Dyspnea (Trouble Breathing) in Dogs

Overview of Dyspnea (Trouble Breathing) in Dogs

Respiratory distress, often called dyspnea, is labored, difficult breathing or shortness of breath that can occur at any time during the breathing process, during inspiration (breathing in) or expiration (breathing out). When your dog has trouble breathing, he may not be able to get enough oxygen to his tissues. Additionally, if he has heart failure, he may not be able to pump sufficient blood to his muscles and other tissues. Dyspnea is often associated with accumulation of fluid (edema) in the lungs or the chest cavity (pleural effusion). This fluid can lead to shortness of breath and coughing.

Causes

• Heart disease or heart failure
• Lung disease
• Tumors or cancer in the lung or which press on the airway
• Infections such as pneumonia)
• Obstructions that occlude the airway
• Trauma
• Bleeding into the lungs or chest
• Abnormal fluid accumulation in/or around the lungs from various causes including heart and lung disease
• Infectious tracheobronchitis (kennel cough) is common in dogs that have been boarded or kenneled, and intact (non-spayed) female dogs are predisposed to breast cancer (metastatic mammary carcinoma). Younger animals are more likely to develop lung infections. In addition, certain breeds are predisposed to some of the conditions that cause dyspnea. For example:
• Brachycephalic breeds (short faced breeds such as bulldogs and Boston terriers) are predisposed to upper airway problems, such as narrowed nostrils, laryngeal paralysis, and elongated soft palate, where they have trouble getting air into their airways. Of course, brachycephalic breeds often have noisy breathing because of the shape of their face and neck, but respiratory difficulty may be exacerbated and become serious when the animal is exposed to the stress of hot or humid weather, undergoes anesthesia, has a fever and/or is excessively excited.
• Boxer and bracycephalic breed dogs are predisposed to tumors that arise near the heart (called heart base tumors) and lung tumors.
• Large and giant breed dogs (e.g. Doberman pinschers, Great Danes) are predisposed to acquired cardiomyopathy and congestive heart failure (CHF).
• Small breed dogs are predisposed to tracheal collapse, chronic bronchitis and chronic mitral valve disease, which is a condition in which the heart valves do not function normally.
• Toy breeds are predisposed to tracheal collapse.

What to Watch For

• Coughing
• Shortness of breath
• Difficulty breathing
• Weight loss
• Fatigue

Diagnosis of Dyspnea in Dogs

Diagnostic tests are needed to determine why your pet is having trouble breathing. Tests that may be performed include:

• A complete medical history and physical examination with emphasis on stethoscope examination (auscultation) of the heart and lungs
• A chest radiograph (X-ray)
• Measurement of blood pressure
• An electrocardiogram (EKG)
• Ultrasound examination of the heart (echocardiogram)
• Laboratory (blood) tests

Treatment of Dyspnea in Dogs

The treatment for dyspnea depends upon the underlying cause. Often, treatment is initiated to help stabilize your pet and allow him to breath easier while tests are being performed to determine the underlying cause. This treatment may include:

• Hospitalization with administration of oxygen
• Minimizing stress
• Thoracentesis, which is drainage of fluid that has accumulated around the lungs (pleural effusion) with a needle
• Diuretics. A “water-pill” such as the drug furosemide (Lasix®) or spironolactone may be administered or prescribed
• Combination drug therapy. If heart failure is suspected, treatment with oxygen, a diuretic such as Lasix, and nitroglycerine ointment is often initiated
• The drug digoxin (Lanoxin®, Cardoxin®) may be prescribed in some situations

Home Care

Dyspnea is usually an emergency. See your veterinarian immediately. When you first note that your pet is having trouble breathing, note his general activity, exercise capacity and interest in the family activities. Keep a record of your pet’s appetite, ability to breathe comfortably (or not), and note the presence of any symptoms such as coughing or severe tiring.

Optimal treatment for dyspnea requires a combination of home and professional veterinary care. Follow-up can be critical and may include the following:

• Never withhold water, even if your pet urinates more than normal, unless specifically instructed to do so.
• Administer all veterinary prescribed medication as directed and be certain to alert your veterinarian if you are experiencing problems treating your pet.
• Schedule regular examinations with your veterinarian. This will include an interview regarding your pet’s clinical symptoms and quality of life. Be prepared to answer questions about your pet’s activity, appetite, ability to sleep comfortably, breathing rate and effort, coughing, exercise tolerance and overall quality of life.
• Bring your medications with you to show your veterinarian. Dosing is critical for heart medication. If your pet is on digoxin, your veterinarian may want to measure levels of that drug in the blood to make sure that the appropriate amount is being administered.

