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Tracheal collapse occurs most commonly in middle-aged, small breed dogs. Clinical signs are usually proportional to the degree of collapse, ranging from mild airway irritation and paroxysmal coughing to respiratory distress and dyspnoea. Diagnosis is made by documenting dynamic airway collapse with radiographs, bronchoscopy or fluoroscopy. Most dogs respond well to medical management and treatment of any concurrent comorbidities. Surgical intervention may need to be considered in dogs that do not respond or have respiratory compromise. A variety of surgical techniques have been reported although extraluminal ring prostheses or intraluminal stenting are the most commonly used. Both techniques have numerous potential complications and require specialised training and experience but are associated with good short- and long-term outcomes.
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Journal of Small Animal Practice Vol 57 January 2016 © 2016 British Small Animal Veterinary Association 9
REVIEW
Journal of Small Animal Practice (2016) 57, 9–17
DOI: 10.1111/jsap.12436
Accepted: 15 September 2015
Canine tracheal collapse
S. W. Tappin *,1
* Dick White Referrals , Cambridgeshire , CB8 0UH
1Corresponding author email: st@dwr.co.uk
Tracheal collapse occurs most commonly in middle-aged, small breed dogs. Clinical signs are usually
proportional to the degree of collapse, ranging from mild airway irritation and paroxysmal coughing
to respiratory distress and dyspnoea. Diagnosis is made by documenting dynamic airway collapse
with radiographs, bronchoscopy or fluoroscopy. Most dogs respond well to medical management
and treatment of any concurrent comorbidities. Surgical intervention may need to be considered
in dogs that do not respond or have respiratory compromise. A variety of surgical techniques have
been reported although extraluminal ring prostheses or intraluminal stenting are the most commonly
used. Both techniques have numerous potential complications and require specialised training and
experience but are associated with good short- and long-term outcomes.
INTRODUCTION
Canine tracheal collapse is a progressive disease occurring mainly
in middle-aged small and toy breed dogs. Degeneration of the
tracheal cartilage rings as a result of reduced glycosaminoglycan
and cellularity leads to dorsoventral flattening of the trachea and
laxity of the dorsal tracheal membrane. Changes can be focal or
generalised and are often associated with the collapse of the main
stem bronchi and lower bronchioles (bronchomalacia). Clinical
signs depend on the severity of the collapse, from mild airway
irritation and a classic paroxysmal “goose-honking” coughing to
respiratory distress and dyspnoea as a result of dynamic airway
collapse. Many dogs improve with medical management (weight
control, use of harnesses, cough suppressants, anti-inflammatory
steroids and bronchodilators) but, in severe cases where airway
collapse and respiratory distress is documented, structural support
of the trachea may need to be considered in the form of surgical
placement of extraluminal protheses or an intraluminal stent.
This article reviews the pathophysiology and diagnosis of canine
tracheal collapse, the treatment options available, discussing the
decision-making process as to when medical management is appro-
priate, whether extraluminal or intraluminal support should be
considered and the evidence supporting the use of each technique.
PATHOPHYSIOLOGY OF TRACHEAL COLLAPSE
The aetiology of tracheal collapse is complex and currently
poorly understood. It is likely multifactorial, with clinical dis-
ease resulting from weakening of the tracheal rings and secondary
factors leading to the initiation of clinical signs. Dogs with tra-
cheal collapse have reduced glycosaminoglycan, glycoprotein and
chondroitin sulphate content of the hyaline cartilage that forms
the tracheal rings (Dallman et al. 1985 , Dallman et al. 1988 ).
These structural changes within the cartilage matrix, alongside its
reduced water content, lead to reduced functional rigidity, caus-
ing the tendency of tracheal collapse. About 25% of affected dogs
show clinical signs by six months of age, supporting a congenital
origin (Done et al. 1970 , White & Williams 1994 ). Many dogs
remain asymptomatic until later in life with degenerative change
of the tracheal cartilage and secondary factors triggering the clini-
cal syndrome of tracheal collapse (Done et al. 1970 , Sun et al.
2008 ). Secondary factors linked with the onset of clinical signs
include airway irritants, chronic bronchitis, laryngeal paralysis,
respiratory tract infection, obesity and tracheal intubation (Mag-
giore 2014 ) as well as postulated alterations of the elastic fibres
in the dorsal tracheal membrane and annular ligament (Jokinen
et al. 1977 , Kamata et al. 2000 ).
Once symptomatic, dynamic collapse of the airway perpetu-
ates a cycle of chronic inflammatory change within the tracheal
mucosa, which is worsened by the coughing this causes. Ongoing
tracheal mucosal inflammation has been associated with epithelial
squamous metaplasia, leading to loss of normal ciliary clearance
(O ’ Brien et al. 1966 ). This mucosal change and hyperplasia of
the subepithelial glands, which secrete increasingly viscid mucus,
causes coughing to become the major tracheobronchial-clearing
mechanism (White & Williams 1994 ).
Tracheal collapse commonly occurs in small breed dogs with
Yorkshire terriers representing between a third and two-thirds of
reported cases (White & Williams 1994 , Buback et al. 1996 ).
