Contributors: Brendan M Corcoran, Yolanda Martinez Pereira

 Species: Canine   |   Classification: Miscellaneous


  • Patients with respiratory disease can present with a variety of clinical complaints such as coughing (most common), sneezing Sneezing , other upper airway noises often referred to as reverse sneezing, nasal/ocular discharge Rhinitis , decreased exercise tolerance, abnormal respiratory noise (stridor and stertor), abnormal breathing pattern, breathlessness, increased panting, collapse Collapse , acute respiratory distress Acute Respiratory Distress Syndrome (ARDS) , dyspnea, cyanosis.
  • Coughing is the most common complaint and can be classified as acute or chronic:
  • Dyspnea is also a common complaint and can be further classified as inspiratory or expiratory:
  • Abnormal respiratory noises can help in identification of the abnormal anatomical area:
    • Inspiratory stertor usually indicates a nasal problem.
    • Inspiratory stridor is usually associated with problems in the larynx (eg laryngeal paralysis).
    • Reverse sneezing is usually associated with problems in the nasopharynx (eg foreign body).
  • Nasal discharge can be bilateral or unilateral, and the discharge can be serous, hemorrhagic, mucoid, purulent:
    • Unilateral nasal discharge can be associated with foreign body, neoplasia, nasal aspergillosis Nasal aspergillosis/penicillosis.
    • Bilateral nasal discharge is more likely associated with lymphocytic-plasmacytic rhinitis (LPR), aspergillosis, neoplasia Nasal cavity: neoplasia.
  • Cyanosis is characterized by a bluish color on the mucous membranes and is due to a low percentage of saturation of hemoglobin with oxygen (which is an increased amount of the reduced form of hemoglobin) or to the presence of metahemoglobin. In anemic patients, cyanosis may not appear obvious due to the decrease amount of hemoglobin in blood. Cyanosis can be central or peripheral and may be intermittent or persistent. A patient with cyanosis represents a true respiratory emergency.
  • Some respiratory diseases have been described more commonly in some breeds, such as:

History taking

Identification of the primary problem

  • The history, combined with the information obtained from the physical examination should help the clinician to indentify the primary problem/s, so a differential diagnosis list and a protocol for investigation can be formulated. Attention must be paid to rule out a cardiovascular explanation for the clinical presentation.

Background history

  • The age of the patient should be recorded, as infectious respiratory diseases are more likely in young patients, whereas neoplastic conditions will be more likely in older or geriatric patients.
  • If multi-pet households, the clinician should enquire if any respiratory clinical signs have been noted in other pets (eg kennel cough is highly contagious).
  • The vaccination and worming state should be recorded, with special attention to ascertain if the worming product used is active against the lungworm parasites. Preventative treatment for dirofilariosis Canine cardiopulmonary dirofilariasis in endemic areas and travel history should be enquired.
  • It is important to obtain information about the environment:
    • Vegetal foreign bodies may be more common in rural environments.
    • Exposure to inhaled irritants (eg house refurbishing) might lead to airway inflammation.
    • Foxes in the locality and contact with slugs etc may predispose to lungworm infection Angiostrongylosis.
  • History of previous diseases and/or traumas should be collected (eg patients with history of mammary gland tumor Mammary gland: neoplasia removal may show metastatic lung disease at a later stage), even if several years have passed.
  • Collection of information regarding current medication, as well as clinical response to previous treatments (eg chronic coughing over years that improves with steroid treatment is more likely to be due to underlying respiratory disease than cardiac disease).
  • It is important to obtain information regarding the level of activity of the patient, as it will help interpreting the severity of clinical signs such as decreased exercise tolerance, eg decreased exercise tolerance is likely to be less noticeable in patients that only go out for short walks on the lead versus patients that have a more active routine of exercise.

History for specific complaints


  • Coughing is one of the most common complaints in patients with respiratory disease, but also in canine patients with cardiac disease.
  • In patients with respiratory disease, the coughing may be triggered by presence of mucus in the airways, by physical compression or mucosal inflammation.
  • Additional history to be taken in patients with coughing:
    • Is it productive, non-productive?
    • What's the frequency? - eg daily, nocturnal, etc.
    • What's the progression (acute coughing versus chronic coughing)?
    • Any triggers?
    • The clinician should try to differentiate coughing from other clinical signs such as gagging, retching, reverse sneezing, sneezing - the difference may not be obvious to the pet owner.

Abnormal respiratory noises

  • The clinician should try to obtain a description of the noise (owners can be encouraged to obtain a video of the abnormal noise):
    • Upper airway respiratory noise: occurs during inspiration:
      • Nasal stertor - may be accompanied with sneezing, nasal discharge.
      • Laryngeal stridor - may be accompanied with changes in barking or coughing triggered by eating or drinking in patients with laryngeal paralysis.
      • Snoring - common in patients with elongated soft palate Soft palate: elongated.
      • Lower respiratory noise:
        • Wheezes: inspiratory and expiratory.
        • Ronchi: inspiratory and expiratory.
        • Crackles: inspiratory only.

