for better healing.

Some minimally invasive procedures can be performed with minimal complications. These procedures include various endoscopic procedures and bronchoscopy techniques.

1. Dilatation Method: Long-standing cases of stenosis and airway stenosis in infants can be corrected by using dilators. Dilators can be of two types; balloon dilators and rigid dilators.

Acquired stenosis in infants is caused by perinatal intubation and mechanical ventilation. In such cases, dilation is done endoscopically using a balloon dilator. For this procedure, the child is placed under general anesthesia, and a French catheter with a balloon with a diameter of 5 to 11 millimeters is used. This balloon is inserted with the help of air to remove stenosis.

Bronchoscopic balloon dilatation is used in adult patients for the treatment of subglottic stenosis and tracheal stenosis. It is particularly useful in patients with a history of previous interventions or comorbidities. A balloon dilation catheter with a diameter of 15 to 18 millimeters is used in this procedure. The flexibility of the balloon and the operator's control over its inflation is the advantages of balloon inflators.

Rigid dilation can be done with the help of bronchoscopes. Gradually, the increased diameter of the bronchoscope is inserted into the stenosis part for dilatation. Sometimes, a silicon stent can be placed to maintain the diameter of the airways.

2. Laser: Laser procedures are one of the most commonly used methods for the treatment of airway stenosis. Carbon dioxide laser is the most commonly used laser in this procedure. Lasers are mainly used for the treatment of subglottic ductal cysts, concentric web-like subglottic stenosis, recurrent subglottic stenosis, and removal of granulation tissue.

Procedures like resection of the portion of the arytenoid cartilage (cartilage of the vocal cord), supraglottoplasty (removal of excess tissue of the upper larynx), and partial arytenoidectomy (enlargement of the laryngeal inlet) can be done with the help of laser.

3. Mitomycin C: This is a chemotherapeutic agent that is used with the help of endoscopic procedures. This is an alkaline agent that inhibits cell divisions, protein lysis, and growth of the fibroblasts. This is very effective for the removal of scar tissue. It is also helpful in the prevention of recurrent stenosis. It is applied in the affected areas after making an incision. The dose of Mitomycin C is 1 to 2 milligrams per milliliter with a contact time of two minutes.

What Is the Surgical Procedure?

The surgical procedure includes the following steps:

• Pre-surgical computed tomographic (CT) scan of the stenosis and assessment of the airway is done, following which grading of the stenosis is done.

• If possible, inhalation anesthesia is done, otherwise, intravenous anesthesia is done.

• Maintenance of ventilation during the surgical procedure is a challenge. Therefore, controlled ventilation is maintained. Jet ventilation is a helpful procedure by which a high volume of oxygen is delivered at high speed. This increases ventilation and oxygen concentration.

• Vocal cord spreaders are used to retract the vocal cord for better visualization. After this, the necessary surgical technique is used to remove the stenosis.

Conclusion

Airway stenosis can cause severe breathing problems. Open surgical techniques are full of complexities and are difficult to perform in patients with comorbidity. Minimally invasive procedures are easy to perform and post-surgical complications are also less.