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* From the Division of Pulmonary and Critical Care Medicine, The Cleveland Clinic Foundation, Cleveland, OH.
Correspondence to: Atul Mehta, MBBS, FCCP, Head, Section of Bronchology, Vice-Chairman, Pulmonary and Critical Care Medicine, The Cleveland Clinic Foundation, 9500 Euclid Ave, Desk A 90, Cleveland, OH 44195; e-mail: mehtaa1{at}ccf.org
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Abstract |
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Design and setting: Retrospective study, tertiary-care hospital.
Patients and methods: The studied population consisted of 82 patients (mean age, 59.1 years; range, 37 to 83 years), who received SEMSs from 1995 to 2001 using Wallstent (Boston Scientific; Galway, Ireland) or Ultraflex (Boston Scientific) stents.
Results: The indications for stent placement were airway obstruction caused by neoplasia (lung carcinoma [CA], n = 50), airway complications of lung transplantation (LTx) [n = 11], and miscellaneous benign conditions (BCs) [n = 21]. The most frequent clinical presentations for the airway obstruction were moderate-to-severe dyspnea (80%) and coughing (45%). The median follow-up duration for the CA group was 42.0 days (range, 1 to 672 days), 329.0 days (range, 35 to 1,540 days) for patients receiving LTx, and 336.0 days (range, 7 to 2,184 days) for the patients with miscellaneous BCs. The observed complications included infection (15.9%), obstructive granulomas (14.6%), and migration (4.7%). The incidence of granulomas was significantly lower in the patients with CA (4.0%) vs LTx and BC groups (17.3% and 33.3% respectively; p = 0.002). All other assessed variables showed no difference between the three analyzed groups. No cases of mucus plugging or fatal hemoptysis were observed. Forty-four patients (53.7%) had no complications related to the SEMS. The incidence of complications was not related to the type of stent (Wallstent or Ultraflex) or SEMS version (covered or uncovered). Fourteen of the 16 patients (87.5%) who were receiving mechanical ventilation could be weaned after the procedure. There were no deaths related to SEMS placement.
Conclusions: An SEMS is a safe and effective modality for malignant as well as selected benign airway obstruction. An SEMS is an acceptable therapeutic alternative in patients with central airway obstruction who are not considered good surgical candidates and are receiving mechanical ventilation. Careful patient selection is of outmost importance for a good outcome after airway stenting. Insertion using FB adds to the ease of the procedure.
Key Words: airway obstruction • benign diseases • flexible bronchoscopy • neoplasia • self-expandable metallic stents
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Introduction |
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TOPAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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In the past 6 years, we have inserted 112 SEMSs into 82 patients with a variety of diseases causing central airway obstruction. We describe our experience and analyze and discuss the observed results after the stent placement in order to evaluate the safety, efficacy, and usefulness of the SEMS in the management of inoperable airway obstructions.
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Materials and Methods |
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TOPAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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Before the airway stent placement, the length of the lesion was addressed by withdrawing the tip of the flexible bronchoscope from its distal to the proximal end and measuring the scope movement. The diameter of the lesion and correspondent normal airway on images was obtained from routine spiral CT scan of the chest. More recently, the sizing of the SEMS to be placed has been carried out using a tri-dimensional CT scan airway reconstruction for a more accurate appraisal of the airway diameter and consequently for a precise stent selection.
Data were collected on both Wallstent and Ultraflex stents (Boston Scientific; Galway, Ireland). The Wallstent is a SEMS made of a cobalt-based super alloy, and the Ultraflex is made of a highly bioadaptable alloy exhibiting low resistance to cough yet adequate resistance to airway compression. They have an effective internal lumen, do not require hooks to prevent migration, and the outward radial force is uniformly applied over the bronchial wall, reducing the risk of mucosal perforation.
The devices were placed according the previously described method.4
An introductory guidewire was inserted through the flexible bronchoscope through the obstructed airway. The bronchoscope was then removed, and under fluoroscopic guidance the constrained stent was advanced over the guidewire until aligned with the previously placed skin markers indicating the proximal and distal ends of the lesion. After positioning, the stent was deployed from its delivery catheter. All stents were placed either under local anesthesia and conscious sedation or general anesthesia according to the severity of the underlying disease and clinical status. For general anesthetic cases, the airway was controlled with a laryngeal mask or endotracheal tube of 
8.5 mm. Pre- and poststenting endobronchial interventions such as electrosurgery, laser ablation, or balloon bronchoplasty were performed, as needed, using FB.
