CONDITION

Pneumothorax

Pneumothorax describes air accumulating in the space between the lung and the chest wall — a space that in health contains only a thin film of fluid. When air enters this pleural space, it can prevent the lung from expanding fully, making breathing harder and less efficient. Owners often notice rapid, shallow breathing, sometimes with visible effort at the chest or abdomen. The animal may be quieter than usual, reluctant to lie down, or standing with the neck extended. These signs can appear suddenly after an injury, or they may develop more gradually when the cause is less obvious. Pneumothorax can occur in any dog or cat, but spontaneous forms — where no clear trauma or wound is apparent — tend to appear in young to middle-aged, large, deep-chested dogs, with the Siberian Husky specifically noted in the literature as unusually susceptible. This page explores what an owner may observe, the mechanisms that allow air to enter the pleural space, how pneumothorax is investigated and confirmed, and the range of approaches used depending on cause, severity, and response to initial management.

Why this matters now

Pneumothorax can occur at any age, though spontaneous pneumothorax—where air enters the pleural space without obvious injury—tends to appear in young to middle-aged, large, deep-chested dogs, with the Siberian Husky specifically noted in the literature as unusually susceptible. Traumatic pneumothorax may follow road traffic incidents, bite wounds, or penetrating injuries at any life stage. In cats, the condition often arises after trauma, though underlying lung disease—especially in older animals—can also create the circumstances in which air leaks into the pleural cavity.

The timeline varies considerably depending on how the air entered and whether the leak remains active. A small pneumothorax may develop slowly, producing subtle signs that the owner notices only in retrospect, while a large or rapid accumulation can produce visible distress within minutes to hours. In some animals the air is reabsorbed by the body over several days without intervention, while in others the leak continues and the volume of trapped air increases. The pattern of progression influences both the urgency with which the condition is addressed and the likelihood that observation alone will be sufficient.

Signals & patterns

Early signals

Faster, shallower breathing

The dog or cat may breathe more rapidly than usual, with each breath appearing smaller in depth. This pattern reflects the effort required to move air when lung expansion is compromised, and may be most apparent during rest or after mild activity.

Reluctance to lie down fully

Many animals with early pneumothorax prefer to sit or stand in a way that keeps the chest upright, as lying flat can make breathing feel more effortful. This postural change is often subtle and may be mistaken for general restlessness.

Reduced willingness to move

An animal may become less interested in play, walks, or stairs, as exertion increases the demand for oxygen and highlights the reduced lung capacity. The reluctance may be gradual and easy to attribute to other causes.

Quieter demeanour

Some dogs and cats become notably calmer or less interactive, conserving energy in response to the increased cost of breathing. This withdrawal can appear as lethargy or a change in personality.

Later signals

Open-mouth breathing in cats

Cats typically breathe through the nose, so breathing with the mouth open suggests significant respiratory distress. This pattern indicates that the usual mechanisms for moving air are no longer adequate.

Prominent abdominal effort

When the chest cannot expand normally, the muscles of the abdomen may be recruited to assist breathing, producing a visible push with each breath. This exaggerated movement reflects the body's attempt to compensate for reduced lung function.

Blue-tinged gums or tongue

In severe cases, insufficient oxygen delivery may cause the mucous membranes to take on a bluish or grey colour. This change suggests that the mismatch between oxygen demand and supply has become pronounced.

Click to read about the biological mechanisms

How this is usually investigated

Investigation typically begins with observation of breathing pattern, chest wall movement, and the animal's posture and effort at rest. Listening to the chest with a stethoscope may reveal diminished lung sounds on one or both sides, though the finding can be subtle if only a small volume of air is present. Imaging is usually needed to confirm the presence of air in the chest cavity and to assess how much lung tissue remains functional, and further tests may be considered to identify an underlying cause if the pneumothorax appears without obvious trauma.

Radiography

Purpose: Radiographs of the chest can show air in the space between the lung and chest wall, often appearing as a dark region where the lung edge has pulled away from the ribcage. The images also reveal how much the lung has collapsed and whether any underlying lung disease, masses, or rib fractures are present.
Considerations: Small volumes of air may be difficult to detect on a single view, and positioning the animal for multiple projections can be challenging if breathing effort is marked. Radiographs taken after some air has been removed may provide a clearer picture of underlying lung structure.

