SECTION 3 Respiratory System

Section Editor: Ronald M. Bright, DVM, MS, DACVS

Acute Respiratory Distress Syndrome

Allergic Bronchitis in Cats

Allergic Bronchitis in Dogs

Brachycephalic Syndrome

Laryngeal Collapse in Dogs

Laryngeal Paralysis

Laryngeal and Tracheal Neoplasia

Laryngitis and Tracheitis

Lung Lobe Torsion

Lung Tumors

Mediastinal Masses

Nasal and Nasopharyngeal Polyps in Cats

Nasal Tumors, Malignant

Pleural Effusion

Pneumonia, Aspiration

Rhinitis and Sinusitis in Cats

Rhinitis and Sinusitis in Dogs

Tracheal Collapse in Dogs

Tracheal Obstruction

Tracheal Trauma

Acute Respiratory Distress Syndrome

Ronald M. Bright, DVM, MS, DACVS

BASIC INFORMATION

TREATMENT AND FOLLOW-UP

Treatment Options

Oxygen therapy is necessary and may require unconventional methods of administration. Routine methods of oxygen supplementation (see the handout on Oxygen Therapy) may be inadequate in ARDS patients. If blood oxygen levels fail to rise with the use of routine methods, the animal may be anesthetized or heavily sedated, intubated, and placed on a mechanical ventilator; oxygen may then be piped into the lungs under positive pressure. The need for mechanical ventilation and intensive care may necessitate referral of your pet to a veterinary specialty center.

Intravenous fluids must be given carefully, because fluid readily leaves the circulation and moves into the lungs during ARDS. Diuretics may be used to remove excess water from the lungs; these drugs are usually helpful in the initial few days but are of no benefit later in the course. Corticosteroids may be tried, but their benefit is poorly defined. Treatment of the underlying or precipitating condition is also very important.

Follow-up Care

Intensive, continuous monitoring of respiratory rate and effort, blood oxygen levels, heart rate and rhythm, blood pressures, urine output, and other parameters is needed. Laboratory tests and chest x-rays are commonly repeated every 24-48 hours until the animal is stable.

Prognosis

Prognosis for ARDS is guarded (uncertain) to poor. Many animals die from the condition.

SPECIAL INSTRUCTIONS:

Allergic Bronchitis in Cats

Ronald M. Bright, DVM, MS, DACVS

BASIC INFORMATION

Description

Feline allergic bronchitis is inflammation of the lower airways (primarily bronchi). The inflammation is often complicated by narrowing of the airways (bronchoconstriction), which can greatly reduce the intake of oxygen.

Allergic bronchitis has two forms. The acute form (sudden onset, less that 3 months’ duration) is associated with reversible inflammatory changes and is also referred to as feline asthma. The chronic form (long-term, often intermittent signs) is associated with irreversible airway damage. It can eventually lead to emphysema, a debilitating disease that results from enlargement and dysfunction of the smallest airways in the lungs.

Causes

The acute form may be triggered by a hyperactive immune response to environmental irritants such as dust (including dust from kitty litter), molds, or smoke. In most cases, the specific inciting cause (allergen) is never identified. Mycoplasmal bacterial infections can trigger this disease in some cats.

Clinical Signs

Most cats are young to middle-aged when they are first affected. The cat usually appears healthy and has no systemic signs of illness. Wheezing and coughing are common signs. The cough can be mistaken for retching associated with hairballs. If signs are mild and intermittent, the cat may be normal between episodes.

Occasionally, episodes of breathing difficulty may progress to become severe and life-threatening. The cat may sit hunched over with the neck extended, trying to take in air. Panting and drooling may be noted. The gums may become blue (cyanotic) from inadequate intake of oxygen. Severe episodes may result in collapse and shock.

Diagnostic Tests

A tentative diagnosis may be made from the history and physical examination findings. Physical examination sometimes reveals severe respiratory distress, a “barrel-shaped chest” (from air being trapped within the lungs), and lung sounds that are typical for this condition. Many diagnostic tests are delayed in severely compromised cats until they are stable.

X-rays may or may not reveal changes compatible with allergic bronchitis but help to rule out other causes of coughing. Laboratory tests may be normal or may show evidence of an allergic response or secondary infection. Examination of airway secretions obtained by a tracheal wash or bronchoscopy often identifies inflammation and elevated numbers of white blood cells. The presence of eosinophils helps confirm the diagnosis. Bacterial culture and tests for heartworm and other parasites are often recommended.

