Lower respiratory tract diseases Flashcards
Clinical examination of lower respiratory tract
Rebreathing exam
- cover horses nose with bin bag to increase effort
- improves sensitivity of auscultation
Haematology/biochemistry for lower respiratory tract
Useful for pneumonia but not asthma
Blood gases for lower respiratory tract diseases
Have to be run within a few minutes of obtaining a sample
Endoscopy for lower respiratory tract diseases
Mucus grading
Visualisation of airway
Collection of samples
Lower respiratory samples collected by endoscopy
Guided BAL (cytology)
Transtracheal wash (cytology)
Triple lumen tracheal washes (culture)
Transtracheal wash
Guided BAL
For cytology, samples one region of lung (diffuse disease)
Sedate with opioid to suppress cough - butorphanol or morphine
Long flexible tube passed blindly up ventral meatus
Approx. 250-300ml saline instilled
Aspirate sample
® Discard first syringe
Good sample should be foamy
EDTA tube to submit
Tracheal wash
For cytology, samples everything washed up into trachea (all of lung)
Via endoscope
Using triple lumen catheter if for culture
® Can be used for cytology, but BAL more reliable
Instil 20-30ml sterile saline
Plain (culture) and EDTA (cytology) for submission
Some bacteria v. likely to be contaminants
E.g. Pseudomonas, S. aureus, Bacillus…
Transtracheal wash
Performed transcutaneously, aseptically
Samples everything washed up into trachea (all of lung)
Best for culture
Ultrasound for lower respiratory tract
Useful for pleural surface
Consolidation, abscesses
Pleural effusions
Radiography for lower respiratory tract
Useful for the rest of the parenchym
Less easy than ultrasound
Equine asthma
(Formerly known as heaves, COPD, RAO, SPARAO, IAD…)
RAO – recurrent airway obstruction
○ Severe asthma
IAD – inflammatory airway disease
○ Mild/moderate asthma
Pathogenesis of equine asthma
Not well defined
Lower respiratory tract inflammation, obstruction, hyperresponsiveness
Phenotype differs according to cell type
§ TH-1 or Th-2 driven -> different cell type dominates
Airway remodelling (esp. severe/RAO)
§ Mild-moderate/IAD seem to recover
Mild (IAD) and moderate to severe (RAO) aren’t necessarily a continuum
Presentation of RAO/severe asthma
> 7 years old
Coughing
Increased respiratory effort at rest
Life long management, not cured
Presentation of IAD/mild-moderate asthma
Any age (usually young to middle aged)
No signs at rest
Occasional cough/exercise intolerance
Seem to resolve
Diagnosis of IAD/mild-moderate asthma
BAL
increase in neutrophils most common +/- mast cells (triggered by exercise), eosinophils
Diagnosis of RAO/severe asthma
More marked increase in non-septic neutrophilia
Environmental management for equine asthma
Low dust
Damp all feed
Feed from ground
Turn out as much as possible
Turn out during mucking out
Ventilation
No straw/dusty bedding
□ Use dust extracted hay
Not near muck heap/neighbours with dusty bedding
Leaf blowers really bad for the horses but makes clearing the yard really easy so owners don’t want to get rid of them
Exercise induced pulmonary haemorrhage (EIPH)
Common in horses undergoing strenuous exercise (race horses, elite event horses)
Rupture of pulmonary capillaries during high intravascular and low airway pressures
○ Pulmonary capillary walls +++ thin
If severe may affect performance
○ But many horses perform well with EIPH
Worse if working in colder weather
+/- epistaxis
Diagnosis of EIPH
Endoscopy 30-120 min after exercise (usually for a fading horse)
§ 0 – 4 grading system for blood in airway
§ Subjective
§ May change from one observation to the next for single animal
BAL haemosiderophages
§ Macrophages that have digested historic bleeding
§ Overestimates prevalence, normal/common finding
§ Persist for weeks/months
Management of EIPH
Nasal diltor (flair) strips
- low quiality/conflicting evidence
Furosemide only preventative meication with good evidence
