Lung and airway diagnostics

Question 1

Basic diagnostic ‘tests’

Answer 1

History, examination

Question 2

Establishing the problem

Answer 2

Respiratory distress/dysponoea (URT/pleural/lung/non-CRS), cyanosis, cough

Question 2

Next steps

Answer 2

imaging (US, CT, radiography), haematology, bronchoscopy, BAL, TTW

Question 2

History Qs

Answer 2

is is a cough or gag/retch? previous illness? kennelling/contact with other dogs? vaccination history? environment (dust/smoke/aerosols/plug ins)? exercise tolerance? trauma to thorax/airway/abdomen? poisons? change in voice (larynx, neuropathy of RLN)? seasonality? relation to eating/drinking?

Question 3

Frequency of cough

Answer 3

all/some of the time. at night only? association with exercise/excitement? paroxysmal (sudden)

Question 3

Type of cough

Answer 3

soft, productive - blood, froth, pus.
harsh, unproductive, retching.
honking/quacking

Question 4

Onset speed

Answer 4

acute (e.g. FB), chronic (e.g. neoplasia, heart failure)

Question 5

Other related signs

Answer 5

resp noise, cyanosis, discharges, associated resp difficulty, swallowing difficulty/regurgitates

Question 5

Indications for tracheal washing

Answer 5

pts suspected to have large airway disease, also provides information about the small airways when cough reflex retained.
indicated in pts where there’s concerns re GA as can be done conscious

Question 5

Benefit of TTW over ETW

Answer 5

with TTW the cough reflex is retained, therefore it gives better information from the lower airways

Question 5

Method of tracheal washing

Answer 5

1. clip and prep area over proximal trachea (around larynx and ventral neck)
2. inject LA over site between tracheal rings, nick skin with scalpel blade to facilitate passage of catheter
3. pass large bore catheter between rings into tracheal lumen (or can go through the cricothyroid ligament triangular depressed at the base of the thyroid cartilage), remove stylet
4. pass long catheter through the large bore catheter down the trachea, inject saline and immediately aspirate to collect material from large airways

Question 5

Sedation for tracheal washing if needed

Answer 5

pure opioids (can reverse once catheter in place) or ketamine/BDZ to retain the cough reflex

Question 5

Types of tracheal washing

Answer 5

trans-tracheal washing (TTW) or endotracheal washing (ETW)

Question 5

Equipment needed for tracheal washing

Answer 5

long soft catheter, LA, large bore catheter, saline, sample tubes, sterile gloves.
ensure the long soft catheter fits through the large bore catheter.
catheter size - 19-22G 8inch (cats and small dogs), 19G 12 or 24inch (larger dogs)

Question 6

Why should you be careful using active suction devices for tracheal washing?

Answer 6

• they can damage the airway and cells

Question 6

Volumes of saline used for tracheal washing

Answer 6

3-5ml for cats and small dogs.
10-20ml for large dogs

Question 7

Indications for bronchoscopy

Answer 7

investigation of unexplained clinical signs (chronic cough, haemoptysis, acute/chronic respiratory distress following other tests or failed therapeutic trials), to obtain diagnostic samples, evaluate radiographic lung lesions, assessment of airways, treatment of airway disease

Question 8

What respiratory pts are unlikely to benefit from a bronchoscopy?

Answer 8

those with primary disease of the vasculature and those with discrete pulmonary lesions

Question 9

Benefits of bronchoscopy

Answer 9

relatively safe, allows collection of samples (material for bacteriology, mycoplasma, cytology, bronchial brushes, transbronchial biopsy/brushings), allows removal of foreign materials, allows assessment of the airways

Question 10

Examples of conditions seen when assessing the airways on bronchoscopy

Answer 10

trachial/bronchial tears, tracheal-bronchial or bronchial-oesophageal fistulas, lung lobe torsion, tracheal/bronchial collapse, aspiration pneumonia, FBs

Question 11

Contraindications for bronchoscopy

Answer 11

care with hyper-responsive airways (e.g. cats with allergic bronchial disease, dogs with wheezing suggesting airway spasm), unstable cardiac failure/arrhythmias, care with pts with tracheal obstruction, haemorrhage (increased risk with PH, uraemia, coagulopathiges, neoplasia/gross lesions)

Question 12

What should you give cats before bronchoscopy?