TREATMENT AND FOLLOW-UP

Treatment Options

Cats in severe respiratory stress require hospitalization and intensive therapy with oxygen supplementation; injectable, rapid-acting corticosteroids; bronchodilators; and intravenous fluids. Once the cat becomes stable, long-term management is mandatory to control inflammation and prevent or minimize recurrence of the signs.

Long-term therapy includes continuation of steroids, which are given in tablet form or via an inhaler.

• High doses of steroids are used initially, then slowly decreased after the signs abate to the lowest dose that controls the disease. Abruptly decreasing or stopping the steroids may cause severe signs to recur.

• Injectable medications may be considered for cats that do not tolerate inhalant therapy or cannot be given oral medications. Injectable medications are often repeated every 2-8 weeks.

• Although the injectable form is convenient, it is not considered the best choice because of a higher risk for side effects. Some possible side effects are urinary tract infections, diabetes mellitus, and the development of refractory allergic bronchitis.

Cyclosporine may be substituted for corticosteroids in those cats that develop resistance to steroids or require large doses of steroids to control the signs. Cyclosporine blood levels must be adjusted to ideal therapeutic levels, so weekly blood tests are often needed until the target level is reached, and then periodically.

Bronchodilators such as albuterol, theophylline, or terbutaline are frequently given as tablets or via metered-dose inhalers. An antihistamine, cyproheptadine, may also be added. Efforts to reduce potential irritants and allergens in the cat’s environment are also very important.

Follow-up Care

Cats with severe signs often require intensive monitoring and hospitalization for several days. Recheck visits are scheduled after discharge. Most cats require periodic monitoring and adjustment of medications for the rest of their lives. Repeated testing may be needed in cats that do not respond to therapy or have recurrent signs.

Prognosis

Most cats respond favorably to therapy, with good control of the clinical signs. Long-term therapy is usually necessary, and occasional relapses are common. If the disease is not controlled, the development of progressive, irreversible changes in the airways and lungs is likely.

SPECIAL INSTRUCTIONS:

Allergic Bronchitis in Dogs

Ronald M. Bright, DVM, MS, DACVS

BASIC INFORMATION

Description

Allergic bronchitis is inflammation of the lower respiratory tract (bronchi) that results from exposure to some type of allergen that is inhaled or carried in the blood. The inflammation may also affect the trachea (windpipe).

Causes

Immunologic stimulation occurs, often from common environmental allergens such as:

• Dusts and molds

• Cigarette smoke

• Aerosol sprays

• Dust and grain mites

Parasites (heartworms) and fungal infections can also cause a hypersensitivity reaction in the airways.

Clinical Signs

Allergic bronchitis most often affects young to middle-aged dogs. It may be more common in obese dogs. Cough is a consistent sign. The cough is usually dry and nonproductive. It may be aggravated by exposure to cold temperatures, exercise, and pressure placed on the trachea or chest. Sometimes respiratory distress occurs, with wheezing and increased effort on expiration (breathing out).

Diagnostic Tests

Routine laboratory, heartworm, and fecal tests, as well as chest x-rays are often recommended to investigate potential causes of a cough. Chest x-rays may be normal or show findings consistent with bronchitis.

Analysis of secretions taken from the trachea and bronchus during a transtracheal wash may reveal a type of white blood cell, the eosinophil. Eosinophils are commonly present with allergic and parasitic diseases and occasionally are seen with fungal infections. The secretions may also be cultured for bacteria. Bronchoscopy, which involves the passage of a fiberoptic scope into the airway, may help eliminate parasites, foreign bodies, a collapsing trachea, or tumors as potential causes of the cough.

If allergic disease is suspected or confirmed, it is important to search for potential allergens in the household. Allergy skin or blood tests may be recommended in some cases. Blood tests for fungal infections may also be considered.

TREATMENT AND FOLLOW-UP

Treatment Options

Antibiotics are administered if a secondary bacterial infection is present. If a fungal disease is present, antifungal drugs are indicated. (See the handouts on Fungal Pneumonia and the specific fungal disease involved.) Corticosteroids are usually administered at high doses for 14 days, then slowly tapered. Bronchodilator drugs may be recommended if increased expiratory effort and wheezing are present. Steroids and bronchodilators may be given in oral form or through an inhaler, or both.

