Laboratory and Imaging Studies
Laboratory studies
Oxygen saturation should be assessed in tracheomalacia.
Fluoroscopy and radiography
The diagnosis can often be confirmed by performing fluoroscopy of the airway.
During the study, the pediatric radiologist observes the airway collapsing and opening up. This finding may appear on anteroposterior images, on which the tracheal air shadow seems to disappear and reappear with respirations in the affected area of the trachea.
The lesion may be observed most easily on lateral images, on which the anterior and posterior walls of the trachea may be observed apposing dynamically.
Loss of the tracheal air shadow with no respiratory changes suggests static collapse of the airway.
CT scanning
Chest computed tomography (CT) scanning may reveal the abnormal shape of the trachea as the apposition of the walls. "Expiratory frown" shapes are observed in CT scans when the area is scanned during an exhalation or cough. [7]
Chest CT scanning may not reveal the dynamic nature of the lesion and may not depict the lesion at all.
A CT scan, especially one obtained with contrast material, may reveal vascular lesions that mimic tracheomalacia and that may eventually lead to tracheomalacia.
According to a European Respiratory Society (ERS) Task Force report, paired end-inspiratory and end-expiratory multidetector computed tomography (MDCT) or paired end-inspiratory and dynamic expiratory MDCT are both reliable imaging techniques. Compared with laryngoscopy/bronchoscopy, the overall diagnostic accuracy of paired airway MDCT is 91%. [8]
In patients with tracheobronchomalacia, dynamic expiratory CT was shown to elicit a larger degree of airway collapse than standard end-expiratory CT. [9]
Esophagraphy
Esophagraphy can be performed to evaluate for a vascular anomaly, for a bronchogenic cyst, or for esophageal duplication.
Esophagraphy does not assist the physician in making a definitive diagnosis.
Other Tests
The definitive method of diagnosis is bronchoscopy. [10] In one series, when a pediatric pulmonologist suspected tracheomalacia, the correct diagnosis was tracheomalacia in 74% of the cases. [3] However, tracheomalacia was not suspected in 52% of patients who were eventually diagnosed with it.
During bronchoscopy, the anterior wall can be observed to collapse against the posterior wall. At the same time, other lesions can be diagnosed or excluded under direct visualization.
The authors prefer flexible bronchoscopy to confirm the diagnosis. With flexible bronchoscopy, the baby is breathing spontaneously with light anesthesia. This method preserves respiratory dynamics better than rigid bronchoscopy. In addition, the rigid bronchoscope may serve as a stent to the airway, masking the diagnosis.
Confirming the diagnosis is important for differential diagnosis. Otherwise, one or more tests may be unnecessarily considered. A sweat test may be performed to reduce the likelihood of cystic fibrosis. Esophagraphy may be performed to eliminate the likelihood of most of the vascular anomalies. These diagnoses are usually eliminated by bronchoscopy. CT scanning to reduce the likelihood of airway foreign body and other lesions that may be compromising the airway. If bronchoscopy is performed, it is an efficient and direct method of looking for foreign bodies.
If tracheomalacia is diagnosed, a sweat test is not necessary unless other manifestations of cystic fibrosis are present. The adage still holds that a sweat test has no contraindication.
If gastroesophageal reflux is a concern, evaluate this condition by using a pH or impedance probe or esophageal biopsy. If bronchoscopy is performed, bronchoalveolar lavage can be done to assess for lipid-laden macrophages.
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Slide tracheoplasty and left PA sling repair. Procedure performed by Giles Peek MD, FRCS, CTh, FFICM, The Children’s Hospital at Montefiore, Bronx, NY.
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This shows the trachea during inspiration and expiration. Tracheal collapse of more than 50% during expiration is diagnostic of tracheomalacia.