Answer 12

a bronchodilator in cats before to prevent bronchospasm

Question 12

How to perform a bronchoscopy

Answer 12

under GA to prevent scope damage, sternal recumbency, elevate head so nose is parallel to the table, pre-oxygenate for 30-45 seconds.
assess the larynx, pharynx and trachea.
entry into right principle bronchus, entry into left principle bronchus

Question 13

IV anaesthesia for bronchoscopy

Answer 13

propofol/alfaxan

Question 14

What can forcing the endoscope down the bronchus cause?

Answer 14

haemorrhage or tearing of the tracheobronchial wall -> pneumothorax

Question 14

What lung lobes are seen by entry of the endoscope into the right principle bronchus?

Answer 14

right cranial, middle, accessory and caudal lung lobes

Question 14

Pt monitoring during bronchoscopy

Answer 14

pulse ox / end tidal capnography

Question 14

Bronchoscopy equipment

Answer 14

sterile large ET tube, Y/T connector (allows passage of the scope into the ETT with pt attached to breathing system [not possible for small dogs or cats, instead pass directly through the larynx]), adaptor self sealing port, sterile lube

Question 15

How can you collect samples during bronchoscopy?

Answer 15

BAL (saline lavage), cytology brush (surface brushing), biopsies

Question 15

What lung lobes are seen by entry of the endoscope into the left principle bronchus?

Answer 15

left cranial lung lobe (2 branches to left cranial lung lobe (cranial and caudal) and the left caudal lung lobe

Question 15

What are the samples collected during bronchoscopy submitted for?

Answer 15

culture (bacterial/mycoplasma/fungal), viral isolation, PCR (for infectious organisms, e.g. mycoplasma), cytology

Question 15

BAL technique

Answer 15

1. pre-oxygenate (2 mins in compromised pts) 2. lodge endoscope in small airway 3. instil sterile saline via catheter 4. immediate suction after instillation of fluid 5. repeat bolus in same position - lavage several lobes - courage whilst fluid is being instilled

Question 15

How does the carina appear on bronchoscopy?

Answer 15

a sharp wedge dividing the trachea into the 2 principle bronchi

Question 15

What does a normal trachea and bronchial mucosa look like?

Answer 15

light pink and moist (minimal secretions)

Question 16

Equipment needed for BAL

Answer 16

- 0.9% sterile saline solution - bacterial swabs - sterile plain tubes (plastic) - EDTA tubes - BAL catheter - urinary catheter - continuous suction device - syringes - assistant - formalin

Question 17

Indications for BAL

Answer 17

lobar or diffuse airway disease, or interstitial lung diseases

Question 18

How much saline should be instilled for BAL?

Answer 18

medium to large dogs ~25ml per lobe (2 lobes washed), small dogs and cats ~10ml per bolus (up to 4 sites)

Question 18

What can happen if there's too much suction on BAL?

Answer 18

airway collapse and damage (100-170mmHg pressure max). suction chambers are more likely to damage cell morphology

Question 19

Non-bronchoscopic BAL

Answer 19

dog urinary catheter or feeding tube, ensure end hole only, sterile ET tube, Y connector, dog in dorsal recumbency, pre-oxygenate, place tube as far as will go until feel resistance, 20-25ml saline and 5ml of air in dogs, 20ml per bolus in 4kg cat (2-3 sites), 7/9 pts right caudal lung lobe, pt under GA therefore no cough

Question 19

A good BAL sample

Answer 19

foam on top - due to surfactant in fluid, >50% fluid retrieved, retrieval volume should increase with each subsequent lavage

Question 20

How to manage pts post-BAL

Answer 20

100% oxygen for 5-10mins, gentle positive pressure ventilation (helps open atelctatic alveoli), if previous stable pt doesn't respond to oxygen consider: obstruction of ET tube, bronchospasm: bronchodilator, pneumothorax. it's normal to auscultate crackles for up to 24h post BAL