Humidification of the environment may help to decrease inflammation and improve clearance of secretions. If an allergen can be identified, it should be avoided or eliminated from the environment. Weight reduction is beneficial in some dogs. Some refractory cases, such as cases of chronic bronchitis or atopic (allergic) dermatitis, may require additional therapy.

Follow-up Care

Initially, close monitoring is needed to evaluate response to treatment and make alterations in medications to ensure that the signs are controlled. The goal of therapy is to aggressively treat the airway inflammation so that a chronic bronchitis does not develop. Notify your veterinarian if any signs recur, because acute relapses may develop that require adjustment of the medications.

Brachycephalic Syndrome

Ronald M. Bright, DVM, MS, DACVS

BASIC INFORMATION

Description

Brachycephalic syndrome occurs when anatomic and acquired abnormalities of one or several structures located in the upper respiratory tract result in partial airway obstruction. The abnormalities make it difficult for the animal to take in air, and progressive breathing problems develop. The syndrome affects primarily the flat-faced, short-nosed breeds of dogs (brachycephalics), which explains its name. Commonly affected breeds include the English bulldog, French bulldog, Boston terrier, pug, Pekingese, shih tzu, boxer, and occasionally other breeds. Rarely, it occurs in brachycephalic cats, such as the Himalayan and the Persian.

Causes

Signs of upper airway obstruction arise from one or a combination of the following conditions:

• Small openings of the nostrils (stenotic nares)

• Elongation of the soft palate

• Eversion or prolapse of laryngeal saccules of the voice box into the tracheal airway

• Underdeveloped, narrowed trachea (primarily in the English bulldog)

• Excessive soft tissue within the throat area that obstructs the airway

Enlarged and inflamed tonsils sometimes contribute to airway obstruction.

Clinical Signs

Because breathing is affected, increased noises are heard from the nose and throat, usually on inspiration (breathing in). Many dogs gag or cough, and some occasionally vomit. Panting is common. When the animal is relaxed or sleeping, loud snoring often occurs.

Some dogs have so much trouble breathing that their tongues and gums turn blue and they become overheated. Engaging in any exercise can cause the dog to collapse. Many affected dogs are obese.

Diagnostic Tests

The presence of these clinical signs in a short-faced breed may allow a tentative diagnosis. Checking for an elongated soft palate, everted saccules, collapse of the larynx, or other problems involving the larynx (such as laryngeal paralysis or the presence of a mass obstructing the opening of the larynx) can be done accurately only with the animal under heavy sedation or briefly anesthetized. Other abnormalities may be diagnosed during an oral examination.

X-rays of the chest help define any additional problems of the trachea (narrowed diameter, collapse) or lungs, as well as the presence of a hiatal hernia, which can accompany this airway problem.

TREATMENT AND FOLLOW-UP

Treatment Options

Emergency therapy may be necessary in a severely compromised animal. Sedation, oxygen therapy, lowering of the body temperature (if the animal is overheated) may all be needed, and possibly a temporary tracheostomy until corrective surgery can be done.

Conservative management in nonemergency cases includes weight loss, exercise restriction, and avoiding situations that may precipitate the respiratory problems (such as excitement or exposure to increased ambient temperatures). Conservative management must usually be followed (in a timely fashion) by surgical correction of the abnormalities to prevent worsening of the problem and development of secondary changes such as collapse of the larynx. In some dogs, esophageal problems, such as hiatal hernia, also require treatment.

Shortening of the soft palate, widening of the nasal openings, and correction of secondary changes in the laryngeal area are done ideally while the animal is young (6-18 months of age) to ensure a better outcome and to prevent any catastrophic respiratory event. Steroids may be given prior to surgery to prevent excessive swelling of the tissues in the throat after surgery. Other drugs may be given to prevent aspiration pneumonia postoperatively.

In high-risk patients (especially English bulldogs), a temporary tracheostomy may be done at the time of surgery and left in place for 24-48 hours postoperatively. This allows time for postoperative swelling to resolve and the airway opening to enlarge. If moderate to severe laryngeal collapse is present, a permanent tracheostomy that bypasses the larynx and provides a permanent opening in the trachea (windpipe) may be necessary.

