Keeping the airway healthy Flashcards
How are Equine Loer resp tract disorders classified?
What diseases fo the airways?
- Asthma -> mild or severe (RAO)
- Infectious airway diseases
Diseases of the lung tissues?
- Pneumonia
→ Bacterial
→ Sterile (Chronic Interstitial Inflammatory Infiltrates/pneumonitis) - Equine Multinodular Pulmonary Fibrosis
- Neoplasia
What other lower resp dx?
- Exercise Induced Pulmonary Haemorrhage
- Congestive HEart Failure (pulm oedema)
Give the clinical picture associated ith infectious airway diseases?
- Any age – young>old
- Acute presentation
- Cough/nasal discharge?
- Fever?
- Dull / inappetent?
What different causes of Infectious Airway diseases?
- Viral: EHV, EIV, ERV, (EVA)
- Bacterial: Streptococci,
Actinobacillus,
Rhodococcus etc. - Parasitic: Dictyocaulus
How do we devide Equine Asthma?
- Severe Equine Asthma (‘SEA’)
→ Equine Pasture Asthma (‘EPA’) - Mild/moderate Equine Asthma (‘MEA’)
Clinical picture for MILD Equine Asthma?
- Common in young performance horses
- Any age – young > old
- Subacute-chronic presentation * poor performance
- Intermittent cough (only 38% of cases?)
- Nasal discharge?
- Lung auscultation – normal sounds
Causation of Mild Equine Asthma?
- Poor ventilation
- Dusty hay / bedding
- NH3,H2S etc,….
- Infectious agents?
Clinical Picture for SVERE Equine Asthma?
- Common in mature horses and ponies
→ (usually > 7 years old) - Subacute-chronic presentation
- Abdominal effort/nostril flaring
- Coughing
- “Wheezes and crackles”
Causation of Severe equine asthma?
- Poor ventilation:
→ Dusty hay/straw bedding (moulds)
→ NH3, H2S,…. - Seasonal environmental allergens?( PAsture asthma?)
What is the pathophysiology of Severe Equine Asthma?
KEY characteristics : REVERSIBLE airway obstruction
How to tell apart different causes ? What is our diagnostic approaches?
- History/signalment
- Clinical signs
- Blood tests
- Endoscopy findings
- Airway cytology
- Airway microbiology
Clinical exam for airway dx?
- Rectal temp
- Nasal discharge
- Lymph nodes
- Auscultation
-> Tracheal sump - mucus accumulation
-> Lung fields (crackles, wheezing)
-> Rebreathing exam (induces coughing?)
-> Heart
Signs of airway dx in horses?
- cough
- Nasal discharge
- Abnormal pattern/sounds
What is the normal breathing pattern of a horse?
→ Normal respiration in the resting adult horse is slow (8–16 breaths/min) with
minimal chest or abdominal wall movement
→ Costo-abdominal (= slight movement of costal arch, followed by the slight endexpiratory abdominal lift)
→ Slight movement of the nostrils.
What is abnormal breathing pattern of a horse?
-> Inc rate & depth
-> changed pattern of breathing should be noted
-> as should any abnormal sounds associated with breathing
What does an expiratory dyspnoea show us?
= exaggeration of the biphasic expiratory phase with increased incorporation of the abdominal muscles → producing an obvious biphasic or double expiratory lift: ‘heave’
Typical of small airway obstruction.
What are signs of Expiratory dyspnoea?
- Prolonged and laboured expiration
- Exaggerated expiratory contraction of the abdominal muscles
- Heave line in chronic cases
- Rhythmic pumping of the anus
- Dilation of the nares throughout the respiratory cycle
- Extension of the head and neck
What does Inspiratory Dyspnoea tell us?
= associated with a stertorous or stridorous noiseduring inspiration
Indicative of upper airway obstruction.
Occasionally, inspiratory dyspnoea may occur with severe restrictive lung diseases (e.g. pneumonia, interstitial disease, pneumothorax, rib fracture).
hat signs of inspiratory dyspnoea?
- Prolonged and laboured inspiration
- Increased respiratory effort
- Dilation of the nares throughout the respiratory cycle
- Extension of the head and neck
What does combined inspiratory and expiratory dyspnoea show ?
Usually with tachypnoea.
= Suggestive of severe upper or lower airway obstruction, diffuse pulmonary disease or pleural disease.
What does combined dyspnoea look like?
Rapid and shallow breathing
Describe Increased audibility og lung sounds?
INCREASED AUDIBILITY of normal breath sounds occurs with hyperventilation and occurs focally over areas of consolidated lung tissue.
→ A generalized increase in the intensity of airflow sounds is suggestive of lower airway disease such as SEA (= inflamed
airways)
Describe Reduced audibility of lung sounds?
What are adventitious sounds?
- Crackles
- Wheezes
- Pleural friction sounds
Describe crackles
Describe Wheezes
Describe Pleural Friction
Make a table comparing features of Infectious vs MEA vs SEA as causes of airway disease
What will haematology / APPs tell us about lower airway dx?
- Asthma -> no changes
- Infectious airway dx : neutrophilia, neutropenia, lymphocytosis? monocytosis, inc fibrinogen, inc SAA?
What might we see on endoscopy of airways?
LYMPHOID HYPERPLASIA
- MAy reflect infectious challenge
-> what is normal / acceptable for that age?
How can e visual grade our assessment of the airway on endoscopy
What is the method for a tracheal wash?
- Exercise pre-sampling?
- Twitch/sedate (?)
- Pass endoscope into pharynx
- Spray 5 ml local anaesthetic onto larynx?
