Pneumothorax in Horses: Collapsed Lung Emergency Signs

Pneumothorax is a buildup of air in the pleural space, the area between the lungs and the chest wall. When air collects there, the lung cannot expand normally, so part or all of a lung may collapse. In horses, this can become life-threatening quickly because their large body size and oxygen needs leave less room for breathing problems.

This condition may affect one side of the chest or both. Horses are somewhat unique because the mediastinum, the tissue between the two sides of the chest, can be incomplete. That means air may sometimes move between sides, making breathing compromise more severe. In some horses with chronic pleural disease, scar tissue and fibrin can reduce that communication.

Pneumothorax is not a diagnosis by itself. It is usually a consequence of another problem, such as chest trauma, a penetrating wound, pleuropneumonia, or rarely a complication of a medical procedure. Your vet's first priorities are usually stabilizing breathing, identifying the cause, and deciding whether the air needs to be removed right away.

Trauma is one of the most important causes. A penetrating chest wound, kick injury, fence or stake injury, rib fracture, or other blunt thoracic trauma can allow air to enter the pleural space. In field emergencies, an open wound over the chest should be considered potentially chest-penetrating until your vet proves otherwise.

Pneumothorax can also develop secondary to lung or pleural disease. In horses, pleuropneumonia is a well-recognized cause because infection, tissue damage, or a bronchopleural fistula can let air leak into the chest. Horses with pleuropneumonia may also show fever, lethargy, reduced appetite, and signs of systemic illness in addition to breathing changes.

Less commonly, pneumothorax can occur after procedures involving the chest, after surgery, or with severe underlying lung damage. The exact cause matters because treatment is not only about removing air. Your vet also needs to address the source of the leak, control pain, reduce infection risk when indicated, and monitor for recurrence.

Your vet will start with an emergency physical exam. Important clues include rapid breathing, increased heart rate, anxiety, poor oxygenation, and reduced or absent breath sounds dorsally over the chest. If there is a visible chest wound, that raises concern immediately. In unstable horses, treatment to improve breathing may begin before every test is completed.

Thoracic ultrasonography is often one of the most useful tools in horses because it is sensitive for pleural disease, including pneumothorax, and can help guide thoracocentesis or chest tube placement. Thoracic radiographs can also help confirm the diagnosis and assess severity, although imaging can be more challenging in adult horses and may be performed after initial stabilization.

Additional testing depends on the suspected cause. If pleuropneumonia is possible, your vet may recommend thoracocentesis, pleural fluid analysis, tracheobronchial aspirate, bloodwork, and culture. Pulse oximetry or arterial blood gas testing may be used to assess hypoxemia and the need for oxygen support. These tests help your vet build a treatment plan that fits both the emergency and the underlying disease.

Not every case can be prevented, but many are linked to trauma or serious respiratory disease. Good fencing, prompt repair of broken boards or metal hazards, careful trailer loading, and reducing overcrowding can lower the risk of penetrating chest injuries and blunt thoracic trauma. Horses recovering from surgery or major injury also benefit from close observation for any change in breathing.

Early attention to respiratory illness matters too. Horses with fever, lethargy, cough, nasal discharge, or signs of pleural disease should be examined promptly, especially after long-distance transport. Pleuropneumonia can become severe and may be complicated by pleural fluid, fibrin, and pneumothorax.

Prevention also includes fast first aid. If your horse suffers a chest wound, keep the horse quiet, avoid unnecessary movement, and contact your vet immediately. Applying a clean airtight covering to an obvious penetrating thoracic wound may help limit further air entry until veterinary care is available, but this should never delay emergency evaluation.