A covered SEMS was chosen when tumor ingrowth/overgrowth was a concern. For all other indications, an uncovered version was used. Balloon bronchoplasty of the involved airway was performed prior to placement of the Ultraflex stent and following the Wallstent placement, using an appropriately sized angioplasty balloon catheter to attain the largest diameter of the device and minimizing the risk of migration.
Improvement of the symptoms was considered "immediate" if the patient related considerable relief of the symptoms within 24 h of the procedure, and "late" if the symptom improvement occurred within 6 weeks of stent placement. One surveillance bronchoscopy was carried out according to the protocol of our department for airway stenting, usually between 6 weeks and 12 weeks after the procedure and as needed, dictated by the patient’s clinical status. Routine clinic visits every 12 to 16 weeks were scheduled to confirm the patient clinical status, development of any complications, and the need for immediate reintervention. No surveillance FB was performed after 12 weeks.
Complications were grouped into the following categories: (1) procedure-related respiratory failure, (2) development of endobronchial granulomas, (3) infection, (4) hemoptysis, (5) chronic cough, and (6) migration. Infectious tracheobronchitis was defined as an acute/subacute process presenting with productive cough, yellowish/greenish sputum, and normal chest radiographic findings. The occurrence of fever was not mandatory for the diagnosis. The overall complication rate was calculated by dividing the total number of complications by the total number of follow-up months of stent use by all patients.
Clinical outcomes consisted of immediate and late improvements of the previous symptoms and freedom from the mechanical ventilator. A Social Security survey was performed for definition of the outcome of patients who were unavailable during long-term follow-up. The last appointment date for the live patients and the date of death were considered the last day of follow-up for the statistics.
The complications on the three groups were compared using 
2 test. Technical difficulties, resolution of symptoms, and comparison between Wallstent and Ultraflex and covered and uncovered stent versions were analyzed using 2 or Fisher exact tests when appropriate. SAS software (Cary, NC) was used for the statistical analysis.
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Results |
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Overall, the most frequent clinical symptoms for central airway obstruction were moderate-to-severe dyspnea (80%) and intractable cough (45%), without any statistically significant difference among the three groups. Of the 82 patients, 46 patients (56.1%) presented with acute symptoms (65% [30 of 46 patients] with respiratory distress), 32 patients (39.0%) with chronic symptoms, and 4 patients (4.9%) with mild respiratory symptoms (mild wheezing and sporadic cough) [Table 2 ]. Sixteen patients were ventilator dependent due to the underlying airway obstruction.
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Complications
The overall observed complication rate was 0.06 complications per patient-month (37 complications in 651.7 months). Forty-four patients (53.7%) did not have any recorded complications related to SEMS placement.
Infectious tracheobronchitis was the most frequent encountered complication, occurring in 13 of the 82 analyzed patients (15.9%). All but one were successfully treated with oral antibiotics without further complications. One patient in the LTx group presented with a fungus ball adherent to the SEMS. He was treated with inhaled amphotericin B and oral fluconazole for 8 weeks without any associated morbidity. None of the patients needed to be admitted to the hospital, and only one patient had the SEMS removed due to a Staphylococcus aureus persistent tracheobronchitis.
The occurrence of obstructive granulomas inside the stent was the second most frequently observed complication (12 of 82 patients, 14.6%). Even considering the follow-up difference among the three groups, the incidence of granulation tissue after SEMS placement was significantly lower at the CA group than in the other two groups (p = 0.002). The granulomas were treated with one or more sessions of laser photoresection and endobronchial electrosurgery delivered by FB when compromise of the respiratory function was present. After the airway stenting, 24 of 50 patients with CA (48.0%), 3 of 11 LTx patients (27.3%), and 10 of 21 patients with miscellaneous BCs (47.6%) required further intervention in order to control granulomas, to obtain optimal airway patency, or to manage recurrence of malignancy obstructing the stent lumen (patients with CA). In one patient, a Dumon stent (Bryan; Woburn, MA) was placed through the Wallstent to control granulation tissue entering the SEMS lumen. Seven patients (8.5%) presented with asymptomatic nonobstructive granulomas detected during surveillance bronchoscopies, but they neither required any intervention nor progressed to stent obstruction.
