Overview of Pneumothorax in Cats
Pneumothorax is the abnormal presence of air within the chest cavity, which restricts the lungs from inflating normally during inhalation. Air is normally confined to spaces within the lungs.
Pneumothorax can be sub-divided into the following categories:
Open pneumothorax – occurs when a penetrating chest wound allows outside air to enter the pleural space
Closed pneumothorax – occurs when the source for the introduction of air into the intrapleural space has closed so that no more air can enter.
Tension pneumothorax – occurs when air fills the chest cavity with each breath and is not allowed to exit (a one-way valve effect)
Spontaneous pneumothorax – a closed pneumothorax that occurs unexpectedly; no trauma is involved.
Traumatic pneumothorax – pneumothorax resulting from traumatic injury to the chest
General Causes of Pneumothorax
Pneumothorax can be the result of any of the following:
Perforation of the chest wall secondary to bite wounds, automobile accidents, gunshot wounds, stab wounds, or other penetrating injuries
Rupture of a pulmonary (lung) cyst, bullae (cyst-like structure within the lungs) or bleb (tiny cyst-like structure on the outer surface of the lungs) that occurs spontaneously. This type of pneumothorax is more common in older animals.
Rupture of a bronchus (main airway)
Rupture of the trachea (the windpipe)
Rupture of the esophagus
Rupture of the lung tissue
Rupture of the mediastinum, which is a confined space within the chest cavity but independent of the lungs
Cats with pneumothorax exhibit difficulty breathing and, in severe cases that are left untreated, pneumothorax can be fatal.
What to Watch For
Increase in the respiratory rate (more than 45 breaths per minute)
Cyanotic (blue) gums or tongue
Intolerance to exercise
Diagnosis of Pneumothorax in Cats
Depending on how much difficulty breathing your cat is experiencing, your veterinarian may want to place him in an oxygen cage immediately before obtaining a history from you regarding his condition. Your veterinarian will perform a thorough physical examination with careful auscultation (listening with a stethoscope) of your cat’s chest to determine the cause of trouble breathing. Additionally, your veterinarian will likely recommend the following tests:
Chest radiographs (X-rays) to look for the presence of air in the chest cavity
Thoracocentesis, which is removal of air from the chest cavity with a needle and syringe.
Arterial blood gas, a test to evaluate the cat’s ability to oxygenate
Pulse oximetry, a non-invasive test to determine the cat’s ability to oxygenate
Complete blood count (CBC) to assess the cat’s general health
Biochemistry profile to evaluate the internal organs such as the liver and kidneys
Treatment of Pneumothorax in Cats
Treatment of a pneumothorax may need to be done as an emergency procedure and may include any of the following:
Supplemental oxygen administration for cats that are having difficulty breathing
Thoracocentesis to remove air from the chest cavity and to improve the cat’s ability to breathe
Chest tube placement to allow larger amounts of air to be removed from the chest cavity more quickly or continuously
Thoracic surgery to repair large air leaks within the chest or to repair damage to the chest wall that may be present with traumatic injuries
Home Care and Prevention
Cats that show signs of difficulty breathing should be taken to your veterinarian immediately. Restrict exercise initially following discharge from the hospital.
Keeping cats indoors can reduce the risk of pneumothorax caused by traumatic injuries due to automobile accidents or attacks by other animals.
There is no way to prevent a spontaneous pneumothorax from occurring.
In-depth Information on Pneumothorax in Cats
The chest cavity does not normally contain air, except for air within the lungs. Any air in the chest cavity is abnormal. A pneumothorax develops when air is allowed into the chest cavity through a breach in the chest wall due to injury (external leak), and/or air leaks into the chest cavity due to a leak in the lung tissue or airways (internal leak).
The presence of air within the chest cavity exerts pressure on the lungs so they cannot expand or inflate when the pet tries to take a breath. Large volumes of air cause the lungs to collapse completely. If the lungs do not inflate normally or are collapsed, the pet cannot obtain enough oxygen and develops signs of difficulty breathing such as rapid, shallow breaths, and cyanotic (blue) gums and tongue. The volume of air and the rate at which it accumulates within the chest varies with the degree of traumatic injury or underlying problem.
Pets with pneumothorax require hospitalization for an average of two to five days.
Related Symptoms or Diseases
There are many other problems involving the lungs that could produce symptoms similar to those observed with pneumothorax, such as:
Pleural effusion. An accumulation of fluid in the chest cavity restricts the lungs from inflating normally when the animal takes a breath. Types of fluid that may accumulate, include blood (hemothorax), chyle (chylothorax), pus (pyothorax), and clear fluid (hydrothorax). The presence of fluid in the chest is abnormal regardless of its origin.
Neoplasia. Cancer can cause difficulty breathing by causing fluid to accumulate in the chest cavity, by replacing normal lung tissue with cancerous tissue, or simply by occupying space required by the lungs. Many different types of cancer can occur within the chest cavity.
Pulmonary contusions. Bruising and bleeding into the lungs are the result of trauma and cause difficulty breathing. Pulmonary contusions and pneumothorax are both common following trauma to the chest and must be distinguished from one another by auscultation and chest radiographs.