- Wait 1 or 2 minutes
- Pass endoscope into upper trachea
- Pass sterile catheter through biopsy channel
- Inject 20-30ml sterile saline
- Continue down trachea and re-aspirate sample
- Place sample in plain and EDTA tubes
Method for Transtracheal Aspirate?
- Sedate (?)
- Clip/scrub area over mid-lower trachea
- Inject 2 ml local anaesthetic
- Stab incision (#11 or #15)
- Insert a 10–14-gauge TTA catheter and remove stylet
- Pass a 5-6 French gauge catheter to thoracic inlet
- Inject 30 ml saline and re-aspirate
- Remove inner catheter before outer ‘sleeve’ (except if
using a needle) - Put sample into plain and EDTA tubes
Method for BAL?
- Sedate
- Pass BAL catheter until resistance is felt
- Pinch catheter with nostril to imobilise
- Inflate cuff
- Allow a few seconds for the horse to settle if coughing a lot
- Inject 300 ml pre-warmed saline
- Re-aspirate (discard first 10 – 20 ml)
- Pool all of collected sample
(plain/EDTA/fixed)
Describe usefulness of sampling airway?
Compare and contrast TW vs BAL in a table
What must we have with TW & BAL Bacteriology?
- No squamous epithelial cells (→ they indicate pharyngeal
contamination) - No feed material (→ indicates oropharyngeal contamination)
- Good technique (impossible with BAL)
- Neutrophilic inflammation
- > 105 cfu/ml ?
What microbiology of the trachea are relevant vs irrelevant?
hat different cell patterns for TW & BAL would indicate disease ?
What cytology differences between MEA and SEA?
How to treat Bacterial infectious dx?
Treatment: Broad-spectrum antibiotic + general supportive care
→ When disease is severe or chronic or involves marked immunosuppression:
guarded prognosis!
How to treat viral diseases?
Supportive
-> Long term anti-inflammatory durgs or corticosteroids may be beneficial in chronic interstitial inflammatory disease
-> Acyclovir or valacyclovior and glucocorticoids may be helpful in early cases of EHV- infection
What main causes fo equine asthma?
AIR HYGIENE -> stables - hay staw, muck heap, dust, dry cereals
Turnout -> pollens, moulds, polluants
What is involved in tx and management of SEVERE asthma?
- environmental control
- Medical treatment
Describe environmental control ?
- AIR HYGIENE – ‘DUST-FREE’ MANAGEMENT
→ Hay, straw, muck heap, general dust, dry
cereals, neighbouring boxes (!),… - Summertime cases?
→ Pollens, moulds, pollutants,…?
What 4 aspects of medical tx?
- GlucoCs
- beta adrenergic agonists
- Muscarinic antagonists
- furosemide.
Detail each part of medical tx?
Compare stable associated vs pasture associated asthma
Stable-associated asthma should (theoretically) only require short term (~ 2
weeks) medication while the air hygiene is corrected.
Pasture-associated asthma is far more
challenging as hard to improve air hygiene
* Long term therapy required (=inhaled
glucocorticoids)
* Intradermal testing and immunotherapy??
How do we manage dust levels in stable?
- Bedding -> shavings/shredded paper etc
- Ventilation
- Ensure horse is in a separate airspace OR all horses in the same airspace must be managed under similar dust-free conditions
- Avoid overhead lofts
- Horse should be OUT of the stable hen it is muckd out
- Feed alternative to hay or steam it
What will glucoCs do for equine asthma?
Coutneract:
→ neutrophil infiltration
→ immune sensitisation to allergens
→ inflammatory mediator release
→ airway wall thickening
→ airway hyperresponsiveness
&
Upregulate β2 receptors
What choice of corticosteroids?
How of beta 2 adrenergic agonists work
= stimulate cAMP production
* relaxes smooth muscle (bronchodilation) - not as potently as muscarinic antagonists
* anti-inflammatory - not as potent as glucocorticoids
* stimulates mucociliary activity
What main 3 adrenergic agonists can we use?
Clenbuterol, Salbutamol, Salmeterol
Detail use fo Clenbuterol?
- oral or iv 0.8(-3.2) microg/kg q 12 h
- tremors, sweating tachycardia after iv dosing
- inconsistent clinical effects?
→ bioavailability is quite variable
→ susceptible to receptor downregulation during therapy
Detail Salbutamol & Salmeterol use
Salbutamol-> * Very short acting (<1h) inhaled product 1-2 microg/kg
Salmeterol -> * Longer acting (8-12h) inhaled product 0.2-0.5 microg/kg q 8-12 h
What do muscarinic antagonists do?
- antagonise parasympathetic effects of acetylcholine
→ smooth muscle relaxation
(parasympathetic M3 receptors = 1° mechanism of bronchoconstriction in the horse)
→ decrease airway secretions
→ may reduce airway hyperresponsiveness
Compare systemic vs inhaled muscarinic anatagonists?
detial use of furosemide for Severe euqine asthma?
- Diuretic
→ decreases pulmonary oedema - Bronchodilator
→ onset < 15 mins
→ PG mediated (NSAIDs antagonises) - 2 mg/kg iv
How can inhaled drugs be administered?
Detail Metered dose inhalers?
→ Widely available for human market
→ Require spacers
→ Cheap
→ Not always well tolerated
Detail nebulsiers?
→ Expensive
→ Well tolerated
→ Must use a “surface acting drug
What is the only licensed inhaler?
Aservo Equihaler
What vaccinations may help with respiratory dx?
- Equine Rhinitis A virus vaccine (USA only)
- Equine Viral Arteritis
- Equine Herpesviruses 1,4
- Equine Influenza
