Subglottic Stenosis

What is Subglottic Stenosis?

Subglottic stenosis is a condition that can occur in people of all ages. It can cause a range of symptoms, from minor discomfort to a serious blockage of the airway that can be life-threatening. The subglottis is an area that is about 1 cm below the lateral margin of the ventricle, ending at the inferior border of a piece of cartilage called the cricoid cartilage. The subglottis is located between another area known as the glottis located above and the trachea or windpipe located below.

The subglottis is unique because it’s the only upper or proximal lower airway segment surrounded by a complete cartilage ring known as the cricoid cartilage. Because of this specific structural characteristic, the subglottis is more prone to stenosis, a narrowing condition.

In newborn babies that are born at term, the subglottic space typically has an average diameter of 4.5 to 5.5 mm. In premature babies, this diameter is usually slightly smaller, averaging at around 3.5 mm. As a person grows older, this diameter naturally gets bigger until it reaches an adult size of 11.6 mm in women and 15 mm in men.

Stenosis in newborn babies is identified when the diameter of the subglottic space is less than 4 mm in full-term newborns or 3 mm in premature newborns. However, there is no universally agreed-upon diameter for diagnosing stenosis in adults.

What Causes Subglottic Stenosis?

Subglottic stenosis, a narrowing of the airway just below your vocal cords, can be caused by either being born with it (congenital) or it can be acquired over time. Usually, those with congenital subglottic stenosis have no history of trauma or airway manipulation like getting a breathing tube placed. Normally, during the third month of a baby’s development in the womb, the airway gets hollowed out so air can pass through. However, in those born with subglottic stenosis, this hollowing out process doesn’t occur.

Possible other causes can be burns, swallowing harmful items, exposure to radiation, infections, and inflammation from acid reflux (GERD). It can also be provoked by immune system disorders such as granulomatosis with polyangiitis, amyloidosis, lupus, sarcoidosis, rheumatoid arthritis, relapsing polychondritis, or IgG4-related disease. Being born with certain genetic conditions like trisomy 21, CHARGE syndrome, 22q11 deletion syndrome, or Pallister-Killian syndrome can also be associated with this condition.

More people have subglottic stenosis that was acquired than those who were born with it, usually as a result of getting a breathing tube for an extended time. Historically, for children, this condition was often caused by the need to have a breathing tube for more than a day. While medical advancements in the ’60s and ’70s reduced death rates for many conditions, they also increased the time patients needed breathing tubes, creating a risk factor for this disease. If the inflatable cuff around the breathing tube is inflated too much, it can harm the airway in as little as 15 minutes. This can lead to tissue dying off, inflammation, and the production of fibrous tissue, leading to a narrowing of the airway.

Many healthcare professionals have a device to measure the pressure of the inflatable cuff. Nonetheless, if they fail to routinely check the pressure and ensure it is at the right level, patients risk getting a permanent injury. Even when the cuff is not over-inflated, having a breathing tube for a long time can cause tissue injury which may also cause subglottic stenosis. Other potential causes can be injuries like car accidents or getting hit by an object like a clothesline that can damage the tissue leading to inflammation and eventually a narrowing of the airway.

In the past, doctors used a formula based on a patient’s age to estimate the appropriate size for a breathing tube. However, further research showed that this method accurately predicted the correct size only between 50% and 75% of the time, potentially causing injury from an oversized tube. More recent studies have shown that a revised formula is more accurate, and some recommend using imaging methods like X-rays or ultrasound to determine the appropriate size. Factors that can increase the risk of developing this condition after getting a breathing tube include having a respiratory infection two weeks before the procedure, getting multiple tubes placed, unexpected removal of the tube, obesity, diabetes, and GERD.

Risk Factors and Frequency for Subglottic Stenosis

In the early 1900s, a condition called subglottic stenosis was relatively rare and mostly seen in babies born with it. However, with the introduction of a medical tube procedure called endotracheal intubation, more people started experiencing this problem after their treatment. This post-treatment issue became more common than the cases detected at birth. In fact, after having the tube removed, almost half of the children in intensive care have a kind of harsh, raspy sound in their breathing, and over half of adults and children show signs of acute throat injury. However, serious cases of this tube-induced stenosis are less common, only ranging between 0.3% to 11.38%.