Physical examination

Purpose: Examination includes assessment of mucous membrane colour, breathing rate and character, heart rate, and whether the chest wall moves symmetrically during breathing. Percussion of the chest—tapping to assess resonance—may suggest air accumulation, though this technique is less reliable in smaller animals.
Considerations: Signs can overlap with other causes of respiratory distress, and a calm demeanour during examination does not exclude significant air accumulation, particularly in stoic individuals or those too exhausted to show overt effort.

Computed tomography (CT)

Purpose: CT imaging provides detailed cross-sectional views of the chest, allowing identification of small blebs, tears, masses, or areas of lung disease that may have caused or contributed to the pneumothorax. It can also reveal air pockets in locations that are difficult to assess on plain radiographs.
Considerations: CT requires general anaesthesia or heavy sedation, which may carry additional risk in an animal with compromised lung function. It is typically considered when the cause remains unclear, when pneumothorax recurs, or when surgical intervention is being planned.

Ultrasound of the chest

Purpose: Ultrasound can detect the absence of normal lung sliding against the chest wall, a finding that suggests air is separating the two surfaces. It can also identify fluid accumulation if both air and liquid are present.
Considerations: Ultrasound is less informative than radiography for assessing the overall extent of lung collapse or identifying structures deeper within the chest. It is useful as a bedside tool in animals too unstable to move to the radiography suite.

Complete blood count

Purpose: A blood count may reveal changes suggestive of infection, inflammation, or blood loss if trauma has involved other organs. It provides context when trying to distinguish between primary lung disease and injury as the underlying cause.
Considerations: Many animals with pneumothorax have unremarkable blood counts, and the test does not confirm or exclude the presence of air in the chest. It is typically part of a broader assessment rather than a diagnostic step specific to pneumothorax.

Options & trade-offs

Management is shaped by the volume of air present, whether the leak appears to be ongoing, and the overall stability of the animal. Some pneumothoraces resolve with rest and observation as the body reabsorbs the air, while others require procedures to remove air from the chest cavity, either once or repeatedly. In cases where the underlying cause is a structural defect in the lung, intervention to seal or remove the affected tissue may be considered. The combination of approaches that proves workable varies widely between individuals and depends on the resources, risk tolerance, and preferences of those involved.

Observation and oxygen supplementation

In animals with small volumes of air and stable breathing, management may involve rest in a quiet environment, sometimes with supplemental oxygen delivered via mask, cage, or nasal prongs. The air in the chest cavity is gradually reabsorbed into the bloodstream over days to weeks, provided no further leakage occurs. Breathing pattern and effort are monitored closely, and repeat imaging may be performed to confirm that the volume of air is decreasing rather than increasing.

Trade-offs: This approach relies on the leak having sealed itself, which cannot be confirmed with certainty in the early stages. Animals that continue to accumulate air, or those with large volumes at presentation, typically require more active intervention. Cage rest can be difficult to maintain in anxious or active individuals.

Thoracocentesis

Thoracocentesis involves inserting a needle or catheter between the ribs to withdraw air from the chest cavity, allowing the lung to re-expand. The procedure may be performed once, or repeated at intervals if air continues to accumulate. In some cases a one-way valve or temporary chest drain is placed to allow continuous or intermittent removal of air without repeated needle insertions.

Trade-offs: Removal of air can produce rapid improvement in breathing effort, but if the underlying leak does not seal, air may re-accumulate within hours to days. Repeated procedures carry a small risk of lung puncture, infection, or discomfort, and animals with ongoing leaks may eventually require surgical intervention. The technique is less effective in cases where air is loculated—trapped in pockets that do not communicate freely with the rest of the chest cavity.

Surgical exploration and repair

Surgery involves opening the chest to identify and address the source of the air leak, which may include removing a lung lobe containing ruptured blebs, sealing a tear, or resecting damaged tissue. The procedure is typically performed under general anaesthesia and may involve post-operative placement of a chest drain to remove any residual air as the lung heals. Surgical intervention is often considered when pneumothorax recurs despite drainage, when imaging identifies a discrete lesion, or when the pneumothorax is thought to result from a mass or other structural abnormality.

