Introduction
Subglottic stenosis is an uncommon condition that can occur in newborns, toddlers, and adults. It is caused due to the narrowing in the part of the airway underneath the vocal cord. Causes can be either congenital or acquired. Management of this condition can be challenging, and the severity of the condition determines it. This article will discuss in detail about subglottic stenosis.
What Is Subglottic Stenosis?
Glottis is an orifice between the vocal cords, and the subglottis is the space in the airway below the vocal cord. When the subglottic space gets narrowed, it can lead to inflammation of the airway or hardening of the area. The diameter of the cavity of the subglottis is normally 0.15 to 0.25 inches in newborns. It is considered narrow when the diameter is less than four millimeters in newborns. Subglottic stenosis can cause difficulty breathing, changes in the voice, and even complete airway obstruction.
What Are the Types of Subglottic Stenosis?
There are two types of subglottic stenosis according to its etiology.
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Congenital subglottic stenosis is a birth defect that occurs when there is an improper formation of the airway cartilage before birth. Rarely are they associated with genetic disorders. Congenital subglottic stenosis ranges from mild constriction of the airway to complete obstruction.
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Acquired subglottic stenosis is the commonly occurring subglottic stenosis. In 90 percent of the cases, it occurs due to prolonged intubation. Intubation refers to the procedure where a tube is inserted into the patient's mouth down to the trachea to deliver air or oxygen.
How Common Is Subglottic Stenosis?
Subglottic stenosis is a rare complication, and the occurrence has greatly reduced since the 1980s. It occurs in approximately one in four lakh people every year. The incidence of subglottic stenosis has reduced due to improved handling of the newborn while ventilating.
What Is the Pathophysiology of Subglottic Stenosis?
During prolonged intubation, the endotracheal tube causes pressure ulcers at the point of intersection with the tissue, which results in swelling and ulceration of the inner lining of the subglottic tissue. This progresses to form pressure necrosis of the mucosa. These changes can result in infection of the cricoid cartilage. The loose and flexible subglottic submucosa and insufficient blood supply of the cricoid cartilage prevent the initial healing of the mucosa. This can cause hardening and scarring of the tissue, resulting in stenosis of the subglottis. An oversized endotracheal tube or an air leak in the tube can increase the risk of necrosis of the subglottic mucosa. Subglottic stenosis often occurs at the cricoid cartilage, which is the narrowest part of the airway.
What Are the Causes of Subglottic Stenosis?
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The most common cause of subglottic stenosis is trauma. The trauma happens from either internal or external causes. External trauma most often occurs from road traffic accidents in adults, and internal trauma occurs from laryngeal trauma and trauma from intubation. Trauma from intubation accounts for 90 percent of cases.
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Congenital subglottic stenosis occurs from malformation in the cricoid cartilage before birth.
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Another common cause of acquired subglottic stenosis is GERD (gastroesophageal reflux disease), where acid contents from the stomach constantly ascend towards the esophagus (food pipe). Because of gastroesophageal reflux, the subglottis gets irritated from the acidic contents, which results in inflammation of the area.
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Low birth weight.
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Infections such as tuberculosis and diphtheria can also cause subglottic stenosis.
What Are the Signs and Symptoms of Subglottic Stenosis?
A few signs and symptoms of subglottic stenosis include :
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Noisy breathing- Abnormal sound during inhalation and exhalation.
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Difficulty in breathing or feeling of suffocation.
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Urge to breathe.
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Change in voice.
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Loss of voice.
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Abnormal crying in newborns.
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Chest retractions in infants and children.
How Is Subglottic Stenosis Diagnosed?
The healthcare provider will do the initial assessment and a thorough physical examination of patients. Various tests are performed to confirm the diagnosis.
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Radiographic imaging plays an important role in diagnosing subglottic stenosis and helps assess the exact location and extent of the stenosis. Plain neck radiography helps in evaluating airway obstruction in newborns. Computed tomography (CT) scan and magnetic resonance imaging (MRI) are used to diagnose subglottic stenosis. Optical coherence tomography is a non-invasive endoscopic imaging technique used to monitor subglottic mucosal injury.
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For the evaluation of the airway, endoscopic examinations are performed, such as flexible fiberoptic fluoroscopy assessing the vocal cord function. Direct visualization with endoscopy evaluates the airway along with the esophagus. A conclusive diagnosis is made through flexible laryngoscopy or bronchoscopy.
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Gastroesophageal and laryngopharyngeal reflux is another common cause of subglottic stenosis. Therefore the evaluation of gastroesophageal reflux is done by pH monitoring to record the activity of the esophagus for a 24-hour period.
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Pulmonary Function Tests- Another major tool in diagnosing subglottic stenosis is spirometry. It is a non-invasive, simple test that assesses lung function. The patients are asked to breathe in and out through a machine called a spirometer to assess the air that is inspired and expired. It also evaluates the patient's post-surgery outcomes.
How Is Subglottic Stenosis Treated?
Management of subglottic stenosis is challenging, and it involves a multidisciplinary approach. It includes topical management and surgical intervention. The surgical approaches include endoscopic, open approach, or tracheotomy. Patients with mild stenosis and not involving the cartilage are considered for the therapeutic endoscopy, whereas patients with complex lesions are preferred for surgical interventions. If there is an underlying cause of GERD, management of the reflex is important.
Endoscopic Approach:
Therapeutic endoscopy is a less invasive approach in which the narrowed portion of the subglottis is dilated by ballooning or with other surgical instruments. The endoscopic technique also includes a radical incision using a carbon dioxide laser and removing tissue in the narrowed portion using a knife without dilation. It often involves stent placement in the narrowed portion at the end. Topical mitomycin and steroid injections are other supporting therapies in the endoscopic approach.
Open Approach:
This technique is used when the patients are unresponsive to conservative management options. Contrary to the endoscopic dilation technique, This involves an open approach by an incision in the front of the neck. Resection of the narrowed area and reconstruction of the windpipe is done.
Conclusion
Subglottic stenosis is an obstruction in the airway due to the narrowing of the subglottis, the portion underneath the vocal cords. They occur commonly in newborns and adults, especially in the female population. The clinical presentation ranges from difficulty in breathing to complete airway obstruction. A proper history, physical examination, imaging investigations, and endoscopic evaluation help diagnose the condition. Therapeutic endoscopy is the preferred management option for subglottic stenosis.
