General Evaluation of the Equine Upper Respiratory Tract

Lecture 32

What is structure A?

arytenoid cartilage

What is structure B?

opening to esophagus

What is structure C?

vocal cord/fold

What is structure D?

epiglottis

What is normal resting respiration rate in horses?

8-20 bpm

What is maximal exercising respiration rate in horses?

80-100 bpm

What minute ventilation is associated with maximal exercising respiration rate in horses?

1500 liters

What is the equation for minute ventilation?

respiratory rate x tidal volume

tidal volume = 5 liters at rest

What is total lung capacity in liters for horses?

40 L

Horses are obligate nasal breathers. Knowing this, does their upper respiratory tract have a high or low resistance to airflow?

high

What is the limiting factor in horse’s exercise capacity?

their upper repiratory tract having a high resistance to airflow

A galloping horse exhales when?

as forehand contacts ground

Is exhalation positive or negative pressure?

positive

Is inhalation positive or negative pressure?

negative

True or false: Exercise increases pressure disparity between inhalation and exhalation.

True

Airway resistance is primarily determined by what?

airway diameter

Cutting the radius of the airway in half increases the resistance by a factor of?

16

List the 4 areas of resistance in the upper airway.

external nares

nasal mucosa

pharynx (soft palate and pharyngeal walls)

larynx (epiglottis and arytenoids)

What is your diagnosis?

left laryngeal hemiplegia

What is your diagnosis?

pharyngeal collapse

What is your diagnosis?

dorsal displacement of the soft palate

What is the major contributor to upper airway stabilization?

muscular tone

Are respiratory noise and exercise intolerance synonymous?

NO

List the steps for evaluation of the upper respiratory tract.

history —> use, complaint, nasal discharge, cough, exercise intolerance, respiratory noise, dysphagia

PE —> respiratory disease, lameness, myopathies, cardiac disease, neurological disease, etc

ancillary diagnostic aids —> endoscopy, radiographs, CT/MRI, ultrasound, blood work

What should the ratio of inspiration to expiration be?

1:1

When performing an endoscopy, the scope should be placed how into the nasal cavity?

through medial aspect of ventral meatus

What structures are located in the lateral compartment of the guttural pouch?

external carotid artery

What structures are located in the medial compartment of the guttural pouch?

internal carotid artery

CN IX, X, XII

What separates the lateral and medial compartments of the guttural pouch?

stylohyoid bone

When performing an endoscopy, should you give sedation?

No

Why do we perform nasal occlusion during an endoscopy at rest?

it allows us to get negative pharyngeal pressures that are similar to exercise and allows then to hold arytenoid abduction longer

What is the best imaging modality for evaluating sinuses?

CT

What is indicated by the star?

opening to airway

What is indicated by the green arrow?

right arytenoid cartilage

What is indicated by the yellow arrow?

left arytenoid cartilage

What is indicated by the orange arrow?

opening to esophagus

What is indicated by the silver arrow?

vocal cord (fold)

What is indicated by the white arrow?

laryngeal saccule (ventricle)

What is indicated by the dark blue arrow?

soft palate

What is indicated by the light blue arrow?

epiglottis