Approach to LRT Disease in SA Flashcards
1
Q
Structure of the mammalian airway?
A
- Airways of the mammalian lung consists of a branching tree of blind ending tubes.
- This design creates physiological problems.
- Mammalian lung contains two types of airways:
- Conducting - carry air to and from respiratory airways.
- Respiratory - responsible for gaseous exchange with blood. (in pulmonary parenchyma)
- Different abnormalities in each of these areas causes different clinical signs.
- The severity of the problem gets worse as you are higher up. Occlusion of trachea or larynx – die quickly c.f. quite a bit of lung needs to be affected to present severely.
- Cyanosis very difficult to generate from lung dz as large surface area, so a lot needs to be abnormal cf. laryngeal paralysis – will get cyanotic quickly.
2
Q
How do we approach animals with lower airway disease?
A
- Signalment (age, breed, sex, neuter status)
- Important for breed related disorders and helping to organise your differentials list
- Brachycephalic dog: URT generally
- Full and thorough clinical history
- Diet, drinking, eating, urination, defecation, fluctuations in body weight
- Abnormal clinical signs at home/outside
- Any changes in activity level at home
- Any changes in personality / behaviour
- Changes in voice – laryngeal lesions
- Change in bark, purr, meow etc.
- Facial deformity
- Seen with nasal dz, tumours, fungal infections etc.
3
Q
How should you approach the case in the consulting room?
A
- Observe the patient closely
- First critical aspect is whether the patient requires emergency admission or appears clinically stable
- A significant number animals with lower airway disease will be presented for acute deterioration
- Condition of patient
- Breathing (respiratory character)
- rate, pattern, regularity, depth and apparent effort
- Mucus membrane colour
- Pale, cyanotic, normal
- Some animals that aren’t anaemic will look like they have resp dz as their rate and effort will increase.
- Behaviours that are worrying the owner
- First critical aspect is whether the patient requires emergency admission or appears clinically stable
4
Q
What breathing patterns are demonstrated?
A
- Normally inspiratory phase is longer than expiratory, in lower airway disease this is often reversed.
- Getting air out more challenging.
- Normal respiratory effort is minimal at rest.
- Upper respiratory tract disease – slow respiratory rate and an exaggerated inspiratory effort (longer phase)
- Inspiratory effort increased
- Rate not that high, but much greater effort. Hence, increased resp effort.
- Lower respiratory restrictive disease e.g. IPF, pleural effusion – fast shallow breaths
- Often both phases of breathing altered
- Interstitial fibrotic lung disease often limited to increased inspiratory effort – due to reduced lung compliance
- Pleural diseases – loss of pleural adhesion increases required effort to breathe.
- Inspiratory effort increased
- Don’t have good pleural seal, so can look like URT because have much more effort to breathe in – have to increase effort to expand lungs.
- Paradoxical respiration – respiratory muscle fatigue leading to opposing movements of the chest and abdominal wall. e.g. inspiration the caudal ribcage collapses inward and the abdominal contents are displaced caudally. Can occur in may cases of respiratory disease but is generally a poor sign.
- Species differences important
- Cats very good at hiding severe respiratory disease
- As a result this species is commonly presented with severe apparently acute onset clinical signs
- Dog’s are quite straight forward, cats are very good at being terminally ill and still appearing ok.
5
Q
How should you approach a thoracic examination?
A
- Thoracic palpation (feel chest – lumps, bumps, pain, rib fractures etc. can you feel heart beat – with significant pleural space dz, you may not feel apex beat or any beat at all).
- Presence of - apex beat, rhonchi, masses, deformities, pain (e.g. rib fractures)
- Thoracic auscultation
- Hindered by purring, panting, growling!
- Use both sides of your stethoscope and listen to both sides.
- Normal sounds
- Inspiratory – soft, low pitched
- Expiratory – none or softer and lower pitched
6
Q
What are
1. Crackles
- Wheezes
associated with?
A
- Crackles = sweet wrappers sound. Can be dry or moist. If moist: CHF and most prominent on inspriation, suggesting fluid in the lungs. If dry, suggests acute or chronic airway disease e.g. pulmonary fibrosis.
- Wheezes = high pitched, rhonchi = low pitched. They suggest narrowing of airway, can be on inspiration or expiration but most commonly expiration esp. lower airway disease.
7
Q
Explain chest percussion findings
A
- pleural effusion: dull below fluid line and normal above it.
- increased tympanic sounds: pneumothorax, feline asthma, emphysema.
- Decreased tympanic sounds: diaphragmatic hernia, chest masses, unilateral pleural effusion.
8
Q
How should you investiage a patient with LRT disease?
A
- History – is the animal coughing or having respiratory difficulty/changed character
- Clinical examination
- Routine haematology and biochemistry
- Specific blood tests - e.g. serum Pro-BNP concentration
- Blood gas evaluation
- Diagnostic imaging
- Thoracic radiographs, fluoroscopy, CT, Ultrasound, scintigraphy, MRI
- Pleural space dz – US best.
- Tracheal washes/Bronchoscopy
- Lung FNA/biopsies
- NB these are often older dogs with concurrent diseaseother tests as clinically indicated!
