Disease of the equine head and neck Flashcards
What are the functions of the upper airway?
- Conduit: airflow to & from lung
- Filtering: Mucus
- Protection of lower airway from aspiration
- Olfaction
- Phonation (vocal sounds)
- Swallowing
- Thermoregulation
Why is a normal upper airway critical for horses?
They are obligate nasal breathers
How do respiratory muscles and the diaphragm provide the force for ventilation?
- Inhalation = negative pressures – air moves into lung
- Exhalation = positive pressures – drives air out
What is the resting respiratory rate of a horse?
8-15 brpm
How odes minute ventilation increase during exercise?
20X increase (up to 1500L)
What are the knock-on consequences of anything narrowing the airway?
- > Increased airflow resistance
- > Increased negative pressure on inspiration
- > Unsupported structures collapse (pharynx / larynx)
- > URT Obstruction
- > Noise + reduced oxygen delivery
How is resistance linked to radius?
Resistance is inversely proportional to Radius to the power of 4
- a small change in radius has a marked effect on resistance
What are some examples of presenting signs of abnormal URT function
- Respiratory noise / distress
- Dysphagia
- Coughing
- Exercise Intolerance
- Nasal discharge - Blood, Purulent material, Ingesta
- Facial deformity
- Neurological signs
Which presenting signs are the most emergency?
Respiratory distress and bloody nasal discharge
What information needs to be gathered about the nature of any nasal discharge?
- Where does it come from? i.e. unilateral or bilateral
- Duration
- Nature of it
- Evidence of trauma
Why is it important to know if nasal discharge is unilateral or bilateral?
Unilateral: at or rostral to nasal septum
• Sinus or nasal passages
Bilateral: behind nasal septum
• GP, Larynx, pharynx, lower respiratory tract
Why is it important to know the duration that the horse has been owned
Important to know how long the owner has had the horse, they might have noticed a problem that has actually been going on for much longer
What are some different natures of discharge
Serous
Blood
Purulent
Food material
What characteristics of any respiratory noise should be noted?
- Severity of obstruction
- When: rest/exercise?
- Inspiratory/ Expiratory/ Both
- What does the noise sound like? i.e. Whistle / roar / gurgle / snoring
- Continuous/intermittent?
- Poor performance?
How should a horse with abnormal URT be examined at rest? Where is being assessed?
- Look, listen, palpate
- General physical examination at rest
- Examine all body systems
- Concurrent disease
- Respiratory rate & character
- AUSCULTATION of thorax and trachea
- REBREATHING
Which easily seen sign on observation shows that a horse has an increased respiratory effort?
Nostril flare – a horse at rest should not have this
What should be examined when looking at the horses head?
- Symmetry
- Nasal/ocular discharge
- Airflow from both nostrils
- Percussion of sinuses
- Palpation of larynx
- Previous surgical scars
Name 4 example sounds that are normal if heard at exercise
- Snorting
- ‘High blowing’
- Sheath noise
- ‘Thick wind’
Name 4 example sounds that are abnormal if heard at exercise
Whistle / roar / gurgle / snoring
Name some methods used for diagnostic head imaging
- Endoscopy
- Radiography
- Sinoscopy
- CT
- Ultrasonography
- MRI
What are the advantages of using endoscopy?
- Widely available, affordable
- Minimally invasive
- Directly visualise regions of the head
What are the 3 main indications for endoscopy use?
- Nasal discharge / malodour
- Respiratory noise
- Dysphagia
What is the gold standard diagnostic method for noise heard at exercise?
Exercising endoscopy
• Important tool for assessment of poor performance
• More accurate assessment of dynamic airway function
What is the gold standard diagnostic method for assessing bony / dental structures?
Radiography
What are the advantages of using radiography?
- Images can be obtained with portable machines
* Easy to perform many of the standard views
What are the disadvantages of using radiography?
- Complex anatomy
* 2 dimensional images
What are the 3 standard views when taking radiographs?
- Latero-lateral
- Lateral oblique
- Dorso-ventral
When is a Latero- Lateral View used?
Good for assessing the paranasal sinuses, guttural pouches & pharynx
When is a Lateral oblique view used?
- Used most commonly to assess the periapical regions of the cheek teeth for evidence of infection
- No Superimposition of teeth apices
- 30 degree angulation maxillary arcades
- 45 degree angulation mandibular arcades
When is a dorso-ventral view used?
- Assessment of paranasal sinuses, nasal septum and teeth
* Helps to determine if lesions unilateral / bilateral
When is an intra-oral view used?
- Assessment of incisor teeth and associated bone
* Fractures of incisor teeth / associated bone
Describe the features and uses of sinoscopy
- More invasive than routine endoscopy
- Easily performed under standing sedation with local anaesthesia
- Minimally invasive means of visualizing the paranasal sinuses
- Enables surgical treatment to be undertaken & ongoing monitoring and lavage of sinuses
What are the advantages of CT?
- Gold standard
- Affordable and cost effective
- Cross-sectional images
- Superior resolution
- Tissue density measurement
What some indications for CT use?
- Dental disease
- Masses within the paranasal sinuses / nasal passages
- Trauma
What are some important used of ultrasonography in the head?
- Ophthalmic
- Soft tissue swellings external to the skull
- Assessment of skull bones / TMJ
- Larynx
Why are MRIs rarely performed?
- Limited to only a few facilities
- Requires general anaesthesia
- £££
- Time
