Tracheal stenosis is a narrowing of the trachea, or windpipe, which carries air from the nose and mouth to the lungs. When the trachea narrows, airflow becomes restricted, making breathing difficult. This condition can develop due to inflammation, injury, or scar tissue within the airway. The term “stenosis” refers to an atypical narrowing in a bodily passage.
Medical Procedures as Primary Causes
Medical procedures are the most frequent causes of acquired tracheal stenosis. Prolonged intubation, which involves inserting a breathing tube into the trachea to assist with ventilation, is a common factor. The pressure exerted by the endotracheal tube’s cuff on the tracheal wall can lead to ischemia, where blood flow is restricted, potentially causing tissue damage. This damage can progress to ulceration, inflammation, and eventually, the formation of scar tissue that narrows the airway.
The duration of intubation significantly influences the risk of stenosis, with higher risk observed in intubations lasting longer than 10 days. Endotracheal tube size and cuff pressure are also considerations; over-inflation of the cuff can result in tracheal tissue necrosis. Repeated intubation attempts and patient agitation, which can cause shearing forces on the airway, may also contribute to injury and subsequent scarring.
Tracheostomy, a surgical procedure that creates an opening in the trachea, can also lead to stenosis. This type of stenosis often develops at the stoma site, where the opening is made, or at the site of the tracheostomy tube’s cuff. Abnormal wound healing, excessive granulation tissue formation around the stoma, or cartilage fracture during the procedure can contribute to narrowing. Higher tracheostomy sites and malpositioning of the tube’s cuff can increase the risk of this complication.
Inflammatory and Autoimmune Conditions
Systemic inflammatory and autoimmune diseases can also contribute to tracheal narrowing. These conditions cause the body’s immune system to mistakenly attack healthy tissues, leading to chronic inflammation and scarring in the trachea.
Granulomatosis with Polyangiitis (GPA), previously known as Wegener’s granulomatosis, is an autoimmune vasculitis that frequently affects the respiratory tract, including the trachea. It can cause inflammation and scarring, leading to subglottic stenosis—narrowing just below the vocal cords.
Sarcoidosis, an inflammatory disease, can affect multiple organs and can also manifest as tracheal stenosis. The inflammation associated with sarcoidosis can lead to the formation of granulomas, which are small clumps of inflammatory cells that can narrow the airway. Relapsing Polychondritis is another rare autoimmune condition characterized by recurrent inflammation and destruction of cartilage throughout the body, including the cartilaginous structures of the trachea. Airway involvement occurs in approximately 50% of patients with Relapsing Polychondritis, potentially leading to collapse and obstruction of the airways due to cartilage damage.
Physical Trauma and External Pressure
Direct physical injury to the neck or throat can also result in tracheal stenosis. Incidents such as blunt force trauma from accidents or penetrating injuries can cause immediate damage to the tracheal structure. This trauma can lead to inflammation, edema, and subsequent scar tissue formation as the body attempts to heal, ultimately narrowing the airway. Surgical complications not related to intubation or tracheostomy procedures may also cause direct injury to the trachea, leading to stenosis.
External masses or tumors can exert pressure on the trachea, causing it to narrow. Both benign and malignant tumors, whether originating in the trachea or spreading from adjacent areas like the thyroid, esophagus, or lungs, can physically compress the windpipe. For example, thyroid tumors or mediastinal masses, which are growths in the chest cavity between the lungs, can press on the trachea and restrict airflow. This external compression gradually reduces the tracheal lumen, leading to breathing difficulties.
Other Origins of Stenosis
Tracheal stenosis can sometimes be present at birth, a condition known as congenital tracheal stenosis. This rare form often results from abnormal development of the trachea, such as the presence of complete tracheal rings instead of the normal C-shaped cartilage. These complete rings prevent the trachea from expanding properly, leading to a constricted airway from birth. While often identified shortly after birth, some milder cases may not be diagnosed until later in childhood or even adulthood.
Less common causes include certain infectious diseases. Tuberculosis, a bacterial infection, can in rare instances involve the trachea, causing tissue damage and scarring that leads to stenosis. Other bacterial and viral infections affecting the respiratory system can similarly contribute to tracheal narrowing through inflammation and scar tissue formation. In some cases, despite thorough investigation, no identifiable cause for tracheal stenosis can be found, a situation referred to as idiopathic tracheal stenosis. This diagnosis is made when other known causes have been ruled out.