Coughing in SA SDL Flashcards
What is the cough reflex and what factors trigger it?
Coughing is a normal function that serves to expel secretions from the airways, prevent inhalation of material into the airways and delay entry of material deeper into the lungs.
Extremely important mechanism in the protection of the respiratory system. Hence, raises the issue of control of coughing in disease situations, where the benefits of coughing might outweigh the benefits of suppressing the cough.
Mechanism of cough:
Relies mainly on the mucociliary escalator to move airway secretions rostrally to contact cough receptors concentrated at airway bifurcations. This stimulates the cough reflex and the material is expelled.
The reflex instigates a deep inspiration and then a forceful expiration against a closed glottis, resulting in high airway pressure.
The glottis is opened suddenly and the marked pressure difference between the airways and the oral cavity forces material out.
In most cases, the expelled material is immediately swallowed. In some cases, there is retching at the end of coughing and the patient may expel a white frothy material.
Need to be able to determine if patient is coughing, gagging, chocking or retching. Can elicit the coughing reflex in the consult room by compressing the trachea at the thoracic inlet and asking the owner to confirm that this is what they have heard.
Causes of coughing?
Coughing is caused by activation of the cough receptors due to: Airway inflammation
Acute tracheobronchitis, parasitic tracheobronchitis and chronic bronchitis.
Airway secretions
Bacterial bronchopneumonia
Airway compression
For a primary lung tumour to cause coughing, it must be large enough to compress a large airway at end-expiration. Suggesting that a cough in this instance is indicative of a relatively long standing disease.
Is a cough from cardiac or respiratory origin?
Can be either.
Can be from a cardiac or respiratory origin.
Certain useful clinical features, such as the presence of a murmur or arrhythmia, increase the likelihood that coughing in a dog is cardiac in origin.
The breed and size of the dog can be a useful discriminator because smaller dogs are more likely to cough with heart disease than larger breeds, and small dogs are also more likely to have tracheal collapse.
The presence of sinus arrhythmia would suggest that the cough is respiratory and not cardiac in origin . Alternately, if there is an arrhythmia, particularly sinus tachycardia or atrial fibrillation, the cough should be considered of cardiac origin until proven otherwise. The presence of a loud left apical heart murmur (indicating mitral valve disease) should also raise suspicion that the cough is cardiac in origin, although if the dog has a sinus arrhythmia, the murmur is more likely to represent compensated endocardiosis and the cough is probably respiratory in origin.
When an arrhythmia, murmur and other signs of left-sided CHF are present, the cough is most likely to be cardiac and appropriate therapy for CHF should be considered. If the cough subsides, this would support a cardiac cause. Persistence of the cough does not exclude a cardiac cause; however, it indicates that concurrent respiratory disease should be considered.
Thoracic radiography (see Chapter 6) is of immense value in determining whether a cough is of cardiac origin. Right lateral recumbent and dorso- ventral (DV) views should be inspected for evidence of left ventricular and left atrial enlargement. This includes measuring the vertebral heart score (VHS) for evidence of cardiomegaly, identifying straightening of the caudal border of the heart, loss of the caudal waist, elevation of the distal portion of the trachea and the mainstem bronchi, splitting and/or compression of the mainstem bronchi, elevation of the caudal vena cava (right lat. Recumbent view)
Questions to ask an owners who brings a dog in with a history of a chronic cough?
What is the dog’s body condition? Has she lost weight?
Is the dog up to date with vaccinations including kennel cough?
Has she been in kennels recently or prior to the initiation of the cough?
Has the dog travelled abroad or within the UK recently? – think parasitic lung disease
What is the exact nature of the cough? Dry, honking, productive?
Is it worse at different times of day?
Is it worse at rest or exercise?
Is appetite/thirst normal?
Any other signs e.g. regurgitation (what is the relevance of this)?
Is it progressive?
Has the nature of the cough changed?
Has she ever suffered collapsing or syncopal episodes?
Have the owners any other dogs and are they affected?
DDx for chronic cough?
Heart disease
Collapsed trachea
Inhaled FB
Kennel Cough (dry cough)
Parasitic tracheobronchitis (Angiostrongylus - lungworm of dogs, Dipylidium caninum)
Chronic bronchitis
Tumour - lung
Bacterial broncho-pneumonia but would expect airway secretions (check hx/PE)
Congenital abnormality
Upper airway differentials for a cough?
Upper airway: nose, larynx and pharynx
Problems in this area are more likely to lead to retching and gagging than a true cough, but some can lead to sequale, especially aspiration, which could cause a cough. The following are worth consideration:
Degenerative: Laryngeal paralysis leading to secondary aspiration pneumonia
Neoplastic:masses of the pharynx or larynx typically cause more stertor, stridor, dyspnoea or retching than a cough but some owners may present these to you as a “cough”.
Inflammation/infection:You might see a dry retching cough again from infection or severe inflammation in this area, but again a true cough would be unusual.
Trauma: A stick injury to this location may again cause gagging but not a true cough.
Trachea differentials for a cough?
The trachea is a common site of origin for coughing which is typically paroxysmal, dry and non-productive - it may be described in many cases as being like a goose honk.
Degenerative: Tracheal collapse is a common cause of a dry, retching cough in small breed and some larger breed dogs.
Anomalous: Ciliary dyskinesia is rare but possible as a differential.
Neoplastic: Tracheal masses are really rare but could well make an animal cough if they compress the lumen.
Infectious/inflammatory: There are several bacterial, viral and parasitic ones which go in here including Bordetella bronchoseptica, Canine parainfluenza virus, and Oslerus osleri - look on WikiVet for more information about these.
Trauma: tracheal traumas such as ruptures and avulsions may cause a cough but more commonly cause dyspnoea and emphysema. Foreign bodies in the airway can certainly cause a cough however.
Bronchi and bronchioles differentials for a cough>
There are cough sensors all the way down here so any pathology in this site could lead to a cough which is triggered by material in the airways, compression from externally or a collapse of the bronichi.
Diseases that can cause alveolar pattern on radiograph?
Left sided heart disease
pneumonia,
coagulopathies and
tumours
Do you see a cough with pleural disease?
Pleural disease is a rare cause of coughing - it much more commonly leads to shallow breathing and dyspnoea so should not really be on your differential list.
What lung pattern can you see?
Alveolar in the right middle lung lobe. caused by bronchopneumonia
