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Introduction
Relief of dyspnea or/and non-productive cough in patients with malignant
or benign large airway obstruction is of primary importance. A variety of
methods have been used, including dilatation, laser ablation, cryoablation,
brachytherapy, photodynamic therapy, and silicone stent placement.
Tracheobronchial stents are used to relieve critical large airway
obstruction due to severe extrinsic pressure, intraluminal spread of malignant
disease or loss of normal cartilaginous support (tracheomalacia)1-7. The
principal complaints of patients with central airway stenosis are dyspnea
and cough. In addition, stents may be placed temporarily in patients
with benign stenosis to allow for adequate time to prepare for surgical management. Tracheobronchial stents are also indicated
for permanent palliation in patients with benign stenosis
who are medically unfit for surgical repair (e.g. due to
poor respiratory reserve or heart failure).
The present study outlines the indications, technique
and outcomes of tracheobronchial Dumon silicone stent
placement in a series of patients with malignant and
benign tracheobronchial stenosis.
Patients and methods
In the period 1999-2004, 57 silicone stents were inserted
in the central airways of 50 patients. Irrespective of airway
obstruction etiology (stenosis, tracheoesophageal fistula
or tracheomalacia), tracheobroncheal stents were inserted
under general anesthesia using alphentanyl and propofol,
along with adequate local anesthesia (10% lidocaine
spray). Patients were ventilated via assisted spontaneous
breathing, without muscle relaxation. The Dumon Harrel
Universal bronchoscope was used. This bronchoscope
consists of two tubular parts joining together by screwing
one part on the other. The upper part is always the same
and includes ports for O2 administration, insertion of
suction catheter or laser probe, as well as a port for the
insertion of a camera. The lower part includes tubes of
varying diameter used during the procedure, depending on
the diameter of the trachea or the bronchi (Figure 1).
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Figure 1. Τhe Dumon Harell Universal bronchoscope and associated equipment. |
In addition to clinical examination and plain chest
radiographs, the assessment of the lesion prior to the
procedure also included flexible fiberoptic bronchoscopy
and spiral computed tomography of the trachea. In two
cases, virtual bronchoscopy was also employed, which is a
computed tomography technique that uses computerized
data to reconstruct three-dimensional images of the
tracheobronchial anatomy.
Initially, the location, diameter and length of the
stenotic lesion were determined. Once a stent of
appropriate length, diameter and configuration was
chosen, it was attached to the delivery system. The
stent was then threaded through the bronchoscope
and pushed to the more distal point possible of the
stenosis, where it was released by gradually pulling out
the bronchoscope. The final positioning of the stent
exactly in the stenotic segment was achieved by pulling
the stent out with mild semicircular movements using a
specially designed clamp.
Results
The age of the 50 patients who received tracheal
stents ranged from 49 to 75 years. Of them, 30 (60%)
patients had stenosis caused by malignancy (Table 1);
17 (34%) had benign stenosis (Table 2); and 3 (6%)
patients presented tracheoesophageal fistula (Table
3). 6 (12%) patients required more than one stents
(Table 4). In particular, two stents were placed in 5
(10%) patients and three stents in one (2%) patient. In
9 (18%) patients, laser ablation of the intraluminal mass projection was performed during the procedure prior to
stent placement.
In total, 57 tracheobronchial silicone stents were
placed, of which 24 (42%) were tracheal (T) stents, 26
(46%) carinal (Y) stents, and 7 (12%) bronchial (B)
stents.
Forty-eight (96%) patients recovered immediately
after the procedure. Of these 48 patients, 44 (90%)
demonstrated immediate improvement in lung function
as evidenced by arterial blood gas and oxygen saturation
measurements before and after the procedure, and had
an uneventful course after stent insertion Three (6%)
patients who tolerated the procedure well, presented
displacement of a straight tracheal stent (T). In 1 (2%)
patient, granulation tissue had developed distally to the
stent 6 months later.
