Tracheal stenosis treated with self-expanding nitinol stent

Concentric photothermal coagulation with basket-integrated optical device for treatment of tracheal stenosis

A basket-integrated optical device is developed to consistently treat tubular tissue by centering an optical diffuser in the lumen. Four nitinol arms in conjunction with the optical diffusing applicator are deployed to induce homogeneous circumferential light emission and concentric photothermal coagulation on tracheal tissue. A 1470-nm laser light is employed for the tissue testing at various irradiation conditions and evaluated in terms of thermal gradient and temperature evolution. Preliminary experiments on liver tissue demonstrate the concentric development of the radial thermal coagulation in the tissue (eccentric ratio = ~5.5%). The interstitial tissue temperature increases with the total amount of energy delivery (around 65°C). Ex vivo trachea testing yields up to 16.5% tissue shrinkage due to dehydration as well as uniform ablation of the cilia and goblet cells in a mucosa layer under 7-W irradiation for 10 s. The proposed optical device may be a feasible therapeutic method to entail the circumferential coagulation in the tubular tissues in a reliable manner.

Metallic expandable stents in the management of malignant tracheal stenosis due to esophageal cancer with lymph node metastasis

Esophageal cancer with post-operative lymph node metastasis (LNM) compressing and infiltrating the trachea causing dyspnea is considered a serious complication. However, chemotherapy or radiotherapy are often ineffective methods for such patients. Approaches employing metallic expandable stents to relieve airway obstruction are extremely effective in advanced-stage cancer patients. The present study reports the use of metallic expandable stents as a treatment for tracheal stenosis. A total of 11 patients with tracheal stenosis due to LNM compressing and infiltrating the trachea were selected between November 2009 and January 2013. All the patients were diagnosed by computed tomography and presented with varying degrees of dyspnea. A total of 13 stents were placed in 11 patients, without significant intraoperative complications. Post-operatively, all patients presented with significant improvement in respiratory function. The Borg score was determined 1 day after stent application. The mean score of dyspnea declined significantly from 7.0 to 0.9 (P<0.01), the mean heart rate decreased from 128 to 86 bpm (P<0.01), the mean respiratory rate decreased from 34 to 23 breaths/min (P<0.01) and the mean oxygen saturation increased from 85 to 97% (P<0.01). Complications included coughing, hemorrhage, chest pain, retention of secretions, halitosis and tumor regrowth. It may be concluded that metallic expandable stent placement is an effective strategy to palliate malignant tracheal stenosis.

Biomedical Applications of Shape Memory Alloys

Shape memory alloys, and in particular NiTi alloys, are characterized by two unique behaviors, thermally or mechanically activated: the shape memory effect and pseudo-elastic effect. These behaviors, due to the peculiar crystallographic structure of the alloys, assure the recovery of the original shape even after large deformations and the maintenance of a constant applied force in correspondence of significant displacements. These properties, joined with good corrosion and bending resistance, biological and magnetic resonance compatibility, explain the large diffusion, in the last 20 years, of SMA in the production of biomedical devices, in particular for mini-invasive techniques. In this paper a detailed review of the main applications of NiTi alloys in dental, orthopedics, vascular, neurological, and surgical fields is presented. In particular for each device the main characteristics and the advantages of using SMA are discussed. Moreover, the paper underlines the opportunities and the room for new ideas able to enlarge the range of SMA applications. However, it is fundamental to remember that the complexity of the material and application requires a strict collaboration between clinicians, engineers, physicists and chemists for defining accurately the problem, finding the best solution in terms of device design and accordingly optimizing the NiTi alloy properties.

