From the Guidelines
The recommended laboratory workup for a patient suspected of having tracheobronchomalacia (TBM) primarily focuses on diagnostic imaging and endoscopic evaluation rather than traditional laboratory tests. The most important diagnostic test is dynamic airway assessment using bronchoscopy during spontaneous breathing, which allows direct visualization of excessive airway collapse during expiration, as suggested by the American College of Chest Physicians clinical practice guideline 1. This should be complemented by dynamic CT imaging with inspiratory and expiratory phases to quantify the degree of airway collapse (with >50% reduction in airway lumen during expiration being diagnostic), as recommended by the ACR Appropriateness Criteria for tracheobronchial disease 1. Pulmonary function tests are also essential, particularly flow-volume loops which may show characteristic flattening of the expiratory limb. Additional testing may include:
- Chest X-ray to rule out other conditions
- Airway manometry to measure pressures within the airway
- Echocardiography in children to assess for vascular compression of the airways. Laboratory blood tests are not specifically diagnostic for TBM but may be ordered to exclude other conditions or identify underlying causes. This comprehensive evaluation is necessary because TBM can be easily missed with standard static imaging, and the dynamic nature of the airway collapse requires specialized testing during both inspiration and expiration. The use of modern multidetector CT scanners, which enable cinematic 4-D volumetric images of the trachea, allows for time-resolved coverage of the entire trachea throughout an inspiratory/expiratory cycle, providing valuable information for the diagnosis of TBM 1. Optimal evaluation of the airways requires thin-section imaging with a slice thickness of 1.5 mm or thinner, and adequate breath holding at inspiration is also important to avoid respiratory motion that can obscure airway lesions 1.
From the Research
Laboratory Workup for Tracheobronchomalacia
The laboratory workup for tracheobronchomalacia involves several diagnostic tests to confirm the condition and rule out other potential causes of symptoms. Some of the key tests include:
- Dynamic airway computed tomography (CT) scan 2
- Dynamic flexible bronchoscopy with forced expiratory maneuvers 2
- Low-contrast volume bronchography 3
- Magnetic resonance imaging (MRI) 3
- Lung function testing, which can provide supportive evidence but is not diagnostic 3
- Flexible bronchoscopy in a free-breathing child 3
Diagnostic Criteria
The diagnosis of tracheobronchomalacia is typically made based on a combination of clinical presentation, medical history, and diagnostic test results. Some of the key diagnostic criteria include:
- Excessive collapsibility of the trachea and bronchi 4
- Greater than 50% reduction in cross-sectional area of the airway 2
- Complete or near-complete collapse (>90% reduction in cross-sectional area) of the airway 2
- Presence of symptoms such as stridor, cough, recurrent pneumonia, or feeding difficulties 4, 3
Classification and Management
Tracheobronchomalacia can be classified as mild, moderate, or severe depending on the degree of collapse of the airway when exhaling 5. Management of the condition may involve medical or surgical treatment, depending on the nature and severity of the lesions 3. Some of the treatment options include:
- Medical management with nebulizer treatments, minimal use of inhaled corticosteroids, gastroesophageal reflux disease therapy, and continuous positive airway pressure 4
- Surgical techniques such as anterior and posterior tracheobronchopexy and anterior and posterior aortopexy 4
- Tracheobronchoplasty with strengthening of the posterior wall 5
- Use of silicone and "Y" stents to identify patients who could potentially benefit from surgical treatment 5