Deformation and migration of Palmaz stents after placement in the tracheobronchial tree

Doxycycline-Eluting Core-Shell Type Nanofiber-Covered Trachea Stent for Inhibition of Cellular Metalloproteinase and Its Related Fibrotic Stenosis

In this study, we fabricated a doxycycline (doxy)-eluting nanofiber-covered endotracheal stent for the prevention of stent intubation-related tissue fibrosis and re-stenosis. The nanofiber was deposited directly on the outer surface of the stent using a coaxial electrospinning method to form a doxy-eluting cover sleeve. Poly(d,l-lactide) was used as the shell-forming polymer and dedicated drug release-control membrane. Polyurethane was selected as the drug-loading core polymer. The compositional ratio of the core to shell was adjusted to 1:0, 1:2, and 1:4 by changing the electro-spray rate of each polymeric solution and microscopic observation of nanofibers using scanning electron microscopy (SEM), transmission electron microscopy (TEM), and the fluorescence microscopy proved core-shell structure of nanofibers. The in vitro release study suggested that the release of doxy could be controlled by increasing the compositional ratio of the shell. The growth of HT1080 fibrosarcoma cells was inhibited by the 10% doxy-containing nanofiber. The real-time polymerase chain reaction (PCR) in HT1080 cells and xenografted tissue models indicated that the doxy-releasing nanofiber inhibited mRNA expression of metalloproteinases (MT1-MMP, MMP-2, and MMP-9). Overall, our study demonstrates that a doxy-eluting core-shell nanofiber stent can be successfully fabricated using coaxial electrospinning and displays the potential to prevent fibrotic re-stenosis, which is the most problematic clinical complication of tracheal stent intubation.

Decreased granulomatous reaction by polyurethane-coated stent in the trachea

BACKGROUND

Reducing granulomatous reaction for stent implantation is important for the treatment of tracheobronchomalacia because formation of granuloma leads to refractory complication causing further respiratory distress. The purpose of this study was to clarify granulomatous reaction of newly innovated coated stents compared to non-coated metal stents.

METHODS

Materials and animal experiments were performed using the newly invented metallic stent (laser-cut stainless steel with a coating of polyurethane). In the materials experiment, the correlation between the holding force and deformity was tested by a compressor. In the animal examination, coated stents were orally implanted into the trachea in five rabbits, while non-coated stents were implanted in another five rabbits. After 3 weeks' observation, the inner diameter was measured by 3-D computed tomography, and the number of granulation tissues was counted by bronchofiberscope. Histological investigation followed in both groups.

RESULTS

In the materials experiment, new stents demonstrated a holding force similar to stainless steel stents. In the animal experiment, no difference was found in the inner diameter of the coated and non-coated stent groups (5.70 ± 0.17 vs 5.60 ± 0.27, P = 0.07). However, the number of granulation tissues was higher in non-coated stents than in coated stents (1.60 ± 0.55 vs 0.40 ± 0.55, P < 0.01). Histological investigation showed direct attachment of metal to the tracheal wall around the non-coated stents where epithelial structure was destroyed, while tracheal epithelia were preserved in the group of coated stents.

CONCLUSIONS

The new polyurethane-coated metallic stent maintains enough holding force, and reduces histobiological reaction to foreign bodies in this experiment.

Long-term outcomes of congenital tracheal stenosis treated by metallic airway stenting

AIM

Congenital tracheal stenosis is an obstructive airway lesion that often presents as a life-threatening emergency. We had introduced the balloon dilatation and placement of the expandable metallic airway stent as a therapeutic option, and this study aimed to clarify the long-term outcomes in pediatric patients.

METHODS

A retrospective review of five infants in whom balloon expandable metallic airway stents (10-40 mm long and 6-8mm in diameter) were inserted in 1997 to 2000 was conducted.

RESULTS

There was an immediate improvement of respiratory obstruction in all five infants (aged 7 days to 12 months) with four weaned from ventilation. One child died after 9 months of palliative treatment. In all inflammation and granulation tissue developed over the stents, but this could be managed by scraping or balloon compression. Metallic stents have been in place a mean of 12 years (range 6 months to 13 years) after insertion without other complications. Four children are alive and well with their stents in place. Recently, an attempt to remove the stent was done in two patients who showed dyspnea on exertion. They underwent tracheoplasty following successful complete removal of metallic stent using cardiopulmonary bypass.

CONCLUSION

Use of expandable metallic airway stents following balloon dilatation can be left for long periods to relieve tracheal obstruction. Development of granulation tissue is a major treatable complication. Removal of the stent was safely completed by open surgical intervention using a cardiopulmonary bypass. The airway stent may provide an important therapeutic option in selected cases with congenital tracheal stenosis.