Two (4%) patients required admission to the intensive
care unit (ICU) immediately after the procedure. Of
them, one patient had lung cancer with malignant carinal
stenosis due to extrinsic compression, which had led to
total atelectasis of the left lung preoperatively. The patient
underwent dilatation and placement of a carinal (Y) stent.
Due to the presence of copious bronchial secretions,
tracheal intubation using fiberoptic bronchoscopy was
necessary to facilitate bronchial toilet and suction. On
day 4 after stent insertion, the patient was extubated and
the lungs were fully expanded. The second patient had
benign tracheal stenosis due to prolonged intubation. Having suffered an acute myocardial infarction 4 months
before which resulted in an ejection fraction of 20%, the
patient developed acute heart failure during recovery.
Fiberoptic bronchoscopy was again used to intubate
the patient, who was transferred to the ICU for the
management of the acute heart failure, which eventually
was successful.
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Figure 2. a. Stent obstructed by dried secretions. b. Appearance of stent lumen after clearing dried secretions. |
Of the three (6%) patients with stent migration, one
had tracheomalacia resulting from total laryngectomy
for the resection of laryngeal cancer and permanent
tracheostomy for two years. This patient underwent repeat
bronchoscopy and the stent was placed back to its place.
The second patient had progressive dyspnea 9 months
after the insertion of a straight stent. Bronchoscopy
revealed that the stent was partially occluded by dried
secretions due to continuation of smoking and negligence
of the necessary humidification (Figure 2). The dried
secretions were removed and mechanical intraluminal
washing of the stent was performed, leaving the stent
in place. One year later, the initial stent was replaced
by a stent greater in diameter and length due to the
development of tracheomalacia distal to the initial stent.
The third patient with stent migration, underwent repeat
bronchoscopy during which the stent was repositioned
(Figures 3, 4).
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Figure 3. Tracheal stenosis due to extrinsic compression before (a) and after stent insertion (b). Two silicone stents were required, a straight and a bifurcated (Y-shaped) one. The bifurcated stent is seen in the background of the picture. |
Another patient developed progressive dyspnea 6
months after the insertion of a tracheal stent, caused by
the formation of granulomas distally to the stent. Firstly,
the stent was removed; the granulation tissue was then
resected using diathermy and a bronchoscopic clamp; and
the procedure was completed with the insertion of a new
stent with the same dimensions to avoid the sequelae of
a possible contamination of the initial stent.
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Figure 4. Malignant tracheal stenosis before (a) and after the insertion of a straight Dumon stent (b). Multiple tracheal dilatations preceded stent insertion. |
The results of the stenting procedure and patient acceptance have been excellent. None of the patients
complained about pain or dyspnea. Only few reported
awareness of the presence of a foreign body for a few
days. To reduce the risk of infection, two measures deem
necessary: (1) adequate sterilization of the stent; and
(2) administration of appropriate antibiotic treatment
for several days according to the results of susceptibility
testing of the pathogens cultured in bronchial secretions,
prior to stent placement.
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Figure 5. Tracheobronchomalacia. Appearance of the carina before (a) and after stent insertion (b). |
Discussion
Several types of stents are available, including: a) metallic (e.g. Palmaz); b) metallic expandable (e.g. Gianturco, Wallstent, Schneider); c) silicone (e.g. Dumon, Montgomery, Hood); and d) silicone covered metallic stents (e.g. Dynamic, Orlowski, Novastent, Ultraflex, Silmet).
The use of metallic stents in the management of tracheobronchial stenoses was first described in 1951 by Belsey8 and Bucher et al9.
The first successful placement of a silicone stent in
the large airways was described by Montgomery in 1965;
he inserted a silicone T-shaped tube in the trachea.
Since then, special silicone stents have been designed
for insertion in the trachea, the bronchi or the carina,
as described by Graziano et al in 19675. Indications for
tracheobronchial stenting include:
1. Malignant stenosis of the trachea or the bronchi
(extrinsic compression of the large airways) in patients
with short life expectancy.
2. Failure of laser ablation or dilatation to improve a
malignant tracheobronchial stenosis.