There is a specific type of subglottic stenosis that mostly affects Caucasian women during the time leading up to menopause. It’s thought that factors like acid reflux, elevated levels of estrogen in a specific part of the windpipe, or immune responses may contribute to this condition. Understanding these factors is crucial to properly treat and prevent this issue.

Early 1900s – subglottic stenosis was rare and generally present at birth.
Introduction of endotracheal tubes caused an increase in this condition post-treatment.
After endotracheal tube removal, about 44% of children in intensive care can experience a raspy sound in their breathing.
Up to 57% of adult and pediatric patients show signs of short-term throat injury post-treatment.
Severe tube-caused stenosis ranges between 0.3% to 11.38%.
A type of subglottic stenosis impacting Caucasian women around menopause is believed to be linked to factors like acid reflux, increased estrogen levels in the windpipe, or immune responses.
Understanding these factors is important for effective treatment and prevention.

Signs and Symptoms of Subglottic Stenosis

People who might have a condition called subglottic stenosis should have a complete medical history review and physical exam. This condition might not always come with a history of constant croup (a childhood condition that causes a barking cough) or exertional stridor (a harsh sound when breathing), however, it is important to gather information about any past experiences with problems affecting the respiratory system, being on a ventilator, any kind of injury to the voice box (laryngeal trauma), any diagnosed syndromes, any abnormalities to the head and face, the status of the person’s feeding, and the quality of his or her voice. It’s also crucial to ask about any signs of chronic acid reflux, because it can irritate the area around the vocal cords and below, making the stenosis (or narrowing) worse.

The primary symptom of stenosis is stridor (a high-pitched, wheezing sound caused by disrupted airflow), which can occur whether a person inhales, exhales, or both, and it doesn’t matter if the stenosis is something a person was born with, or something he or she acquired. Should it be present from birth, symptoms usually appear soon after a child is born, and could include shortness of breath, rapid breathing, and the pulling in of skin between the ribs when breathing. If the stenosis is affecting the vocal cords, there could be changes in the cry, loss of voice, or a hoarse voice.

Stridor (high-pitched, wheezing sound)
Shortness of breath
Rapid breathing
Skin pulling in between the ribs during breathing
Changes in the cry
Loss of voice
Hoarse voice

For those people who were not born with, but acquired subglottic stenosis, many have a history of some kind of injury to their voice box or being put on a ventilator. Symptoms can show up as early as 3 to 4 weeks after the first voice box injury, but can also take several years to become evident. As such, any person experiencing stridor needs to have a full medical investigation. This often means having an ear, nose, and throat specialist perform a flexible laryngoscopy, which is a procedure that uses a flexible tube with a light and camera to examine the inside of the throat. Although a primary care doctor may not always find anything unusual during a physical exam that would suggest a diagnosis, the flexible laryngoscopy can show the narrowing of tissue below the vocal cords.

Testing for Subglottic Stenosis

Subglottic stenosis, a condition where your throat narrows just below the vocal cords, is primarily diagnosed through a procedure called endoscopic examination. A tool called flexible fiberoptic laryngoscope is used in this procedure. This tool provides a visual check of the subglottis, which is the area just below your vocal cords. It also helps observe the functioning of your vocal cords and the openness of your windpipe. This procedure is performed while you are awake and can be done to individuals of all ages. Sometimes, for a more detailed view of the subglottis, a procedure known as rigid laryngoscopy and bronchoscopy is carried out in an operating room under general anesthesia.

Spirometry, a test that measures how much and how quickly you can move air out of your lungs, is another useful tool for monitoring people who have subglottic stenosis. It measures three parameters: peak inspiratory flow rate (PIFR) – maximal speed of inhaling, peak expiratory flow rate (PEFR) – maximal speed of exhaling, and forced vital capacity (FVC) – total amount of air exhaled forcefully and quickly after inhaling as deeply as possible. When these readings change, it might signal a need for surgery.

While imaging techniques like CT scans and MRIs usually don’t play a big part in diagnosing adult subglottic stenosis, they can help assess abnormalities in patients whose cause of stenosis isn’t clear. They allow the doctor to look at the narrow part of the throat and measure its length. But these may not always provide specific useful information.

Long-range optical coherence tomography (OCT), a type of imaging test, is a potential tool for diagnosing this condition in newborns. OCT can detect changes in the subglottic mucosa, the moist tissue lining in the subglottic area, that come from using a tube inserted into the windpipe (endotracheal intubation). However, its use is limited because it isn’t automated and requires a lot of work to obtain results.