Interventional techniques in the management of airway complications following lung transplantation

The last four decades have seen tremendous advances in the field of pulmonary transplantation. Vast improvements in the areas of surgical transplantation techniques, immunosuppressive agents, and postoperative care have all contributed to improved survival of patients. Advances in noninvasive imaging and bronchoscopy have allowed the pulmonary transplant team to intervene early in patients presenting with airway complications, often using minimally invasive procedures such as endobronchial balloon dilation or stent placement, or both. Stent technology itself has also improved and stents may sometimes be customized for treatment of short airway lesions or to optimize continued airflow through the sides of stents by creating openings using balloons or bronchoscopically directed laser. Preliminary work with brachytherapy may be decreasing the need for secondary reinterventions. The authors present an overview of some of these conventional and novel approaches to the treatment of airway complications after lung transplantation.

Airway stents in children

Airway obstruction in children is a rare, but difficult clinical problem, with no clear agreement on optimal therapeutic approach. Stenting of the airway has been used successfully in adults, and is an attractive alternative in children. Fundamental differences of pediatric compared to adult use include the benign nature of most stenoses, the narrow and soft airways of children, the required long-term tolerance and adaptation to growth. These differences may significantly alter the therapeutic balance, calling into question the precise role stents play in the treatment of airway obstruction in children. Stent placement can be technically demanding but is not exceedingly difficult. Experience is necessary to select the proper size and type of stent. Metal stents usually achieve airway patency and clinical improvement in the majority of cases, while this is less frequently the case with silicone stents. Some complications such as granulation and secretion retention seem to occur in most children after stent implantation. Unfortunately, severe complications including death have been reported in a significant proportion of children. Stent related mortality can be estimated at 12.9% from published data, but these include complication centered reports. The initial euphoria for airway stents in children has largely abated and most authors agree that they should only be employed in circumstances with no good alternatives. It is crucial that all surgical and medical alternatives are considered and the decision to place a stent is not made because other options are overlooked or not available locally. Stent use in a palliative setting has also been reported and is probably reasonable. Stents will only allow limited adaptation for the growth of pediatric airways by balloon dilatation. All metal stents should be considered as potentially permanent, and removal sometimes may only be possible through a surgical and sometimes risky approach.

Outcomes of Tracheobronchial Stent Placement for Benign Disease

PURPOSE

To retrospectively determine long-term outcomes in patients who have undergone tracheobronchial stent placement for benign diseases.

MATERIALS AND METHODS

Institutional Review Board approval was obtained for this retrospective HIPAA-compliant study, with waiver of informed consent. Forty patients (22 female, 18 male; mean age, 52.0 years) who were treated with metallic airway stents for benign stenosis were identified from an interventional radiology database. Causes of airway stenosis included transplant stricture (n = 13), tracheal tube injury (n = 10), inflammation (n = 6), tracheobronchomalacia (n = 4), infection (n = 3), and extrinsic compression (n = 4). Follow-up, which ranged from 6 to 2473 days, was performed by means of chart review for deceased patients and by means of clinical visit or telephone interview for surviving patients. Survival, primary patency, and assisted patency were estimated by using the Kaplan-Meier product limits method.

RESULTS

Initial technical success was achieved in all cases. Symptomatic improvement was present in 39 of 40 cases. At review, 15 patients were alive and had clinical improvement, 18 had died of comorbid causes, one had died of uncertain causes, three had undergone subsequent airway surgery, two had undergone airway stent retrieval, and one was lost to follow-up. Survival at 1, 2, 3, 4, 5, and 6 years was 79%, 76%, 51%, 47%, 38%, and 23%, respectively. Loss of primary patency was most rapid during the 1st year. With repeat intervention, assisted patency was 90% at 6.8 years.

CONCLUSION

Attrition of tracheobronchial stent patency is most rapid during the 1st year, and a high rate of long-term patency can be achieved with secondary interventions. Metallic airway stents are well-tolerated and useful adjuncts for management of select benign tracheobronchial stenoses.

Treatment of airway obstruction by metallic stents in infants and children

OBJECTIVE

The internal metallic stent is a relatively new and controversial method for the treatment of airway collapse in infants and children. The study examined the outcomes of this treatment in a large group of patients and defined clear indications for airway stenting.

METHODS

A retrospective review was conducted of 32 patients in whom 42 stents were inserted. The patients were divided into three groups with respect to the stented segment: group A, trachea (n = 14); group B, bronchi (n = 16); and group C, trachea and bronchi (n = 2).