Physical examination

General examination

  • Patient demeanor and responsiveness, eg bright, alert and responsive.
  • Body condition score - a scale out of 9 can be used Body condition scores.
  • Assessment of the resting respiratory rate and the breathing pattern: inspiratory dyspnea, expiratory dyspnea, restrictive breathing pattern, paradoxical breathing pattern.
  • Lymph node palpation.
  • Assessment of mucous membranes: color (pink, pale, cyanotic, congested), moisture (dry, tacky, moist), CRT, presence of halitosis.
  • Assessment of pulses (femoral, peripheral): presence of pulse deficits, pulse quality.
  • Chest palpation: the apex beat is usually displaced caudally in patients with cardiomegaly, or muffled or displaced in patients with intrathoracic fluid or masses. In patients with loud murmurs (grade 5 and 6/6) a thrill is palpable over the point of maximum intensity of the murmur Murmur: overview.
  • Chest percussion Coupage : a fluid line might be noted in patients with pleural effusion. In pneumothorax thoracic resonance is increased, whereas it will be decreased in presence of lung consolidation or effusion.
  • Chest auscultation: should include cardiac and lung auscultation (see next)
  • Fluid thrill and hepatojugular reflux.
  • Abdominal palpation.

Respiratory examination and thoracic auscultation

  • In animals with nasal discharge:
    • Check nasal airflow patency with a piece of cotton wool or a chilled glass slide.
    • Check for facial asymmetries or facial pain on palpation.
    • Check ocular retropulsion.
  • The larynx and trachea should be palpated carefully - patients with respiratory disease are prone to cough on tracheal palpation. Dorso-ventral flattening of the trachea might be appreciated on palpation.
  • Respiratory auscultation:
    • Laryngeal and tracheal auscultation should be performed to help localizing upper respiratory tract noise (eg laryngeal stridor in laryngeal paralysis):
      • In brachycephalic breeds and dogs with any form of upper airway obstruction it is common to hear referred upper respiratory noise during lung auscultation.
    • Lung auscultation should cover the 4 quadrants of the chest (dorsally, ventrally, right and left).
    • Normal breath sounds (also known as bronchovesicular sounds) (should be present - and can be absent with pleural effusion, pneumothorax, presence of mass or lung consolidation Lung: atelectasis.
    • Adventitious sounds (abnormal) should not be present - if they are present they suggest underlying pathology:
      • Wheezes - air passing through narrowed airways (eg asthma).
      • Crackles - fine crackles can be heard in patients with severe pulmonary edema during inspiration; coarse crackles can be heard in patients with parenchymal lung disease such as interstitial fibrosis.
      • Rhonchi - can be found in patients with airway obstruction or where there is increased ventilatory demand requiring motre rapid and/or deeper breaths; they can be heard for example with presence of mucus in distal airways in patients with chronic bronchitis).
  • Cardiac auscultation:
    • Assessment of the audibility of the heart beat - muffled heart sounds can be found in patients with pericardial or pleural effusions, obesity Obesity , pneumothorax, pneumonia, intrathoracic masses Thorax: masses.
    • The heart rate and rhythm should be assessed and recorded. Normal rate and rhythm would suggest the presenting complaint is not due to cardiac disease:
      • Regular rhythm; with normal rate (sinus rhythm).
      • Sinus arrhythmia; so called irregularly irregular rhythm that might vary with phases of breathing (faster during inspiration, slower during expiration) with a normal rate.
      • Regular rhythm with bradycardia; sinus bradycardia or third degree heart block.
      • Irregular rhythm with tachycardia; atrial fibrillation or ventricular dysrhythmia/tachycardia.
    • The presence of murmurs should be noted, described and recorded, but their presence does not imply a cardiac cause for the clinical presentation Heart: disease - clinical investigation.
    • Intensity of the murmur:
      • Grade I - only heard in very quiet environment in a calmed patient, difficult to hear.
      • Grade II - very quiet murmur but can be heard clearly when in the right position.
      • Grade III - easy to hear but not louder than the cardiac sounds (S1, S2 or loop-doop).
      • Grade IV - easy to hear, louder than the cardiac sounds.
      • Grade V - loud murmur, a thrill can be palpated.
      • Grade VI - loud murmur, a thrill can be palpated and the murmur can be heard when the stethoscope is not touching the chest wall.
    • Timing:
      • Systolic - the most common murmur in small animals, caused by mitral/tricuspid valvular regurgitation and aortic/pulmonic stenosis.
      • Diastolic - less common murmur, found associated to aortic insufficiency or mitral/tricuspid stenosis. Can be a sign of endocarditis.
      • Continuous - found in conditions such as congenital patent ductus arteriosus.
      • To-and-fro - less common murmur, usually caused by complex congenital heart disease Congenital heart disease: overview.
    • Character:
      • Harsh or ejection murmur; typically due to a stenotic lesion.
      • Soft or regurgitant murmur.
    • Point of maximum intensity:
      • Left base.
      • Left apex.
      • Right side.
    • Presence of other abnormal heart sounds should be assessed such as:
      • Split S2 - found in patients with pulmonary hypertension (eg secondary to respiratory disease - cor pulmonalePulmonary Arterial Hypertension (PHT).
      • Gallop sound - relatively common in feline patients with cardiomyopathy and less frequently in dogs with cardiac disease.
  • Other parts of the physical examination are important in patients presenting with decreased exercise tolerance, as for example:

Diagnostic tests