Pneumothorax in Cats: Causes, Respiratory Distress and Emergency Care

1. Pathophysiology: How Air Enters the Pleural Cavity

Normally, the visceral and parietal pleurae glide together lubricated by a minute amount of serous fluid under negative intrapleural pressure. Breathing relies on this negative vacuum to draw ambient air into the alveoli during thoracic expansion.

When a tear breaches either the chest wall or pulmonary visceral pleura, air rushes into the low-pressure pleural space. The lungs recoil away from the chest wall, drastically lowering functional residual capacity, resulting in severe ventilation-perfusion mismatch and hypoxemia.

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2. Classifications: Traumatic, Spontaneous and Tension

Pneumothorax is categorized by its underlying trigger:

• Closed traumatic: Most common in cats, caused by vehicular impact or falls from windows/balconies (high-rise syndrome) where sudden chest compression against a closed glottis ruptures alveoli.
• Open traumatic: Penetrating wounds such as dog bites or sharp projectile injuries creating direct communication with the atmosphere.
• Spontaneous: Occurs without trauma due to underlying lung disease—ruptured subpleural blebs/bullae, pulmonary neoplasms, parasitic granulomas, or severe chronic asthma.
• Tension pneumothorax: The most perilous presentation where injured tissue allows air entry during inspiration but seals during expiration, creating massive positive intrathoracic pressure that kinks the vena cava and stops venous return.

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3. Clinical Presentation and Orthopneic Stance

Cats in respiratory crisis instinctively display classic distress behaviors:

• Tachypnea and shallow breathing: Respiratory rates spiking past 60-80 breaths/min with synchronous abdominal pumping.
• Orthopneic posture: Sternal recumbency with an extended neck, open-mouth panting, and abducted elbows to maximize thoracic expansion.
• Cyanosis or pale gums: Blueish or pale mucous membranes indicating tissue hypoxia.
• Dorsal quiet auscultation: Lung sounds are markedly muffled or absent dorsally where air gathers, with resonant hyperresonance on gentle thoracic percussion.

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4. Emergency Triage and Thoracocentesis Decompression

In severe feline dyspnea, stress can quickly precipitate cardiac collapse. Diagnostics must never compromise immediate respiratory stability:

• Immediate oxygen support: Flow-by oxygen or an oxygen cage with minimal physical restraint.
• Diagnostic/therapeutic needle thoracocentesis: A 20-22G butterfly catheter attached to a three-way stopcock and syringe is placed in the dorsal 7th to 9th intercostal space. Evacuating air produces immediate relief and expands collapsed lobes.
• Point-of-Care Ultrasound (TFAST): Fast non-invasive ultrasound confirms loss of the normal pulmonary 'glide sign' (lung sliding) without forcing the cat into stressful radiographic positioning.

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5. Advanced Care, Thoracostomy Tubes and Prognosis

Ongoing management focuses on continuous monitoring and definitive seal:

• Thoracostomy tube placement: If air rapidly reaccumulates after repeated needle aspirations, a chest tube is placed under light sedation for continuous or frequent intermittent drainage.
• Multimodal analgesia: Opioid protocols (fentanyl, buprenorphine) manage associated rib fracture pain without depressing the respiratory center.
• Surgical intervention: Persistent air leaks or spontaneous bullous disease require exploratory thoracotomy and partial lung lobectomy.

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Scientific Sources and References

• Silverstein, D. C., & Hopper, K. (2015). Small Animal Critical Care Medicine, 2nd ed. Elsevier Health Sciences.
• Mooney, E. T., et al. (2012). Spontaneous pneumothorax in 12 cats (2000-2010). Journal of Feline Medicine and Surgery, 14(6), 384-391.
• Puerto, D. A., et al. (2002). Surgical and non-surgical management of and selected risk factors in cats with pneumothorax: 67 cases. JAVMA, 220(11), 1670-1674.
• King, L. G. (2004). Textbook of Respiratory Disease in Dogs and Cats. Saunders.