A diaphragmatic hernia. A tear in the diaphragm, the tissue that separates the chest from the abdominal cavity, allows abdominal organs to move into the chest cavity. A diaphragmatic hernia is often the result of trauma, although some cats may be born with this condition. This problem is diagnosed using X-rays or abdominal ultrasound.
Pneumonia. An infection in the lungs can result from aspiration of vomit or other debris into the airways or can be spread via the bloodstream. Pets with pneumonia often have a fever, which is not typical with a pneumothorax.
Your veterinarian may recommend any of the following in order to make a definitive diagnosis:
Chest radiographs are taken to visualize the lungs and the chest cavity. Normally, two X-rays are taken to allow complete assessment. Radiographs are evaluated for the presence of air within the chest cavity, fluid in or around the lungs, or space-occupying lesions in the lungs or chest cavity. The radiographs are also analyzed for the presence of rib fractures, bullae, and chest wall defects, which often accompany pneumothorax resulting from trauma. With pneumothorax, typical X-ray findings include elevation of the heart off the sternum (normally they touch), collapse of the lungs, and inability to follow the edges of the lungs out to the rib cage.
Thoracocentesis is both a diagnostic and therapeutic technique and is performed to remove air from the chest cavity. During this procedure, a local anesthetic is carefully injected into the muscles of the chest wall where the needle will be inserted. A needle is then passed through the chest wall into the chest cavity, and air is removed manually by aspiration with a syringe. In pets that do not have a pneumothorax, no air will be aspirated and negative pressure will be present. In other words, no air can be pulled into the syringe except with great effort and if released, the syringe will spring back to empty.
An arterial blood gas is a test performed to determine the pet’s ability to oxygenate the blood by measuring the amount of arterial blood that is oxygenated. Normally, 95 to 100 percent of arterial blood is oxygenated. In pets with a pneumothorax, the amount of oxygenated blood is much lower. The most common artery for sampling blood is the femoral artery located on the inside of the thigh.
Pulse oximetry is another means to measure a pet’s ability to oxygenate without having to draw blood. A probe is clipped onto the pet’s lip, ear, tongue or skin fold or is inserted into the rectum and, using an infrared light source, detects the level of oxygenated blood. This test is an easier, less stressful means of measuring oxygenated blood in a pet that is having difficulty breathing but, under some circumstances, is not as accurate as an arterial blood gas.
A complete blood count (CBC), is a test that is performed to aid in the overall assessment of a pet’s health when a pneumothorax is present. A CBC helps to identify anemia (low red blood cell count) that may occur due to blood loss following traumatic injuries, and helps to identify high or low white blood cell counts that occur with infection or inflammation.
A biochemistry profile is a blood test that allows evaluation of the internal organs such as the liver or kidneys. In pets that have a pneumothorax from cancer or trauma, this test is particularly important to determine whether the internal organs are affected.
Supplemental oxygen administration is given to all cats that are showing signs of difficulty breathing. In cases of mild pneumothorax, oxygen administration and cage rest may be the only treatments required while the body heals itself.
Thoracocentesis is indicated to remove moderate to large volumes of air from the chest cavity when the cat is exhibiting signs of difficulty breathing. By removing air from the chest cavity, the lungs are able to inflate normally and the cat breathes more easily.
A chest tube is placed when the volume of air removed via thoracocentesis is excessive. Chest tubes allow larger volumes of air to be removed more quickly or continuously. Tubes may be aspirated by hand, every few hours, or aspirated continuously by attaching the chest tube to a suction unit. The circumstances that dictate chest tube placement include the following:
– No endpoint is reached during thoracocentesis indicating a large continuous leak in the airways
– An endpoint was reached during thoracocentesis but thoracocentesis must be repeated more than two to three times, indicating a slow but continuous leak in the airways
– The volume of air removed during thoracocentesis was excessive for the patient’s size.
Chest tubes are also placed following chest surgery to allow removal of residual air for the first 24 to 48 hours post surgery. Chest tubes are placed using sterile techniques, and require that the cat be heavily sedated or anesthetized. The tubes are held in place by sutures in the skin where the tube exits the chest, and with a bandage placed around the chest. Tubes are removed when minimal volumes of air or negative pressure are obtained during aspiration over a 6 to 12 hour period, indicating the leaky airway has sealed.
Surgery is indicated when the pneumothorax does not resolve over a period of 48 hours or longer despite the use of a chest tube and continuous suction. Surgery is also indicated to repair damage to the chest wall following traumatic injuries. If the pneumothorax involves only one side of the chest, a lateral thoracotomy is performed, which involves approach to the chest between the ribs on the affected side. If the source of the airway leak is unknown or the pneumothorax is evident on both sides of the chest in X-rays, a median sternotomy is performed, which is an approach to the chest through the sternum or midline of the chest. Pneumothorax caused by trauma rarely requires surgery whereas spontaneous pneumothorax often requires surgery.
Home Care of Cats with Pneumothorax
Cats that show signs of difficulty breathing should be taken to your veterinarian immediately.
Restrict exercise following discharge from the hospital. Cats that are recovering from a pneumothorax should be rested for at least 1 week following discharge from the hospital and then gradually reintroduced to their regular activities. Cats that are allowed to exercise too soon may cause a sealed leak to re-open or may tire easily and prolong their recovery.