- cannot compete on furosemide
Interstitial pneumonia
Parenchymal disease
Bronchopneumonia
Parenchhyma + bronchi
Pleuropneumonia
Parenchyma + bronchi + extension to pleural space
Bacterial pneumonia
Commonly opportunistic infection involving bacteria from naso/oropharynx
Muco-cilliary escalator is not good enough to work when the horses head is up all the time
Risk factors for bacterial pneumonia
Long distance transport without letting head down/breaks
Cross tying
Concurrent respiratory tract disease
Aspiration
Signs of bacterial pneumonia
Tachypnoea/respiratory distress
Weight loss
Pyrexia
Lethargy
Cough
Nasal discharge
□ Mucopurulent, haemorrhagic (necrosis)
Pleurodynia
Diagnosis of bacterial pneumonia
Clinical exam
Haematology/biochemistry
Thoracic ultrasound
Radiography
Bacteriology
Haematology/biochemistry for bacterial pneumonia
Leukocytes (+/- left shift), increased acute phase proteins… anaemia
Thoracic ultrasound of bacterial pneumonia
Consolidation, pleural effusion
Fibrinous effusion - true pleuropneumonia
Radiography of bacterial pneumonia
Broncho-interstitial pattern,
alveolar pattern,
abscesses,
effusion
Bacteriology for bacterial pneumonia
Culture and sensitivity
- Transtracheal wash/triple lumen catheter sample
- Tracheal samples vs pleural fluid
Mixed growth common
- S. qui zooepidemicus
- Empirical antimicrobial selection needs to cover +/-/anaerobes
- Don’t delay treatment initiation to wait for bacteriology
Treatment of bacterial pneumonia
Appropriate antimicrobial selection
□ Penicillin, gentamycin, and something to treat the anaerobes
Consider draining effusions/rtPA use for fibrinous effusions
□ Antimicrobial efficacy improved
Some may require surgical intervention
□ Thoracotomy
Complications of bacterial pneumonia
Abscessation
Bronchopleural fistulae
Pericarditis
Cranial thoracic masses
Thrombophlebitis
Laminitis
Prognosis of bacterial pneumonia
Dependent on severity
Worse with anaerobic bacteria
Fungal pneumonia
Rare in UK
Either primary respiratory pathogen species
§ Histoplasma, Coccidiodes, Cryptococcus etc.
Or secondary to immunocompromise
§ Aspergillus, Candida etc.
Treatment of fungal pneumonia
Challenging and very expensive
Azoles generally best
Prognosis of fungal pneumonia
Variable but often poor
Parasitic pneumonia
Dictyocaulus arnfieldi (adult)
§ Faecal flotation
P. equorum (migrating larvae)
§ Not producing eggs yet
Exercise intolerance, coughing, nasal discharge, (fever)
Neutrophilic/eosinophilic tracheal wash
Bronchointerstitial pattern on radiography
Pathogenesis of interstitial pneumonia
Acute parenchymal changes and alveolar disease
Ventilation-perfusion changes due to loss of surface area
Reduced lung compliance and progressive fibrosis
Signs of interstitial pneumonia
Exercise intolerance
Increased effort at rest
Pulmonary hypertension/cor pulmonale
Causes of interstitial pneumonia
Not always clear, often not identified
Infectious
□ Viral (EHV-1,4/2,5, influenza, EVA etc.)
□ Secondary bacterial pathogens?
Toxins (none common in UK)
Smoke inhalation
□ Barn fires
Oxygen toxicity
□ Ventilation with FIO2 >50%, ventilation injuries
Equine multinodar pulmonary fibrosis (EMPF)
Interstitial fibrosis and inflammatory infiltrate
EHV-5 associated with disease
□ Unclear exact aetiopathogenesis
□ Also EHV-2?
Don’t respond well to bronchodilators
□ C.f. asthmatics
Radiographs: large discrete, or multiple smaller coalescing opactities
Poor prognosis for survival (14% survive 6mo after discharge)
Often severe at time of diagnosis
Diagnosis of interstitial pneumonia
Rule out asthma
Rule out bacterial pneumonia
Radiography helpful, especially EMPF
Biopsy only definitive diagnosis
Steroids
Pneumothorax
Bronchopleural fistulae
○ Secondary to pneumonia
Penetrating thoracic injuries
○ Clingfilm!
Other
○ e.g. oesophageal perforations etc.
Might be well tolerated if unilateral
Drain
