Tracheomalacia happens when the walls of the trachea (windpipe) are too soft and floppy to hold their shape, causing them to collapse inward during breathing. The underlying cause is always weakened or damaged cartilage, the semi-rigid rings that normally keep the airway open. But what damages that cartilage varies widely depending on whether the condition is present at birth or develops later in life.
Congenital Tracheomalacia in Infants
In newborns, tracheomalacia occurs when the tracheal cartilage rings don’t develop properly during fetal growth. Instead of forming firm, C-shaped supports, the cartilage remains immature and soft. This typically affects the lower third of the trachea. The airway stays open during calm breathing but collapses when the infant coughs, cries, or feeds, often producing a characteristic barking cough or a vibrating noise during exhale.
Primary congenital tracheomalacia sometimes occurs on its own, but it frequently appears alongside other birth defects. Up to 75% of infants born with a tracheoesophageal fistula (an abnormal connection between the windpipe and esophagus) also have a tracheal defect. Congenital heart defects, developmental delays, and gastroesophageal reflux are also common companions. Connective tissue disorders like Ehlers-Danlos syndrome and conditions like bronchopulmonary dysplasia can produce an innately weakened trachea as well, because the body’s structural proteins are abnormal from the start.
Vascular Compression From Abnormal Blood Vessels
Sometimes the trachea develops normally but gets squeezed from the outside by blood vessels that formed in the wrong position. These vascular anomalies, called vascular rings, result from the persistence of a double aortic arch after the second month of fetal life. The abnormal vessel wraps partially or fully around the trachea and esophagus, pressing on the airway and distorting the cartilage over time.
A double aortic arch compresses the front and back of the lower trachea. A pulmonary artery sling, where the left pulmonary artery takes an abnormal path, typically compresses the front of the lower trachea and the right main bronchus. Complete vascular rings and pulmonary artery slings tend to cause symptoms earlier in life because they create tighter compression. Innominate artery compression is the most common type overall, accounting for roughly 80% of vascular compression cases in one surgical series.
Prolonged Intubation and Tracheostomy
In adults, the most common causes of acquired tracheomalacia are medical procedures that involve placing a tube in the airway for extended periods. Prolonged endotracheal intubation with a cuffed breathing tube damages the tracheal wall through sustained pressure. When the inflatable cuff that seals the tube against the airway wall is overinflated, it cuts off blood flow to the tracheal lining. Over days or weeks, the cartilage beneath that contact point degenerates, leaving a segment of floppy, structurally compromised airway behind.
Tracheostomy, a surgically created opening in the neck for long-term ventilation, carries a similar risk. The tube and its cuff create chronic pressure and inflammation at the stoma site, gradually softening the surrounding cartilage.
COPD and Chronic Lung Disease
Chronic obstructive pulmonary disease (COPD), which includes chronic bronchitis and emphysema, has a strong association with tracheomalacia. The connection appears to run through chronic inflammation. Years of irritation thicken the bronchial walls, and research shows that bronchial wall thickness is significantly higher in patients with airway malacia and correlates directly with how much the airway collapses.
In nearly all COPD-related cases (92% in one study), the collapse pattern is distinctive: the back wall of the trachea, which is a flexible membrane rather than cartilage, bows forward during exhale. This differs from the side-to-side collapse seen in some congenital forms. The persistent coughing, mucus production, and air trapping that define COPD likely accelerate cartilage breakdown over years.
Thyroid Surgery and Goiter
A large, long-standing goiter (enlarged thyroid) can press on the trachea for months or years, slowly weakening the cartilage beneath it. When the thyroid is finally removed, the damaged segment of trachea may lack the structural strength to stay open on its own.
In a study of 149 thyroidectomy patients, 12.1% developed post-surgical tracheomalacia. The strongest risk factors were younger age (under 30) and surgeries lasting longer than three hours, with nearly 78% of affected patients falling into that longer-surgery group. Young women with multinodular goiter were the most frequently affected. The tracheomalacia in these cases isn’t caused by the surgery itself but rather unmasked by it, as removing the goiter reveals cartilage that had been weakened by prolonged external pressure.
Autoimmune and Inflammatory Conditions
Relapsing polychondritis is a rare autoimmune disorder in which the body’s immune system attacks cartilage throughout the body, including the ears, nose, joints, and airway. Tracheomalacia is the most common airway problem in these patients. The inflammation progressively destroys the cartilage rings, and the airway involvement can be severe enough to require intervention. In the largest study of relapsing polychondritis patients described in English-language medical literature, symptomatic airway involvement was common, and one patient died from progressive airway disease during follow-up.
Mounier-Kuhn Syndrome
This rare condition causes the trachea and main bronchi to become abnormally wide and floppy. The problem is a near-complete loss of elastic fibers in the tracheal wall, which are the stretchy proteins that help the airway spring back to its normal shape after each breath. Without them, the trachea dilates far beyond its normal diameter and collapses during exhale and coughing.
Diagnosis is based on airway measurements: a tracheal diameter greater than 30 mm, a right bronchus wider than 20 mm, or a left bronchus wider than 18 mm on CT imaging. For reference, a normal adult trachea is roughly 15 to 25 mm wide. Biopsy specimens from affected patients show almost complete absence of elastic fibers in some areas, along with atrophy of the smooth muscle that normally helps stiffen the airway wall. The condition is thought to be inherited through an autosomal recessive pattern, though no specific gene has been identified. Mounier-Kuhn syndrome is often associated with other connective tissue disorders, including Ehlers-Danlos syndrome, Marfan syndrome, and cutis laxa.
How Severity Is Measured
Regardless of the cause, tracheomalacia is graded by how much the airway collapses when you breathe out. Mild tracheomalacia involves modest narrowing. Moderate cases show roughly 25% loss of the airway’s cross-section. Severe tracheomalacia involves 50% or greater collapse, which is the threshold where breathing symptoms typically become significant and intervention may be considered. Doctors evaluate this using CT imaging during both inhale and exhale, or by direct visualization with a flexible camera (bronchoscopy) while the patient breathes naturally.
Many mild cases, especially in infants, resolve without treatment as the cartilage matures. Congenital tracheomalacia in otherwise healthy babies often improves substantially by age two. Acquired forms in adults tend to persist unless the underlying cause, such as removing a compressive mass or treating chronic inflammation, is addressed.