To assess the severity of subglottic stenosis, doctors use the Cotton-Myer grading system. It entails putting the patient under general anesthesia and then examining the obstruction in the airway. The severity is calculated by comparing the smallest endotracheal tube size that can pass through the subglottic lumen, the inside space of a tubular structure, to the expected endotracheal tube size appropriate for the patient’s age. The percentage of obstruction helps grade the stenosis into four categories:

Grade 1 stenosis: Obstruction of the airway is between 0% and 50%.
Grade 2 stenosis: Obstruction of the airway is between 51% and 70%.
Grade 3 stenosis: Obstruction of the airway is between 71% and 99%.
Grade 4 stenosis: Complete blockage of the airway.

This understanding can play a critical role in forming the treatment plan.

Treatment Options for Subglottic Stenosis

Subglottic stenosis, or the narrowing of the airway just below the vocal cords, can be managed in various ways. These methods include observation, injections, or surgical procedures. For patients with minor symptoms, routine monitoring at home or in a clinic using a spirometry machine might be suitable. Spirometry is a non-invasive and practical way to measure any blockage in your upper airway, and it offers useful information about the need for surgery and stability after the operation.

A minimally invasive option is the serial injection of steroids into the affected area, which can often yield good long-term results. It works by turning the fibrosis (scar-tissue formation) in the area into anti-fibrosis, thereby softening the narrowing and improving both the subjective feelings of breathlessness and the objective measurements of the airway.

If injections are not enough, further interventions such as surgery or dilation might be considered. This process involves making cuts using a knife or a laser to aid in dilation, or ‘stretching’ of the narrowed area, to improve airway patency. Many patients may need multiple dilation procedures.

Another method called balloon dilation is often the first choice of treatment for acquired subglottic stenosis. It’s successful in over 90% of cases, improves symptoms, and reduces the need for additional procedures.

If frequent dilation is necessary, and the patient wishes to avoid more complications from open-airway surgery, another option is endoscopic laryngotracheoplasty, also known as the Maddern procedure. This involves removing the scarred and stenosed (narrowed) mucosa, or lining of the subglottis, which doesn’t affect the cartilage of the airway.

In severe cases of stenosis that cannot be managed endoscopically, more extensive open-airway procedures may be required. These can include laryngotracheal reconstruction (LTR), cricotracheal resection, or tracheostomy, depending on the severity and extent of the stenosis.

For babies born with subglottic stenosis, common treatment steps include a tracheostomy and regular airway evaluations carried out every three months to identify the need for and timing of any airway reconstruction surgery.

Different options are available based on the severity of subglottic stenosis. For instance, patients experiencing less than 70% airway obstruction might be managed conservatively with observation or endoscopic procedures. On the other hand, when there is severe stenosis or obstruction of over 70%, more aggressive surgical interventions may be required.

Problems with the trachea and larynx (parts of your airway) can be sorted into four main categories:

Narrowed airways (stenosis)
Infections
Tumors (neoplasm)
Aspiration (inhaling food, fluid, or other foreign material into the airways)

Airway narrowing can be caused by a variety of factors such as:

Subglottic and tracheal stenosis (narrowing in the area below the vocal cords or in the windpipe)
Vascular ring (a rare condition where the blood vessels form a ring around and put pressure on the airways)
Aberrant innominate artery (a misplaced blood vessel that can press on the airway)
Laryngeal web (a thin layer of tissue that can form across part of the airway)

Causes of these airway narrowing conditions can involve prolonged use of a breathing tube, surgical procedures, autoimmune or inflammatory diseases, infections, and GERD (Gastroesophageal Reflux Disease), which is a type of digestion disorder.

When diagnosing the exact cause of subglottic stenosis (narrowing below the vocal cords), doctors consider a variety of benign and malignant causes. Benign causes could include:

Post-traumatic sequelae (after-effects of injury)
Infections
Rheumatic diseases (diseases related to joint and muscle pain)
Benign tumors like papillomas, hemangiomas, and granular cells

Cancerous causes, on the other hand, could include squamous cell carcinoma, chondrosarcoma, and laryngeal lymphoma (types of throat cancers).

