I. Indications (diseases):
A. Non-small cell lung cancerB. Small cell lung cancer
C. Metastatic carcinoma
D. Lymphoma
E. Tracheomalacia
F. Relapsing polychondritis
G. Post tuberculosis bronchostenosis
H. Bronchostenosis due to Wegener's granulomatosis
I. Amyloidosis
J. Tracheo-bronchial trauma
K. Post traumatic bronchostenosis
L. Post-anastamotic bronchial stricture (eg, post-transplant)
M. Post-tracheostomy tracheostenosis
N. Extrinsic compression of airways
O. Kyphoscoliosis with airway compression
P. Iatrogenic obstruction
Q. Tracheo-esophageal fistula
R. Tracheal obstruction after placement of esophageal stent
II. When to use a stent?
A. Indications (symptoms):1. Limiting dyspnea2. Post-obstructive pneumonia
3. Symptomatic hypoxemia
4. Failure to wean from the ventilator
5. Remember: just because you can place a stent does not mean that you should place a stent
B. Choosing between different modalities to improve airway patency in malignant disease:
1. External beam radiation:a) If symptoms are mild to moderate and the patient has not exceeded the maximal radiation dose previouslyb) In patients with more severe respiratory symptoms if stent placement is not available
c) In certain situations, radiation may be relatively contraindicated because of high risk of radiation fibrosis and brachytherapy, laser, cyrotherapy, or stent may be preferable:
(1) Co-existant collagen vascular disease(2) Recent use of bleomycin, Adriamycin, or mitomycin
(3) Pre-existant pulmonary fibrosis
2. Brachytherapy:
a) Technique:(1) A bronchoscopic catheter is placed across the obstructing tumor(2) A radioactive iridium source is advanced through the catheter
(3) The catheter is withdrawn after Å 15 minutes
(4) The radiation delivered is high potency but has a relatively shallow depth of penetration (Å 1 cm)
b) Indications:
(1) If symptoms from the obstruction are mild to moderate(2) In general, used only after a full course of external beam radiation
(3) If the airway is completely occluded and the patient can withstand the Å 2 weeks prior to brachytherapy-induced tumor regression
(4) In short bronchial segments where a stent will likely overhang otherwise patent bronchi (eg, right upper lobe bronchus)
c) Contraindications:
(1) Previous maximal brachytherapy to the aread) Complications:
(1) Fibrinous obstruction(2) Bleeding
(3) Fistula formation
3. Stent:
a) Advantages: see belowb) Disadvantages: see below
c) When should they be used?
(1) If the patient has respiratory failure from airway obstruction(2) If the patient has non-resolving post-obstructive pneumonia
(3) If the patient has impending obstruction of a major bronchus that would be life-threatening if it became completely occluded during the 3 week brachytherapy course
(4) Impending obstruction of the trachea
(5) If the patient has obstruction after completing a course of brachytherapy
(6) If the patient has malignant obstruction and refuses or cannot undergo brachytherapy
(7) If brachytherapy for malignant obstruction is not available
4. Cryotherapy
a) Technique:(1) Requires a 2.6 mm working channel through a fiberoptic bronchoscope(2) Nitrous oxide cools the cryotherapy probe tip to -40°C
(3) One to three 1 minute freeze-thaw cycles
(4) Can be used for malignant or benign strictures
b) Advantages:
(1) Safer than laser(2) May be able to cure some carcinoma in situ
(3) Equipment is less expensive than laser equipment
c) Disadvantages:
(1) Does not provide immediate effect(2) May require multiple treatments
5. Laser
a) Indications:(1) Airway obstruction(2) Bleeding
(3) Carcinoma in situ
(a) Can be curative in this situationb) Contraindications:
(1) Extrinsic compression(2) Excessively bulky tumor
(3) Technical difficulty in aiming the laser because of tumor location
(4) Upper lobe lesions (can be difficult to appropriately direct laser due to upward direction of the lumen)
(5) Total occlusion of the airway
c) Complications:
(1) Hemorrhage(2) Pneumothorax
(3) Respiratory failure
(4) Fire
d) Types:
(1) Carbon dioxide(a) Shallow penetration(b) Absorbed by water
(c) Limited hemostasis
(d) Requires rigid bronchoscope
(2) Argon
(a) Mainly used in conjunction with photosensitizing agents(3) Neodymium YAG
(a) Greatest depth of penetration(b) Best hemostasis
(c) Can be used with rigid or flexible bronchoscope
6. Personal preferences for malignant airway obstruction:
