Small Animal Surgical Respiratory Diseases

Question 1

describe tracheal collapse

Answer 1

1. normal tracheal width to height ratio is 1:1, but once starts to collapse is a progressive, irreversible condition
2. laxity of trachealis muscle progressing to weakness of cartilage rings and eventual obliteration of the lumen
3. collapse is in a dorsoventral direction

Question 2

describe pathophysiology of tracheal collapse

Answer 2

1. loss of glycoprotein and glycosaminoglycans leads to loss of water
   -equates to loss of rigidity of cartilage
2. coughing leads to inflammation
   -loss of normal epithelium leads to squamous metaplasia and loss of cilia
   -increased mucous secretion

Question 3

describe signalment of tracheal collapse

Answer 3

1. toy and small breed dogs: yorkies, mini poodles, pomeranians, chihuahuas
2. middle-aged

Question 4

describe clinical signs of tracheal collapse

Answer 4

1. coughing: goose honk, elicited by palpation on exam
2. episodic dyspnea
3. exercise intolerance
4. cyanosis
5. syncope

Question 5

contrast normal respiration to respiration with trachea collapse

Answer 5

1. inhalation: expansion of the chest by respiratory muscles
   -pressure gradient (negative pressure within the chest)= thoracic expansion and cervical region compression
2. exhalation is the reverse

with tracheal collapse:
-inhalation: collapse of cervical trachea
-exhalation: collapse of the intrathoracic trachea

-MUST TAKE IMAGES IN BOTH PHASES OF RESPIRATION
-fluoroscopy is also helpful
-extrathoracic trachea: collapse on inhalation
-intrathoracic tracheal collapse on exhalation

Question 6

describe bronchial collapse

Answer 6

1. occurs in up to 83% of dogs with tracheal collapse
2. pomeranians have a higher incidence of bronchial collapse
3. canNOT be treated surgically
   -even if tracheal collapse is treated, coughing will still occur

Question 7

describe medical management of tracheal collapse

Answer 7

1. acute treatment: present cyanotic, etc.
   -oxygen
   -sedatives
   -cough suppressants
   -short acting corticosteroids: antiinflammatory dose
   -bronchodilators
2. chronic treatment:
   -weight loss
   -controlled exercise (when cold outside)
   -harness: no neck leads
   -environmental modifications: no smoke, no scented candles, no airway irritants
3. medications:
   -cough suppressants
   -sedatives
   -bronchodilators
   +/- corticosteroids: anti-inflammatory dose for short periods (not long term CSA)
   +/- antibiotics: if suspect respiratory infection

good news: 71% of cases can be successfully managed medically for >1 year; delayed need for surgery and may eliminate need for surgery in some cases

-must EXHAUST medical management before attempting surgery; surgical correction may eventually fail

Question 8

describe surgical management of tracheal collapse: extraluminal prosthetic tracheal rings

Answer 8

1. treats cervical trachea only
   -does not treat intrathoracic trachea or bronchial collapse
2. immediate improvement seen postoperatively
   -75-85% success rate
3. complications: 10-30% of dogs
   -laryngeal paralysis
   -tracheal necrosis
   -pneumothorax

Question 9

describe surgical manangement of tracheal collapse: intraluminal tracheal stent

Answer 9

1. treats entire trachea
   -first tracheal ring to bifurcation
   -does not treat bronchial collapse
   -no incision
2. immediate clinical improvement: 83-89% success at 1 year
3. post-op care
   -cough suppressants
   -sedatives as needed
   -tapering dose of anti-inflammatory corticosteroids
   -antimicrobials (2 week course)
   -regular re-eval with radiograph
4. complications:
   -stent fracture
   -exuberant granulation tissue
   -stent migration

Question 10

describe laryngeal anatomy- cartilage

Answer 10

1. epiglottis: rostral most cartilage, rests on the soft palate
2. thyroid cartilage:
   -largest cartilage
   -covers the sides of the larynx (armor to protect the sides)
3. cricoid cartilage:
   -complete ring
   -connected to the first tracheal ring caudally
4. arytenoid cartilage:
   -paired
   -cuneiform, corniculate, vocal, muscular processes
5. rima glottidis:
   -opening of the larynx through which air passes
   -narrowest portion of the larynx