The use of metallic expandable tracheal stents in the management of inoperable malignant tracheal obstruction

Tracheal neoplasms account for less than 1% of all malignancies. In spite of their low incidence, these tumors represent potentially lethal phenomena. In cases of airway compromise and unresectable disease, the airway may be maintained by repeated bronchoscopic debulkings, and the use of CO(2) laser, silicone Montgomery T-tube and tracheal stents. The use of metallic expandable stents to relieve airway obstruction in advanced tracheal tumors was previously reported. Our aim was to evaluate the use of metallic expandable tracheal stents as a palliative relief from severe airway obstruction in cases of locally advanced, inoperable malignant tracheal tumors. Patients suffering from severe airway obstruction secondary to locally advanced tracheal tumors, who presented to the Otolaryngology Head and Neck Surgery and Chest Diseases Departments at the Main Alexandria University Hospital, Egypt, were included in this study. After endoscopic and radiological evaluation, expandable metallic tracheal stents (SENS; Ultraflex tracheal prosthesis; Boston Scientific Corp, Watertown, MA, USA) were inserted under general anesthesia to relieve airway obstruction. Postoperative follow-up with regard to improvement of respiration, tolerability of the stent and reporting of complications was done. Twelve patients were included, eight males and four females with a mean age of 61 years. Four patients (33.3%) had primary tracheal tumors and eight (66.7%) suffered from tumors infiltrating the trachea from nearby structures. The stent was easily inserted in all patients with no significant intraoperative complications. Postoperatively, the stent was well tolerated and all patients experienced good respiration with significant improvement of respiratory function test results. The most common complication reported was granulation tissue formation. Other complications were displacement of the stent, bad breath, re-growth of tumor tissue at the lower end of the stent and retention of secretions. We concluded that Ultraflex self-expandable stent is a good alternative for palliative relief from airway obstruction in cases of inoperable malignant tracheal tumors. Strict follow-up is mandatory for early detection and management of expected complications.

Laryngeal framework reconstruction using titanium mesh in glottic cancer after frontolateral vertical partial laryngectomy

OBJECTIVES

To investigate the feasibility and efficacy of laryngeal framework reconstruction using titanium mesh in patients with glottic cancer after frontolateral vertical partial laryngectomy.

STUDY DESIGN

Prospective study.

METHODS

Defect of laryngeal framework, caused by frontolateral vertical partial laryngectomy in nine patients with T2 or T3 squamous cell carcinoma of glottic, were reconstructed with titanium mesh from 2007 to 2009. Computed tomography (CT) and fiberscopic examinations were performed at two weeks and three months postoperatively.

RESULTS

No aspiration and laryngeal stenosis was observed in the nine patients. CT scanning showed that titanium mesh was fastened well without displacement and deformity and that there was no laryngeal stenosis. Fiberscopic inspection showed that the larynx lumen was maintained well without stricture, shrinkage, and necrosis. No titanium mesh was exposed to the larynx lumen.

CONCLUSIONS

Titanium mesh was a good alternative for reconstruction of the laryngeal framework. It provided adequate structural support to maintain airway patency.

Laryngotracheal augmentation using titanium mesh

Background:

The management of laryngotracheal stenosis is still a serious surgical challenge. The fact that there are currently numerous reconstruction procedures indicates that there is at present no standard treatment.

Study design:

Titanium mesh was used instead of traditional homografts in reconstruction of the anterior laryngotracheal wall in 12 tracheostomised patients with benign chronic laryngotracheal stenosis. The anterior laryngotracheal wall was split, followed by excision of scar tissue and fixation of the titanium plate at the split end. A Silastic®stent was inserted above the tracheostomy tube and fixed in place by running sutures fixed to the skin by buttons. The stent was removed endoscopically six weeks later and a trial of decannulation was undertaken.

Results:

Endoscopically, good epithelisation was seen on the inner surface of the mesh in 10 cases and decannulation was possible. Four of these patients required endoscopic debulking of granulation tissue. Decannulation was impossible in two cases, one due to excessive granulation tissue and the other due to prolapse of the titanium mesh into the tracheal lumen (the mesh was removed endoscopically and a Montgomery T-tube inserted).

Conclusion:

Titanium mesh was found to be a good alternative for augmentation of the anterior laryngotracheal wall. It offered rigid support, with fewer of the complications reported with other grafts.

Fixation of silicone stents in the subglottic trachea: preventing stent migration using a fixation apparatus

Silicone stents are widely used to treat benign or malignant airway stenosis. However, since straight silicone stents placed into the subglottic trachea to treat stenosis display a high risk of migration, novel approaches are required. The present report outlines our method of external fixation for silicone stents in the subglottic trachea. This technique utilizes a fixation apparatus, is readily performed, and may help to overcome the hesitation seen in placing silicone stents for subglottic tracheal stenosis.