Follow-up Care

After surgery, very close monitoring is required. Aspiration pneumonia is a serious problem that can occur, and x-rays may be recommended to monitor for this condition. Gagging and coughing are common after surgery and may last for several days. Food is generally withheld for at least 18-24 hours after surgery. Water intake is unrestricted.

Prognosis

Prognosis without surgery is poor, because respiratory distress often worsens over time and may become life-threatening. Most dogs recover from surgery with immediate improvement in their respiratory signs.

SPECIAL INSTRUCTIONS:

Bronchitis, Acute

Ronald M. Bright, DVM, MS, DACVS

BASIC INFORMATION

Description

Acute bronchitis is the sudden onset of inflammation or irritation of the small airways (bronchioles) and medium-sized airways (bronchi) in the lungs. It is usually short-lived and associated with coughing.

Causes

There are many different causes of acute bronchitis, including the following:

• Bacterial or viral infections

• Parasites

• Inhaled foreign bodies

• Irritation from smoke, dust, fumes, or other substances

• A tumor that has grown large enough to put pressure on the bronchus

• Allergies

Clinical Signs

The cough is either dry and hacking or has a moist-sounding component. A moist cough is often associated with mucus production. A dry hacking cough is typical of a virus infection, whereas a moist-sounding cough is more common with a bacterial infection. A cough that is often confused with bronchitis is the “goose-honking” dry cough associated with tracheal collapse in toy breeds of dogs. Sometimes the affected dog is systemically ill, especially if the lungs are also involved.

Diagnostic Tests

Diagnosis of acute bronchitis is largely dependent on the presence of compatible clinical signs and physical examination findings. X-rays of the lungs are not often helpful in confirming the diagnosis but can demonstrate pneumonia that may accompany the bronchitis and can rule out other problems in the chest. Laboratory tests may show an elevated white blood cell count in animals with bacterial infections but may be normal in other cases.

Analysis of secretions taken from the trachea and bronchus during a transtracheal wash can help determine a specific cause. Culturing of the secretions may demonstrate bacteria in some cases. Bronchoscopy, which involves the passage of a fiberoptic scope into the airway, may demonstrate parasitic lesions, a foreign body, a collapsing trachea, or possibly a tumor.

Determining the underlying cause of acute bronchitis can be difficult because there are so many potential causes and the disease is often short lived.

TREATMENT AND FOLLOW-UP

Treatment Options

If an inciting cause can be found and eliminated, the bronchitis usually resolves quickly and spontaneously. If an infection is diagnosed, antibiotics are usually needed. When a foreign body is suspected, bronchoscopy can often be used to retrieve it. Removing the animal from irritants, such as smoke or dust, may allow spontaneous recovery.

Symptomatic treatment may also be tried. Sometimes placing a humidifier near the animal while it is confined in a small space can be helpful. If the cough is the dry hacking type and there is no evidence of a bacterial infection, then cough suppressants may be recommended. If breathing is affected and wheezing is noticed, bronchodilator drugs may be helpful. In some cases, a short-term course of corticosteroids may be warranted.

Follow-up Care

If the cause is identified and specific therapy is instituted, the clinical signs usually resolve. Failure to eliminate the cause and any delay in starting therapy may allow the condition to progress to chronic bronchitis. Recheck visits may be scheduled to monitor response to treatment. Notify your veterinarian if any signs persist or return.

Prognosis

Aggressive treatment of acute bronchitis usually results in complete recovery, especially if the underlying cause is not serious.

SPECIAL INSTRUCTIONS:

Bronchitis, Chronic

Ronald M. Bright, DVM, MS, DACVS

BASIC INFORMATION

Description

Chronic bronchitis is inflammation or irritation of the small airways (bronchioles) and medium-sized airways (bronchi) in the lungs that lasts for longer than 2 months. Chronic bronchitis is associated with a cough that may persist indefinitely, because the cause may never be identified. Pathologic changes (damage from the inflammation) to the airways are irreversible in most cases.

Causes

Usually, the cause is not determined. Chronic bronchitis may be related to inhaled irritants (smoke, dust, fumes), allergies, or chronic infections. In rare cases, it is caused by a congenital abnormality of the airways (primary ciliary dyskinesia) that prevents them from clearing inhaled substances. Pneumonia and tumors do not often cause bronchitis alone; they usually also involve the lungs.

