Results
A total of 54 PDO stents were placed in 26 patients during the study period and 14 (53.8%) required more than one stent for management (median, 2 stents). The cohort was constituted by 14 boys and 12 girls with a median age of 4 months [IQR 3-7] when the first stent was placed. The youngest patient in our series was 2 months of age and the lowest weight was 3 kg, while the oldest was 6 years of age and 20 kg.
All patients showed severe symptoms of airway obstruction due to one of the following diseases: tracheomalacia (TM, 9 patients), bronchomalacia (BM,5), tracheobronchomalacia (TBM, 10) and postsurgical tracheal stenosis (TS, 2 cases). As shown, congenital airway malacia was the most frequent disease causing central airway obstruction (92.3%): 13 (54.1%) corresponded to primary malacia and 11 showed airway collapse secondary to extrinsic vascular compression. Respiratory clinical status when airway stenting was as follows: 14 patients had a tracheostomy for ventilatory support, 3 were intubated and ventilated, non-invasive ventilation was required in 5, oxygen therapy in 3 and one patient showed recurrent respiratory infections requiring hospitalization.
Endoscopical placement of PDO stents was uneventful in every patient. In some cases minor readjustements with a semirigid 1mm alligator forceps were performed in order to accurately match the lesion. Balloon dilation of the stent was deemed necessary in 22 stents (40.7%) in order to immediately achieve the nominal diameter and expected radial force. Median stent diameter and length were 7 mm (IQR 5-9) and 22.5 mm (IQR 15 – 35) respectively. Regarding anatomic location, 29 stents (53.7%) were placed in the trachea and 25 in the main bronchi (7 right and 18 left) (figure 1). All patients showed severe comorbidities being cardiovascular anomalies most frequent (65.3%). Ten patients (38.4%) exhibited more than one associated anomaly including genetic syndromes (Table I).
Clinical respiratory status achieved after stent placement was the main outcome measure in our study. According to the previously mentioned cathegorization, 8 (30.7%) patients showed complete resolution of their symptoms and 13 (50%) partial clinical improvement. Airway stenting did not have an impact on the clinical condition of 4 patients (15.3%) and in one (3.8%) it became even worse due to stent-related complications. Additionally, we evaluated the potential contribution of the collected variables to the four different clinical outcomes observed. Analysing those patients with complete resolution of their respiratory symptoms after stenting and comparing them to the other 3 groups with a different clinical outcome (partial improvement, unchanged, worsen), we observed that age had significantly positive impact (6 months vs 3 m; p=0.024) (Table II). Moreover, putting together patients with complete or partial improvement and comparing them to those with no change or clinical deterioration, we observed that a smaller PDO stent was associated with a better outcome (median length, 20 vs 26 mm; p=0.044) (Table III).
Granulation tissue formation was the most frequent stent related complication observed in our study. Because PDO stents represent a foreign body in the airway, some minor degree of granulation tissue formation is usually expected (fig. 2). Nevertheless, granulation tissue requiring a bronchoscopic procedure in order to remove it with forceps, ballooning or laser, was a relevant issue observed in 34.6% (9/26) of our cases (5 tracheal and 4 bronchial) (fig. 3). Mean size of tracheal stents causing granulation was 23 x 7.6 mm, while bronchial stents were 18.7 x 5.2 mm. These patients were more prone to accumulate secretions needing aspiration and lavage when bronchoscopy was performed. Additionally, stent migration was observed in one case (oldest patient) due to a mismatch between the stent size and the lesion, and severe tracheal stenosis in another requiring surgical resection and Montgomery T-tube insertion. No bleeding, infection or airway erosion were detected in the cohort. No patients showed difficulties in coughing or expelling stent fragments during biodegradation. One stent was too long and we decided to cut it to match the bronchial malacic lesion. This proved to be a wrong decision so it was removed and a new one ordered. In another case of BM the stent was too short to give effective support so it was removed and replaced by a longer one. Stent surveillance relied mainly on clinical assessment. Due to our institutional wide availability for bronchoscopic exploration, FB was immediately performed by our team if deemed necessary.
Five patients (19.2%) died during follow-up due to severe associated anomalies: two with polymalformative syndromes and 3 with complex congenital cardiopathy with pulmonary hipertension or sepsis (2 patients). Currently, no ventilatory support is required in 14 patients (53.8%), 5 (19.2%) carry a tracheostomy without assistance and 2 more patients have a tracheostomy with intermitent ventilatory support. Median follow-up was complete with a median value of 58 months [IQR 12-77].