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Ann Thorac Surg 2008;85:2100-2103. doi:10.1016/j.athoracsur.2007.11.076
© 2008 The Society of Thoracic Surgeons
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New Technology

A Novel Anatomy-Conforming Metallic Stent for Tracheobronchial Stenosis

Chang Chen, MDa,*, Sen Jiang, MDb

a Department of General Thoracic Surgery, Tongji University-Affiliated Shanghai Pulmonary Hospital, Shanghai, China
b Department of Radiology, Tongji University-Affiliated Shanghai Pulmonary Hospital, Shanghai, China

Accepted for publication November 28, 2007.

* Address correspondence to Dr Chen, Zhengmin Rd 507, Shanghai, 200433, China (Email: changchenc{at}hotmail.com).


   Abstract
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Purpose: A metallic stent for tracheobronchial stenosis provides a possible solution for poststenting complications such as sputum retention. We describe our experience with a novel anatomy-conforming metal stent placement at the carina.

Description: A windowed stent was designed to match the tracheobronchial anatomy. The lateral window was used as a passage from the trachea to the contralateral main bronchus.

Evaluation: Six windowed stents were placed in 6 patients (mean age, 52.3 years). Two patients received an additional short straight stent placed in the contralateral bronchus, forming an overall Y stent at the carina. All patients had immediate relief from respiratory distress, and no sputum retention or stent migration occurred during the subsequent treatment period. Follow-up data showed that 4 patients are still alive. One patient died 2 months after stent placement of postradiation hemoptysis, and another died of metastasis 14 months after stent placement.

Conclusions: This anatomy-conforming metal stent has several advantages and its application in carinal stenosis is both effective and safe.


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Stent placement in the carinal region has been technically challenging because of anatomic constraints. Although Dumon (Tracheobronxane Y; Novatech, Grasse, France) and Dynamic (Rüsch, Kernen, Germany) bifurcated stents are widely used [1, 2], they are associated with complications. Expectoration difficulties caused by the cylindrical shape of the stent and the silicone construction have been documented. Severe sputum retention in some patients may necessitate frequent bronchoscopic aspiration.

An effective solution to avoiding such complications is the use of an uncovered metallic stent [3, 4]. To meet this demand, a wired, uncovered "<"-shaped stent with a pre-preserved lateral window at the inflexion and a good fit with the tracheobronchial anatomic structure was developed. When used together with a second short straight metallic stent, a Y stent can easily be created. This novel stent has several advantages and closely conforms to the carinal shape. This study investigated the effectiveness of the clinical application of this novel stent.


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Informed consent from each patient and consent from the Ethics Committee of Shanghai Pulmonary Hospital were obtained for stent placement in May 2006.

Patient Population
The study comprised 6 patients (1 woman, 5 men) who underwent stent placement for tracheobronchial stenosis between May 2006 and September 2007. Their mean age was 52.3 years. All 6 patients had severe dyspnea and respiratory distress on admission. Orthopnea was especially pronounced in 5 patients. Arterial blood gas analysis showed severe hypoxemia in all patients, with average PO 2 of 55.5 mm Hg and PCO 2 of 43.8 mm Hg. Roentgenograms on admission confirmed that tumor occlusion or compression had caused severe airway stenosis involving both the distal trachea and at least one main bronchus that required stent placement from the trachea through the bifurcation.

Only 2 patients were able to tolerate bronchoscopy to assess stricture severity, length, and for diagnostic biopsy. Diagnosis was successfully confirmed in 4 patients by sputum cytology and in the other 2 patients by bronchoscopic biopsy. Pathology confirmed primary squamous lung cancers in 5 patients and small cell carcinoma in 1. Upon consultation for the discussion of comprehensive treatment options, these 6 patients were excluded from surgery because of advanced disease stage. A consensus was reached in these patients for stent placement as the first-line treatment.

Stent Design
The stent was manufactured according to the specified design but was adapted to each patient (Nanjing Mini-invasive Med Co, Nanjing, China). It was woven using one intact metallic 0.12-cm-diameter nitinol alloy wire. A lateral window was left between the tracheal and bronchial branches. This side hole was designed to exactly face the opposite bronchi (Fig 1A). A 145° to 155° angle between the tracheal and bronchial branches conforms to tracheobronchial anatomy. Computed tomography (CT) images were used to calculate the precise measurements of the stent with reference to the diameter and length of the two branches and the lateral window.


Figure 1
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  		Fig 1. (A) Model of the specially designed tracheobronchial stent. Note the window on lateral wall of the metallic wall (arrow). (B) The anatomy of a Y carinal stent is achieved by adding a short straight stent. This short stent is placed into the opposite bronchus, exactly facing the window.