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S. W. Tappin
10 Journal of Small Animal Practice Vol 57 January 2016 © 2016 British Small Animal Veterinary Association
Other breeds commonly affected include the miniature poodle,
pugs, Maltese, Chihuahua and Pomeranian (Macready et al.
2007 ). No gender predisposition has been reported. Clinical
signs can develop at any age. Most dogs present in middle age
although many will have had signs for significant periods previ-
ously. Cats and large breed dogs are rarely affected by tracheal
collapse. Concurrent bronchomalacia is reported in 45 to 83%
of dogs with tracheal collapse, and it most commonly affects the
right middle and left cranial bronchi (Moritz et al. 2004 , John-
son & Pollard 2010 ). Bronchomalacia can occur without tracheal
collapse in large breed dogs, suggesting the pathophysiology of
collapse may not be the same in the trachea and the bronchus
(Adamama-Moraitou et al. 2012 ). Within a sample population
of coughing dogs, those with dynamic airway collapse were sig-
nificantly older, of lower body weight and in higher body con-
dition compared to those without airway collapse (Johnson &
Pollard 2010 ).
PRESENTATION AND DIAGNOSIS
Most dogs with a tracheal collapse are presented for evaluation
of a paroxysmal, dry harsh cough, which is usually described as
“goose-honking” (Maggiore 2014 ). The cough is often triggered
by excitement, exercise or eating and may be associated with
upper airway stridor. The history is usually chronic with signs
developing over weeks to months. Some dogs will present acutely
with respiratory distress due to airway obstruction, which is often
precipitated by heat, excitement, stress or concurrent respiratory
disease such as pneumonia (Beal 2013 ).
Clinical examinations of affected dogs often reveal them to
be overweight but may otherwise be normal depending on the
severity of the collapse. The respiratory pattern will also depend
on the location of the collapse: extrathoracic trachea collapse
is usually associated with increased inspiratory effort, whereas
collapse of the intrathoracic trachea and bronchomalacia is
associated with increased expiratory effort. The trachea should
be palpated carefully because it is often sensitive, and examina-
tions may elicit paroxysmal bouts of coughing. It is occasionally
possible to palpate abnormalities in tracheal structure, such as
flattened cartilage rings. Auscultation of the laryngeal area may
elicit stridorous inspiratory upper airway noise due to the nar-
rowing of the extrathoracic trachea, but concurrent laryngeal
paralysis should be considered and has been documented in up
to 30% of cases (Johnson 2000 ). Careful thoracic auscultation
should be performed to document any evidence of concurrent
respiratory or cardiac disease. A study of coughing dogs docu-
mented that 17% of dogs with airway collapse also had a mur-
mur associated with mitral valve disease compared to 2% of dogs
without airway collapse (Johnson & Pollard 2010 ). The role of
the left atrial enlargement in the aetiology of coughing in dogs
with airway collapse is controversial. A recent study documented
similar severity and location of airway collapse in dogs with and
without left atrial enlargement, suggesting other factors such as
airway inflammation, rather than external compression by the
left atrium, as the cause of the cough (Singh et al. 2012 ). Mild
hepatomegaly is commonly associated with tracheal collapse, and
elevations in bile acids have been reported, suggesting hypoxic
liver changes (Bauer et al. 2006 ).
History and clinical examination findings may be very strongly
suggestive of tracheal collapse, but the diagnosis, as well as its
location and severity, needs to be confirmed. Because tracheal
collapse is a dynamic process, care must be taken to interpret
radiographs in light of the respiratory phase: inspiratory films
can often appear normal, even in dogs with severe collapse, and
contrary to the normal radiographic technique, expiratory films
should also be obtained (Fig 1 ). Even so, radiographs frequently
underestimate the severity of tracheal collapse and may fail to
document collapse at the carina (Macready et al. 2007 ). As a
result, films taken under negative pressure ventilation may be
useful (Weisse 2015 ). Radiographs are essential to evaluate the
lung fields for concurrent respiratory disease. Radiographs have
been shown to underestimate tracheal diameter compared to
computed tomography, which may be important when selecting
tracheal stent sizes (Montgomery et al. 2015 ).
Where available, fluoroscopy offers superior evaluation of air-
way collapse, allowing the dynamic, real-time evaluation of the
trachea during all phases of respiration as well as during episodes
of coughing. Fluoroscopy has been shown to be more accurate
in documenting the location of tracheal collapse compared to
radiographs, and one study documented tracheal collapse that
could not be documented on radiographs in 8% of dogs (Mac-
ready et al. 2007 ). Ultrasound has been used successfully to
document real-time, dynamic tracheal collapse through changes
in the tracheal air shadow during the respiratory cycle (Rudorf
et al. 1997 ).
FIG 1 . Right lateral radiograph of a Yorkshire terrier at peak inflation to positive 20 cm of water (A); this reveals no evidence of tracheal collapse.