What to expect with Subglottic Stenosis

Most people with a condition called subglottic stenosis – a narrowing of the airway just below the voice box – tend to have good outcomes. They usually react positively to treatments such as injections or procedures done using a tiny camera inserted through the nose or mouth (endoscopic procedures). These treatments are usually safe and don’t cause significant side effects. The chance for success is highest when the initial stenosis, or narrowing, is less severe.

However, because this condition can come back often, all patients with a history of subglottic stenosis are advised to have regular check-ups in the future. This is to monitor the condition and ensure any potential complications or recurrence can be managed quickly.

Possible Complications When Diagnosed with Subglottic Stenosis

Subglottic stenosis can cause several complications including an increasing risk of acute airway obstruction which can happen after infection, inflammatory conditions or trauma to the larynx. There is also a risk of restenosis, which is the narrowing of the airway again, in about 25% of patients. Even though all surgical treatments have some risk attached, which can include the possible loss of the airway, they are generally considered safe if performed by experienced surgeons.

In the case of tracheostomy, the complications require special care because they are associated with a higher risk of sickness and even death. Sudden removal of the tracheostomy can result in an abrupt loss of the airway, which leads to oxygen desaturation and potentially, fatal outcomes. In the early days following a tracheostomy, wrongly inserting the tracheostomy tube can lead to the creation of a false tract. If not recognized, this could lead to severe crepitation when connected to a ventilator, potentially leading to mediastinitis, which is infection of the chest tissue, and fatal outcomes. Thus, only qualified personnel should carry out tracheostomy tube changes after the tract has had adequate time to mature.

Tracheoinnominate fistula, another serious complication of tracheostomy, usually shows up within 3 weeks of the procedure in 75% of cases. About half of these patients will experience minor bleeding before a major hemorrhage. When diagnosed, the tracheostomy balloon must be inflated immediately and a finger should be inserted through the neck incision to put pressure on the innominate artery, a technique known as the Utley maneuver. The patient should be swiftly taken to the operating room for definitive repair, which can be performed by an ear, nose, and throat specialist, or possibly a heart and chest surgeon. Other risks related to tracheostomy include a hole between the trachea and esophagus (tracheoesophageal fistula) and a hole between the trachea and skin (tracheocutaneous fistula). These complications, however, generally lead to lower levels of illness compared to the previously mentioned complications.

The following is a simplified list of complications:

Increased risk of acute airway obstruction
25% risk of restenosis or airway narrowing again
Potential loss of the airway during surgery
Risk of an abrupt loss of the airway following tracheostomy
Creation of a false tract leading to mediastinitis
Serious complication like Tracheoinnominate fistula within 3 weeks of procedure
Risk of minor bleeding before a major hemorrhage
Other risks like tracheoesophageal fistula and tracheocutaneous fistula

Preventing Subglottic Stenosis

Understanding the common risks associated with subglottic stenosis is very important for preventing it or reducing its severity. Subglottic stenosis is a condition where the airway just below the voice box (also known as the subglottis) narrows. This can be triggered by various factors such as acid reflux (GERD), certain autoimmune and inflammatory conditions, infections, and surgeries. Therefore, patients need to be well-informed about these influences.

When patients need a breathing tube during a surgical operation or whilst in intensive care, the medical staff have a crucial role in managing the pressure in this tube. Keeping this pressure below a certain level (30 mmHg) is important to allow for timely removal of the tube and prevent subglottic stenosis.

After diagnosis, patients should be educated about what they should expect in terms of how subglottic stenosis progresses. This education forms a vital part of the partnership between patients and their healthcare providers. It helps manage patients’ expectations and allows for common goals in treatment to be established.

Frequently asked questions

Most people with subglottic stenosis tend to have good outcomes and react positively to treatments such as injections or endoscopic procedures. These treatments are usually safe and don't cause significant side effects. The chance for success is highest when the initial narrowing is less severe. However, because this condition can come back often, patients with a history of subglottic stenosis are advised to have regular check-ups to monitor the condition and manage any potential complications or recurrence.

Subglottic stenosis can be acquired over time or can be present from birth (congenital). It can be caused by various factors such as burns, swallowing harmful items, exposure to radiation, infections, inflammation from acid reflux (GERD), immune system disorders, genetic conditions, injuries, or prolonged use of a breathing tube.