3. Malignant tracheobronchial stenosis in patients
requiring radiation therapy.
4. Subglottic stenosis due to prolonged mechanical
ventilation, in which the use of laser failed or is
contraindicated.
5. Benign tracheal stenosis in patients medically unfit
for a surgical repair.
6. Benign tracheal stenosis of inflammatory origin
pending response to systemic therapy, or in preparation
for operation.
7. Local or extensive tracheo-bronchomalacia (Figure
5).
8. Anastomotic stenosis after lung or heart-lung transplantation or tracheal surgery.3
9. Tracheo- or bronchoesophageal fistula (only silicone
stents).
10. Incomplete laser resection of intraluminal mass.
The issue of the ideal stent has been, and still is under
study. The ideal material would not be susceptible to
infection, would not induce reaction to foreign body
and would be relatively easy to insert. Metal, silicone,
marlex or combinations of these materials have been
used in various stents11-14.
Currently, silicone stents and silicone covered metallic
stents are most commonly used worldwide. Dumon stent
is made of soft silicone and is available in various lengths,
diameters and configurations (Figure 6).
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Figure 6. The Dumon silicone stent. |
To reduce the risk of stent migration, the outer
surface of the stent has projections (barbs) that ensure
fixation of the stent in the right position in the trachea
or the bronchi. This leads to limited stent migration and
reduced ischemia of the tracheal or bronchial wall.
These stents are invariably inserted through a rigid
bronchoscope specially designed for this purpose and
equipped with a stent delivery system. The bronchoscope
initially dilates the stenotic segment and then is pulled
out to insert the stent in the right position. Silicone stents
are currently most widely used in Europe and North
America. Essential advantages of silicone stents include
their availability in a variety of lengths and diameters,
as well as in a Y-shape configuration, which has not yet
been feasible with metallic stents. Hence, they can be
used to restore carinal pathology. In addition, they can
be easily removed. Accordingly, they present a further
comparative advantage, as they can be removed after
1-2 years of acting like a tracheal “splint”. It is worthy of note that in the comment of Naunheim on the work
of Madden et al14, the non-removability of the metallic
stents is particularly stressed, with special reference to
the injury caused by the metallic ends to the respiratory
epithelium, which should be considered in patients with
benign stenosis in particular.
In large benign stenoses, the average time a stent
stays in place is 1-2 years, whereas in malignant stenoses
the respective time is four months, which equals the life
expectancy of these patients. However, in cases of lowgrade
malignancy, stents have been reported to remain
in place for up to seven years6.
During the early post-insertion period, patients should
be instructed to use inhalations of a normal saline spray, at
an average of four times daily. The number of inhalations
may be gradually reduced to finally reach a point of
using saline inhalations only in the event of copious
expectoration and low humidity.
Follow-up bronchoscopy to confirm satisfactory stent
position is necessary and should be performed once or
twice a year. Stents displaced due to migration should
be either repositioned or removed. Acute respiratory
distress indicates obstruction or migration, which is
commonly associated with cough.
Progressive respiratory distress may be due to: a)
granulation tissue formation; b) obstruction by secretions;
and c) disease recurrence distally to the stent. In these
cases, the stent should be removed; the tracheal or
bronchial lumen should be opened up using diathermy
or laser ablation; and the same stent or a greater one
(in length, diameter) should be inserted to cover the neoplastic lesion. Halitosis suggests bacterial or fungal
growth and should prompt stent replacement.
The Dumon stent can be easily removed using the
endobronchial capture clamp for foreign body removal.
The stent is slightly turned around to detach from the
tracheal wall; its upper end is squashed and finally drawn
toward the end of the rigid bronchoscope to be pulled
out along with it. Once the stent has been removed, it
is essential to remove excess tissue that has formed in
the margins of the stent, such as debris and granulation
tissue.
Conclusively, the insertion of silicone stents is a
safe and effective technique for the management of
extrinsic compression stenosis, be it benign or malignant
in origin, which may extend to the level of the secondary
carina11.
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