Clinical Signs

Most dogs with chronic bronchitis are middle-aged or older small-breed dogs that are overweight. A chronic, persistent, moist or dry cough is the main sign. Generally the dog’s overall health is good. Exercise intolerance may be noted in some dogs. Episodes or spasms of coughing and difficulty breathing may be noted in some instances. Signs may worsen with excitement, stress, exposure to irritants in the air, and secondary infections.

Diagnostic Tests

The diagnosis is often made by excluding other potential causes of chronic coughing, such as heart disease, tumors, pneumonia, collapsing trachea, and other airway problems. X-rays of the lungs may reveal certain changes consistent with a chronic bronchitis. X-rays are also helpful in ruling out other causes of coughing. Laboratory tests may be recommended to look for evidence of infections, allergies, and other conditions.

Analysis of secretions taken from the trachea and bronchi during a transtracheal wash may help determine a cause. Culturing of the secretions may demonstrate bacteria associated with chronic infections of the respiratory tract, such as mycoplasmosis. Bronchoscopy, which involves the passage of a fiberoptic scope into the airway, may help eliminate parasites, foreign bodies, a collapsing trachea, or tumors as potential causes. Other tests may be recommended to rule out other diseases that can cause a chronic cough.

TREATMENT AND FOLLOW-UP

Treatment Options

Because the cause is not often identified, symptomatic treatment is usually begun. If a cause is found, therapy is also directed at the cause. Potential therapies include the following:

• Obese dogs benefit greatly from a weight-reduction plan.

• Environmental irritants, such as smoke, dust, heat, and low humidity, should be eliminated.

• Humidifiers can be used intermittently while the dog is confined to a small space.

• Antibiotics are used if an infection is suspected or confirmed.

• Cough suppressants may be recommended if no infection is present.

• Drugs used to dilate the bronchioles may help reduce some clinical signs, such as exercise intolerance, breathing difficulty, or wheezing.

• A short course of corticosteroids can be helpful in some cases to decrease the amount of inflammation in the airways; however, they are used cautiously and in situations where the bronchitis is not complicated by respiratory infection, heart disease, or infection elsewhere in the body.

Follow-up Care

Lifelong therapy is usually required to control or minimize the clinical signs. If the disease is not treated adequately, the inflammation usually worsens, so recheck visits and repeated x-rays and testing may be needed to monitor response to therapy. Repeat testing may also be needed if signs flare up and do not respond to the usual therapy. Notify your veterinarian if any signs recur or worsen.

Prognosis

Complete recovery from chronic bronchitis is not a realistic goal, and owners should be prepared for lifelong therapy for their affected pet. Adequate, consistent therapy allows many affected animals to have a good quality of life. It is important that owners comply with prescribed therapies. If an infection is part of the disease, it usually responds to antibiotics, but they may need to be administered for some time.

SPECIAL INSTRUCTIONS:

Bullous Lung Disease

Ronald M. Bright, DVM, MS, DACVS

BASIC INFORMATION

Description

Bullous lung disease is the formation of contained or confined pockets of air and fluid in one or more portions of the lungs. These pockets ultimately form cysts (bullae) that are air-filled and surrounded by normal lung tissue.

When bullous lesions rupture, air escapes into the chest cavity (pneumothorax), which decreases the ability of the lungs to expand. The presence of a large number of cysts within the lungs may also affect normal lung function.

Causes

Bullous cysts can be congenital (present at birth), but most often they are acquired lesions. Inflammation, emphysema, trauma, and unknown factors (idiopathic) can result in their formation. Sometimes a lung fluke (parasite), Paragonimus kellicotti, forms inflammatory lesions that become air-filled cysts. Bullae may develop when air enters the central portion of an abscess or tumor in the lung. Large, deep-chested breeds of dogs, such as sight hounds, are predisposed to idiopathic bullous lung disease.

Clinical Signs

Some affected animals have a history of chronic bronchitis, prior chest trauma, or other lung diseases. Significant leakage of air into the chest cavity can cause severe respiratory distress, with increased respiratory rate and effort, cyanosis (blue gums from lack of oxygen), and collapse. Occasionally, bullae are found as incidental lesions on chest x-rays, and the animal has no clinical signs.

Diagnostic Tests

Routine laboratory tests and chest x-rays are often recommended to investigate potential causes of the respiratory distress. Chest x-rays may show one or more air-filled cystic structures in the lungs. Free air in the chest and lung collapse are indicative of pneumothorax. Animals in severe distress often require therapy, such as removal of the free air, before x-rays and other tests can be performed.

