1.1.4: Feline asthma and chronic bronchitis Flashcards
Signalment for feline asthma
Young adult to middle aged cats; but can affect cats of any age
* Older cats -> more suspicious of other diseases e.g. neoplasia, cardiac disease, hyperthyroidism
* Younger cats -> more suspicious of infectious diseases
History and clinical signs associated with feline asthma
- Lower airway disease in cats is variable in presentation
- Usually low grade, chronic disease
- Sometimes “acute on chronic” emergency presentation
Clinical signs
* Coughing (dry, harsh cough)
* Audible wheezing
* Exercise intolerance (less playful, reluctance to jump or play, being lazy etc.)
* If emergency presentation: acute development of clinical signs such as resp distress, mouth breathing, tachypnoea
Questions to ask when you suspect feline asthma
- Any trigger factors (these are rare) e.g. environment, new cat litter, passive smoking, seasonal?
- Is the cough productive?
- Is anything brought up? (Often confused with hairballs)
- Any significant weight loss, anorexia -> helps w/ other differentials e.g. heart failure, neoplasia
Discuss your approach to clinical exam of cat with breathing problems / history of a cough
These cats have minimal respiratory reserve and are easy to destabilise. If you stress them you can kill them.
* Initial exam: hands-off
* Remember transport to vets / being in consult room may be stressful
* Prioritise oxygenation - this is low risk and high benefit. Ensure cat does not overheat in an oxygen cage.
* Watch breathing
* Auscultate and listen for expiratory wheeze
* Auscultate and listen to heart rate, rhythm, check for murmurs etc. Remember that cats with heart disease may not have signs on auscultation!
You suspect a dyspnoiec cat to have heart disease such as HCM. On clinical exam, you find the cat is open-mouth breathing and stressed. On auscultation, there is no heart murmur. How does this alter your primary differential in this case?
- Not all cats with heart disease have murmurs!
- You cannot necessarily rule out HCM based on this finding alone - consider an echo / TFAST.
- It would be sensible to reduce stress and provide oxygen to this cat before further diagnostics
Signs of upper airway disease
Laryngeal disease
* laboured inspiration (stridor, increased effort, slow inspiratory phase)
* ± change in purr or vocalisation (in dogs, bark becomes more high pitched)
- Dysphagia ± salivation
- Coughing/ gagging might be triggered by eating or drinking
- Head shaking or behavioural signs may suggest nasal disease
Signs of lower airway disease
Often more subtle than upper airway disease.
* Laboured expiration: prolonged expiratory phase, additional expiratory push, audible expiratory wheeze
* Increased airway resistance due to bronchospasm, mucus, and bronchial wall thickening
* Occasionally may see paroxysmal cough (owners may think it’s a furball)
When does bronchial wall thickening occur and how long does it last?
- Bronchial wall thickeneing occurs with repeated / prolonged lower airway disease
- Over time, this becomes permanent
Characteristics of feline asthma
- Reversible
- Occurs secondary to inhaled allergen and airway hyperreactivity
- There is bronchoconstriction
- There is eosinophilic airway inflammation
Clinical signs of feline asthma
- Episodic resp distress
- Dyspnoea
- Coughing
Clinical signs of chronic bronchitis
- Coughing is a key feature
Characteristics of chronic bronchitis
- Occurs in response to infectiion or inhaled irritants
- There is airway damage and excess mucus
- There is neutrophilic airway inflammation
True/false: feline asthma and chronic bronchitis are two distinctly different conditions.
False: it is basically a continuum between the two. They can be difficult to diagnose and overlap in presentation. They are also managed in similar ways.
What is air trapping and how could a cat with lower airway disease develop a pneumothorax?
Air trapping: trapping of air behind mucus and constricted airways, causing destruction of the alveoli.
* In rare cases, alveolar damage is so bad that leakage of air occurs (pneumothorax)
True/false: spontaneous rib fractures may be seen in cats with chronic lower airway disease.
True
Why do cats with lower airway disease present with dyspnoea?
- Acute bronchoconstriction in response to a trigger factor
- Inflammation of the bronchial mucosal lining with histamine and leukotriene release
- Hyperreactivity of the bronchial smooth muscle in a Type ! hypersensitivity reaction. There is mucociliary imbalance.
Airway obstruction occurs due to bronchoconstriction, inflammation, and mucus plugs in the narrowed bronchioles.
True/false: lack of eosinophilia on haematology means feline asthma can be ruled out.
False
We may see an inflammatory haemogram inclduing eosinophilia in a cat with feline asthma. However, absence of eosinophilia does not mean we can rule out feline asthma.
Differentials for coughing in cats
- URT disease
- Inflammatory lower airway disease
- Infectious cause: bacterial, viral, parasitic
- Foreign body
- Neoplasia
- (Heart disease rarely causes coughing in cats; would expect them to present with dyspnoea).
Where is oedema formation typically in cats with heart failure and how does this impact their presenting signs?
- Oedema is in pleura or abdomen
- Even in there is alveolar oedema, cats tend not to cough
- Tend to present with dyspnoea
Differentials for hyperpnoea / tachypnoea in cats
- Stress / pain / fear
- Cardiac disease (causing pleural effusion / pulmonary oedema)
- Resp disease (airways, lung parenchymal disease)
- Pleural space disease
- Mediastinal disease
- Ruptured diaphragm
- (Pericardial peritoneal diaphragmatic hernia - usually congenital and animals are fine)
- Anaemia / hypovolaemia
- CNS disease
- Heatstroke
When might you do a faecal analysis in a cat presenting with lower airway disease?
- When suspicious of Aelurostrongylus abstrussus
What might you need to take into account if performing bronchoscopy / BAL on a cat with asthma?
- Take care - the airway is already hypersensitivie
- You could cause severe bronchospasm
When might you perform a trans-tracheal wash in a cat?
Never.
The risk of iatrogenic damage is too great.
Could instead perform an endotracheal wash.
True/false: it is important to obtain a definitive diagnosis before treating the cat with dyspnoea.
False
You may choose to pursue a treatment trial (e.g. for feline asthma) if the cat is unstable and further investigations are risky, or if finances are limited.
