Pneumothorax in Dogs and Cats

What parts make up the chest (thoracic) cavity?

The thoracic cavity houses several vital organs in a dog’s and cat’s body, including the lungs and heart. This is also where some of the major blood vessels and nerves traverse, providing communication between the animal’s brain and abdomen. The chest cavity and its organs are separated from the animal’s abdomen by a thin layer of muscle called the diaphragm.

The diaphragm not only separates the chest cavity from the abdomen but also plays an important role in the animal’s breathing. When a dog or a cat breathes and inhales air, the diaphragm expands and increases the area of the thoracic cavity, allowing the lungs to inflate and accommodate more air. During expiration, the diaphragm relaxes and helps push out air from the lungs.

The thoracic cavity is designed in such a way that it allows optimal inflation and deflation of the lungs during respiration. This is achieved by maintaining negative pressure in the space between the lungs and the chest wall, called the pleural space. This space contains a very tiny amount of clear fluid that serves as a lubricant for the lungs as it inflates and contracts during respiration.

The negative pressure in the animal’s pleural space must be maintained. Any health condition that results in changes in the negative pressure of the pleural space will lead to inefficient lung inflation and cause breathing problems for the dog or cat. This usually occurs when the pleural space gets filled up with excessive amounts of fluid, resulting in thoracic or pleural effusion.

In some cases, instead of fluid, the pleural space gets filled up with air, resulting in a condition called pneumothorax. Just the same, the accumulation of air in the pleural space hinders the lungs’ ability to expand fully, resulting in breathing problems for the pet. There are several causes of pneumothorax in dogs and cats and knowing the specific cause is key to providing effective treatment for the problem.

What is pneumothorax?

Pneumothorax is defined as the accumulation or collection of gas or air in the animal’s pleural space. This extra air disrupts the static negative pressure of the pleural space and prevents the lungs from fully expanding when the pet breathes. Dogs and cats with mild pneumothorax usually don’t need medical treatment as the small pockets of air in the pleural space eventually get reabsorbed, but severe cases will require immediate treatment. If left untreated, severe pneumothorax can be fatal to both dogs and cats.

Causes of pneumothorax in pets include:

• Chest trauma (puncture wounds, car accidents, etc.)
• Primary lung disease (pneumonia, chronic obstructive pulmonary disease, asthma, etc.) Excessive pressure on the lungs
• In some cases, the specific reason cannot be identified, and the condition is considered idiopathic.

There are several types of pneumothorax in dogs depending on how the air penetrates and enters the animal’s pleural space.

Types of Pneumothorax in Pets

There are three primary categories of pneumothorax in dogs and cats:

1. Open pneumothorax - described as a type of pneumothorax where the air accumulating in the pleural space originates from outside the body. This occurs when an injury penetrates the animal’s chest wall allowing air from outside to enter the chest cavity. Common causes of open pneumothorax in both dogs and cats are animal bites, puncture wounds, and automobile accidents.

2. Closed pneumothorax - this type occurs when there’s an accumulation of air in the pleural space but there’s no break in the animal’s chest wall. The air filling up the chest cavity usually comes from a lung cyst or a break in the different structures of the respiratory system such as the lung lobes, bronchi, or trachea. In some cases, closed pneumothorax can develop when there’s a break in the animal’s esophagus.

3. Iatrogenic pneumothorax - described as the accumulation of air in the pleural space and chest cavity as a complication from lung surgery.

4. Tension pneumothorax - this type of pneumothorax is often seen when the dog or cat is intubated (during surgical procedures). An increase in the pressure of the external ventilation can rupture the lungs, allowing the air to escape and accumulate into the chest cavity.

5. Spontaneous pneumothorax - this is the accumulation of air in the chest cavity of the animal without the presence of any trauma or injury. Primary spontaneous pneumothorax happens when the lungs become dilated and inhaled air cannot get out during exhalation, causing the development of “bullous emphysema”. Secondary spontaneous pneumothorax occurs as a complication to underlying lung disease such as lung cancer, lung abscesses, heartworm disease, allergic bronchitis, and severe pneumonia.

Diagnosing and Treating Pneumothorax in Pets

Diagnosis of pneumothorax in dogs and cats is based on clinical signs, physical exam, medical history, and diagnostic imaging. Symptoms associated with the condition include pain in the chest area, exercise intolerance, increased respiratory rate, and in worse cases, breathing difficulties and cyanosis (mucus membranes turning blue due to lack of oxygen).

The presence of air in the pleural space or the chest cavity can be confirmed through x-rays. Your vet will likely request additional diagnostic tests such as a complete blood count and a biochemistry profile to rule out other possible causes of respiratory distress.

Treatment will depend on the type and severity of the pneumothorax. Mild cases often resolve on their known with 1-2 weeks of rest. More severe pneumothorax cases in dogs and cats are considered an emergency and need to be seen by a vet as soon as possible. Your vet may need to place a chest tube to remove the accumulated air in the chest cavity and allow the lungs to inflate.

Patients suffering from severe pneumothorax will also require hospitalization in an oxygen cage for proper oxygen support and recovery. In cases of traumatic open pneumothorax, surgery is indicated to close the break in the chest wall. Severely damaged lung lobes may need to be removed surgically.

The prognosis of pneumothorax in dogs and cats depends on the severity of the condition and how early the treatment was administered.

Read more:

How to Measure Resting Respiratory Rates in Dogs

Canine Infectious Respiratory Disease Complex (CIRDC)

Upper Respiratory Infections in Cats

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