a) Use external beam radiation for initial management of mild-moderate symptoms of malignant obstructionb) Use brachytherapy, cryotherapy, or laser for patients failing external beam radiation or for patients in whom external beam radiation is contraindicated
c) Use stents for patients with severe symptoms of malignant obstruction and for patients who have already had brachytherapy and/or cryotherapy
III. Types of stents
A. Silicone stents:1. Advantage:a) Removable2. Disadvantage:
a) Reduce intralumenal diameterb) Retained secretions
c) Migration
d) Must be placed with a rigid bronchoscope
(1) Airway should generally be pre-dilated with rigid scope prior to stent placement3. Types:
a) Rüsch Y (Rüsch Inc., Duluth, GA)(1) Combined tracheal/bronchial stent with a "Y"biforcation to permit simultaneous stenting of the trachea and both main bronchi(2) Has the advantage of a silicone body with stainless steel rings which simulate the tracheal rings
(3) In general, "Y" stents are less likely than straight stents to migrate proximally
b) Hood bronchial stent (Hood Laboratories, Pembroke, MA)
(1) Sialastic stent suitable for areas of tight stenosis where proximal migration is unlikelyc) Dumon bronchial stent (Bryan Corp., Woburn, MA)
(1) Sialastic stent with struts that project into the bronchial wall to help anchor the stent in placed) Montgomery T-tube
(1) One of the first stents available clinically(2) Best suited for upper or mid-tracheal lesions
B. Metal stents:
1. Advantages:a) Permanentb) Generally become covered with new epithelial tissue consisting of ciliated pseudostratified epithelium within 3-4 months
c) Can be placed with a flexible bronchoscope
d) Do not require general anesthesia
e) Can be done on an outpatient basis
f) Can be done on ventilated patients in the ICU
2. Disadvantages:
a) Permanentb) Can cause compression necrosis if over distended
c) If they collapse, they can cause airway obstruction
d) Tumor can re-grow through the stent with recurrent obstruction
3. Types of metal bronchoscopic stents:
a) Wallstent (Schneider, Inc., Minneapolis, MN)(1) Soft and flexible(2) Consist of a woven mesh of stainless steel
(a) Currently available model consists of 20 braided stainless steel filaments(b) A polyurethane covered metal mesh stent is also available to prevent turmor growth through the stent mesh
(3) Self-expanding to a set maximal diameter as an outer covering sheath is withdrawn
(4) Do not require a balloon dilation (although this can be helpful in some circumstances)
b) Palmaz (Johnson & Johnson Interventional Systems, Warren, NJ)
(1) Very stiff(2) Metal stent which is loaded over a balloon which is used to distend the stent to a desired diameter
(3) It can be irreversibly deformed and crushed with the force of coughing resulting in airway obstruction
c) Gianturco (Cook Inc, Bloomington, IN)
(1) "Zig-zag" metal stent(2) More likely to migrate
(3) More likely to perforate the bronchus
(4) Not currently used in the United States
d) Ultraflex (Boston Scientific, Watertown, MA)
(1) Soft and flexible(2) Made of a single woven nitinol wire (nitinol = titanium + nickel; nitinol is safe for patients undergoing MRI)
(3) Self-expanding to a maximum set diameter
(4) Requires initial placement of a guidewire via a flexible bronchoscope
(5) Does not require balloon dilation
(6) Has a nylon braid at either end of the stent which can be grasped by transbronchial forceps for easy re-positioning of the stent after deployment
(7) A major advantage over the Wallstent is that as it expands, it does not shorten, thus making ideal positioning of the proximal and distal ends of the stent easier
IV. Placement of metal stents:
A. Stent selection1. Of the currently available metal stents, the Ultraflex and the Wallstent are probably the safest, easiest to place, and least likely to migrate or perforate the airway. These are the stents that we use most commonly at Ohio State2. The decision of whether to use an Ultraflex or a Wallstent requires experience with both devices. The Ultraflex is more forgiving for the less experienced operator but the Wallstent anchors itself into position better than the Ultraflex. The Wallstent also has greater radial force than the Ultraflex. At OSU, we require a minimum of 10 supervised stents for credentialling purposes.