 
Four minor metal clips were attached to the stent as the positioning marks: 1 clip was placed on the lower edge of lateral window, which labels the carina; the other 3 were attached to the wall to direct the position of the side hole. The mesh stent was then compressed into the cylinder delivery catheter, with the side hole facing the desired direction. Figure 1B shows the composite Y stent that was created with an additional short straight mesh stent as the complementary part in the contralateral main bronchi. The diameter of this short metal stent was usually 1- to 2-mm smaller than the lateral window.

Stent Placement
General anesthesia was initiated and the stent was placed with radiographic and bronchoscopic guidance. The patient was in the supine position and was hand-ventilated through an endotracheal tube. A flexible bronchoscope was inserted for both tissue biopsy and remeasurement of stenotic length. Under fluoroscopy, the position of the carina was labeled with a metal clip on the patient's chest. A Seldinger wire was advanced into the distal diseased bronchi through a bronchoscope. The delivery catheter equipped with stent was introduced over this wire. Overlapping of the surface clip and the inside metal mark indicated that the lower end of the lateral window had reached the carina. The stent was then gently advanced in for distal deployment, with the small branch released first. The other 3 metal clips on the stent were used to position the lateral window before the tracheal branch of the stent was deployed.

When a Y stent was indicated, the short straight mesh stent was placed first with its proximal end exactly on the carina. In the second step, the windowed tracheobronchial stent was inserted as described. The whole procedure was usually completed within 30 minutes. Figure 2 shows the bronchoscopic view of the windowed stent.


Figure 2
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  		Fig 2. Bronchoscopic view of a newly placed tracheobronchial stent. Note that the lateral window is facing the right main bronchus. The lower edge of the window is exactly located on the carina.

 

   Clinical Experience
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Involvement of both the distal trachea and one main bronchus was confirmed in 4 patients, which resulted in placement of the specially designed uncovered "<"-shaped stent. In the remaining two patients, both branches of the bronchial bifurcation were stenotic; therefore, Y stents were indicated. To accommodate stent design and manufacture, a 24-hour delay time was requested before stenting.

Compared with their severe dyspnea before stent placement, all 6 patients had immediate and significant relief after stenting. They were ambulant, rather than oxygen-dependant after stent placement, and normal gas exchange was demonstrated in all patients on the first postoperative day, with a mean PO 2 of 81.5 mm Hg and PCO 2 of 40.3 mm Hg.

Nebulization was administered routinely to each patient in the 3 days after stent placement, but no other special poststenting nursing care was required. Neither coughing difficulties nor sputum retention were noted. Two patients had minor hemoptysis after stent placement, but this was resolved within 2 days after the administration of oral hemostatics. Chest pain was noted in all patients, but this was quickly relieved with oral analgesics.

Follow-up CT examinations demonstrated good stent function and position. The stents remained in place for an average of 159 days. They were very well tolerated, with no stent migration or granulation growth encountered. The longest stent placement was for 14 months. The lateral window on the stent was in the correct position in all patients. The bifurcation for the Y stent demonstrated good patency, as expected (Fig 3).


Figure 3
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  		Fig 3. (A) Chest computed tomography image demonstrates a well-preserved air passage from the trachea to the right main bronchus. (B) In this roentgenogram of another female patient, the Y shape shows good conformity.

 
Despite radiotherapy and chemotherapy, 1 patient died of metastasis 14 months after stent placement. Another patient died 2 months after stent placement of massive hemoptysis after radical radiotherapy. The remaining 4 patients are still alive. Table 1 describes the general characteristics and survival of these patients.


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  		Table 1 Summary of Patient Characteristics and Survival
 

   Comment
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Although stenting procedures have been well described and standardized, carinal stenting is still regarded as the most challenging owing to anatomic constraints. Successful outcomes have been reported with a variety of airway stents, including the T-Y tube, wire-reinforced Y tracheostomal tube [5, 6], Dumon silicon Y stent [1], and Freitag Dynamic (Rusch, Kernen, Germany) stent [2]. These stents have associated negative aspects, however, such as the requirement for tracheotomy or rigid bronchoscope with the tracheostomal Y or T-Y tube [5, 6], and a weak radial expansion force in silicone or rubber stents. In addition, grasping forceps dependence and possible vocal cord injury are associated with the Dynamic stent [1, 2]. Weakened cilia movement may lead to prominent sputum retention and recurrent bacterial colonization [7].

The current study demonstrated that the self-expendable uncovered metallic stent is a good alternative to other stent options owing to its advantages of easy placement under flexible bronchoscope with a comparatively short learning curve for handling and less risk of injury to the vocal cords [3, 4]. The absence of cough difficulties as well as maintenance of good airway patency in present series is mostly attributed to the unaffected cilia function amongst the metallic mesh.