RESULTS

In 30 cases, there was immediate improvement of respiratory obstruction, and 23 patients could be weaned, at least temporarily, from ventilation. Excessive granulation developed after the stenting in 26 patients. In 6 patients, all in group A, the granulation and inflammatory reaction generated severe airway obstruction, necessitating thoracotomy in 2 cases. One patient died of airway obstruction, and another died during the attempt to remove the stent; both were in group A. Stents placed for 2 to 72 months (mean 8.7 months) have now been removed in 11 patients. Six children are alive and well with stents in place, 2 from group A and 4 from group B. Fifteen patients died during the follow-up period; in 13 cases, death was related to the associated disease.

CONCLUSION

The use of metallic stents, especially in the trachea, is associated with a high rate of complications. Granulation tissue, which often develops after stenting, is a major concern. Removal of the stents is arduous and carries a high risk of complications. The use of stents should be restricted to the limited situations in which conventional initial therapy has failed.

Tracheal Reaction to Three Different Intraluminal Stents in an Animal Model of Tracheomalacia

Three different internal airway stents were studied in an animal model of tracheomalacia: the Palmaz stent (Johnson & Johnson, Warren, New Jersey) and the NIR stent (Medinol Ltd., Tel Aviv, Israel)--both made of stainless steel in the form of tubular mesh--and the Nitinol stent, made of nickel-titanium formed into a spiral shape. All three stents could be adequately stabilized in the malacic tracheal segment. The Nitinol stent (Medinol Ltd., Tel Aviv, Israel) proved to be less reactive to the tracheal mucosa, demonstrated higher biocompatibility with significantly less granulation tissue formation, and showed superior radial resistance. Extraction of the Nitinol stent also proved to be much smoother. This stent may be the stent of choice in the treatment of tracheo- and bronchomalacia.

An interesting case of a wandering foreign body in the tracheobronchial tree

Inhaled foreign body (FB) is a rare clinical entity for the ENT surgeon. We present a case of an inhaled foreign body in the right main bronchus shown to move to the left main bronchus by repeat chest X-ray during a delay prior to removal. The role of repeat chest X-ray if there is a significant delay before removal of an inhaled foreign body and the optimal management are discussed.

Central Airway Obstruction

Central airway obstruction is a problem facing all medical and surgical subspecialists caring for patients with chest diseases. The incidence of this disorder appears to be rising because of the epidemic of lung cancer; however, benign causes of central airway obstruction are being seen more frequently as well. The morbidity is significant and if left untreated, death from suffocation is a frequent outcome. Management of these patients is difficult, but therapeutic and diagnostic tools are now available that are beneficial to most patients and almost all airway obstruction can be relieved expeditiously. This review examines current approaches in the workup and treatment of patients suffering from airway impairment. Although large, randomized, comparative studies are not available, data show significant improvement in patient outcomes and quality of life with treatment of central airway obstruction. Clearly, more studies assessing the relative utility of specific airway interventions and their impact on morbidity and mortality are needed. Currently, the most comprehensive approach can be offered at centers with expertise in the management of complex airway disorders and availability of all endoscopic and surgical options.

Covered retrievable tracheobronchial hinged stent: an experimental study in dogs

PURPOSE

To evaluate the safety and technical feasibility of the use of a covered retrievable tracheobronchial hinged stent and investigate the histopathologic airway changes after placement and removal of the stent in dogs.

MATERIALS AND METHODS

The experimental stent was composed of tracheal and bronchial stents that were connected together at their ends. Each stent was woven from a single thread of 0.2-mm-diameter nitinol wire filament in a tubular configuration and covered with polyurethane solution by a dipping method. Drawstrings were attached at the upper end of the tracheal stent for stent removal. Under fluoroscopic guidance, 20 stents were placed at the lower trachea and left main bronchus in 20 dogs and were electively removed 4 weeks (n = 10) or 8 weeks (n = 10) after placement. Ten dogs were killed just after stent removal and the remaining 10 were killed 2 weeks after stent removal.

RESULT

Stents were successfully placed in all dogs. Pneumonia was observed in three dogs. Stent migration occurred in seven dogs (35%). Except for two cases of stent expectoration, 18 stents were easily removed within a few minutes. There was considerable granulation tissue proliferation and inflammatory reaction in the airways of the dogs that were killed just after stent removal. The pathologic changes of the airways returned to almost-normal conditions 2 weeks after stent removal.

CONCLUSION

Placement and removal of a covered retrievable tracheobronchial hinged stent seems to be feasible, and histopathologic changes of the airway related to the stents returned to normal 2 weeks after stent removal.