Overall, five patients (6.1%) [all from the CA group] had symptomatic disease recurrence inside the formerly placed stents. All other addressed complications had no statistical significant difference when comparing their incidence among the studied groups (Table 4 ).
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One patient treated for anastomosis dehiscence after LTx had an Ultraflex partially removed 2 years after implantation due to metal fatigue of the mesh. At this time, the stent was not functional and the dehiscence had resolved. No complications associated with the eventual removal of the device were observed, yet in three patients it was done in piecemeal fashion due to the incorporation of the metal mesh into the bronchial mucosa (two Wallstents, one Ultraflex). Two patients had the SEMS completely removed after 1 month and 48 months, respectively, using FB and suspension laryngoscopy and jet ventilation under general anesthesia, with minimal bleeding as the only observed complication. All of the cases of hemoptysis (12 cases, 10.7%) were considered mild and transitory and did not require intervention or admission to the hospital.
Four patients had respiratory failure right after the procedure and remained intubated for 6 to 48 h until weaning was possible. Extubation in the operating room was not possible due to extensive laryngeal edema (n = 1), hypotension due to ventricular arrhythmia (n = 2), and a case of bronchial perforation associated with tension pneumothorax (n = 1). All four patients had the SEMS inserted successfully and were discharged later without further complications.
No cases of mucus plugging, chronic cough, or fistula formation related to SEMS placement were observed in the studied groups. The complication rates and resolution of symptoms were neither related to the type of stent placed into the airway (Wallstent or Ultraflex) nor to the version (covered or uncovered) of the device (Table 5 ).
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Discussion |
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Over the past decade, several studies addressed the efficacy and complications of the silicone stents. Despite the advantage of being removable, these devices are being gradually substituted, in selected cases, by the new SEMS due to the more favorable internal/external diameter ratio, decreased risk of mucus plugging, and migration.4 13 14 SEMS can be easily inserted under local anesthesia using FB even in patients receiving mechanical ventilation without the need of displacing the endotracheal tube. They adapt without difficulty to tortuous airways and rarely migrate; once deployed, their intrinsic radial force keeps them in position and embed their ends into the bronchial mucosa.14 If required, patients can be intubated through the SEMS placed into the tracheal lumen.1
A 1991 survey published by the American College of Chest Physicians states that < 10% of bronchoscopists utilized the rigid bronchoscope in their practices.15 A following survey by the American Association for Bronchology found that only 6% of the US pulmonologists were able to perform rigid bronchoscopy.16 The rigid bronchoscope is essential for the placement of airway silicone stents, and experience with this method is also desirable when stent removal is considered. At present, there are no randomized trials comparing those two modalities on SEMS placement.
Almost 50% of the patients presented with some sort of complication; however, it is relevant to note that the majority had minor complications such as infectious tracheobronchitis, asymptomatic nonobstructive granulomas, or minor hemoptysis. On the contrary, 53.7% of the patients had no complications after the procedure. We presume that the proper sizing during the initial evaluation using CT scan and more recently the tri-dimensional CT scan and the careful selection of the patients are main factors that contributed to the good results specially in the miscellaneous BC group.
Overall, our granuloma incidence (14.6%) was within the range previously reported on the literature (3 to 36%).1 7 9 13 17 We believe that the placement of a improperly sized SEMS can lead to a highest incidence of granulation tissue formation either because of excessive friction of the metal against the wall (undersized stent) or to excessive radial pressure alongside the bronchial mucosa (oversized stent). Second, it is of outmost importance to avoid the deployment of a SEMS in patients with exuberant bronchial mucosal inflammation to prevent the occurrence of recurrent obstructing granulomas.9 18 19 We also believe that the placement of any type of stent in the subglottic trachea is associated with a higher rate of granuloma formation and should be avoided. Four of our patients had significant obstruction: two patients required removal of the stent, and one patient had a Dumon stent placed inside the Wallstent. The cartilaginous structure leading to impaired lymphatic and vascular drainage in the presence of the endobronchial prosthesis probably makes the subglottic mucosa more prone to such complication. SEMS placement in this particular area should be avoided as much as possible. The influence of corticosteroids in the granuloma formation could be indirectly observed in the LTx group. This drug either used topically or systemically, did not interfere with the inflammatory reaction or the granulation tissue formation rate. When comparing the LTx group (patients receiving regular corticosteroids and other immunosuppressive drugs) to the BC group, the incidence of granulation tissue was similar. There are no reports in the literature addressing the effects of corticosteroids in this fashion, and a prospective randomized study is warranted.