Question 11

describe the crycoarytenoideus dorsalis muscle

Answer 11

origin: dorsolateral surface of cricoid cartilage

insertion: muscular process of the arytenoid cartilage

function: abduction of arytenoids to open glottis to inhale

innervation:
a. recurrent laryngeal nerves
-arise from the vagus nerve in the cranial thorax
-terminate as caudal laryngeal nerves
-provide motor supply to larynx

b. cranial laryngeal nerves: arise from vagus nerve, mostly sensory and part of cough reflex

Question 12

describe laryngeal anatomy in cats

Answer 12

arytenoid cartilages do NOT have cuneiform or corniculate processes

Question 13

describe larynx functions (3)

Answer 13

1. assists in swallowing: pulled cranially to allow epiglottic coverage
2. controls airway resistance: decreases resistance with abduction during inhalation
3. voice production: tension on vocal cords, purring in cats

Question 14

describe laryngeal paralysis

Answer 14

1. loss of ability to abduct arytenoids on inhalation
   -degeneration of recurrent laryngeal nerves causes loss of function of cricoarytenoideus dorsalis muscle

Question 15

describe congenital laryngeal paralysis

Answer 15

1. siberian huskies, dalmations, rotweilers, bull terriers
2. onset of clinical signs before 1 year of age
3. often a component of diffuse neurologic disease

Question 16

describe acquired laryngeal paralysis

Answer 16

1. most common form!
2. labradors, goldens, saint bernards, irish setters
3. average age 9 years; males > females
4. causes:
   -idiopathic most common: potential link with hypothyroidism, generalized polyneuropathy, GOLP
   -trauma, surgery, tumors, etc.

Question 17

describe clinical signs of laryngeal paralysis

Answer 17

1. acute or chronic onset of signs
   -acute onset is often an aggravation of chronic disease
2. early signs:
   -change in bark
   -gagging or coughing bc things feel weird back there
   -decreased exercise
3. later signs:
   -inspiratory stridor/dirty panting (can be subtle change!)
   -dyspnea
   -cyanosis
   -syncope
   -heat stroke: panting = cooling, no pant = no cool (tends to be spring/early summer dz)

Question 18

describe laryngeal paralysis diagnostics

Answer 18

1. CBC/chem/UA: often unremarkable or consistent with hypothryoidism
2. thyroid panel: may be hypothyroid
3. thoracic rads:
   -check for aspiration pneumonia or megaesophagus (in about 10% of cases)
4. esophageal dysfunction
   -esophagrams (swallowing study)
   -laryngeal paralysis = worse esophageal function, could be an indicator, often more research setting and not clinically
5. upper airway examination
   -performed under light plane of anesthesia
   -if too deep, normal larynx can appear paralyzed
   -premeds: can make them too deep so be careful, usually use acepromazine/butorphenol
   -propofol: induction agent but WATCH apnea side effect with bolus! give doxapram to stimulate respiratory center in brain if respirations absent or weak

Question 19

describe upper airway exam to diagnose laryngeal paralysis

Answer 19

-performed under light plane of anesthesia
-if too deep, normal larynx can appear paralyzed

-premeds: can make them too deep so be careful, usually use acepromazine/butorphenol

-propofol: induction agent but WATCH apnea side effect with bolus! give doxapram to stimulate respiratory center in the brain if respirations absent or weak

Question 20

describe the 4 diagnoses of laryngeal paralysis

Answer 20

1. normal: abduction during inhalation, passive relaxation during exhalation
2. unilateral laryngeal paralysis: only one arytenoid abducts, not common and most dogs compensate well
3. bilateral paralysis: neither arytenoid abducts, most common presentation
4. bilateral laryngeal paralysis with paradoxical motion: neither arytenoid abducts, but moves with airflow

–can look like normal!!

–as animal breathes in, vocal folds appear to adduct, as animal breathes out air passively forces larynx open, mimicking abduction; MUST match breathing in or out with the motion

Question 21

describe treatment of laryngeal paralysis

Answer 21

1. emergency management
   -for dyspneic animals: inflammation and swelling can exacerbate dyspnea
   -medical therapy: acepromazine/butorphenol for sedation, oxygen, cooling, corticosteroids to decrease swelling
   -intubate or temporary tracheostomy if deteriorates
2. medical management: for dogs that are mildly symptomatic
   -weight loss
   -exercise restriction
   -avoid being outside in heat
   -will likely progress with time (unilat to bilat)

Question 22

describe surgical treatment of laryngeal paralysis: unilateral arytenoid lateralization

Answer 22

a referral procedure!!

