What is Tracheomalacia?
Tracheomalacia is a condition characterized by flaccidity and structural weakness of the tracheal walls due to loss of cartilaginous integrity, resulting in excessive dynamic collapse of the airway during forced expiration, coughing, or increased intrathoracic pressure. 1
Pathophysiology
The fundamental defect is the loss of structural support from the cartilaginous rings and/or posterior membrane, which normally maintain airway patency. 1, 2 This weakness allows the airway to collapse excessively during expiration:
- In healthy individuals, the coronal diameter narrows by less than 40% during forced expiration or coughing 1
- In tracheomalacia, this narrowing exceeds 50%, representing pathologic collapse 1, 3
- The collapse is dynamic, meaning it worsens with increased mediastinal pressure such as coughing, Valsalva maneuvers, or forced expiration 4
Etiologies in Adults
Tracheomalacia can result from multiple causes that damage or weaken the cartilaginous support structures 1:
- Iatrogenic injury: Pressure necrosis from prolonged endotracheal intubation 1
- External compression: Thyroid lesions, vascular anomalies 1
- Trauma: Direct airway injury 1
- Chronic infection: Bronchiectasis and recurrent major airway infections 1
- Radiation therapy: Post-treatment cartilage damage 1
- Inflammatory conditions: Relapsing polychondritis 1
- Congenital disorders: Tracheobronchomegaly, Ehlers-Danlos syndrome, cutis laxa, Marfan syndrome 1
Important caveat: The airway collapse seen in COPD patients does not represent true tracheobronchomalacia, despite similar appearance. 1
Clinical Presentation
The two hallmark symptoms present in almost all patients are 1, 5:
- Chronic cough: Persistent and often severe
- Expiratory wheeze: Due to dynamic airway narrowing during expiration
Additional symptoms may include 5, 2:
- Dyspnea and stridor
- Recurrent respiratory infections
- In severe cases, life-threatening airway obstruction or acute life-threatening events
Common diagnostic pitfall: Patients are frequently misdiagnosed with asthma due to the wheezing component, delaying appropriate diagnosis and treatment. 1, 3
Diagnostic Approach
Imaging studies like chest X-ray and CT have limited value for diagnosing tracheomalacia, as these large airway disorders don't show characteristic abnormalities on static imaging. 1 However, modern techniques have improved detection:
- CT chest with IV contrast during forced expiration is first-line imaging, allowing visualization of dynamic airway collapse 3
- Flow-volume curves can provide clues to excessive airway collapse 1
- Bronchoscopy is essential for definitive diagnosis, allowing direct visualization of the excessive coronal narrowing (>50%) during coughing in conscious patients 1, 5
The diagnosis requires a high index of suspicion, as tracheomalacia should be considered an uncommon cause of chronic cough when common causes have been ruled out. 1