(B) At peak expiration; this reveals marked tracheal collapse across the thoracic inlet. Note: a marker catheter is positioned within the oesophagus
Canine tracheal collapse
Journal of Small Animal Practice Vol 57 January 2016 © 2016 British Small Animal Veterinary Association 11
Bronchoscopy allows direct dynamic examination of the tra-
cheal and lower airway structures to document the severity and
location of the collapse (Fig 2 ). Collapses can be graded from
I to IV (Tangner & Hobson 1982 ) during bronchoscopy and
allow more detailed evaluations of bronchial changes compared
to fluoroscopy (Bottero et al. 2013 ). Bronchoscopy requires
general anaesthesia, meaning that tracheal diameter cannot be
assessed during normal respiration although the application of
negative pressure will allow the location and degree of collapse
to be documented; induction gives an opportunity to evaluate
laryngeal function. Common findings include evidence of air-
way inflammation such as hyperaemia and mucus accumulation.
Bronchoalveolar lavage aids the diagnosis of possible concurrent
lower airway disease. Mild neutrophilic and lymphocytic infil-
trates are commonly documented in dogs with tracheal collapse,
but it is unclear if the inflammation precedes or follows airway
collapse (De Lorenzi et al. 2009 , Bottero et al. 2013 ).
TREATMENT
Priorities at presentation depend on the severity of tracheal col-
lapse and clinical signs. If the animal is in severe respiratory dis-
tress, then stabilisation is essential before diagnostic evaluation and
a firm diagnosis is reached. Oxygen supplementation with inspired
concentrations >40%, minimising stress and a cool environment
should help the patient to settle. When needed, sedation with
acepromazine [0·01 to 0·03 mg/kg intravenously (iv) or intramus-
cularly (im)] or butorphanol (0·05 to 0·1 mg/kg iv or im) either
alone or in combination can be very effective. In severe cases, the
patient may require intubation in which case diagnostics should be
performed at this point, and procedures such as surgery or stent
placement may be more appropriate than medical management.
MEDICAL MANAGEMENT
Many dogs will respond well to medical therapy, with surgi-
cal interventions reserved for those refractory to treatment or
with severe clinical signs, such as cyanosis, exercise intolerance
or dyspnoea. The aim of medical management is to break the
cycle in which inflammation triggers coughing which worsens
inflammation. Studies have shown that between 71-93% of dogs
respond well to medical management for a period of more than
12 months, with 50% able to have medication gradually with-
drawn (White & Williams 1994 , Ayres & Holmberg 1999 ).
FIG 2 . Bronchoscopic images of tracheal collapse. (A) Grade I collapse (resulting in loss of 25% of the tracheal lumen), (B) Grade II collapse (resulting
in loss of 50% of the tracheal lumen), (C) Grade III collapse (resulting in loss of 75% of the tracheal lumen) and (D) Grade IV collapse with complete
loss of the tracheal lumen
S. W. Tappin
12 Journal of Small Animal Practice Vol 57 January 2016 © 2016 British Small Animal Veterinary Association
A good proportion of dogs with tracheal collapse are over-
weight, and the accumulation of intrathoracic adipose tissue may
reduce respiratory function by limiting thoracic movement and
chest wall compliance. Strict weight loss regimes, with dietary
management and controlled exercise programmes, improve clini-
cal signs in many dogs (Herrtage 2009 ). Avoidance and removal
of inhaled environmental irritants (specifically tobacco smoke)
will help in many dogs although compliance may be difficult to
achieve. A harness rather than a collar should be used to reduce
tracheal compression and associated irritation. Diligent manage-
ment of comorbidities such as congestive heart failure and respi-
ratory tract infection will also improve clinical signs (Maggiore
2014 ). Additionally, any upper airway narrowing, for example
secondary to brachycephalic upper airway syndrome or laryn-
geal paralysis, will increase intrathoracic pressure gradients and
worsen tracheal collapse; careful consideration of surgical man-
agement of the upper airway should be given in the cases of these
dogs.
Antitussive therapy
In the United Kingdom, co-phenotrope [Lomotil (Amdipharm
Mercury) which contains diphenoxylate hydrochloride and atro-
pine] has been the mainstay of medical management for dogs
with tracheal collapse. Diphenoxylate acts as a narcotic antitus-
sive with the atropine purportedly acting to reduce the volume
of mucus secreted into the lower respiratory tract and also acts as
a muscarinic bronchodilator. Atropine is present in the formula-
tion as a bittering agent to prevent the abuse of the narcotic agent
diphenoxylate but whether the atropine present is at a dose that
causes clinical effects is unknown. Although no clinical studies are
available to support its use, anecdotally, there has been widespread
acceptance of its benefit in affected dogs (Herrtage 2009 ). Doses
of 0·2 to 0·5 mg/kg every 12 hours have been suggested, with con-
stipation an occasional side-effect (these effects are usually man-
aged easily with dietary manipulation or the addition of faecal
softeners). Due to supply and manufacturing issues, co-pheno-
trope is currently inconsistently available to the veterinary market.
In the United States, 0·22 mg/kg hydrocodone every 6 to 12
hours is used commonly, and 0·5 to 2 mg/kg codeine every 12
hours and 0·5 to 1 mg/kgbutorphanol every 6 to 12 hours are
more commonly used as antitussives in Europe. Anecdotally, spe-
cific agents may be more effective in individual dogs, and drugs
may need to be changed over time to find those most beneficial.
