8 – Brachycephalic Respiration

Question 1

What is the width:length ratio of a brachycephalic?

Answer 1

> 0/81
*selected trait from decades of breeding

Question 2

What is the cost of ‘cuteness’ with brachycephalic animals?

Answer 2

-reduced skull size
-soft tissue and teeth remain unchanged
*extra skin/tissue/teeth relative to skull size
=skin problems and massive under bite

Question 3

Brachycephalic animals have increased incidences and severity of:

Answer 3

-respiratory disorders
>not all breeds will show clinical signs

Question 4

Anatomical features of Brachycephalic Obstructive Airway Syndrome (BOAS): PRIMARY

Answer 4

1. Stenotic nares
2. Hypertrophic nasal turbinate
3. Elongated soft palate

Question 5

Anatomical features of Brachycephalic Obstructive Airway Syndrome (BOAS): SECONDARY

Answer 5

1. Hypoplastic trachea
2. Everted laryngeal saccules

Question 6

Stenotic nares:

Answer 6

-obstructs nose breathing
-varying degrees

Question 7

Hypertrophic nasal turbinate:

Answer 7

-increase number of cells
-extra folds
-protrudes into nasopharynx

Question 8

Elongated soft palate:

Answer 8

-narrows pharyngeal and nasopharyngeal path
-extends into larynx=audible breath sounds

Question 9

Hypoplastic trachea:

Answer 9

-less number of cells
-thinner and narrower trachea
*prone to collapse

Question 10

What is the function of laryngeal saccules?

Answer 10

-not well defined
-may provide lubrication to vocal cord

Question 11

Everted laryngeal saccules:

Answer 11

-pulled into airway from excess negative pressure
>obstructs path of airflow=increased airway resistance

Question 12

All the anatomical features of BOAS lead to:

Answer 12

-very high airway resistance
*inspiration AND expiration become an active process

Question 13

Airway resistance influences:

Answer 13

-compliance
>how easy/difficult can air go through tip of nose and mouth?
»alveoli distend
*increase resistance=shift in compliance curve=more pressure required to reach TLC

Question 14

Normal airway resistance steps:

Answer 14

1. Generate pressure gradient
2. Inflow of air
3. Air travels through respiratory system (encounters resistance)
4. Air reach alveoli=distension

Question 15

Brachycephalic airway resistance steps:

Answer 15

1. Generate pressure gradient
2. Inflow of air
3. Airflow encounters SIGNIFICANT resistance
4. Reduced air reaching alveoli=partial distension
5. Forced inspiration to generate more negative pressure to further expand alveoli
   *more mouth breathing

Question 16

More mouth breathing due to forced inspiration:

Answer 16

-path of reduced airway resistance
>air is less humidified=easier DEHYDRATION

Question 17

Increased airway resistance leads to:

Answer 17

-more negative pleural pressure required to meet compliance/expand alveoli
*increased inspiration and expiration effort to overcome resistance=work harder for every breath

Question 18

What are some consequences of increased pressure requirements?

Answer 18

-increased respiration effort generates more high negative pressure
-audible breathing sounds
-poor thermoregulation
-exercise intolerant

Question 19

Consequence of increased respiration effort generates more high negative pressure

Answer 19

-sucks soft tissues into airway
-tissues become hyperplastic
>laryngeal cartilage can collapse=exacerbates the obstructions

Question 20

Tissues that are hyperplastic:

Answer 20

-stretch and expands
Ex. laryngeal saccules

Question 21

Audible breathing sounds are caused by:

Answer 21

-high velocity turbulent airflow

Question 22

Poor thermoregulation:

Answer 22

-overheating
>panting allows heat to escape as moisture evaporates in air
-BOAS causes exhalation to be a FORCEFUL process
>generates more heat

Question 23

Exercise intolerant:

Answer 23

-obesity
>excess fatty tissue impede thoracic cage expansion during respiration
*increased risk for metabolic disorders

Question 24

Stertor: respiratory noises

Answer 24

-caused by elongated and thick soft palate that extends into larynx
*extra effort is needed to move soft palate out of larynx to allow air to pass=triggers vibration

Question 25

Normal sleep breathing:

Answer 25

-metabolism is decreased = slower respiratory activity

Question 26

Sleep disorder breathing:

Answer 26

-abdominal muscles are engaged=forced exhalation
-apnea period
-gasp in breath to forcefully reopen the airways (haven’t breathed in the last 3-4 cycles)
>all muscles contract at same time

Question 27

Apnea: sleep disordered breathing

Answer 27

-paused breathing in sleep that can lead to hypoxia
*50% reduction in breath movement
>oxyhemoglobin 97% to 89% (period of hypoxemia)

Question 28

Apnea in humans can lead to:

Answer 28

-hypertension
-heart failure
-heart disease

Question 29

Treatment options: surgical corrections

Answer 29

-resection of stenotic nares
-soft palate resection

Question 30

Treatment options; management

Answer 30

-kept in thin body condition to avoid obesity
-minimize extreme activation/exertion and heat climate
-use harness rather than neck collar

Question 31

Treatment options; prognosis

Answer 31

-surgical corrections earlier in life have improved it
-once develop secondary issues have diminished prognosis
>hyperplastic tissue
>infection
>airway diseases

Question 32

Anesthesia:

Answer 32

-relaxes muscle of respiration
>cannot generate forceful inhalation or exhalation
*extra pressure is need to pull air through the excessive tissue
*passive recoil is insufficient to exhale air

Question 33

Brachycephalic and anesthesia:

Answer 33

-need to be intubated with an endotracheal tube
>bypass elongated soft palate
>overcomes hypoplastic trachea