In-depth Information of Trouble Breathing in Dogs

The causes of respiratory difficulty can be classified as follows:

• Infections. Pneumonia or infection of the lung can lead to symptoms that are similar to those of dyspnea. Heartworm disease, a parasitic infection of the heart and blood vessels of the lung, must be excluded as a possible diagnosis. This infection can lead to lung injury as well as dyspnea.
• Inflammatory diseases of the lungs and airways such as chronic bronchitis. This is similar to a smoker’s cough. The cause of most canine bronchitis is not known but treatment is different than for other causes of dyspnea.
• Lesions causing airway obstruction or compression
• Trauma
• Diseases of the lung tissue. These include edema, hemorrhage, pneumonia, cancer and fibrosis.
• Tumors of the mediastinum, which is the area between the left and right lungs. These tumors can cause symptoms that resemble those of dyspnea.
• Fluid surrounding the lungs (pleural effusion). When fluid accumulates within the chest cavity, it can cause shortness of breath. Pleural effusion is a common problem in dogs.
• Diseases of the heart and blood vessels of the lungs.
• Other causes of altered respiration include: metabolic diseases, neurologic disease, steroid or drug (for example, phenobarbital) administration, ingested toxins and drug reactions.
• A detailed list of potential causes of dyspnea include:

Mechanical Disorders Causing Airway Obstruction

• Obstructed nostrils or nasal cavity
• Pharyngeal (throat) disorder, such as post-nasal drip, overlong soft palate, pharyngeal polyps (cysts)
• Hair, hairballs or foreign bodies
• Laryngeal (voice box) diseases, including paralysis; granuloma, polyp or tumor; trauma; edema (abnormal accumulation of fluid in tissues)
• Aspiration of liquid or solid into the lungs
• Tracheal (windpipe) diseases. Collapse or hypoplasia (incomplete development of trachea), foreign body, trauma/hematoma (blood clot), compression from thyroid mass lesion
• Primary bronchial collapse (collapse of airways)
• Bronchial compression from hilar lymphadenopathy
• Bronchial foreign body
• Trauma to the bronchopulmonary tree

Non-infectious Inflammatory Causes

• Bronchitis. Idiopathic (occurring without known cause), allergic
• Bronchiectasis, which is chronic dilatation of the bronchi and bronchioles with secondary infection
• Pulmonary granulomatosis, which is a collection of tumor-like masses in the lungs
• Pulmonary infiltrates (foreign bodies in the lungs) with eosinophilia (collection of specific white blood cells in the blood)
• Inhalation of noxious gases or smoke
• Alveolitis (inflammation of the walls of the alveoli in the lungs) leading to pulmonary fibrosis

Infectious Causes of Respiratory or Thoracic Disease

• Viral, including infectious tracheobronchitis, viral pneumonia
• Rickettsial infections, which is a type of parasite
• Bacterial infections, including pharyngitis (infection of the voice box), tonsillitis (infection of the tonsils), bronchitis (infection of the breathing tubes/airways), pneumonia, lung abscess (growth, cysts and tumors)
• Mycoplasma pneumonia
• Toxoplasmosis, which is a contagious disease caused by a parasite
• Systemic mycosis, which is any disease caused by fungi, including histoplasmosis, blastomycosis and coccidioidomycosis
• Osleri osleri, including nematodes and traveling parasites
• Lungworms
• Larval migrans, which is migration of parasites through the lung
• Dirofilariasis, which is infection with heartworms

Other Causes to Trouble Breathing in Dogs

• Bronchopulmonary dysplasia, which is abnormal development of adult cells
• Acidosis
• Anemia, hypoxemia or hemoglobin abnormality
• Neurologic (brain, spinal cord) lesions that alter ventilation
• Neuromuscular weakness or disease
• Rupture or paralysis of the diaphragm, including diaphragmatic hernia
• Flail chest or rib fractures
• Severe ascites or abdominal space occupying lesion
• Drugs, such as steroids that may cause panting, phenobarbital, preservatives in injectables