Dosing can also be a problem because there are no licensed vet-
erinary products in the United Kingdom, and tablets manufac-
tured for human use are often very large for the small breed dogs
affected. Re-compounding pharmacies may be able to help with
drug formation into liquids or smaller tablets for smaller-sized
dogs.
Steroid therapy
The use of carefully judged steroid therapy is likely to be benefi-
cial to many dogs with tracheal collapse through the reduction
of airway inflammation. They should be used strategically, for
short courses and at the lowest doses possible to control clini-
cal signs because adverse effects may worsen clinical signs in the
longer term. Their use may particularly increase the risk of bacte-
rial infection, increase respiratory rate and may make weight loss
difficult. Initial doses of 0·5 mg/kg prednisolone every 12 hours
have been suggested, with the dose tapered quickly to the lowest
level that controls signs. Inhaled steroids such as 125 to 250 µg
fluticasone used through a spacer every 12 hours may be of ben-
efit to some individuals that are dependent on oral steroids to
reduce airway irritation but in which the side effects are adversely
affecting their quality of life (Bexfield et al. 2006 , Weisse &
Berent 2010 ).
Recently, an experimental study evaluating the administra-
tion of stanozolol, an anabolic androgenic steroid, documented
its potential beneficial effects in the management of dogs with
tracheal collapse. It is postulated that stanozolol may enhance
protein synthesis, increase collagen synthesis and chondroitin
sulphate content (Adamama-Moraitou et al. 2011 ).
Bronchodilators
Bronchodilators are suggested in the management of tracheal
collapse because they reduce intrathoracic pressure during expi-
ration and reduce expiratory tracheal collapse (Ettinger 2010 ).
Methylxanthine-based bronchodilators (such as 15 to 20 mg/kg
theophylline every 12 to 24 hours) may potentially be benefi-
cial by improving mucociliary clearance and reducing diaphragm
fatigue as well as increasing the airway diameter (Rozanski et al.
2007 ). β 2 -adrenergic bronchodilators such as terbutaline have
also been suggested with injectable or inhaled administration the
most useful in the emergency setting. The benefit of bronchodi-
lators in dogs with tracheal collapse has not yet been fully evalu-
ated, so their introduction should be regarded as a therapeutic
trial and withdrawn if there is no improvement. Some, especially
older, dogs appear very susceptible to the effects of methylxan-
thines. Restlessness and anxiety are common side-effects, and if
these affect the patient s quality of life, the medication should be
swiftly withdrawn.
Antimicrobials
Antimicrobial administration is not usually indicated unless there
is evidence of concurrent secondary infection that can incite
airway irritation. When antimicrobials are indicated, agents
with efficacy against Mycoplasma infection, such as doxycycline,
should be considered pending culture results from bronchoalveo-
lar lavage (Johnson & Fales 2001 ).
SURGICAL INTERVENTIONS
If options for medical therapy have been fully explored and have
failed to control clinical signs, then surgical management should
be considered. The aim of surgical intervention is to improve the
tracheal anatomy to allow increased airflow without disrupting
the mucociliary system (Vasseur 1979 ). No surgical procedure
will cure tracheal collapse, and so continued medication is often
needed to control coughing or manage concurrent lower airway
collapse although the quality of life of many dogs can be greatly
improved when medication alone is inadequate. Patient selection
Canine tracheal collapse
Journal of Small Animal Practice Vol 57 January 2016 © 2016 British Small Animal Veterinary Association 13
is key to obtaining good outcomes, and only dogs with severe
collapse (Grade II and higher) should be considered surgical can-
didates (Sun et al. 2008 ). Age at intervention also appears to be
associated with long-term outcomes, with dogs less than six years
of age reported to have better outcomes compared to dogs older
than six despite having less severe tracheal collapse (Buback et al.
1996 ). Various different surgical procedures have been reported
for the management of tracheal collapse and include procedures
such as tracheal ring chondrotomy and plication of the dorsal
tracheal membrane [which have largely fallen out of favour due
to reported tracheal narrowing (Fingland et al. 1987 )], the place-
ment of extraluminal ring prostheses and, more recently, intralu-
minal stent placement.
Extraluminal ring prostheses
Extraluminal support of the trachea with placement of synthetic
prostheses allows restoration of the tracheal diameter during res-
piration and coughing and does not interfere with mucociliary
function (Tangner & Hobson 1982 ). C-shaped prostheses are
placed via a ventral median approach, separating the sternohyoi-
deus muscles to expose the cervical trachea (Fig 3 ). The thyroid
arteries and recurrent laryngeal nerves are identified and gently
dissected from the trachea to allow prosthesis placement. Pros-
theses are placed at regular intervals, usually every 2 to 3 tracheal
ring spaces, from the cranial portion to the thoracic inlet and
sutured to the tracheal cartilages and trachealis muscle (Nelson
2003 ). Prostheses have been formed from polypropylene syringe
casings (Hobson 1976 , Fingland et al. 1987 ), polyvinyl chlo-
ride drip chambers of giving sets (Ayres & Holmberg 1999 ) and
commercially available ring prosthesis (Chisnell & Pardo 2015 ).
