Pneumothorax in Dogs

My dog was kicked by a horse,  then developed difficulty breathing and his tongue started looking blue.  I took him to an animal emergency room and was told that he had a “traumatic pneumothorax”. The doctor said air was leaking out of his lungs because he got kicked. What is a pneumothorax, and what are the different types?

pneumothoraxThe definition of a pneumothorax is an accumulation of air outside the lungs, but inside the chest wall. The air outside the lung prevents the lungs from inflating normally, and can lead to lung collapse. There are several variations of pneumothorax, and it might be easiest to think about them separately.

 

Traumatic pneumothorax

In a traumatic pneumothorax, air accumulates in the chest space outside the lungs, following some type of trauma (such as being kicked by a horse). Because there was no opening in the chest wall, this pneumothorax is considered “closed”. Most often in a traumatic pneumothorax, there is enough damage to the chest wall to create a defect. This is called an “open” pneumothorax, in which there is communication between the chest cavity and the outside atmosphere. Another possibility is enough damage to the lung to cause one-way air transfer from inside to outside the lung during inhalation. The air cannot then be exhaled and becomes trapped within the chest cavity.

"With a traumatic pneumothorax,
there is typically evidence of a recent trauma"

With a traumatic pneumothorax, there is typically evidence of a recent trauma, and with obvious damage to the chest wall, it is straightforward to diagnose an open pneumothorax. These dogs present with rapid breathing, difficulty breathing, and they may be in respiratory distress. Dogs that are experiencing the respiratory distress associated with pneumothorax will often stand with their elbows pushed away from their bodies in an attempt to increase their lung capacity. They may exhibit what is called “abdominal breathing” in which the origin of each breath seems to be the abdominal wall moving rather than the chest expanding. Pneumothorax patients may also have a higher than normal heart rate.

Trauma patients with pneumothorax may also have pale or bluish mucous membranes, they may be in shock, and they may have air trapped under the skin. This is called “subcutaneous emphysema” and it feels like “crackling” when they are petted over the affected areas.

 

The actual causes of traumatic pneumothorax can be quite varied and include:

• Blunt trauma (like being kicked by a horse)
• Chest injuries that penetrate into the chest cavity
• Following a surgical incision into the chest (this is, of course, a planned and controlled trauma to the chest cavity)
• Perforation of the esophagus on its way to the stomach
• Trauma to the windpipe
• Lung disease
• Foreign body migration (like a grass awn migrating through the tissues of the body)

 

Spontaneous pneumothorax

In a spontaneous pneumothorax, air leaks from the lungs or the large air passages and accumulates in the chest space outside the lungs in the absence of any trauma. Because there are no defects, injuries or openings in the chest wall, any spontaneous pneumothorax would be considered closed. Spontaneous pneumothorax is more common in large, deep-chested dogs, and the Siberian Husky may be unusually susceptible.

"The symptoms of spontaneous pneumothorax are
the same as those of traumatic pneumothorax."

Dogs that develop a spontaneous pneumothorax may or may not have previous signs of lung disease. It may have a slow, progressive onset, but what typically occurs is a sudden loss of the ability to compensate for the air that is outside the lungs and preventing the lungs from expanding properly for breathing. The symptoms of spontaneous pneumothorax are the same as those of traumatic pneumothorax. The causes, however, are quite different.

"The causes of spontaneous pneumothorax
originate in the lungs themselves"

The causes of spontaneous pneumothorax originate in the lungs themselves. The most common cause is a condition in which the airspaces in the lungs become dilated, and the air can get in (on inhalation) but cannot get out (on exhalation).  This is called “bullous emphysema”. Lung cancer, lung abscesses, severe pneumonia, lung worms or flukes, bubble-like structures in the lungs, and lung nodules causes by fungal infection are all potentially to blame for spontaneous pneumothorax.

 

How is pneumothorax treated?

Definitive treatment of pneumothorax depends upon the underlying cause, but there are commonalities across the spectrum of patients who develop this condition. Most dogs require hospitalization until the air accumulation within the chest cavity has stopped or has stabilized. If the dog presents in respiratory distress, then part of the treatment involves extracting the air from inside the chest cavity to allow the lungs to expand. Oxygen therapy is typically provided until the dog is stable.

"In traumatic pneumothorax...
it is important that effective pain relief be provided"

In traumatic pneumothorax, or for dogs requiring surgery to resolve the underlying issue that led to the pneumothorax, it is important that effective pain relief be provided. If there is a significant defect in the chest wall, surgery will be required once the dog is stable and receiving adequate oxygen into the tissues. Removal of part or all of a lung may be necessary if there are localized lesions, masses, etc. Any traumatic lacerations of the lung may be sutured closed. A closed, traumatic pneumothorax may not require any intervention beyond stabilization. Sometimes a chest tube is required to provide access to remove additional air that accumulates in the chest cavity. If there is a chest tube placed, then it is important that the dog not be allowed to dislodge it.

Most dogs require strict rest for at least a week (and often longer) following resolution of pneumothorax, in order to minimize the chance of recurrence.

What sorts of complications can arise from having a pneumothorax? 

It is possible for pneumothorax to cause a fatal cardiovascular event from too low a level of oxygen in the blood. Another important potential complication of pneumothorax is recurrence.  It is important to monitor the dog’s breathing rate, as an increased breathing rate may suggest a recurrence. Follow-up x-rays may be required, as may additional measurements of blood oxygen levels.

What is recovery like and the long term outlook after suffering a pneumothorax?

For traumatic pneumothorax, if the chest trauma is not too severe and if treatment goes according to plan, the expectation is for a full recovery. If the chest trauma is severe, it is possible for the dog to decline despite all interventions and emergency efforts. If there is bleeding into the lungs or bruising of the heart, these patients can deteriorate very quickly. The recovery and long term outlook for a dog with spontaneous pneumothorax is a bit more complicated because it depends on the underlying cause. A well-identified, single, localized lesion that can be removed surgically provides a better outlook than if the underlying cause cannot be identified or if there is disease throughout the lungs.

While pneumothorax is a very serious condition, it is important to note that with advances in diagnostic and treatment options, these dogs can often be treated for a very successful outcome.

This client information sheet is based on material written by: Robin Downing, DVM, DAAPM, DACVSMR, CVPP, CRPP

© Copyright 2016 LifeLearn Inc. Used and/or modified with permission under license.

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