CONDITION
Pneumothorax
Pneumothorax describes a situation in which air accumulates in the space between the lung and the chest wall. This air prevents the lung from expanding fully, which can reduce the efficiency of breathing. The condition can arise spontaneously, follow an injury to the chest, or develop as a consequence of underlying lung disease. Owners often notice signs related to breathing effort—rapid or shallow breaths, reluctance to lie down, or a posture that suggests discomfort. In some cases the signs appear suddenly, while in others they build more gradually. The degree of distress varies widely depending on how much air has accumulated and how quickly it appeared. This page explores the patterns that may raise the question of pneumothorax, the mechanisms by which air enters and remains in this space, the imaging and other investigations used to confirm it, and the range of approaches—from observation through to procedures that remove the air—that may be considered depending on the circumstances.
Why this matters now
Pneumothorax can occur at any age, though certain patterns emerge in different populations. Spontaneous pneumothorax—where air enters the chest cavity without obvious injury—tends to appear in young to middle-aged dogs, particularly in large, deep-chested breeds such as Siberian Huskies and Afghan Hounds. Traumatic pneumothorax, arising from blunt force or penetrating wounds, shows no age preference and reflects the circumstances of injury. In older animals, pneumothorax may develop as a secondary consequence of underlying lung disease, including infection, neoplasia, or chronic airway conditions.
The speed at which signs develop depends on how quickly air accumulates and whether the leak continues. In traumatic cases, signs often appear within minutes to hours of the injury, though small volumes of air may cause only subtle changes initially. Spontaneous pneumothorax may announce itself suddenly or build over days, with breathing effort worsening as the volume of trapped air increases. Some animals stabilise once the leak seals itself and the body begins to reabsorb the air; others continue to accumulate air, particularly if a one-way valve effect allows air to enter the chest cavity during inhalation but prevents it from escaping during exhalation.
Signals & patterns
Early signals
Faster breathing at rest
An owner may notice that their pet's chest is rising and falling more frequently than usual, even when lying quietly. This reflects the body's attempt to compensate for reduced lung volume by taking more breaths per minute, though each breath may move less air than normal.
Shallow chest movement
The chest wall may appear to move less with each breath, creating a sense that the animal is breathing carefully or tentatively. This pattern arises because deep breaths become uncomfortable when the lung cannot expand fully against the trapped air.
Reluctance to settle
A pet may seem restless, shifting position frequently or avoiding lying down for long periods. This restlessness often reflects difficulty finding a posture that allows comfortable breathing, particularly if lying flat compresses the chest further.
Preference for sitting upright
Some animals adopt a sitting position with the elbows held slightly away from the body and the head extended forward. This posture can make breathing easier by maximising the space available for the parts of the lung that are still expanding.
Later signals
Pale or blue-tinged gums
The mucous membranes inside the mouth may lose their normal pink colour, appearing pale or taking on a bluish tint. This change suggests that oxygen transfer in the lungs has become significantly compromised, though the colour alone does not indicate the cause.
Pronounced abdominal breathing
The muscles of the abdomen may begin to work visibly with each breath, creating a pumping motion along the flanks. This pattern indicates that the animal is recruiting additional muscle groups to help move air when chest expansion alone is insufficient.
Collapse or inability to stand
In severe cases, an animal may lose the ability to remain upright, lying on its side with laboured breathing. This state reflects profound impairment of oxygen delivery and suggests that a large volume of air is preventing effective lung function.
Click to read about the biological mechanisms
How this is usually investigated
Investigation typically begins with observation of breathing pattern and effort, followed by listening to the chest with a stethoscope to assess whether breath sounds are reduced or absent on one or both sides. Radiography forms the cornerstone of confirming pneumothorax, though the decision about which images to obtain and when depends on how stable the animal appears. In some cases, additional tests help clarify whether an underlying condition contributed to the air leak.
Physical examination
Thoracic radiography
Point-of-care ultrasound
Computed tomography
Blood gas analysis
Options & trade-offs
Management of pneumothorax ranges from observation alone, when small volumes of air are reabsorbing and the animal remains comfortable, through to procedures that actively remove air from the chest cavity. The approach chosen reflects the volume of air present, whether it continues to accumulate, the animal's breathing effort, and any underlying cause that has been identified. Different combinations suit different circumstances, and what works well in one case may be less practical in another.
Observation and rest
When a small pneumothorax appears stable and the animal shows minimal breathing effort, the air may be left to reabsorb over days to weeks as the body gradually moves it into the bloodstream. This approach involves restricting activity to reduce oxygen demand and monitoring breathing pattern for signs that air is reaccumulating. Serial radiography or physical examination helps confirm that the volume of air is decreasing rather than increasing.
