Dogs have two lungs within the chest cavity under the ribs. Each lung is divided into sections called lobes. Each lobe is covered by a membrane called the pleura. Within each lung lobe, branching tree-like hollow air tubes collectively called ‘airways’ carry air into the body. The larger airways, branch into smaller and smaller tubes that become microscopic. Air travels down deep into the lungs and ends at microscopic sacs called alveoli. It is at the level of the alveoli that oxygen is transferred to the body. The space between the lungs and chest wall is called the pleural space. This space normally contains a small amount of fluid to allow the lungs to slide easily within the chest as they expand and contract with each breath.
Pneumothorax can happen due to a number of causes; however, the end result is the collapse of the lungs because of air within the pleural space. The abnormal air “squeezes” the lungs, which severely interferes with your pet’s ability to breathe. There are two main types of pneumothorax, traumatic and spontaneous. The traumatic type is due to an injury that punctures the lungs, esophagus (the tube that connects the throat and the stomach) or chest cavity and results in the leaking of air into the pleural space. Spontaneous pneumothorax is typically caused by a disease of the lungs. The most common cause is a pulmonary bulla, an air blister that develops on the surface of the lung, which ruptures and leaks air into the pleural space. Other causes of spontaneous pneumothorax may include a foreign object within the lung, lung abscess, migrating parasites, and lung tumors.
Signs and Diagnosis
The most common sign of pneumothorax is increased respiratory rate. As the lungs progressively collapse, marked breathing difficulty may be noted along with a grey to blue color of the gums and tongue. Weakness may also be noted and is caused by a lack of oxygen. Other nonspecific signs may include coughing, vomiting, tiredness, and lack of appetite. Your veterinarian may detect decreased lung sounds with the aid of a stethoscope. The diagnosis of pneumothorax is based on chest X-rays that demonstrate air within the pleural space and collapse of the lungs. In the absence of any traumatic event, a presumptive diagnosis of spontaneous pneumothorax is made. A CT (computerized axial tomography) scan is useful to further define the underlying cause of the pneumothorax. Tests done prior to surgery may include a complete blood count, blood chemistry profile, fecal analysis, and urinalysis to check internal organ health.
Conservative treatment for spontaneous pneumothorax commonly fails and therefore is not usually recommended. If the pneumothorax is severe, the air may be aspirated from the pleural space with the use of a needle or in some cases with a chest tube. Surgery commonly requires exposure of both sides of the chest via an incision made through the breast bone. The offending lung lobe is identified and surgically removed. A chest tube is routinely placed and will be removed once fluid production within the chest is minimal. In some cases, oxygen therapy may be needed until the patient’s respiratory function has stabilized. Prognosis The long prognosis associated with a spontaneous pneumothorax varies based on the ability to find and manage or treat the underlying cause. Various papers have been published looking at outcomes associated with several different causes. A veterinary surgeon is typically the best person to discuss a prognosis specific to your pet. Even then, a surgeon may not be able to speak to prognosis until after thoracic surgery is done and biopsies are read out. Determining the cause of a pneumothorax, even in surgery, can be the equivalent of searching for a needle in a haystack.
Whenever your pet is showing signs of a health issue, your first step is to contact your primary care veterinarian. If it is indicated that your pet may suffer from spontaneous pneumothorax or other serious condition, a veterinary specialist is available at an ExpertVet certified or affiliated hospital.