If fluid is also present in the chest cavity, it may be withdrawn and analyzed. Sometimes fluke eggs may be found when the fluid is examined microscopically. Direct aspiration of a bulla with a needle is not recommended, because it can lead to significant escape of air from the cyst and pneumothorax.

TREATMENT AND FOLLOW-UP

Treatment Options

Pneumothorax is usually treated as an emergency, with aspiration of air via a syringe and needle (thoracentesis). If air accumulates quickly after withdrawal of large amounts by thoracentesis, insertion of a chest tube is necessary to allow more effective evacuation of the air. If air continues to leak or large amounts of air accumulate, the chest tube may be hooked to a continuous suction device.

Some cystic lesions heal spontaneously after several days. As the bullae scar over, the leakage of air begins to subside. If the pneumothorax does not resolve within 48-72 hours or if evacuation efforts do not keep up with leakage of air, open chest surgery is done. It is usually necessary to enter the chest cavity through the sternum (breast bone), so that lung lobes on both sides of the chest can be inspected for bullae. A portion of a lung lobe or an entire lobe (containing one or several bullae) may need to be removed. In instances in which multiple, intact cysts are present throughout the lungs, the surfaces of the lungs may be rubbed with a rough piece of surgical gauze so that they subsequently stick to the lining of the chest wall (pleurodesis). Pleurodesis is an attempt to obliterate the space into which air can escape if a bulla ruptures in the future.

Follow-up Care

Careful monitoring of respiration, heart rate, blood pressure, lung sounds, color of the gums, and blood oxygen levels is done after surgery. Chest tubes usually remain in place until all air leakage stops. The chest tubes must be carefully monitored to ensure that they are working well and that no air is leaking around or into the tube and back into the chest.

X-rays are repeated to monitor the presence or absence of air in the chest. Most animals remain in the hospital at least 24 hours after chest tube removal, so that they can be closely monitored. The incision is usually rechecked and sutures removed 10-14 days after surgery. X-rays may be obtained again at that time.

Prognosis

It is possible for more bullae to form in different areas of the lung in the future, so x-rays are periodically taken to monitor for their development. If bullae are found on x-rays in the future, no treatment may be recommended unless pneumothorax recurs. One in every eight animals develops a recurrence of a pneumothorax after surgical treatment.

SPECIAL INSTRUCTIONS:

Diaphragmatic Hernia

Ronald M. Bright, DVM, MS, DACVS

BASIC INFORMATION

Description

The diaphragm is the muscle that separates the abdominal cavity and its contents from the chest cavity. A hernia is a disruption of this muscle that allows movement of abdominal organs into the chest cavity. Diaphragmatic hernias may be congenital or acquired. (See the handout on Peritoneopericardial Diaphragmatic Hernias for a discussion of congenital hernias.) This handout discusses acquired diaphragmatic hernias, which usually result from trauma.

Causes

Traumatic diaphragmatic hernias can arise from any type of blunt trauma to the abdomen, including an automobile accident, being kicked, or jumping or falling from a high elevation. The last condition is a common cause in cats.

Clinical Signs

Traumatic diaphragmatic hernias are more commonly seen in animals younger than 2 years of age. The hernia can be discovered within hours or up to several years after the incident. Most of the clinical signs are caused when various abdominal organs are displaced into the chest cavity and cause collapse of the lungs or when the production of fluid further impairs lung expansion. Approximately 40% of animals with a traumatic hernia have some degree of breathing difficulty, ranging from panting to open-mouth breathing.

If the trauma is severe, many animals are in shock and have concurrent injuries, such as fractured ribs, bruising within the lungs, or bleeding from abdominal organs such as the spleen or liver. The gums may be pale or cyanotic (blue from lack of oxygen) in an animal with severe respiratory compromise and/or shock. Occasionally, an affected animal becomes jaundiced or develops a dilated (bloated) stomach that moves into the chest cavity and compresses the lungs.

Diagnostic Tests

The inciting traumatic event may or may not be witnessed, but a history of trauma may help the veterinarian in formulating a tentative diagnosis. Listening to the chest cavity with a stethoscope may reveal sounds that indicate the presence of fluid and organs in the chest cavity and damage to the lungs.