Trade-offs: This approach avoids the risks associated with placing needles or tubes into the chest, but it requires time and carries the possibility that the air leak will recur or that signs will worsen before reabsorption is complete. It suits animals with small, stable pneumothoraces but may not be feasible if breathing effort is marked or the owner's circumstances make close monitoring difficult.
Thoracocentesis
A needle or catheter is placed through the chest wall into the space containing the air, and the air is drawn out using a syringe or suction. This procedure can be performed as a single event or repeated if air reaccumulates. In some cases, removing even a portion of the air provides enough relief that the animal stabilises while the remaining air is reabsorbed.
Trade-offs: Thoracocentesis offers relatively quick relief with minimal equipment, but it does not address an ongoing leak; if air continues to enter the chest cavity, the procedure may need repeating multiple times. There is a small risk of lung puncture during needle placement, and sedation may be required depending on the animal's temperament and degree of distress.
Chest drain placement
A flexible tube is inserted through the chest wall and left in place, allowing air to be removed intermittently or continuously via a one-way valve or suction device. This approach is often used when air reaccumulates quickly after thoracocentesis or when a tension pneumothorax has developed. The drain remains in place until the volume of air being removed each day falls below a threshold that suggests the leak has sealed.
Trade-offs: Chest drains allow repeated air removal without repeated needle placement, but they require hospitalisation, careful monitoring to prevent kinking or blockage, and sometimes analgesia to manage discomfort at the insertion site. Infection can develop along the tube tract, and the drain itself may inadvertently puncture lung tissue if the animal moves suddenly or the tube migrates.
Surgical exploration
In cases where air continues to leak despite chest drainage, or when imaging identifies a bleb, bulla, or mass that appears responsible for the pneumothorax, the chest may be opened surgically to remove the affected tissue or repair the defect. Techniques include thoracotomy, in which the chest wall is opened via an incision between the ribs, or thoracoscopy, which uses smaller incisions and a camera to guide instrument placement.
Trade-offs: Surgery offers the possibility of definitive repair and may reduce the chance of recurrence, but it carries the risks associated with general anaesthesia and opening the chest cavity, including pain, infection, and a period of reduced activity during recovery. Not all leaks are visible or accessible at surgery, and some animals continue to develop new blebs or bullae over time despite removal of the initial lesion.
Oxygen supplementation
Providing supplemental oxygen via a mask, nasal prongs, or oxygen cage increases the proportion of oxygen in each breath, which can ease the work of breathing while other measures—observation, thoracocentesis, or drainage—address the pneumothorax itself. This approach is often used in the early stages of stabilisation.
Trade-offs: Oxygen therapy does not remove air from the chest or stop further leakage, but it can improve comfort and reduce respiratory distress in the short term. Some animals tolerate the delivery method poorly, and prolonged high concentrations of oxygen carry theoretical risks of oxygen toxicity, though this is uncommon in clinical practice.
Common misconceptions
"If a pneumothorax resolves once, it will not happen again."
Recurrence is common, particularly in animals with spontaneous pneumothorax caused by blebs or bullae, because the underlying tendency to form these structures often persists. Some animals experience multiple episodes over months or years, while others remain free of signs after a single event. The likelihood of recurrence varies with the cause and whether surgical intervention was pursued.
"A chest drain must be removed as soon as the animal seems comfortable."
The decision to remove a chest drain depends on the volume of air still being retrieved each day, not solely on the animal's apparent comfort. If significant air continues to accumulate, removing the drain too early may result in re-collapse of the lung and return of respiratory distress. The drain typically remains in place until the amount of air removed falls below a threshold that suggests the leak has sealed.
"All pneumothoraces require surgical repair."
Many pneumothoraces resolve with air removal and time, particularly when the leak seals spontaneously and no underlying structural abnormality is identified. Surgery is typically considered when air continues to leak despite drainage, when imaging shows a discrete lesion such as a bleb or mass, or when recurrence becomes frequent enough that ongoing medical management feels impractical. The choice depends on individual circumstances rather than a single protocol.
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.
Pneumothorax often raises questions about underlying lung structure, particularly in breeds known for spontaneous cases, and about the likelihood of recurrence in animals that have experienced one episode. The broader context of respiratory function—how the chest wall, airways, and cardiovascular system interact during breathing—appears in the respiratory health section. For animals with traumatic pneumothorax, understanding wound healing and the timeline for tissue repair may be a useful area to explore at a future appointment.
Last reviewed: 30 June 2026 · Dr Alastair Greenway MRCVS