The distinguished feature of the stents mentioned in this report has been the lateral window, which is deliberately designed to meet the carinal bifurcation shape for the purpose of maintaining a good passage into the opposite main bronchus. Similar design modes had been previously reported by Jacobs and colleagues [8], who intentionally used side holes on cannulas for contralateral ventilation. The rationale behind the present design is that one of the main bronchus may be spared in some cases, when a single "<"-shape stent placement is sufficient. Moreover, this design makes carinal stenting a simplified one-stage method for the creation of a Y stent, as we have described.

Several comparable strategies for carinal stent placement are currently being used. A popular one has been inserting a lateral short branch through the mesh wall of a tapered long tracheobronchial stent with aid of balloon dilation or laser resection [3, 4]. Others include placing a single stent into each passage; namely, 1 stent in each main bronchus as needed and 1 in the trachea and have them meet at the carina; or sequentially (usually 1 or 2 weeks as an interval) placing 2 overlapping Z stents for the carina [4]. All such options, however, are time-consuming and the outcome of an artificial lateral passage had not been clearly defined. Such problems were minor in the present study because the lateral window has eliminated the need for balloon dilatation and the short-first long-next sequence guarantees that the 2 stents are both in good positions.

It is doubtful that the lateral window weakens radial expansion force around the carina. Although we did not measure these indicators, no incomplete expansion was observed, probably because the window's diameter is smaller than that of the tracheal part (0.9 to 1.1 vs 1.6 to 1.8 cm), and the stent was woven with relatively strong metallic wires that were 0.12 cm in diameter. The tumor response to subsequent anticancer treatment was also contributory.

As suggested in previous studies, the selection and application of tracheobronchial stents primarily depends on physicians' preference, stent availability, and the nature of the airway stenosis. The difficulties of stent removal and complications after stenting, such as granulation stimulation, prohibit the use of metallic stent in benign strictures. Other important factors that should be considered before selection include the poststenting care required, such as conscientious nebulizing for silicone stents, stent-related sputum retention problems, and the technical experience necessary for stent placement in addition to the risks of mechanical injury during stenting [1, 4, 5]. Considering these altogether, the presently described metal stent is a good candidate because it is both safe and effective for malignant stenosis in the carinal region.


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The stent discussed in this report was designed by the researchers, and its manufacture was commissioned at Nanjing Mini-invasive Med Company, Nanjing, China. The authors do not have any other material or financial relationships with this commercial enterprise. The authors had full control of the design of the study, methods used, outcome parameters, analysis of data, and production of the written report.


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Disclaimer The Society of Thoracic Surgeons, the Southern Thoracic Surgical Association, and The Annals of Thoracic Surgery neither endorse nor discourage use of the new technology described in this article.


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  1. Dutau H, Toutblanc B, Lamb C, Seijo L. Use of the Dumon Y-stent in the management of malignant disease involving the carina: a retrospective review of 86 patients Chest 2004;126:951-958.[Medline]
  2. Freitag L, Lekolf E, Stamatis G, Greschuchna D. Clinical evaluation of a new bifurcated dynamic airway stent: a 5-year experience with 135 patients Thorac Cardiovasc Surgeon 1997;45:6-12.[Medline]
  3. Lo CP, Soo TB, Hsu AA, Eng PC. Treatment of severe carinal stenosis with overlapping metallic endoprosthesis Ann Thorac Surg 2001;71:1335-1336.[Abstract/Free Full Text]
  4. Hosokawa Y, Tsujino I, Kiyofuji K, et al. Placement of two types of spiral Z-stents at the bronchial carina for the treatment of terminal lung cancer–a new method J Int Med Res 2006;34:556-562.[Medline]
  5. Shiraishi T, Okabayashi K, Kuwahara M, et al. Y-shaped tracheobronchial stent for carinal and distal tracheal stenosis Surg Today 1998;28:328-331.[Medline]
  6. Shiraishi T, Kawahara K, Shirakusa T, Inada K, Okabayashi K, Iwasaki A. Stenting for airway obstruction in the carinal region Ann Thorac Surg 1998;66:1925-1929.[Abstract/Free Full Text]
  7. Wassermann K, Eckel HE, Michel O, Müller RP. Emergency stenting of malignant obstruction of the upper airways: long-term follow-up with two types of silicone prostheses J Thorac Cardiovasc Surg 1996;112:859-866.[Abstract/Free Full Text]
  8. Jacobs JP, Quintessenza JA, Botero LM, et al. The role of airway stents in the management of pediatric tracheal, carinal, and bronchial disease Euro J Cardiothorac Surg 2000;18:505-512.[Abstract/Free Full Text]

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Invited Commentary
Sudish Murthy
Ann. Thorac. Surg. 2008 85: 2104. [Extract] [Full Text] [PDF]



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S. Murthy
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Ann. Thorac. Surg., June 1, 2008; 85(6): 2104 - 2104.
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