Spiral rings have also been used because they are flexible and pro-
vide circumferential support to a collapsing trachea compared to
C-shaped rings; however, the dissection required for placement
has been shown to disrupt the lateral pedicles containing the tra-
cheal vasculature, and as a result, individual C-shaped rings are
preferred (Kirby et al. 1991 , Coyne et al. 1993 ).
Good outcomes have been reported in 75 to 89% of dogs after
the placement of extraluminal C-shaped prostheses (Tangner
& Hobson 1982 , Buback et al. 1996 , Chisnell & Pardo 2015 ).
Weight, gender, breed, severity of collapse and duration of clinical
signs do not appear to affect outcomes. In one case series, 72% of
the dogs were reported to no longer need medication and returned
to normal exercise tolerance with no coughing at follow-up 6 to
36 months after surgery (White 1995 ). A recent study reported
median survival times of 4 years and 6 months after the placement
of extraluminal tracheal rings (Becker et al. 2012 ).
Complications associated with the placement of extraluminal
tracheal rings are frequent, with 5% perioperative mortality and
~20% dogs requiring a tracheostomy in one series of 90 dogs
(Buback et al. 1996 ). In this series, coughing, dyspnoea and
laryngeal paralysis where reported in ~31% dogs after a month
and 56% at some point after the surgery; 23% of the treated
dogs died of respiratory complications with a median survival
time of 25 months. In early studies, vascular damage to the tra-
chea resulting in necrosis was reported in a small number of dogs
(White & Williams 1994 , White 1995 ), but this has not been
reported in more recent studies (Becker et al. 2012 , Chisnell &
Pardo 2015 ). Tracheal ring migration has also been reported in
one dog (Moser & Geels 2013 ).
Postoperative laryngeal paralysis, due to iatrogenic nerve dam-
age, is a well-documented complication of extraluminal ring
placement and is reported in ~11 - 21% of cases in the immedi-
ate postoperative period (Buback et al. 1996 , Becker et al. 2012 ).
Immediate postoperative paralysis, which occurs in ~50% of
those affected by this complication, is attributed to intraopera-
tive damage to the recurrent laryngeal nerves, with a smaller pro-
portion developing paralysis as a late complication, potentially
due to long-term rubbing, granulation tissue formation or con-
tact with a prosthesis (Sun et al. 2008 , Chisnell & Pardo 2015 ).
Concurrent left arytenoid lateralisation has been reported in con-
junction with extraluminal ring placement, and lower rates of
postoperative complications of 4% were reported with 75% of
dogs having a good long-term outcome (White 1995 ). Laryn-
geal lateralisation has been performed when needed rather than
routinely in other series because of the potential complications of
fixing the larynx in an open position (Johnson 2000 , Chisnell &
Pardo 2015 ).
Due to the high morbidity documented in association with
the placement of extraluminal prosthesis around the intratho-
racic trachea, the technique is usually limited to the support of
the extrathoracic portion of the trachea (Vasseur 1979 , Buback
et al. 1996 ). Extraluminal support of the cervical trachea has
generally been discouraged in dogs with concurrent collapse of
the intrathoracic trachea (Nelson 2003 , Gibson 2009 ) although
a recent study documented that intrathoracic collapse did not
significantly affect survival and outcome in dogs treated with
extraluminal rings along the cervical trachea (Becker et al. 2012 ).
Intraluminal stent placement
The placement of intraluminal tracheal stents is a minimally
invasive procedure compared to the placement of extraluminal
ring prostheses, with rapid postoperative improvement in most
cases (Weisse 2015 ). A number of different stent types have been
evaluated for the treatment of canine tracheal collapse. These
FIG 3 . Intra-operative picture of external ring prostheses being placed to
support a collapsing trachea (image cour tesy of Chick Weisse, Animal
Medical Centre, New York)
S. W. Tappin
14 Journal of Small Animal Practice Vol 57 January 2016 © 2016 British Small Animal Veterinary Association
include balloon-expandable (Palmaz) stents (Radlinsky et al.
1997 ), self-expanding stents made from stainless steel, woven
(Fig 4 ) and laser cut nitinol (Norris et al. 2000 , Gellasch et al.
2002 , Moritz et al. 2004 ).
Stents are placed with the dog in lateral recumbency using
fluoroscopic guidance. Prior to placement, measurements of the
tracheal width and length are taken from lateral radiographs or,
where possible, under fluoroscopy (Fig 5 ). Stent sizing is critical
to the successful outcome of stent placement; if too small, the
stent will migrate or shorten, and if too large, pressure necrosis
of the wall can occur. Stent shortening was initially documented
in a high proportion of dogs, but recent advances in the under-
standing of appropriate stent sizing have reduced the reported
rate of stent shortening from 30 to 11% (Weisse 2014 , Moritz
et al. 2004 ). Current advice is that the stent diameter chosen is
oversized by approximately 10 to 20% to minimise the risk of
shortening and migration (Beal 2013 ).
To enable accurate measurements, an endotracheal tube
is placed just caudal to the larynx, and the maximal tracheal
diameter is measured during positive pressure ventilation (to
+20 cm of water). This is then compared to a measurement
catheter placed within the oesophagus to determine the effect
of magnification. Evaluation of the collapsing portion is done
under negative pressure (to –20 cm of water), and it is possible
to only stent the extrathoracic or intrathoracic portion of the
trachea. Most clinicians stent the whole length of the trachea
because disease progression will usually mean that a second stent
is needed if only a short portion of the trachea is treated initially.