1. cricoarytenoid lateralization
   -suture from the cricoid cartilage to the muscular process of the arytenoid: mimics action of cricoarytenoideus dorsalis muscle- FYI

-causes permanent abduction of the arytenoid- understand this part

-does not restore function: just decreases airway resistance

-how far to abduct?
-too wide = epiglottis won’t cover entirely when swallowing so risk aspiration (only do unilaterally, not bilaterally to avoid risk!)
-even a small change will magnify to a much larger effect!!

Question 23

describe post-op care of tie back surgery

Answer 23

1. no food or water until morning after surgery
   -if coughing or gagging after drinking/eating, hold off and try again later
   -offer meatballs of food (preformed bolus)
   –meatballs for 2-4 weeks
   –canned food for 2-4 weeks
   –can slowly reintroduce kibble
2. avoid heavy sedation
   -want to maintain swallowing reflexes
   -decrease risk of vomiting
3. no neck leads!
   -risk of damaging suture holding the arytenoid in abduction
4. no swimming
   -uncontrolled intake of water can increase risk of aspiration pneumonia
5. monitor for aspiration pneumonia:
   -coughing, fever, lethargy, anorexia

Question 24

describe complications and outcomes of tie back surgery

Answer 24

complications:
1. aspiration pneumonia
-lifelong risk
-esophageal dysfunction not corrected with surgery

2. persistent coughing or gagging
3. persistent recurrent respiratory signs
4. failure of surgery:
   -suture breakage
   -cartilage breakdown

outcomes:
-90% of animals improve after unilateral arytenoid lateralization
-70% still alive at 5 years

-long term: acquired laryngeal paralysis is one component of a peripheral neuropathy (GOLPP); some have peripheral neurologic signs at diagnosis that owners typically attribute to old age or arthritis and 100% have neuro signs at 1 year (slowly progressive, will die of something else)

Question 25

describe brachycephalic obstructive airway syndrome clinical signs

Answer 25

1. stertorous breathing
2. dyspnea
3. cyanosis
4. collapse

Question 26

describe PE of BOAS

Answer 26

1. resp rate, effort, quality
2. auscultation: referred upper airway sounds (stertor) = hard to hear anything else
3. palpation of trachea
4. evaluation of nares
5. body temp

Question 27

describe pathophysiology of BOAS

Answer 27

1. increased resistance to airflow = increased pressure gradient during inhalation
2. leads to tissue inflammation:
   -laryngeal saccule eversion
   -tonsil eversion
   -pharyngeal mucosal hyperplasia
   -larynx and trachea can weaken and collapse
3. vicious cycle:
   primary abnormalities obstruct airflow, causing increased airway resistance, so they have to exceed normal negative pressure, exceeding resistance of surrounding structured, leading to collapse of secondary structures, and soft tissues drawn into lumen and becoming hyperplastic

Question 28

describe the 4 main components and then other findings of BOAS

Answer 28

four main:
1. stenotic nares:
2. elongated soft palate
3. everted laryngeal saccules
4. hypoplastic trachea

other findings:
-altered turbinate anatomy
-redundant/hyperplastic pharyngeal mucosa
-macroglossia
-everted tonsils

Question 29

describe medical management of BOAS

Answer 29

non-emergency cases:
1. weight loss
2. exercise restriction: walk in morning/evening (when cooler)
3. cool, shaded, AC environment
4. no neck leads: harness

emergency cases:
1. oxygen
2. cool environment
3. acepromazine/butorphenol for sedation
4. dexamethasone to reduce laryngeal swelling
5. intubate

Question 30

describe diagnosis of BOAS

Answer 30

1. upper airway examination under heavy sedation
   -thorough eval of nares, palate, pharynx, larynx (+ function)
2. surgery performed during same anesthesia

Question 31

describe anesthesia of BOAS

Answer 31

1. high risk patients!!
   -especially on recovery
   -don’t do late in the day or on fridays
2. pre-oxygenate
3. steroids to decrease swelling