B. Pre-stent placement assessment:
1. Normal bronchial anatomy:a) Trachea = 60 - 90 mm in an adult (intrathoracic component only)(1) Average transverse diameter:(a) Women = 15.2 ± 1.4(b) Men = 18.2 ± 1.2
b) Left mainstem bronchus Å 45 mm
c) Right mainstem bronchus Å 25 mm
d) Right upper lobe bronchus Å 10 mm
e) Bronchus intermedius Å 20 mm
f) Right middle lobe Å 12 mm
g) Left upper lobe Å 9 mm
h) Normal bronchial diameters range from 8-12 mm for main and lobar bronchi
2. Radiographic assessment:
a) Plain chest radiographs(1) Occasionally sufficientb) Helical CT
(1) Measure contralateral analagous bronchus(2) Determine if the lesion is calcified (ie, firm and unlikely to open without balloon dilation)
(3) Measure the diameter of the bronchus below and above the area of obstruction
(4) Measure the distance between the desired distal end of the stent and desired proximal end of the stent
3. Bronchoscopic assessment:
a) Visualize location of lesion relative to patent bronchib) Determine if lesion is pliable and soft
c) If bronchoscope can be forced beyond the lesion, determine the length of the lesion and the length between patent bronchi by measuring the length of bronchoscope withdrawn as it is pulled back from beyond the lesion
C. Stents are available in multiple sizes:
1. 5 - 24 mm diameter by 20 - 90 mm length2. Typical selections:
a) Bronchus intermedius: 8 x 20 mmb) Right mainstem bronchus: 10-12 x 20 mm
c) Left mainstem bronchus: 10-12 x 20-42 mm
d) We generally keep 8 x 20, 10 x 20, 12 x 20, 12 x 40, 16 x 60, and 18 x 60 mm stents in stock since these are the most frequently used stents in our patient population
3. If in doubt about appropriate length, use a shorter length - a second stent can always be placed later
4. Catheter sizes (in which stents are loaded for deployment) are measured in French scale
a) 1 French = 0.33 mmb) Transbronchoscopic stent catheters are generally 7 French (2.3 mm) and thus require at least a 2.6 mm working channel in the bronchoscope for passage
D. Placement issues:
1. Positioninga) Fluoroscopy must be usedb) Mark desired distal position of stent with a radio-opaque marker taped to the chest (eg, a paper clip)
2. If airway is completely or near completely occluded, use a guidewire to feed the stent through
a) Flexible tipped guidewires are preferable since they less likely to perforate the bronchusb) Need ³ 200 cm guidewire (generally .035) to extend the length of the stent and the lesion in front of it
c) Guidewires are unnecessary for most lesions, especially those with a partially patent airway
3. If airway if completely or near completely occluded, consider initial balloon dilation prior to stent placement
a) Angioplasty balloons can be fed over the same guidewire used to feed the stent overE. Stent deployment:
1. First pass the stent catheter beyond the position of the obstruction2. The stent is deployed slowly by sliding the the plastic sheath backward over the metal guide tube
3. Initially partially deploy stent (allow about 1/4 to 1/3 of the length of the stent to expand) 4-5 mm beyond the desired distal final position of the stent and "snug" the stent up so that the distal end to the stent coincides with the location in the bronchus previously marked with the paperclip
4. Once the distal end of the stent is appropriately positioned, slowly deploy the remaining, proximal end of the stent
5. When placing a stent in the trachea
a) If an endotracheal tube is present, it must be withdrawn up to a position well above the anticipated proximal end of the deployed stent so as to not interfer with the expansion of the stentb) Start the deployment in the right mainstem bronchus and pull the partially deployed distal end of the stent into the carina so that it is appropriately positioned in the lower trachea, then fully deploy the stent
6. Inadequate deployment
a) Results in a stent that is too narrow and too long (for Wallstents)b) Post-deployment balloon dilatation can result in widening of the stent diameter and shortening of the stent length to appropriate size
V. Complications:
A. Cough1. Fairly uncommon with metal stents2. Generally only occurs if the stent selected is too small for the airway lumen
B. Obstruction of bronchial orifaces
1. Often this is an asymptomatic condition although it can on occasion cause:a) Localized wheezing as air passes through the mesh of the stentb) Impaction by secretions wtih dyspnea due to obstruction of the airway lumen
c) Pneumonia
2. If the stent is so long that it overhangs an otherwise patent bronchus (eg, a right mainstem stent extends 6 mm into the trachea and obstructs the left mainstem bronchus) there are several options for treatment:
