Lower respiratory tract diseases Flashcards by Josie Campbell

Clinical examination of lower respiratory tract

Rebreathing exam
- cover horses nose with bin bag to increase effort
- improves sensitivity of auscultation

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Haematology/biochemistry for lower respiratory tract

Useful for pneumonia but not asthma

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Blood gases for lower respiratory tract diseases

Have to be run within a few minutes of obtaining a sample

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Endoscopy for lower respiratory tract diseases

Mucus grading

Visualisation of airway

Collection of samples

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Lower respiratory samples collected by endoscopy

Guided BAL (cytology)

Transtracheal wash (cytology)

Triple lumen tracheal washes (culture)

Transtracheal wash

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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

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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…

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Transtracheal wash

Performed transcutaneously, aseptically

Samples everything washed up into trachea (all of lung)

Best for culture

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Ultrasound for lower respiratory tract

Useful for pleural surface

Consolidation, abscesses

Pleural effusions

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Radiography for lower respiratory tract

Useful for the rest of the parenchym

Less easy than ultrasound

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Equine asthma

(Formerly known as heaves, COPD, RAO, SPARAO, IAD…)

RAO – recurrent airway obstruction
○ Severe asthma

IAD – inflammatory airway disease
○ Mild/moderate asthma

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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

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Presentation of RAO/severe asthma

> 7 years old

Coughing

Increased respiratory effort at rest

Life long management, not cured

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Presentation of IAD/mild-moderate asthma

Any age (usually young to middle aged)

No signs at rest

Occasional cough/exercise intolerance

Seem to resolve

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Diagnosis of IAD/mild-moderate asthma

BAL

increase in neutrophils most common +/- mast cells (triggered by exercise), eosinophils

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Diagnosis of RAO/severe asthma

More marked increase in non-septic neutrophilia

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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

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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