adverse effects with frequent stent migration. In fact, in one study of malignant CAO, among various stents (Ultrafex, Aero and silicone) only silicone tube stents had a signi cant effect on migration risk with a HR of 3.52 [14]. Stent migration requires a revision procedure to maintain satisfactory airway patency and prevent further complications.

Bronchoscopy is currently the standard for the detection and treatment of stent-related complications and, in non-urgent situations, usually involves a two-step procedure. Initially, diagnostic fexible bronchoscopy is performed to detect and characterize a stent complication; if a treatable complication is detected, rigid bronchoscopy may be required for therapeutic intervention. In this regard, from regulatory perspective, the stent insertion package should probably contain information about stent’s biomechanics, sterilization (although this may not affect the infection rate) [14] in addition to reporting indications, expected results, incidence rates of long-term complications as well as potential contraindications to stent insertion.

Contraindications

There are certain circumstances when stent insertion should not be offered. For instance, in idiopathic or secondary benign subglottic stenosis (within 2 cm from the vocal cords), stents may extend the length of the stenotic segment [93]. This is particularly true for metallic stents. In one study, all patients with laryngotracheal stenosis who had undergone covered or uncovered metallic stent placement developed new strictures or granulation tissue that precluded de nitive surgical treatment or required more extensive resections [93]. In fact, some tracheal surgeons believe that SEMS should never be used in patients who are potential candidates for resection because these are likely to cause additional airway injury and possibly make a potentially resectable disease, unresectable 10 [115].

10 In this regard, histologically benign CAO should be treated surgically or for non surgical candidates, with silicone stents whenever possible.

The absence of a functional “distal airway” such is the case with signi cant and chronic (usually >1 month) distal parenchymal tumor in ltration or con rmed lack of perfusion of underlying lung are also contraindications to stent insertion and, for the same reasons, for any endoluminal therapy aimed at restoring airway patency. In patients with CAO (lobar or mainstem bronchi), assessing the functionality of the lung parenchyma distal to the obstruction is useful when considering interventions meant to establish airway patency. Functionality of the lung distal to the obstruction may not be restored in patients who have had chronic complete obstruction and lack of ventilation (Fig. 16.8). Determining whether there is functional airway and lung parenchyma beyond an obstruction is essential to any successful bronchoscopic intervention, 11 in part because signi cant friability of bleeding from in ltrated bronchial mucosa, or lack of lung perfusion 12 despite restored airway patency, might preclude intervention. In one study, 71% of patients who initiated radiation therapy within 2 weeks after radiological evidence of atelectasis had complete re-expansion of their lungs, compared with only 23% of those irradiated after 2 weeks [116]. Studies pertaining to successful bronchoscopic treatment and time to treatment are lacking. In addition, signi cant mucosal friability and bleeding of bronchial mucosa might also preclude interventions because stent insertion may result in broncho-mediastinal stula, loss of the stent within the mediastinum, or hemorrhage (Fig. 16.8).

11 Other conditions include experienced bronchoscopist and team, experienced anesthesiologist, control of patient’s overall performance status, additional systemic or local therapy still possible, and control of comorbidities.

12 One way to assess the perfusion status of lung parenchyma distal to an airway obstruction is to attempt bypassing the stenosis using a high-resolution EBUS radial probe.

Follow-Up and Patient Education

Immediately after stent insertion, a chest radiograph is performed to con rm its location. Because stents are associated with signi cant adverse events, a stent alert card should be given to the patient upon discharge from the hospital; this provides information both for patients and for the doctors that may encounter patients with airway stents. They are informed that even though some stents (i.e., silicone) are not radio-opaque, one can still identify them on the chest radiographs as straight lines. In addition, the card includes the patient’s name, indication for stent insertion, type, location and size of stent inserted, contact information, and instructions for both patients and physicians in case of stent-related complications. Also, if intubation is necessary for whatever reason, bronchoscopic intubation using a cuffess # 6 ETT to avoid stent dislodgement or mucosal trauma is advisable.

Granulation tissue, secretions, migration, tumor progression, and stula formation are usually detected during follow-up bronchoscopy or on chest CT. Studies show that the extent of air pockets around the stent on follow-up chest CT correlate with the success of stent removal, and indicates regression of stenosis, and may help guide the optimal time for stent removal [117]. Stent-related complications, however, are usually detected by the onset of new respiratory symptoms and may not necessitate systematic (scheduled) routine fexible bronchoscopy. In those patients suspected of having stent-related adverse effects, however, bronchoscopy should be performed for diagnosis and potentially for therapy. While routine follow-up bronchoscopy in the lack of symptoms may not be warranted in all patients after stent insertion, given that most complications occur within 6 weeks post-stent insertion [14, 16, 17], one could choose to perform surveillance bronchoscopy in patients at high risk for complications after stent insertion. A recent retrospective study enrolling 70 patients who underwent to either silicone stent or SEMS for malignant CAO showed an increase in cumulative incidence of complications between 1 and 6 months after stent placement, which highlights

the need for close clinical and bronchoscopic surveillance among these patients [98].

In a study of 134 patients with 147 stents, 94 patients (n = 100 stents) had follow-up bronchoscopy at a mean of 42 days. The authors showed that stent-related complications were seen in 69% of stents inserted, with the majority requiring an intervention such as aspiration of secretions, stent removal, and stent replacement [118].

There are reports suggesting that time to granulation tissue detection after SEMS insertion is longer in patients with dynamic airway obstruction than in those with structural airway obstruction (396 vs. 95 days p = 0.02) [106], so a need for prolonged follow-up in these patients may be warranted. Some physicians perform routine bronchoscopy every couple of months, while others only do it when patients complain of new symptoms [119]. We perform follow-up bronchoscopy 30 days after stent insertion and then based on clinical judgment depending on concurrent systemic therapy as well as the status of the airway and the stent at the time of rst follow-up bronchoscopy. Preventive measures for obstruction by mucus such as aerosol therapy, respiratory physiotherapy, and clinical visits are advocated. Also, while not a universal practice, saline nebulization is offered by many bronchoscopists to keep the stent humidi ed in order to avoid excessive mucus plugging. In fact, severely disabled patients such as those who are bedridden and with poor cough or impaired metal status are unlikely to bene t from indwelling airway stents since the risk of obstruction by mucus may outweigh the bene t gained by placing the stent and only temporarily restore airway patency.

Summary andRecommendations

Airway stents improve symptoms of selected patients with malignant and benign central airway obstruction, esophago-respiratory, and bronchial stump stulas but in general, their insertion should be reserved to patients for whom curative open surgical interventions are not feasible or contraindicated. Metallic stents should be avoided in benign disease unless surgery or sili-

cone stent placement is not possible or feasible and there are no other alternatives for maintaining airway patency. For malignant disease, stents are placed with a palliative intent. They should therefore be inserted by operators able to handle intraoperative, short-term, and long-term complications. Long-term complications after placing such prostheses are not uncommon and can occasionally be fatal. Airway stents are not equal in terms of biomechanics and stent-tissue interactions and currently, these data are considered con dential, proprietary, and regulatory bodies do not mandate their reporting. However, in our opinion, manufactures should describe some key biomechanical properties including the resistance to angulation, expansile force, and time to mechanical failure (cough cycles) to help physicians better predict successful airway patency restoration, as well as immediateand long-term stent-related complications.

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