Trade-offs: Surgery carries the risks associated with anaesthesia and thoracic procedures, including infection, bleeding, and prolonged air leakage from the surgical site. Recovery typically involves several days of hospitalisation and restricted activity for weeks afterward. Not all causes of pneumothorax are amenable to surgical repair, and in some cases the source of the leak is not found even during exploration.

Medical pleurodesis

Pleurodesis involves introducing an irritant substance into the chest cavity to provoke inflammation and adhesion formation between the lung surface and the chest wall, obliterating the space where air accumulates. The technique is less commonly used in veterinary medicine than in human practice, but may be considered in animals that are poor candidates for surgery or in whom pneumothorax has recurred despite other interventions.

Trade-offs: The procedure can cause discomfort and requires careful monitoring during the inflammatory phase. Success is variable, and adhesions do not always form uniformly or prevent further air accumulation. Pleurodesis does not address the underlying defect in the lung, so recurrence remains possible if the source of the leak persists.

Common misconceptions

Misconception:

"Pneumothorax always requires surgery to fix."

Reality:

Many cases of pneumothorax resolve with rest and observation, or with drainage procedures alone, particularly when the air leak seals spontaneously. Surgery is typically reserved for recurrent cases, those with ongoing leaks that do not respond to drainage, or situations where imaging identifies a structural defect that can be repaired. The need for surgical intervention depends on the individual circumstances rather than the diagnosis itself.

Misconception:

"If an animal is breathing fast, it means the pneumothorax is getting worse."

Reality:

Breathing rate and effort reflect the balance between available lung capacity, the animal's oxygen needs, and its level of anxiety or pain. An increase in rate may signal worsening air accumulation, but it can also result from stress, discomfort, or increased metabolic demand unrelated to the chest. Serial assessment of other signs—such as mucous membrane colour, posture, and willingness to rest—provides a fuller picture than breathing rate alone.

Misconception:

"Once the air is removed, the problem is solved."

Reality:

Removing air from the chest cavity can produce marked improvement in breathing effort, but it does not address the underlying defect that allowed air to enter in the first place. If the leak has not sealed, air may re-accumulate, sometimes within hours. Monitoring after drainage is important to determine whether further intervention is needed, and some animals require repeated procedures or surgery to prevent recurrence.

Related conditions

Pleural Effusion

Pleural effusion and pneumothorax both involve abnormal accumulation within the pleural space—fluid in one case, air in the other—and both can produce similar signs of breathing effort and reduced lung expansion. Imaging is typically used to distinguish between the two, though in some cases they may occur together.

Pneumonia

Pneumonia and pneumothorax can both cause respiratory distress and reluctance to lie down, and in some cases underlying lung infection or inflammation may contribute to structural changes that allow air to leak into the pleural space. Distinguishing between them often requires imaging and consideration of the broader clinical picture.

Tracheal Collapse in Dogs

Tracheal collapse can cause chronic coughing and increased airway pressure during breathing, and in rare cases these forces may contribute to rupture of small airways or lung tissue, allowing air to enter the pleural space. Both conditions can present with increased breathing effort, though the pattern and sound of breathing often differ.

Pulmonary Hypertension

Pulmonary hypertension and pneumothorax may occasionally overlap when chronic lung disease contributes to both elevated pressure in the pulmonary vessels and structural changes that predispose to air leakage. Both can result in reduced exercise tolerance and signs of respiratory compromise.

Pericardial Effusion

Pericardial effusion and pneumothorax can both present with rapid breathing, reluctance to lie down, and reduced tolerance for activity, though pericardial effusion involves fluid around the heart rather than air around the lungs. Imaging is used to distinguish the location and nature of the abnormal accumulation in each case.

The pattern of breathing effort, the speed with which signs develop, and the response to initial management often shape the trajectory more than the diagnosis itself. Related conditions affecting the chest cavity—such as fluid accumulation or masses—may produce overlapping signs and can coexist with pneumothorax. In animals with recurrent episodes or those in whom an underlying cause has been identified, the broader context of lung health and breed-related thoracic structure may be useful territory to explore over time.

Last reviewed: 30 June 2026 · Dr Alastair Greenway MRCVS