Lung Disorders

• Pneumonia
• Pulmonary edema from electrocution, airway obstruction, seizures, smoke inhalation, aspiration of gastric contents into the lungs, pulmonary embolism (the sudden blocking of an artery by a clot or foreign material), heartworm thrombus, drug reaction, uremia (an excess of waste products in the blood when the kidneys are not working properly) and DIC (disseminated intravascular coagulation)
• Pulmonary hemorrhage (heavy bleeding into the lung) from trauma; rodenticide coagulopathy, which is a disorder of blood coagulation due to ingestion of rodent poison; DIC; disseminated pulmonary neoplasia (tumor)
• Pulmonary fibrosis (scarring of lung tissue)

Tumors and Mass Lesions

• Nasal tumor
• Pharyngeal/tonsillar tumor or polyps
• Laryngeal tumor or polyp
• Chondromatous hematoma of the trachea
• Tracheal adenocarcinoma (cancer)
• Lymphoma (cancer of lymphoid tissue) in the respiratory tree, lung, mediastinum or lymphatics
• Thymoma (disease or cancer of the thymus)
• Primary lung tumors (carcinomas)
• Metastatic (pertaining to the transfer of disease from one organ or part to another not directly related to it) lung tumors
• Cardiac or heartbase tumors

Cardiac and Vascular Diseases

• Left bronchial compression from left atrial dilatation
• Left-sided congestive heart failure (pulmonary edema and/or pleural effusion)
• Heartworm disease (canine)
• Pericardial disease (disease of the sac enclosing the heart and the roots of the great vessels)
• Heartbase tumors
• Pulmonary thromboembolism (blood clot in the lungs)
• Air embolism (e.g. with IV lines or urinary negative contrast studies)

Diseases of the Mediastinum and of the Pleural Space

• Mediastinal mass, which is a mass in the tissues and organs separating the two lungs, including lymphoma, thymoma and teratoma
• Thymic hemorrhage
• Hilar lymphadenopathy (disease of the lymph nodes) with bronchial compression. These include mycosis (any disease caused by fungi), granulomatous lung diseases, lymphoma and other neoplasms.
• Pleural effusion caused by:
• – Congestive heart failure (CHF)
  – Hydrothorax (fluid in the pleural cavity that encases the lungs and thoracic cavity)
  – Chylothorax (milky fluid in the chest)
  – Hemothorax (collection of blood in the chest)
  – Pyothorax (accumulation of pus in the chest)
  – Pneumothorax (entry of air into the chest)
  – Metastatic neoplasia (tumor)
  – Pleuropneumonia (pneumonia accompanied by inflammation of the pleura)
  – Pulmonary embolism
  – Diffuse lymphatic dysplasia
  – Protein losing enteropathy (disease of the intestine)
  – Idiopathic pleuritis
  – Idiopathic pleural effusion

A complete medical history and physical examination should be performed by your veterinarian. These diagnostic tests depend on the duration of signs, presence of other abnormalities, and what is found on the physical examination. They may include:

• Complete medical history and physical examination with emphasis on stethoscope examination (auscultation) of the heart and lungs. Identification of abnormal heart sounds such as heart murmurs or irregular heart rhythms (arrhythmia) is extremely important. During physical examination, your veterinarian will pay particular attention to your pet’s breathing, the character of his/her heart and lung sounds, and mucous membrane color. Care must be taken not to stress your dog during the examination. Your dog should also be evaluated for weight loss and any concurrent disease.
• Your veterinarian will want to know the following:
• What medications your dog has been taking?
• Is there a history of illness and if so, did your pet respond to therapy?
• Has your dog has been anesthetized recently?
• Is your dog intact or spayed?
• Does your dog cough?
• What circumstances make the breathing worse?
• Has your dog ever had heartworms and are you giving preventative medication?
• What is your dog’s home environment and travel history?
• Has there been any exposure to toxins (such as rat poison)?
• Has your dog had any trauma?
• Does your dog vomit or gag?

Diagnosis In-depth

Diagnostic tests to determine why a dog may have trouble breathing may include:

• A chest radiograph (X-ray) to identify heart enlargement and fluid accumulation in the lung and to exclude some of the previously mentioned conditions that can mimic dyspnea.
• Measurement of blood pressure with the special device that measures blood flow noninvasively. High and low blood pressure values may be identified because either can occur in patients with dyspnea.
• An electrocardiogram (EKG) to identify heart enlargement and determine the electrical activity of the heart. The electrocardiogram is a noninvasive test done by attaching small contact electrodes to the limbs and body.
• Ultrasound examination of the heart (echocardiogram) for a definitive diagnosis. This noninvasive test requires sophisticated equipment that creates high frequency sound waves much like the sonar of a submarine. An image of the heart is created. The echocardiogram is usually the test of choice to establish the final diagnosis of the cause of dyspnea, but this examination may require referral to a specialist.
• Laboratory (blood) tests to evaluate other organ function, such as the kidney, and exclude anemia as a complicating factor. This can be critical to evaluating the effect of dyspnea on other organs and to monitor the effects of treatment.
• A blood test to detect heartworm infection
• A complete blood count (CBC) and serum biochemistry in sick or older animals.
• Your veterinarian may recommend additional diagnostic tests to ensure optimal medical care. These are selected on a case-by-case basis if indicated from the examination, prior test results or lack of response. Tests may include:
• Serologic tests for toxoplasmosis and systemic fungi
• Respiratory cytology and culture if clinical signs and prior laboratory test results do not explain dyspnea with abnormal densities in the lungs. Samples for culture and respiratory cytology (characterizing the cells by looking at a sample under a microscope) may be obtained by using one of the five methods listed below; the method of choice depends on your veterinarians experience, availability of supplies and equipment, and nature of the lung disease.
• Tracheal aspiration (removing a fluid sample using suction)
• Bronchoscopy to obtain samples for culture and cytology and to provide a visual examination of the trachea and bronchopulmonary tree
• Bronchoalveolar lavage (BAL), performed through a wedged bronchoscope, if no exudate (fluid high in protein) is observed in the trachea and main bronchi
• A fine needle aspirate (FNA) of the lung is an alternative for assessment of the dyspneic patient with some types of lung disease.
• Endoscopy. This direct visualization of the upper airways, trachea and bronchi is indicted when intraluminal masses, foreign body, Osleri osleri (a type of traveling parasite) nodules or other causes of unexplained airway obstruction or inflammation are suspected.
• Biopsy of the lung (by thoracoscopy or mini-thoracotomy). This test is sometimes the only method for attaining a diagnosis in disseminated pulmonary disease, especially interstitial disorders, unexplained by previous less-invasive test results. When a singular localized lung lesion is evident and either a foreign body or tumor is suspected consider surgical removal of the affected lobe.
• Direct fecal smears and special sedimentation methods (Baerman), along with fecal flotation to screen for lungworms, in pets that have radiographs that are compatible with lungworm infection
• Fluoroscopy or endoscopy to demonstrate dynamic collapse of a major airway when it cannot be shown by routine X-ray films
• Cytologic evaluation of conjunctival membranes (for distemper inclusions), skin ulcers (for systemic fungi) and enlarged lymph nodes (for infection or tumors)
• Esophagoscopy to diagnose esophageal-tracheal fistula or causes of aspiration pneumonia
• Specialized blood tests, such as blood taurine, in cases of dilated cardiomyopathy
• Thyroid tests to exclude abnormal function of the thyroid gland
• Blood cultures in suspected infection of the heart valves
• Consultation with appropriate specialists as needed

Definitive therapy is always dependent on establishment of a diagnosis. Since there are numerous potential causes of dyspnea, it is necessary to identify a specific cause to provide optimal therapy. Goals in therapy may include improving heart function, preventing fluid accumulation, preventing further deterioration of the heart muscle and antagonizing chemicals and hormones produced in excessive quantities in dyspnea. Rarely is it possible to cure heart disease.

The most important causes of dyspnea in dogs are valve degeneration and cardiomyopathy (heart muscle disease). Definitive treatment likely would require valve replacement (which is rarely done in dogs) or heart transplantation (not done currently).

Dyspnea caused by fluid accumulation in the sac around the heart (pericardial effusion) is not treated by drugs but instead requires drainage of the fluid or removal of a portion of the pericardial membrane. Congenital (present at birth) heart defects should be referred to a specialist for management.

Animals with respiratory distress must be handled with care because struggling can result in respiratory arrest.

Treatment In-depth

Initial treatments may include:

• Minimize stress and handling
• Provide oxygen and cage rest
• Mild sedation
• Remove fluid or air from the chest cavity (thoracentesis) if present in large quantities
• Perform tracheal intubation and ventilation if life-threatening dyspnea is evident and respiratory arrest is imminent
• Administer furosemide (Lasix®), oxygen and possible vasodilator therapy (Nitroglycerine®) for pulmonary edema
• Treat acute dyspnea of infectious origin with rest, inhalation of humidified air and antibiotics if bacterial infection is suspected. Maintenance of hydration is essential and administration of certain drugs, such as expectorants and bronchodilators, might be useful in bronchitis and pneumonia.