32 General Evaluation of the Equine Upper Respiratory Tract

Obligate nasal breathers

Where do horses have to breathe out of?

osce throwback

FYI Guttural pouch from the outside.

Horses must have efficient gas exchange for speed

Horses are built for speed. How is this related to the respiratory tract?

Nostril

What is A?

Ventral nasal meatus

What is B?

Ventral conchae

What is C?

Dorsal conchae

What is D?

Middle nasal meatus

What is E?

Ethmoidal conchae

What is F?

Septum to guttural pouch

What is G?

Arytenoid cartilage

What is H?

Epiglottis

What is I?

Soft palate

What is J?

Nasal septum

What is K?

Right arytenoid cartilage

What is 1?

Left arytenoid cartilage

What is 2?

Opening to esophagus

What is 3?

Opening to airway

What is 4?

Vocal cord (fold)

What is 5?

Laryngeal saccule (ventricle)

What is 6?

Epiglottis

What is 7?

Soft palate

What is 8?

8-10 bpm

What is typical resting respiration rate in horses

80-100 bpm with 1500 L

What is MAX exercising respiration rate? How many liters in minute ventilation?

GATHER PHASE: Gut contents move back, hindlegs engage, lungs expand = inhalation

EXTENDED PHASE: Gut contents move forward against diaphragm, hindlegs extend = exhalation

basically, they exhale as the forehand contacts the ground

Talk about when a horse breathes in versus out in the gallop stride?

Exhalation = positive pressure

Is this showing *inhalation or exhalation*

Inhalation = negative pressure

Is this showing *inhalation or exhalation*

Laryngeal area

Where is this showing you is the place of most resistance?

Inhalation

Are there often more issues on *inhalation or exhalation* in horses?

Airway diameter (aka LUMEN SIZE)

What is the primary determinant of airway resistance in horses, where even cutting this in half increases the resistance by a factor of 16?

External nares, nasal mucosa, pharynx like soft palate, larynx like epiglottis and arytenoids (most common)

Name the areas of airway resistance in the horse

a. left laryngeal hemiplegia

What is your diagnosis:

a. left laryngeal hemiplegia

b. right laryngeal hemiplegia

c. dorsal displacement of the soft palate

d. pharyngeal collapse

d. pharyngeal collapse

What is your diagnosis:

a. left laryngeal hemiplegia

b. right laryngeal hemiplegia

c. dorsal displacement of the soft palate

d. pharyngeal collapse

c. dorsal displacement of the soft palate

What is your diagnosis:

a. left laryngeal hemiplegia

b. right laryngeal hemiplegia

c. dorsal displacement of the soft palate

d. pharyngeal collapse

Inspiration

Horses have more airway resistance on *inspiration or expiration*

Muscular tone

What is the major contributor of upper airway stabilization?

Horses who need to keep their heads round will struggle to breathe if they have nerve innervation problems

What is important to note about horses who need to be collected for work (like dressage) but have nerve innervation problems?

FALSE = they are not

TRUE OR FALSE: respiratory noise and exercise intolerance are synonymous

1:1

What is the inspiration to expiration ratio in horses

cricoarytenoideus dorsalis muscle

When palpating the upper respiratory tract in horses, you feel the laryngeal cartilage. What muscles should you feel for around here?

paranasal sinuses

What should you percuss in a physical exam of the respiratory tract in horses

Ethmoid turbinates = healthy

What is this on an endoscope?

Medially, and aspect of ventral meatus

Where do you place the scope when doing endoscopy on a horses nasal cavity?

At rest

You should always start your nasal cavity endoscopy when a horse in *in motion or at rest*

The L and R openings of the guttural pouch

What are the L and R letters showing you?

Stylohyoid bone

What is 1?

external carotid artery

What is 2?

lateral compartment

What is 3?

medial compartment

What is 4?

internal carotid artery

What is 5?

cranial nerve 10 (X, vagus)

What is 6?

cranial nerve 12 (XII, hypoglossal)

What is 7?

cranial nerve 9 (XI, glossopharyngeal)

What is 8?

Most people sedate on the left side. This is where the L. recurrent laryngeal nerve is, and this may cause a false positive effect on the endoscopy if looking for collapse

Why should you never use sedation for an endoscopy at rest?

Nasal occlusion (will it open with a higher negative pressure with nasal occlusion?)

What can you do to evaluate an endoscopy at rest? What can you do to the horse's nose to watch the structures move?

Swallowing

Arytenoid abduction is better correlated with *swallowing or nasal occlusion*

Dynamic endoscopy

What is this?

Dorsal displacement of soft palate

What condition are you more likely to see in dynamic endoscopy than at rest?

Hard to interpret (here there is an occluded sinus around a root abnormality in the tooth third from the back M1. in front of that, the sinus is air filled and normal)

What is the problem with radiograph diagnostic for nasal problems??

Fluid lines

What are these?

CT

What is the best option for sinuses but is VERY EXPNESIVE