Thoracostomy Tube

Spontaneous pneumothorax can occur in both dogs and cats and is defined as air entering the chest cavity without a clinical history of trauma or iatrogenic penetration of the thorax. Under normal conditions, the chest maintains a physiologic negative pressure that keeps the lungs expanded. When that negative pressure is lost, air accumulates in the pleural space and the lungs partially or completely collapse.

There are two main anatomic pathways by which air can enter the chest and cause spontaneous pneumothorax: through the airways or through the esophagus. The airway route occurs when lung or tracheal tissue is damaged, allowing inhaled air to escape into the chest cavity and collect around the lungs. This is most commonly associated with bullae or blebs located along the edges of the lung lobes—small, air-filled sacs that can rupture into the chest (Figure 1). In dogs, bullae/blebs are most often found without other lung disease and represent the most common cause of spontaneous pneumothorax. In cats, bullae and blebs are less frequent, and most spontaneous pneumothorax cases are linked to underlying lung disease.

Figure 1

The second pathway is esophageal perforation, which can lead to pneumothorax and also cause air to track into other locations (for example under the skin and around the heart structures). Additional (secondary) causes of spontaneous pneumothorax include:

Dogs

• cancer
• bacterial pneumonia
• pulmonary abscess
• fungal infection
• heartworm disease
• pulmonary thromboembolism
• grass awn migration

Cats

• lung disease
• inflammatory airway disease
• heartworm infection
• lungworm infection
• bronchopulmonary dysplasia
• unknown

Spontaneous pneumothorax most often affects deep-chested, large-breed dogs, with no sex predisposition. Siberian Huskies and other Northern breeds are reported more frequently than expected. In cats, no consistent common association is known. Common signs include:

Dogs

• increased breathing rate
• coughing
• anxiety
• dark or bluish mucous membranes (gums)
• an overinflated-looking chest
• an orthopneic posture—an effort to open the airways, characterized by extension of the neck and elbows held outward

Cats

• respiratory distress (increased rate and effort)
• cough
• collapse
• lethargy and decreased appetite
• vomiting
• hiding behavior

When a pet is examined by a primary care veterinarian, chest radiographs are typically recommended to identify air within the chest cavity that is not contained inside the lungs (Figure 2). X-rays are highly accurate for confirming that a pneumothorax is present, but they rarely establish the underlying cause, so advanced imaging such as a CT (CAT) scan is often needed (Figure 3). An ACVS board-certified veterinary surgeon can recommend the most appropriate imaging approach and review likely causes and treatment options based on the imaging findings.

Figure 2
Figure 3

Treatment depends on how severe the clinical signs are. Immediate stabilization is crucial because spontaneous pneumothorax can be life-threatening due to impaired ventilation. A primary care veterinarian may initially perform thoracocentesis, in which a small needle is placed into the chest cavity to remove free air around the lungs so the pet can breathe more comfortably. This is a temporary measure that does not correct the cause, but it can allow lung re-expansion and may be lifesaving.

Long-term management is generally divided into medical versus surgical therapy, and the underlying cause determines which option is most appropriate. The primary veterinarian and an ACVS board-certified veterinary surgeon work with the owner to select the best approach.

Medical management includes:

• supplemental oxygen
• a thoracostomy (chest) tube

Oxygen is important because lung collapse from loss of negative intrathoracic pressure reduces the body’s ability to oxygenate tissues. Providing oxygen supplementation improves oxygen delivery to organs. Thoracostomy tubes are hollow tubes placed through the skin into the chest cavity (Figure 4), allowing intermittent or continuous evacuation of air so the lungs can expand more normally and maintain adequate oxygenation. In many cases, spontaneous pneumothorax cannot be controlled medically over the long term, and surgery is needed to eliminate the primary source of air leakage.

Surgical treatment most commonly involves removing the affected lung lobe(s) via lung lobectomy after entering the chest (Figure 5). Three approaches may be used: minimally invasive thoracoscopy, median sternotomy (through the sternum), or lateral thoracotomy (between ribs). Each has advantages depending on the cause, the location of the affected lobe, and equipment availability. The ACVS board-certified surgeon evaluates the individual case to determine the best recommendation.

Figure 4
Figure 5

For dogs, long-term results are excellent when surgery removes the cause of the air leak. Some causes cannot be surgically resected, and in those cases prognosis depends on disease severity and extent. Recurrence occurs in about 3% of dogs treated surgically and can be as high as 50% without surgery. Mortality statistics underscore the importance of surgical management: approximately 12% mortality with surgery versus over 50% with medical management alone.

Outcome information in cats is less extensive. Prognosis can still be favorable overall, depending on cause and response to treatment. A 2012 study reported 54% survival to hospital discharge, with most cats managed medically. For cats with small-volume pneumothorax, conservative therapy may yield good results, although surgery may be required in severe cases or when pneumothorax persists. Discussion with an ACVS board-certified veterinary surgeon can help determine the most appropriate plan for an individual patient.