Management of the ear, nose, and throat manifestations of Wegener granulomatosis: an otorhinolaryngologist's perspective

A diagnosis of Wegener granulomatosis requires granulomatous manifestations in the respiratory tract. With the increasing use of antineutrophil cytoplasmic autoantibodies as a diagnostic tool, Wegener granulomatosis is diagnosed earlier than in the past, and not infrequently when only ear, nose and throat manifestations are present, placing the otorhinolaryngologist in a central role in diagnosis and management. Diagnostic biopsies should be obtained from active lesions in the nose and paranasal sinuses and concomitant infection should be identified. Because of the apparent relation between infection and activation of disease, the management of infections-especially those due to Staphylococcus aureus-requires special attention. The increasing numbers of early cases identified warrants further investigations of whether less toxic treatment regimens will be of advantage in such cases. Medical and surgical treatment of the acute and chronic manifestations presents specific problems because of altered immune competence, prevalent superinfection, and tissue destruction, and is therefore best taken care of by specially dedicated otorhinolaryngologists.

Implantation of ultraflex nitinol stents in malignant tracheobronchial stenoses

STUDY OBJECTIVE

To assess the uncovered Ultraflex nitinol stent (Boston Scientific; Natick, MA) for its efficacy and safety.

DESIGN, SETTING, AND PATIENTS

Between October 1997 and October 1998, we carried out a prospective multicenter study at six hospitals in Japan. Fifty-four Ultraflex stents were inserted in 34 patients with inoperable malignant airway stenosis using a flexible and/or a rigid bronchoscope under fluoroscopic and endoscopic visualization.

MEASUREMENTS AND RESULTS

Clinical, endoscopic examination, and pulmonary function on days 1, 30, and 60 after stent implantation showed improvement. In 19 patients (56%), stent implantation was performed as an emergency procedure because of life-threatening tracheobronchial obstruction. Immediate relief of dyspnea was achieved in 82% of the patients. The dyspnea index improved significantly after implantation (before vs. days 1, 30, and 60; p<0.001). Significant improvements were observed in obstruction of airway diameter (81+/-15% before vs. 14+/-17% on day 1, 12+/-12% on day 30, and 22+/-28% on day 60; p<0.001). Vital capacity (VC), FEV(1), and peak expiratory flow (PEF) increased significantly after stent implantation: before vs immediately after VC (p<0.01), FEV(1) (p<0.001), and PEF (p<0.05). The main complications were tumor ingrowth (24%) and tumor overgrowth (21%). After coagulation with an Nd-YAG laser or argon plasma coagulation, mechanical coring out using the bevel of a rigid bronchoscope was necessary in patients showing tumor ingrowth or overgrowth. Removal and reposition were possible in case of misplacement. There were no problems with migration and retained secretions. The median survival time of patients was 3 months. The 1-year survival rate was 25.4%.

CONCLUSIONS

In this study of the Ultraflex nitinol stent, we have demonstrated that patients were relieved from dyspnea, which contributed to improved quality of life, with minimal complications. This stent can be used safely, even in the subglottic region. Owing to its excellent flexibility and biocompatibility, the stent is also indicated in certain complicated situations, eg, narrow stenosis, hourglass stenosis, curvilinear stenosis, bilateral mainstem bronchial stenoses, and long stenosis of varying diameters.

Stenting of the tracheobronchial tree

Endoscopic treatment of endobronchial obstructions is becoming increasingly important. Tracheobronchial stents often are needed in the treatment of obstructions from submucosal or extrabronchial lesions. Tube stents have been available since the early 1960s but are underused because their insertion requires the use of a rigid bronchoscope. With the recent development of metallic stents, interventional radiologists increasingly are involved in the treatment of tracheobronchial obstructions. Metallic stents, easily placed with flexible bronchoscopy, are growing in popularity. All available tracheobronchial stents have been shown in various clinical series to be able to achieve immediate resolution of respiratory symptoms from various tracheobronchial obstructions. A stent's performance, however, should not be based solely on short-term response. Presently, there is no ideal stent because none is free of complications and none are able to consistently maintain life-long patency. Gianturco stents are associated with serious major complications (bronchial perforations and strut fractures) and are no longer recommended for use in the tracheobronchial tree. The Palmaz stent has also fallen into disfavor, because a strong external force, such as a vigorous cough, can recompress it. The Strecker stent can only be used in smaller airways, but may be useful in the accurate stenting of short segment stenoses because it does not foreshorten on deployment. The Wallstent and Ultraflex are our present metallic stents of choice. Both are easy to deploy, available in covered forms, exert adequate radial force, remain relatively stable in position, and have good longitudinal flexibility for use in tortuous airways. Disadvantages include excessive granulation tissue formation and difficulty of removal once the stent has been epithelialized. Metallic stents should be chosen very carefully for use in benign lesions with ongoing active local inflammation or when temporary stenting is needed. In the absence of an ideal stent, technologic advancements will continue. Potential developments include removable metallic stents, biodegradable stents, and chemically and radioactively coated stents. Unquestionably, the expanding stent market will drive scientific research toward the development of the ideal stent. Clearly, physicians need to be ready to assess these technologic advancements.