Placement should be at least 5 mm caudal to the larynx, and the
cricoid cartilage is usually used as this landmark; stenting within
the larynx may lead to laryngospasm, cough and laryngeal dys-
function. The caudal edge of the stent should be placed at least
5 mm cranial to the tracheal bifurcation, and placement that
is too caudal can lead to the caging of a main stem bronchus,
FIG 4 . (A) A deployed self-expanding metallic stents tracheal stent and one fully constrained within the delivery system sheath. Note that the
constrained length is much longer than the length of the stent when fully deployed. (B) A partially deployed self-expanding metallic stents tracheal
stent with the sheath constraining the remainder of the stent
FIG 5 . Fluroscopic images taken in right lateral recumbancy at peak inflation to positive 20 cm of water (A). This film should be used to identify the
measurement landmarks of the tracheal bifurcation and this carina to measure tracheal length as well as assess tracheal width. (B) Images taken
under negative pressure (to negative 20 cm of water) allow documentation of the area of collapse; here the whole length of the trachea is af fected.
Note: a marker catheter is positioned within the oesophagus
Canine tracheal collapse
Journal of Small Animal Practice Vol 57 January 2016 © 2016 British Small Animal Veterinary Association 15
leading to mucus entrapment and complications such as infec-
tion. To avoid these potential problems, the suggested guidelines
for stent measurement is that the stent is placed 10 mm caudal
to the cricoid cartilage to 10 mm cranial to the tracheal bifurca-
tion (Fig 6 ).
Studies have documented improvement in 75 to 90% of dogs
treated with intraluminal stainless steel self-expanding stents
(Moritz et al. 2004 ) and long-term improvement in 10 out of
12 dogs treated with nitinol self-expanding metallic stents, with
9 dogs alive after one year and 7 dogs alive after two years (Sura
& Krahwinkel 2008 ). An owner-based survey of the owners of 18
dogs with nitinol self-expanding metallic stents reported good to
fair improvement in all dogs after stent placement (Durant et al.
2012 ). Stent placement is not a curative procedure, and owners
should be carefully counselled that continued long-term medical
management and monitoring is essential to achieve a good long-
term outcome.
Tracheal stents are made from durable materials, but exces-
sive compression or movement, such as that caused by coughing,
can lead to metal fatigue and subsequent fracture. Case series
reported relatively high rates of stent fracture, with fractures
reported in 5 of 12 dogs (Sura & Krahwinkel 2008 ) and 4 of
18 dogs (Durant et al. 2012 ) that had had self-expanding niti-
nol stents placed in them. Recent advancement in stent design
has led to the development of more flexible stents, with more
elastic materials expected to reduce the risk of fracture through
metal fatigue (Weisse 2014 ). Care not to oversize the stent by
more than 20% and control of coughing may limit this risk. The
introduction of tapered stents has helped to reduce the need to
“over-size” stents in the trachea (Fig 7 ), where there is a marked
difference in the proximal and distal tracheal diameter (Dhupa
et al. 2014 ). If stent fracture occurs, stability is usually obtained
by the placement of a second stent within the lumen of the frac-
tured stent (Ouellet et al. 2006 ). This can be more technically
challenging, and the placement of a guidewire through the frac-
tured stent lumen is suggested to confirm that stent placement
will be intraluminal before deployment (Mittleman et al. 2004 ).
Alternatively, it may be possible to remove the stent and apply
extraluminal prostheses (Woo et al. 2007 ).
A common consequence of stent placement is the formation
of excessive inflammatory tissue within the trachea (Fig 8 ), and
this is reported in 28 to 33% of cases (Moritz et al. 2004 , Durant
et al. 2012 ). This occurs most commonly at the ends of the stent
and is likely to be associated with excessive movement of the
stent, most often as a result of coughing. The development of
woven stents with rounded edges and a high quality finish to
the nitinol anecdotally appear to have reduced the formation of
inflammatory tissue compared with open mesh steel stents. This
has not been rigorously proven, and it may be that other factors
such as better stent sizing and more aggressive cough suppression
have reduced the apparent frequency of this complication. Rigor-
ous attention to the control of coughing and inflammation after
stent placement are key to limiting the formation of inflamma-
tory tissue, which requires owners to understand that continued
medication after placement is required and to be compliant with
its longer-term administration.
Inflammatory tissue within the trachea reduces tracheal diam-
eter and leads to reduced airflow, with signs of exercise intolerance
and respiratory distress. Radiographs may document inflamma-
tory tissue, but it is best observed endoscopically. Most excessive
inflammatory tissue will respond rapidly to medical therapy with
steroids, and a six to eight week course (starting dose 2 mg/kg/
day prednisolone) tapering to the lowest dose that controls clini-
cal signs is suggested (Scansen & Weisse 2014 ). Oral colchicine
use has also been reported and may be useful in the management
of refractory cases (Brown et al. 2008 ). In some instances, excess
granulation tissue can be removed endoscopically with loop elec-
trocautery or laser resection.