Chronic subglottic and tracheal stenosis: endoscopic management vs. surgical reconstruction

Laryngotracheal stenosis has been and remains one of the most vexing problems in the field of head and neck surgery. Two treatment modalities prevail, endoscopic and external. The indication for each modality is not yet clearly defined. This undefined situation motivated our current work, and we decided to assess laser-assisted endoscopy (with or without stenting) vs. open surgery for treating chronic laryngotracheal stenosis. Our study included 28 cases of chronic laryngotracheal stenosis that were classified according to treatment in two main groups: group I included 13 patients who were endoscopically treated and group II included 15 patients with surgical reconstruction. The mean follow-up period was 12.58 months for group I and 27.43 months for group II. Respiratory function tests (RFT) were carried out preoperatively, 1-month postoperatively and on completion of follow-up. Except for age, which was significantly higher in group I (P<0.001), there was no significant difference between both groups. Although the incidence of complications was higher in group I (69%) than in group II (47%), it was nonsignificant. The postoperative RFT improved significantly in both groups. Although the improvement was higher in group I than group II, the difference was nonsignificant. The correlation between preoperative stridor and all other variables demonstrated that preoperative stridor correlated with the diameter of the stenosed segment (rs=-0.631, P<0.001) and the peak expiratory flow rate (PEFR) (rs=-0.488, P=0.030). Our results indicate that open surgery is the treatment of choice. Compared with endoscopic treatment, it provides a higher success rate and better functional results, especially long term. However, if contraindications to open surgery exist, whether local or general, laser-assisted endoscopy with stenting can offer good palliative results.

Ultraflex stents for the management of airway complications in lung transplant recipients

OBJECTIVE

We present our experience with the use of the Ultraflex (nitinol) stents in the management of airway complications in lung transplant (LT) recipients.

METHODOLOGY

Nine LT recipients underwent insertion of uncovered Ultraflex stents. Mean change in FEV1, duration to formation of granulation tissue and follow-up post-stent insertion were compared with results obtained in LT recipients who had undergone Gianturco stent (n = 10) and Wallstent insertion (n = 16).

RESULTS

Mean improvement in FEV1 after insertion of Gianturco, Wallstent and Ultraflex stents was 670 +/- 591 mL, 613 +/- 221 mL and 522 +/- 391 mL, respectively. No patient with an Ultraflex stent developed mucus plugging or stenosis at stent extremity at a follow up of 263 +/- 278 days. The mean and median duration to stenosis at stent extremity for patients with Gianturco stents was 102 +/- 85 days and 73 days, respectively, compared with 132 +/- 87 days and 142 days, respectively, for patients with Wallstents. Stricture formation in the middle of the Ultraflex stent occurred bilaterally, at the level of anastomosis in one patient in whom stent placement was undertaken in the presence of inflammation. Stent migration in one patient was related to undersizing of the stent diameter relative to the airway diameter. A larger diameter relative stent was subsequently inserted successfully.

CONCLUSION

Ultraflex stents appear to have fewer long-term complications when used in the management of airway complications following LT.

Nitinol stent for the treatment of tracheobronchial stenosis

OBJECTIVE

The purpose of this study was to evaluate the potential utility of implantation of a nickel-titanium alloy (nitinol) stent for the treatment of malignant or benign tracheobronchial stenosis.

METHODS

We evaluated 18 patients (14 men and 4 women) who received 24 nitinol stents, between November 1997 and May 2000. All 18 patients had severe dyspnea caused by tracheobronchial stenosis. The underlying condition was malignant disease in 15 patients, and benign tracheal collapse in the other 3 patients.