9
Q
Explain the use of
- Thoracic radiographs
- Fluoroscopy
- Thoracic CT
- Thoracic US
A
Thoracic radiographs
- Where thoracic disease is suspected thoracic radiographs (at least 2 views) should always be taken
- Mets – at least 3 views.
- Radiographs should only be taken when the patient is stable enough to do so!
- Severely dyspnoeic patients should be stabilised prior to radiographs in all but extremely exceptional circumstances
- Can consider horizontal beam radiographs for patients too dyspnoeic to lay down
- Aids with fluid identification and free gas
- Radiation safety issues may preclude this approach
Fluroscopy
- Valuable to assess dynamic integrity of airway
- Useful for dynamic airway disease.
Thoracic CT
- Gold standard.
- Helps work out if have pleural involvement or mediastinal disease.
- Advantages over radiographs
- Increased sensitivity (high resolution CT: 300 micrometers)
- Spatial assessment of disease
- Value to differentiate pleural, extrapleural and mediastinal disease
- Disadvantages
- Unable to perform easily in conscious patient
- Increased costs and limited availability
Thoracic Ultrasound
- Value for pleural disease, to identify poorly aerated lung (atelectasis, consolidation, torsion)
- No real value in normal lung tissue as US cannot pass through air
- Lumps, bumps or fluid.
10
Q
Indications for bronchoscopy?
A
- Investigation of unexplained clinical signs
- If cannot identify reasons for a cough.
- To obtain diagnostic samples
- Chronic cough – inflammation etc.
- Evaluate radiographic lung lesions
- Lesion that we think will exfoliate.
- Assessment of airways
- Look for airway collapse.
- Treatment of airway disease
- Can pull stuff out e.g. FB via bronchoscope.
- Relatively safe and can be diagnostic in a lot of cases.
- Bronchoscopy usually follows H, PE, rads, blds, ? Therapeutic trials have failed to give an answer for the LRT disease
- Chronic cough, haemoptysis, acute / chronic resp distress
- Animals unlikely to benefit are those with primary disease of the vasculature and those with discrete pulmonary lesions
11
Q
What are the benefits of bronchoscopy?
A
- Relatively safe procedure
- Diagnostic for a number of conditions
- Allows collection of samples
- Allows removal of foreign material
- Obtain material for bacteriology, mycoplasma, cytology, bronchial brushes, transbronchial biospy / brushings
- Assesment of airways – tracheal / bronchial tears, trachealbronchial, or bronchialoesophgeal fistulas, lung lobe torsion, tracheal / bronchial collapse
- Assessment of airway injury – noxious gases, aspiration pneumonia
- Removal of FB, suction aspirated material, removal of viscous substances – mucus plugs in some cases aid diff intubation.
12
Q
Contraindications of bronchoscopy?
A
- Care with hyper-responsive airways
- e.g. cats with allergic bronchial disease
- Dogs with wheezing suggesting airway spasm
- Will have increased risk of spasm in airways that have a wheeze.
- Unstable cardiac failure / arrhythmias
- Care in those patients with tracheal obstruction
- Masses or FB in trachea are challenging in anaesthetics.
- In small patients, they can occlude a lot of the diameter of the airway, if they already have obstruction, this can be really bad.
- Haemorrhage – increased risk with:
- Pulmonary hypertension
- Uraemia
- Coagulopathies
- Neoplasia/gross lesions
- NB WHWT
- Tracheal obstruction –partial / complete stenosis / FB
- Important that in patients with wheezing or suspected hyperresponsiive airwyas
- Eg cats – bronchodilators before bronchoscopy to prevent bronchospasm.
13
Q
Treatments for Lower airway disease?
A
- Inhaled medications (directly)
- Corticosteroids
- Bronchodilators
- Nebulisers
- Oral therapy
- Anti-inflammatories
- Corticosteroids, NSAIDs, anti-leukotrienes
- Bronchodilators
- Terbutaline
- Theophylline
- Anti-inflammatories
- Antibiotics, anthelminthics
- Mucolytics – N-acetyl cysteine (NAC)
14
Q
Example of inhaled bronchodilators
A
Salbutamol (ventolin)
- Beta 2 agonist
- Fast onset of action
- Lasts >3hrs
- Cleared renally following metabolism in tissues and blood.
- 10-20% inhaled reaches lower airways
- SE: tachycardia, arrhythmias, tremors
Absorbed from lower airways into the pulmonary tissue and circulation, then metabolised by liver or excreted in urine as drug. Rest of drug deposited in orophaynx as is swallowed. Absorbed by GIT and high first passs metabolism
15
Q
Example if inhaled glucocorticoids
A
- Fluticasone propionate
- Flixotide in UK
- Slowly absorbed from lung
- Long dwell time in lungs
- Rapid first pass metabolism in liver
- Less systemic side effects
- Long half life
- Least bioavailable
- Side effects
- Oral infections e.g. candidiasis, coughing, wheezing
- Side effects oral thrush, coughing and wheezing (minimized with concurrent use of bronchodilator), using space and washing mouth afterwards reduces risk.
