What is Pneumothorax? A pneumothorax condition is defined as free air within the pleural space (chest cavity). The naturally occurring intra-pleural pressure maintains an equilibrium of roughly 5 cmH20, similar to a vacuum which allows easy expansion of the lungs. However, unwanted air can enter this vacuum system and the equilibrium is set to match that of the chest cavity rather than the lungs. Pneumothorax can occur due to trauma, such as the action of a punctured lung will allow atmospheric air to enter the pleural space. Pneumothorax in cats is characterized by air occupying the space surrounding the lungs. The lungs are the body’s natural oxygen storage organs, expanding as the feline inhales, but if air is surrounding the lungs it restricts normal lung activity. Pneumothorax in cats can be caused by ruptured lung tissues, blunt force trauma and bite wounds. If your cat is suffering from pneumothorax, he or she will have a great breathing difficulty, which is often fatal if left untreated. Symptoms of Pneumothorax in Cats Pneumothorax in cats will make inhalation and exhalation extremely difficult for the feline. The most prominent symptom of cats suffering from pneumothorax is difficulty breathing (dyspnea), but other clinical signs a cat owner may notice in the case of pneumothorax in cats includes: Exercise intolerance Cyanotic (blue tinged) gums and tongue Labored breathing Increased respiratory rate Restlessness Sternal recumbency lying (the feline will lay on her sternum in an upright position in an attempt to bring more air into her lungs) Anorexia Tachypnea (shallow, rapid breath) Open-mouthed breathing.