a) Use transbronchial scissors to make a longitudinal cut in the stent and allow the stent to expand open(1) In the example, make a 6 mm longitudinal cut in the proximal left wall of the stent so that the left mainstem bronchus becomes patent(2) This is the easiest option for most pulmonologists but does require some degree of extra skill in transbronchial scissor technique
b) Laser a hole in the stent
c) Remove the stent and replace it with a shorter stent
(1) Stent removal is difficut if even possible at all once the stent has become epithelialized; Ultraflex stents can be removed easir than Wallstents(2) Wallstents require use of rigid bronchoscope for attempted removal
C. Secretion retention
1. Generally occurs if stent is obstructing a bronchial orifaceD. Tumor regrowth through stent mesh with recurrent obstruction
1. Can be avoided by placement of a covered stentE. Proximal migration of stent
1. More common with fixed diameter stents (eg, Palmaz)2. More common when stent placement is followed by radiation and/or chemotherapy with tumor regression
F. Obstruction of stent by bent wires
1. Can occur due to suction catheters, etc2. Wires can be bent back into appropriate position by transbronchial biopsy forceps
G. Erosion into nearby blood vessels
1. More common with rigid metal stents (eg, Strecker or Palmaz)2. Stents should be used cautiously if at all when airway obstruction is due to compression by a vessel
VI. The Ohio State Stent Experience:
A. We have placed 75 stents in 53 patients (as of 8/17/98)B. Types of stents:
1. 33 Wallstents2. 5 Palmaz stents
3. 37 Ultraflex stents
4. 5 Rusch-Y stents
C. Indications:
1. Pneumonia2. Dyspnea/hypoxemia
3. Failure to wean from the ventilator
4. Tracheo-esophageal fistula
D. Diseases for which we have placed stents:
1. Non-small cell lung cancer2. Small cell lung cancer
3. Melanoma metastatic to the lung
4. Lymphoma
5. Tracheomalacia
6. Relapsing polychondritis
7. Post tuberculosis bronchostenosis
8. Bronchostenosis due to Wegener's granulomatosis
9. Malignant & traumatic tracheo-esophageal fistula
10. Post tracheostomy tracheostenosis
11. Post strangulation tracheostenosis
E. Anatomic locations:
1. Trachea = 272. Right mainstem = 11
3. Left mainstem = 18
4. Bronchus intermedius = 11
6. Right middle lobe = 3
7. Right lower lobe = 2
8. Left lower lobe = 3
F. Outcome:
1. Clinically improved = 82%2. Clinically unchanged = 18%
G. Patients undergoing stent for failure to wean from the ventilator (24% of patients)
1. Diagnoses:a) Tracheomalaciab) Bronchostenosis due to remote TB
c) Malignancy (lung cancer, metastatic melanoma, metastatic sarcoma)
2. 61% of patients successfully weaned
a) All were eventually discharged or transferred from the hospitalb) Longest living post discharge to date = 3 years
3. 4/12 died
a) All died of progressive pneumoniab) All had extensive stage IV lung cancer
c) All died within 5 days of stent placement
(1) There were no complications of the stent in any patient4. Importance:
a) Previous reports of stents in patients with respiratory failure all suggested that the stent represented futile treatment and that being on a ventilator was a contraindication to stent placmentb) Although an expandable metal stent is expensive (Å $1,500 wholesale cost for the stent alone), even when the cost of the bronchoscopy is included, it is cheaper than a day in the ICU on a ventilator in most hospitals
H. Complications:
1. Mispositioned = 11 (15%)2. Occlusion by tumor or granulation tissue = 9 (12%)
3. Second stent required = 14 (18%)
4. Post-placement migration = 3 (4%)
5. Required eventual removal = 6 (8%)
I. Conclusions:
1. Stents most likely to be of clinical benefit when obstruction is in:a) tracheab) left or right mainstem bronchus
c) bronchus intermedius
2. The Palmaz stent is very rigid and can become bent or migrate after placement which strongly limits its use
3. The Wallstent maintains excellent radial force which when coupled with the exposed metal prongs at the proximal and distal ends results in the stent being securely fixed in position. However, the tendency of the stent to remain longer than anticipated if it is inompletely deployed can result in the stent overhanging bronchial orifaces. It is very difficult (and often impossible) to remove after placement.
4. The Ultraflex stent maintains good radial force but lacks the exposed metal prongs at the ends to rigidly lock the stent in place. Unlike the Wallstent, it can be repositioned or removed relatively easily using the flexible bronchoscope making it a more forgiving device.
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last updated August 17, 1998
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