BRONCHIAL COLLAPSE
Dogs with tracheal collapse often have concurrent bronchial
collapse due to progressing cartilage weakness. At present, stent
placement within the bronchus is not routinely recommended
because the stent will “cage off” lower bronchi, preventing mucus
drainage (Weisse 2010 ). In addition, disease progression will
usually lead to lower airway collapse, limiting the efficacy of the
FIG 6 . Stent deployment under fluoroscopic guidance. (A) The caudal edge of the stent is positioned 5 to 10 mm cranial to the tracheal bifurcation.
(B) The stent is slowly deployed within the trachea; if positioning is suboptimal, the stent can be re-constrained and its position adjusted. (C) Once
deployed, the delivery system is removed and positioning assessed. The caudal edge should be no closer than 5 mm but ideally 10 mm from the carina
S. W. Tappin
16 Journal of Small Animal Practice Vol 57 January 2016 © 2016 British Small Animal Veterinary Association
FIG 9 . A tapered tracheal stent placed in an 11-year-old female, neutered
Yorkshire terrier in whom marked bilateral bronchial collapse was also
present. Placement of a tracheal stent alone markedly improved airflow
although ongoing medical management was needed
stent. In dogs with both tracheal and bronchial collapse, tracheal
stent placement may help to improve airflow (Fig 9 ), especially
if the main sign is inspiratory dysponea (Weisse & Berent 2010 ).
Short bronchial stent placement may also be useful in dogs who
have not improved after tracheal stenting due to focal mainstem
bronchial collapse (Kramer 2015 ). A recent case report (Dengate
et al. 2014 ) documented a successful outcome after bronchial
stent placement in a dog with focal left mainstem bronchial col-
lapse and left atrial enlargement. Although the case report docu-
ments severe respiratory distress after stent placement, quality of
life was improved in the longer term.
CONCLUSION
Most dogs will respond well to medical management; however,
those that do not, or that have respiratory compromise, may ben-
efit from surgical intervention. Making the decision as to when,
and which, surgical intervention may be beneficial is complex
and multifactorial, depending on personnel experience, owner
preference and available finance.
In recent years, procedures to provide extraluminal support
to the trachea have fallen out of favour due to the development
of intraluminal stenting because of the less invasive nature of the
procedure and perceived lower perioperative morbidity. Experi-
ence with the long-term management of dogs post stent place-
ment is growing, but information about long-term outcomes
is limited. Ongoing medical management is required in most
dogs after stent placement to prevent coughing and inflamma-
tion, which contrasts with the majority of dogs with successful
extraluminal support being able to stop medication completely
(White 1995 ).
Recent work has suggested that the placement of extraluminal
tracheal rings is still a valid option for the treatment of tracheal
collapse, especially if cervical collapse alone is present. The find-
ing that dogs with intrathoracic collapse appear to have a good
outcome with extraluminal support of the cervical trachea has
led to the questioning of the previously held view that extralumi-
nal support is not appropriate for the management of dogs with
intrathoracic tracheal collapse (Becker et al . 2012 , Chisnell &
Pardo 2015 ).
As a result, the best approach to providing intraluminal or
extraluminal support in dogs with tracheal collapse remains
unresolved, with decisions needing to be made on a patient-by-
patient basis.
Conflict of interest
The author has no financial or personal relationship with other
people or organisations that could inappropriately influence or
bias the content of this paper.
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The principal function of the respiratory system is the exchange of gases between the internal milieu of the body and external environment. The nasal cavities provide a path for airflow, provide surface area for olfaction, and humidify, filter, and warm the air prior to delivery to the lungs. The nasal septum is associated with the vomeronasal organ, which is a pheromone receptor for odors associated with reproductive function. Infectious and noninfectious inflammatory diseases of the nose, paranasal sinuses, or both are common in domestic mammals, and more commonly undergo imaging than inflammation of the pharynx, larynx, and trachea. Respiratory neoplasms may arise from any part of the respiratory tract, but sinonasal neoplasms are especially common respiratory tract neoplasms in dogs and cats and occasionally seen in other species. Laryngeal paresis or paralysis is unilateral or bilateral failure of the intrinsic laryngeal muscles to maintain the rima glottidis open.
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A 9‐year‐old Dartmoor cross‐gelding was referred for investigation and treatment of exercise intolerance, cough and abnormal respiratory noise. Endoscopic examination revealed the presence of left 90‐degree rotation and dorsoventral collapse of the entire cervical trachea. Although the tracheal collapse was not obvious on laterolateral radiographs, these showed the abnormal presence of tracheal cartilages along with the dorsal and ventral limits of the trachea. Oblique radiographs showed partial tracheal collapse in the caudal aspect of the neck. Ultrasound examination revealed the presence of tracheal cartilages on the right side of the neck, dorsal tracheal ligament along with the left side of the neck and the junction between tracheal cartilage and dorsal tracheal ligament coursing over the ventral aspect of the neck. This report highlights the value of detailed examination of standard and non‐standard radiographic and ultrasound imaging of the trachea to achieve correct diagnosis of tracheal collapse when associated with tracheal rotation.