X-rays often demonstrate a loss of the outline of the diaphragm, the presence of organs and fluid in the chest cavity, and a decreased number of organs in the abdominal cavity. Sometimes a liquid contrast material (a dye that shows up white on x-rays) is injected into the abdominal cavity and x-rays taken shortly afterward show this material in the chest cavity, which indicates a hole in the diaphragm. Barium is sometimes given orally to help demonstrate that the stomach and/or small intestines have moved into the chest.

Fluid in the chest sometimes decreases the accuracy of x-rays, and in this instance ultrasonography is very helpful to clearly delineate a herniation. In rare cases, advanced imaging with computed tomography (CT scan) or magnetic resonance imaging (MRI) may be necessary to define the hernia. Laboratory tests are often recommended to assess the effects of trauma and the hernia on other organs.

TREATMENT AND FOLLOW-UP

Treatment Options

Surgery is the only viable option for correcting a diaphragmatic hernia. The objective of surgery is to return the abdominal organs to the abdominal cavity, inspect the organs of the chest cavity for signs of trauma, and repair the rent in the diaphragm.

The approach for repairing the hernia is usually through the abdomen. If the hernia is thought to be chronic or long-standing, adhesions may have formed that make the surgical correction more challenging. A median sternotomy, which involves splitting the breast bone, may be required for some chronic hernias to improve exposure of the chest cavity.

Follow-up Care

Postoperative monitoring of cardiac and respiratory function is important. Bleeding (from adhesions broken down during replacement of organs into the abdomen) can result in severe anemia and possibly shock. A chest tube is left in place at the end of the surgery to monitor and remove any air (pneumothorax) or blood (hemothorax) that collects within the chest cavity. Oxygen is often administered in the immediate postoperative period. Accumulation of fluid in the lungs (pulmonary edema) may be a postoperative problem, especially in cats, that requires medical therapy.

Prognosis

Surgical complications are relatively rare, and prognosis is generally good, especially for hernias that have not been present for a long time. If the animal survives the first 24 hours after surgery, the prognosis improves. Older cats and those animals with other serious injuries are more likely to die after hernia repair.

SPECIAL INSTRUCTIONS:

Flail Chest

Ronald M. Bright, DVM, MS, DACVS

BASIC INFORMATION

Description and Cause

Flail chest arises with trauma and occurs when several contiguous ribs are broken in such a way that a segment of the chest wall moves in and out independent of the movement of the remaining normal rib cage. The fractured segment of ribs moves paradoxically, meaning that it moves inward on inspiration (breathing in) and outward on expiration (breathing out), which is opposite to normal chest cage movement.

For this paradoxical movement to occur, a certain amount of damage to soft tissues (muscles, tendons) must also be present. The degree of trauma responsible for multiple rib fractures usually results in damage to the underlying lung tissue.

Clinical Signs

Because of damage to the lungs, difficulty breathing, panting, cyanosis (blue gums caused by lack of oxygen), and open-mouth breathing may occur. Paradoxical movement of a segment of the thorax is always seen. Pain is usually present over the traumatized area, and the animal is often reluctant to move. Other signs of trauma may also be present.

Diagnostic Tests

A preliminary diagnosis may be made based on a history of trauma and the typical clinical findings. Abnormal lung sounds are often heard through a stethoscope. Chest x-rays confirm multiple rib fractures and other lung or chest cavity abnormalities.

TREATMENT AND FOLLOW-UP

Treatment Options

The first objective of emergency care is to ensure adequate intake of oxygen and to treat the animal for shock, often with intravenous fluid therapy and oxygen supplementation. Pain management is very important and is usually accomplished by administration of narcotics and a local anesthetic nerve block during the first several days after injury.

A soft-padded bandage is usually applied around the chest, and the animal may be placed with the affected side down to prevent excessive movement of the flailed segment. An external splint is sometimes used, with sutures being placed around the middle of the fractured ribs and tied to the splint to stabilize the segment. Rarely, the ribs are stabilized with an open surgical approach, using orthopedic fixation devices such as pins. In animals with severe, crushing injuries, the entire fractured segment may be removed and the chest wall reconstructed with a muscle flap or synthetic mesh.

Follow-up Care

Continuous, close monitoring of cardiovascular and respiratory functions (particularly blood oxygen levels) is needed until the animal is stable. The animal may be hospitalized in a 24- hour veterinary facility during this time. Chest x-rays are usually repeated on a daily basis for a few days to evaluate any accompanying lung problems.