RESULTS

Implantation of the stent was successfully performed in all patients. Seventeen patients experienced immediate clinical improvement in respiratory symptoms. The remaining 1 patient with a bronchial fistule after lobectomy did not benefit, and died of pneumonia at 16 days after the implantation. In 15 patients, the procedure was performed using a flexible bronchoscope under local anesthesia alone, while the remaining 3 patients needed intravenous sedation. There was no complication resulting from the stent implantation. Among the 3 patients with benign tracheal collapse, 2 patients were alive at 746 and at 401 days after the stent implantation, at the time of this report. One patient with cicatricial stenosis after intubation died of heart failure due to previous myocardial infarction. Among the 15 patients with malignant disease, 4 patients have survived for 177 to 305 days to date, while the other 11 patients have died of primary malignancy with a mean survival duration of 60.2 days.

CONCLUSION

The nitinol stent was effective in treating malignant or benign tracheobronchial stenosis, and had some remarkable advantages compared with other tracheobronchial stents. In stenting, most procedures can be performed using flexible bronchoscope under local anesthesia.

Inflammatory endobronchial stenosis

We encountered a 71-year-old woman with inoperable bronchial stenosis of the right main bronchus, which was caused by inflammatory granulation infected with Pseudomonas aeruginosa in posttuberculous bronchiectasis. Two months after placement of self-expanding nitinol stents, fiberoptic bronchoscopic examination to investigate hemosputum revealed endobronchial granuloma formation. Endobronchial granulation has disappeared with long-term oral administration of tranilast.

Nitinol - its use in vascular surgery and other applications

OBJECTIVES

to describe the physical properties of shape-memory alloys and the surgical, scientific and commercial applications of nitinol, in particular.

DESIGN AND METHODS

a Medline, Internet and library search with contributions from commerce to describe the alloy's structure, behaviour and biocompatibility, and design for devices constructed from nitinol.

RESULTS

nitinol has the properties of thermal shape memory and superelasticity that make it ideal for many vascular and general surgical prostheses and disposables, and for various commercial applications.

CONCLUSIONS

further research into shape-memory alloys from scientific and commercial groups should widen their use in vascular and endovascular surgery.

Surgical palliation of airway obstruction resulting from lung cancer

Bronchogenic carcinoma remains a relentless plague of modern society causing far more deaths than the well-popularized "AIDS epidemic" and secondary only to cardiovascular disease as a cause of death in America. Despite medical advances and treatment breakthroughs, only 40% of newly identified lung cancer patients are "potentially curable". Therefore, a large portion of this patient population will require palliative care and treatment. Surgical palliation is somewhat a misnomer in that most endobrachial lesions causing significant obstruction that result in dyspnea are not amenable to surgical intervention, i.e., operative resectional therapy. The palliative management options of airway obstruction resulting from advanced stage lung cancer will be reviewed, including the historical aspects, development and current use of laser resection, airway stenting, and endobrachial brachytherapy for management of unresectable airway tumors. These modalities frequently are used simultaneously in the same patient and may be used in conjunction with current chemotherapeutic and conventional external-beam radiation protocols.

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.

Flexible bronchoscopy: a safe method for metal stent implantation in bronchial disease

BACKGROUND

Endoscopic bronchoplastic procedures, such as metal stent implantation, are for safety reasons and mainly performed using rigid bronchoscopy. Major complications, such as bleeding and accidental airway occlusion, are thought to be better managed with the rigid device. An increasing number of pneumologists, however, use the flexible fiberscope for endobronchial stenting.

METHODS

Sixty-five stent implantations were performed in 51 patients with flexible fiberoptic bronchoscopy. We implanted 27 Tantalum Strecker stents (Boston Scientific Co, Watertown, MA), 20 Nitinol Accuflex stents (Boston Scientific Co) and 18 Wallstents (Schneider, Zurich, Switzerland). Underlying conditions were malignant disease in 84% and benign bronchial collapse in 16%. Sites of implantation were the trachea (45%), the main bronchi (35%), and other locations (20%). In 47 cases the patients received intravenous sedation combined with high frequency jet ventilation, and in 18 cases the patients were treated with topical anesthesia alone.