The signs and symptoms of Subglottic Stenosis include: - Stridor: a high-pitched, wheezing sound caused by disrupted airflow - Shortness of breath - Rapid breathing - Skin pulling in between the ribs during breathing - Changes in the cry - Loss of voice - Hoarse voice If the stenosis is present from birth, symptoms usually appear soon after a child is born and may include shortness of breath, rapid breathing, and the pulling in of skin between the ribs when breathing. If the stenosis affects the vocal cords, there could be changes in the cry, loss of voice, or a hoarse voice. For those who acquired subglottic stenosis, symptoms can show up as early as 3 to 4 weeks after a voice box injury or may take several years to become evident. It is important for anyone experiencing stridor to undergo a full medical investigation, which may include a flexible laryngoscopy performed by an ear, nose, and throat specialist.

The types of tests that are needed for Subglottic Stenosis include: 1. Endoscopic examination: This procedure uses a flexible fiberoptic laryngoscope to visually check the subglottis, observe the functioning of the vocal cords, and assess the openness of the windpipe. 2. Spirometry: This test measures the peak inspiratory flow rate (PIFR), peak expiratory flow rate (PEFR), and forced vital capacity (FVC) to monitor the movement of air in and out of the lungs. Changes in these readings may indicate the need for surgery. 3. Imaging techniques: CT scans and MRIs can be used to assess abnormalities in patients whose cause of stenosis is unclear. They allow the doctor to examine the narrow part of the throat and measure its length. 4. Long-range optical coherence tomography (OCT): This imaging test is used for diagnosing subglottic stenosis in newborns. It can detect changes in the subglottic mucosa caused by endotracheal intubation. 5. Cotton-Myer grading system: This system is used to assess the severity of subglottic stenosis by comparing the smallest endotracheal tube size that can pass through the subglottic lumen to the expected tube size for the patient's age. The percentage of obstruction helps grade the stenosis into four categories.

The doctor needs to rule out the following conditions when diagnosing Subglottic Stenosis: 1. Narrowed airways (stenosis) 2. Infections 3. Tumors (neoplasm) 4. Aspiration (inhaling food, fluid, or other foreign material into the airways) 5. Subglottic and tracheal stenosis (narrowing in the area below the vocal cords or in the windpipe) 6. Vascular ring (a rare condition where the blood vessels form a ring around and put pressure on the airways) 7. Aberrant innominate artery (a misplaced blood vessel that can press on the airway) 8. Laryngeal web (a thin layer of tissue that can form across part of the airway) 9. Prolonged use of a breathing tube 10. Surgical procedures 11. Autoimmune or inflammatory diseases 12. Infections 13. GERD (Gastroesophageal Reflux Disease), which is a type of digestion disorder 14. Post-traumatic sequelae (after-effects of injury) 15. Rheumatic diseases (diseases related to joint and muscle pain) 16. Benign tumors like papillomas, hemangiomas, and granular cells 17. Squamous cell carcinoma 18. Chondrosarcoma 19. Laryngeal lymphoma (types of throat cancers)

The side effects when treating Subglottic Stenosis can include: - Increased risk of acute airway obstruction - 25% risk of restenosis or airway narrowing again - Potential loss of the airway during surgery - Risk of an abrupt loss of the airway following tracheostomy - Creation of a false tract leading to mediastinitis - Serious complication like Tracheoinnominate fistula within 3 weeks of the procedure - Risk of minor bleeding before a major hemorrhage - Other risks like tracheoesophageal fistula and tracheocutaneous fistula

An ear, nose, and throat specialist (ENT) or an otolaryngologist is the type of doctor you should see for Subglottic Stenosis.

Subglottic stenosis is relatively common, with severe tube-induced stenosis ranging between 0.3% to 11.38%.

Subglottic stenosis can be treated in various ways depending on the severity. For patients with minor symptoms, routine monitoring using a spirometry machine at home or in a clinic may be suitable. Another option is the serial injection of steroids into the affected area, which can yield good long-term results. If injections are not enough, further interventions such as surgery or dilation may be considered. Balloon dilation is often the first choice of treatment and is successful in over 90% of cases. In severe cases that cannot be managed endoscopically, more extensive open-airway procedures like laryngotracheal reconstruction or tracheostomy may be required. For babies born with subglottic stenosis, tracheostomy and regular airway evaluations are common treatment steps.

Subglottic stenosis is a condition characterized by a narrowing of the subglottic space, which is located below the ventricle and above the trachea. It can range from minor discomfort to a life-threatening blockage of the airway.