Chapter
This chapter presents a brief overview of relevant ventilatory concepts and strategies, respiratory physiology, sedative/anesthetic agents, and specific case management. Respiratory rhythm and pattern are continuously altered by homeostatic control mechanisms that allow the animal to “adapt” to physiologic respiratory challenges or pathologic conditions. There are three ventilatory cycle phases: inspiration, expiration, and an expiratory pause. Normal respiratory volumes can be affected in anesthetized/sedated patients or in patients with altered physiology. In many patients with respiratory insufficiency, O 2 supplementation can be beneficial. Since respiratory function is frequently diminished simply by using respiratory‐depressant agents such as inhalants and opioids in many species, respiratory complications from coexisting diseases can impair ventilation even further. Anesthetic management of these cases should focus on keeping the patient oxygenated, ventilated, and perfused. The choice of anesthetic/analgesic agents themselves is likely not as important as specific case management during respiratory disease.
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This chapter discusses the background, potential risks, complications, expected outcomes, equipment, procedure, special considerations, and the complication examples for bronchial collapse and stenting. Bronchial collapse in dogs is associated with a number of causes including chronic bronchitis, neoplasia, heart disease, chondromalacia, and strictures. Treatment for most cases of bronchial collapse consists of a combination of medical therapies including cough suppressants, antibiotics, bronchodilators, anti-inflammatory medications, and sedatives. The indication for bronchial stenting is the inability of medical therapy to adequately control clinical signs and provide a reasonable quality of life. Some dogs with tracheal collapse may also present with bronchial collapse; the vast majority of these dogs do not require bronchial stenting. While fluoroscopy and chest radiography are helpful, the extent of bronchial collapse is best made via bronchoscopy. The majority of candidates for bronchial stenting have significant underlying valvular heart disease.
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This chapter discusses the background, potential risks, complications, expected outcomes, equipment, fluoroscopic procedure, special considerations, and the complication examples for intraluminal tracheal stenting. Intraluminal stenting is a palliative, minimally invasive therapy used for restoration of an obstructed or narrowed tracheal lumen. While the most common indication is for treatment of intractable dyspnea, honking/raspy breathing, and/or possible coughing associated with the tracheal collapse syndrome, stenting can also be performed in animals with obstructions secondary to strictures or tumors in both dogs and cats. When stenting for tracheal malformations, incomplete tracheal wall apposition by the stent is one of the most common complications encountered. Tracheoscopy performed prior to and following stent placement can help identify these cases and ensure there is good wall apposition; if not, the endotracheal tube cuff can be used to gently expand the stent to improve wall apposition.
Article
A number of procedures have been described for the surgical correction of collapsed tracheas, primarily in toy breeds. Most of these techniques have been tried by this author during the past 10 years. For the past four to five years, this author has used a complete ring prosthesis applied to the external surface of the trachea with the tracheal rings and the trachealis muscle sutured to the plastic rings. Absorbable suture is currently being used. Fibrous tissue proliferation around the rings and through the holes provides a permanent support for the previously collapsing trachea. In the author's hands, this technique has far surpassed the others both in immediate postoperative relief and in long term functional recovery.
Article
Objective To report complications, long-term outcome, and disease progression in dogs with extrathoracic tracheal collapse treated by surgical placement of commercially available extraluminal rings. Study DesignRetrospective case series. AnimalsDogs (n=23). Methods Medical records (2002-2011) of dogs treated with extraluminal rings for extrathoracic tracheal collapse were reviewed. Owner interviews, conducted at >10 months postoperatively, determined response to surgery, progression of clinical signs after surgery, and frequency of medication administration. Long-term re-evaluation (>10 months after surgery) was offered for surviving dogs, including radiographs and tracheoscopy if indicated. ResultsOf 23 dogs, 22 survived to discharge after surgery. Clinical signs improved in all dogs at 2 weeks after surgery and at long-term re-evaluation. Fourteen dogs (65%) required no medical management for respiratory signs after surgery. Four dogs (17%) were diagnosed with laryngeal paralysis at some point after surgery, but only 9% were diagnosed within 48hours of the surgery. Additional rings were placed between previously placed rings in 2 dogs, and 1 dog was treated with an endoluminal stent for intrathoracic tracheal collapse. Three dogs had clinical signs consistent with progression of tracheal collapse. Based on owner questionnaire, all owners were satisfied with surgical outcome. Conclusions Treatment of severe cervical tracheal collapse with commercially-available extraluminal ring placement leads to an overall improvement in quality of life and good long-term results, with about one-third of dogs requiring continued medical management. Most dogs do not have clinical signs consistent with disease progression after surgery.
Article
Objective To compare radiographic and computed tomography (CT) measurements of tracheal size as would be made for the purpose of tracheal stent size selection. Study DesignCross-over. AnimalsDogs (n=15). Methods Canine cadavers without evidence of tracheal or respiratory disease were used for CT and digital radiography of the neck and thorax. Three observers each made 3 independent measurements at each of 5 tracheal locations, and also measured tracheal length, on each radiograph and for each CT scan on each cadaver. ResultsCT tracheal measurements were on average 1.03mm larger (P<.01) compared with radiographic measurements for all 3 observers. Conclusions Radiographic measurements of the canine trachea consistently underestimate tracheal size, and CT measurements are preferable for selecting tracheal stent size.