Question 32

describe stenotic nares

Answer 32

1. abnormally narrowed nostrils (axial deviation of dorsolateral nasal cartilage/nostril
   -subjective
2. causes significant upper airway obstruction
3. greater inspiratory effort required
   -increased negative pressure
   -laryngeal and tracheal collapse (supraphysiologic stress)
4. treatment: surgical correction
   -wedge resection: horizontal or vertical
   -dorsal offset rhinoplasty
   -trader’s technique (wing amputation)
   -can use blade, laser, or electrosurgery

Question 33

describe elongated soft palate of BOAS

Answer 33

1. normal length: soft palate no longer than caudal aspect of tonsillar crypt; tip of epiglottis should rest on soft palate
2. elongated: covers the bulk of the epiglottis
   -may enter the rima glottidis/larynx
   -palate pulled caudally during inhalation: obstructs dorsal aspect of glottis, laryngeal mucosa becomes inflamed/edematous
3. treatment: staphylectomy (soft palate resection)
   -how long should it be? caudal 1/2 to 1/3 of the tonsil is appropriate length; use a stationary measurement tool like the tonsils, NOT the tongue

Question 34

describe everted laryngeal saccules

Answer 34

1. secondary change due to increased respiratory effort
2. prolapse of the mucosa lining the laryngeal crypts
   -increased intraluminal pressure causes saccules to evert and obstruct the ventral glottis
3. treatment: surgical excision
   -resection with scissors, no closure required
   -can recur if airway resistance is not reduced: should address stenotic nares and elongated soft palate at same time

Question 35

describe hypoplastic trachea of BOAS

Answer 35

1. small tracheal lumen compared to dog size
2. ratio of tracheal diameter to thoracic inlet:
   -normal dogs: 20%
   -brachycephalic dogs: <16%
   -english bulldogs: 12.7%
3. not treatable, just a fact of life
   -is good to know about so can warn owner and try to fix the rest

Question 36

describe post-op care from BOAS component correction

Answer 36

1. corticosteroids to reduce swelling
   -dexamethasone
2. extubate only when the patient is FULLY awake
3. keep them calm!!
   -butorphenol
   -acepromazine or dexmedetomidine

Question 37

describe complications of BOAS surgery

Answer 37

1. dyspnea:
   -can occur if soft palate swells after staphylectomy
   -may require temporary tracheostomy
2. death:
   -aspiration pneumonia
   -failure to recover from anesthesia

Question 38

describe abnormal nasal conchae of BOAS

Answer 38

1. brachycephalic dogs also have intranasal obstruction from abnormal conchal development
2. normal conchae packed into a significantly shorter space
   -increased contact between conchae leads to increased obstruction
3. two places in US will do laser assisted turbinectomy, so refer if want to fix (but try fixing everything else first)

Question 39

describe everted tonsils of BOAS

Answer 39

1. secondary change due to inflammation and airway pressure
2. most commonly not treated
   -treatment of elongated palate, everted saccules, and stenotic nares should lead to resolution of clinical signs

Question 40

describe laryngeal collapse due to BOAS

Answer 40

most commonly in brachycephalic dogs due to chronic upper airway resistance and breathing effort, collapse from ventral to dorsal

stage I: laryngeal saccule eversion
-most ventral = collapse first

stage II: cuneiform processes of arytenoids collapse and displace medially

stage III: corniculate processes of arytenoids collapse and displace medially

end stage brachycephalic airway disease

Question 41

describe treatment of laryngeal collapse due to BOAS

Answer 41

1. laryngeal collapse is a secondary disease, must treat the primary disease: BOAS (palate, saccules, nares then reassess)
2. medical management
3. surgery:
   -permanent tracheostomy really only option (risk factors if older, needed post-op CSA, or post-op aspiration pneumonia)
   -unilateral arytenoid lateralization NOT effective; cartilage too melty, suture will not hold and cartilage too saggy to stay in place

Question 42

describe GI signs associated with BOAS

Answer 42

1. relationship between rep and GI disease
   -more severe resp signs = more severe GI signs
   -due to trying to overcome increased intrapleural pressure from upper airway obstruction
   -esophageal deviation, gastroesophageal reflux, hiatal hernia, esophagitis, pyloric mucosal hyperplasia
2. treating BOAS may reduce/eliminate GI signs, but may also require therapy for GI signs