Prognosis

Prognosis for recovery from the trauma that produced the flail chest is primarily based on the severity of underlying lung damage and how well it responds to therapy. Cats have a poorer prognosis with multiple rib injuries than with a single fracture. If lung damage is not too severe, recovery can be expected in 10-14 days. Movement of the flail segment usually decreases within that same time period.

SPECIAL INSTRUCTIONS:

Laryngeal Collapse in Dogs

Ronald M. Bright, DVM, MS, DACVS

BASIC INFORMATION

Description

Laryngeal collapse is also referred to aryepiglottic collapse or corniculate collapse. This condition arises when the cartilages of the larynx (voice box) become weak and lose their structural rigidity. It almost always leads to severe inspiratory distress (difficulty breathing air in). Laryngeal collapse usually occurs in dogs older than 2 years of age, but it may develop earlier in dogs with severe upper airway obstruction from other causes. (See also the handout on Brachycephalic Syndrome.)

Causes

Most often, the condition results from chronic airway obstruction related to brachycephalic syndrome. Fatigue of the cartilages that surround the laryngeal opening occurs because of the chronic negative pressures produced by the increased effort needed to take in air. Rarely, the condition can arise from direct trauma to the cartilages.

Clinical Signs

Noisy breathing and difficulty breathing have usually been present for years. A sudden worsening of respiratory distress may occur in dogs with various components of brachycephalic syndrome. Cyanosis (blue color of the tongue or gums caused by lack of oxygen), gagging, choking, vomiting, and restlessness are often seen. Labored, open-mouth breathing; retraction of the lips (indicating great effort is being made to breathe); panting; and elevated body temperature from exaggerated breathing effort may all occur. In severe cases, the animal may collapse and possibly die before therapy can be started.

Diagnostic Tests

A tentative diagnosis is often based on a history of chronic breathing problems in certain breeds. Diagnosis is confirmed by examination of the larynx (laryngoscopy) under anesthesia. X-rays of the chest help define any additional problems of the trachea (narrowed diameter, collapse) or lungs, as well as the presence of a hiatal hernia, which can accompany chronic airway problems.

TREATMENT AND FOLLOW-UP

Treatment Options

Emergency treatment of dogs with acute respiratory distress usually consists of oxygen therapy, sedation, and administration of anti-inflammatory drugs. If these measures are unsuccessful, a temporary tracheostomy may be needed to stabilize the dog until corrective surgery is done.

If the laryngeal collapse is mild, treatment consists of surgical correction of the underlying cause of the problem, such as shortening of an elongated soft palate, enlargment of the external openings of the nose, or removal of any excessive, obstructive tissues within the throat area. In instances of moderate to severe laryngeal collapse, a portion of one of the collapsed cartilages may be surgically removed via an oral approach (through the mouth). In severe cases or if signs persist after surgical therapy, a permanent tracheostomy may be required.

Follow-up Care

Close, continuous monitoring for airway obstruction is required after recovery from surgery. In some animals, a temporary tracheostomy is needed for several days until postoperative swelling subsides. Aspiration pneumonia is a serious problem that may occur.

Following a permanent tracheostomy, it is critical that the new opening be kept clean and that the trachea remain clear of mucus and blood. Postoperative care and monitoring often requires 4-5 days of hospitalization before it is safe to discharge the animal.

• The opening will decrease in size over several months to approximately 30-40% of the original size.

• The dog should not be allowed to engage in swimming, and harnesses (rather than collars) are preferred for restraint.

• The hair around the new opening must be kept short.

• Secretions around the opening sometimes irritate the skin, which can be treated with petrolatum or zinc oxide ointments for a short time.

• In some breeds (pugs, English bulldogs), a significant amount of skin around the new opening must be removed to prevent the excessive skin folds from obstructing the new opening. Overlapping skin folds may also become a problem months to years later and require additional surgery.

• In extremely cold environments or in dusty conditions, a lightweight scarf or wrap should be placed over the opening.

• Most dogs can no longer bark (vocalize).

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Tags: Small Animal Practice Client Handouts

Sep 11, 2016 | Posted by admin in SMALL ANIMAL | Comments Off

Fastest Veterinary Medicine Insight Engine

3: Respiratory System

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