Disease recurrence inside the SEMS was detected in five patients from the CA group (6.1% of the total patients). The presented recurrence rates are lower than the ingrowth/overgrowth rates reported by Miyazawa et al3 (24% and 21%, respectively). In our series, only symptomatic recurrences were considered, as routine surveillance bronchoscopy was not part of the post-SEMS follow-up. The previous report considered any growth inside the device, detected during surveillance bronchoscopies, for the analysis.
Comparing the CA group with the BC and LTx groups, a significantly increase in the incidence of obstructing granulomas was detected (4.0% vs 33.3% and 27.3%, respectively; p = 0.002), even when the data were corrected for their different follow-ups. One possible explanation could be the use of radiotherapy in 84% (42 of 50 patients with CA), either before or after the SEMS placement. Ionizing radiation is known to have potent growth inhibitory effects reducing the amount of collagen synthesis and deposition in a scar site.20 There are two anecdotal reports20 21 of the use of brachytherapy to control granuloma formation in patients with endobronchial stents for benign conditions with good results, but no prospective controlled trials were performed.
Infection after stenting of the airways has been reported in the literature, but still no relation with higher mortality has been shown.1 5 22 Airway colonization after stent placement was demonstrated prospectively by Noppen et al.23 The authors described the occurrence of colonization by pathogenic bacteria in 78% of the patients 3 to 4 weeks after stenting and no more than 72 h of hospitalization immediately after the procedure. Despite the high rate of colonization, the occurrence of infection was not detected. The occurrence of infectious tracheobronchitis was the most common observed complication (15.9%) in our studied group of patients. This high rate can be the result of the combination of three variables: (1) a longer follow-up period allowing the detection of late infections, (2) the high rate of infection among the LTx patients probably due to the combination of immunosuppression and an underlying airway obstruction, and (3) the SEMS altering local defense mechanisms, impairing the mucociliary clearance and expectoration.
SEMS placement facilitated weaning from mechanical ventilation in 87.5% of the patients. Previous reports pointed out this benefit in patients with relapsing polychondritis12 and malignant tracheobronchial stenosis.24 25 26 This advantage seems to be directly related with SEMS stability in the airway, low risk of migration, and good internal/external diameter ratio.
Ten patients remained symptomatic after SEMS placement. The prosthesis failed to re-establish airway patency in two patients with BCs (tracheoesophageal fistula and relapsing polychondritis) and one patient with CA due to extensive disease beyond the central airways. Six patients in the CA group progressed to extensive metastatic disease, and one patient from the LTx group acquired severe bronchiolitis obliterans shortly after the SEMS placement, remaining symptomatic. The observed failure reflects poor patient selection for airway stenting, as part of the natural learning curve, by the investigators.
It should be emphasized that due to the retrospective nature of this study, its interpretation must be cautious. Extrapolation of the present data to the general population must consider the high level of selection of these patients undergoing SEMS placement. Spirometric follow-up data were not available for all patients due to the heterogeneity of the studied group, as some of the patients were receiving mechanical ventilation and others had multiple simultaneous procedures (laser ablation, balloon bronchoplasty, electrosurgery) along with SEMS placement. The complication rates could have been underestimated because in some asymptomatic patients follow-up bronchoscopies were postponed.
SEMS placement is a safe and effective modality for malignant and benign airway obstruction. It is an acceptable therapeutic alternative in patients with central airway obstruction who are not considered good surgical candidates and are receiving mechanical ventilation. SEMS placement should be considered when all other therapeutic options are exhausted. It should be stressed that SEMS placement is not a temporary therapeutic alternative, and silicone stents are still the "gold standard" for such situations, as they are relatively easy to readjust, remove, and replace.3 Unfortunately, only 6% of US pulmonologists can perform rigid bronchoscopy, the required method for such type of stents.16 Despite the reported benefits of rigid bronchoscopy, there are less than a handful of training programs providing adequate experience to pulmonary or thoracic surgery fellows.27
A precise patient selection warrants good outcomes and less morbidity, especially when patients with benign diseases are considered. The insertion using FB adds to the ease of the procedure.
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Footnotes |
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Received for publication December 27, 2002. Accepted for publication March 31, 2003.
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