Stent Fracture

This is a rare complication seen with metal stent insertion, but it may result in airway wall perforation and hemoptysis, potentially fatal events [14, 39, 113]. United States Food and Drug Administration warned that metallic tracheal stents in patients with benign airway disorders should be used only after thoroughly exploring all other treatment options (such as surgical procedures or placement of silicone stents) [39]. The use of these stents as a bridging therapy to surgery is also not recommended, because the removal of these stents is associated with signi cant complications.

Stent Associated Lower Respiratory

Infection and Mucus Obstruction

When a de nition of respiratory infection is based on the presence of clinical ndings (fever, increased volume and purulence of sputum, and worsening cough), with or without radiographic evidence of pneumonia but requiring the managing physician to prescribe antibiotics, the incidence proportion of lower respiratory tract infections was 36–39% in patients suffering from cancer [14]. The authors of this study found that respiratory infections led to signi cant morbidity and mortality: over half the patients were hospitalized, and 23% of patients with respiratory infections died within 14 days of their infection. Respiratory infections were more frequent in patients with Aero stents compared with silicone or Ultrafex. Various degrees of obstruction by mucus are not uncommon. This tends to be more common in patients with ineffective cough and in smokers. In patients with malignant CAO, having a left-sided stent (HR = 3.07), age (HR = 0.97), having a silicone stent (HR = 2.72) versus Ultrafex stents, and having chemotherapy post-­ stent placement (HR = 0.32) had signi cant impact on time to mucus impaction. The higher risk with left sided stents makes sense; because of the sharper angle 9 between the left main bron-

9Especially in patients with tumors who might have a nearly horizontal left main bronchus due to large subcarinal adenopathy.

chus and trachea, the patient may have dif culty in raising secretions and also because the left mainstem bronchial stents are longer than the right sided ones, for simple anatomical reasons. In addition to obstructing the airway, in time this could also lead to halitosis because the stent becomes covered chronically with a bio lm (Fig. 16.8). Recent in vitro studies evaluated a new methodology to create highly hydrophobic micro-/nanostructured silver antibacterial surfaces against Gram-positive and Gram-negative bacteria, using low-pressure plasma. This micro-/ nanostructured silver coating demonstrated antibacterial properties causing a reduction in Gram-­ positive and Gram-negative bacteria viability on airway stents [114].

Migration

While an oversized stent could cause granulation tissue formation, an undersized stent would likely migrate. In one study, stent migration was 5.26%, 6.06%, and 15.38% in patients in whom the stentto­ airway diameter was between 90% and 100%, 80% and 90%, and <80%, respectively [102]. The migrated stent, in addition to not palliating the airway narrowing for which was initially placed, could result in inability to clear secretions, in continuous friction between the wall of the stent and the airway mucosa, and cause granulation as well. Ideally, a stent is well compressed once is deployed, but even if it is sized appropriately and placed properly and sitting tightly at the end of the procedure, it can still migrate later because of the viscoelastic properties of the tracheal tissues (Fig. 16.8). This complication is seen more commonly in benign disease or in patients with cancer undergoing therapy, likely because patients with benign disease survive longer and because of the changes in airway viscoelastic properties (in time the airway stenosis progressively dilates). This probably explains why about 20% of patients with strictures may have their stent removed after ~18 months. For patients with ECAC, silicone stent insertion improves functional status immediately post-­ intervention, but is associated with a high rate of