RESULTS

Mean examination time was 58.3 (standard deviation 29.1) minutes. Eighty percent of patients experienced immediate clinical improvement in respiratory symptoms. Spirometric parameters (forced expiratory volume in one second, peak expiratory flow rate, forced vital capacity) increased. Complications included hypertension (17%), hypotension (12%), hypoxia (5%), bronchospasm (4%), initial displacement of the prosthesis (11%), and diameter mismatch between stent and bronchus (5%). All complications were managed safely. Relevant bleeding or asphyxia during the procedure has not been observed. Late stent migration was observed in 12% of cases. There were 3 fatalities within 30 days of stent placement which, however, were not attributed to the implantation technique.

CONCLUSIONS

Flexible fiberoptic bronchoscopy is a safe and suitable method to perform endobronchial metal stent implantation. Complications were rare and not serious. Initial misplacement of the prosthesis occurred in some cases and necessitated removal and replacement within the same procedure.

Elastic deformation properties of implanted endobronchial wire stents in benign and malignant bronchial disease: A radiographic in vivo evaluation

PURPOSE

To evaluate the long-term mechanical behavior in vivo of expandable endobronchial wire stents, we imaged three different prostheses in the treatment of tracheobronchial disease.

METHODS

Six patients with bronchial stenoses (three benign, three malignant) underwent insertion of metallic stents. Two self-expandable Wallstents, two balloon-expandable tantalum Strecker stents and two self-expandable nitinol Accuflex stents were used. Measurements of deformation properties were performed during voluntary cough by means of fluoroscopy, at 1 month and 7-10 months after implantation. The procedures were videotaped, their images digitized and the narrowing of stent diameters calculated at intervals of 20 msec.

RESULTS

After stent implantation all patients improved with respect to ventilatory function. Radial stent narrowing during cough reached 53% (Wallstent), 59% (tantalum Strecker stent), and 52% (nitinol Accuflex stent) of the relaxed post-implantation diameter. Stent compression was more marked in benign compared with malignant stenoses. In the long term permanent deformation occurred with the tantalum Strecker stents; the other stents were unchanged.

CONCLUSION

Endobronchial wire stents can be helpful in the treatment of major airway collapse and obstructing bronchial lesions. However, evidence of material fatigue as a possible effect of exposure to recurrent mechanical stress on the flexible mesh tube may limit their long-term use. This seems to be predominantly important in benign bronchial collapse.

Airway stents

Considerable progress has been made since the initial stents were manufactured. Despite the reported side effects, cumulative evidence suggests beneficial effects in properly selected patients. The technology is still in evolution, and design modifications strive to find the perfect stent. The Dumon stent remains the gold standard against which the functions of all other stents are being measured. Unfortunately requirement for the RB for deployment has restricted widespread application at least in the United States. The Wallstent can be inserted using FB and has a great potential among the metal stents. Its biggest drawback is that once inserted it is difficult to remove. Studies with the nitinol Ultraflex and the polyester/silicone Polyflex prototype stent also show promise, although extensive experience and long-term follow-up data are still not available. It is possible that combining the strength of the tube stents with the flexibility of the metal stents may one day help to develop the ideal stent.

Stenting therapy for stenosing airway disease

Stenosing airway disease is classified as intraluminal obstruction, extrinsic compression, and malacia by the anatomical site of the lesion. Stenting therapy is indicated for symptomatic relief of life-threatening dyspnea caused by the last two types. Airway stents are made with metal mesh and/or silicone rubber, and currently more than 20 kinds of stent are available. The metal stent (e.g. Gianturco stent, Wallstent) is easy to insert, may not need general anesthesia, and has wider internal lumen. Because it is very hard to reposition or remove, it is mainly used in malignant airway obstruction. Among many kinds of silicone stent, the Dumon stent is most widely used for benign and malignant airway stenoses, but general anesthesia and rigid bronchoscopy are needed for insertion. It can be removed when the stenosing airway disease subsides completely. In many clinical studies, most patients (85-90%) improved immediately after stenting, and procedure-related mortality is low (< 3%) in experienced centers. Stent displacement, mucus impaction, and granulation tissue formation are potential complications. Stenting is one of many effective therapeutic modalities for stenosing central airway disease. Careful patient selection, experiences, and continuous development of new technology will bring better results.