Pneumothorax is accumulation of free air in the pleural space and is one of the most common causes of respiratory distress in animals with blunt thoracic trauma. Pneumothorax is usually unilateral but can be present on both hemithoraxes and is always present in penetrating trauma. Small animals tolerate a substantial amount of free air in the thorax. Insufflation of up to 3 times the functional residual capacity is necessary to produce consistent respiratory and cardiovascular effects. In reality, minimal free pleural air can produce significant respiratory compromise, as pneumothorax is most of the time associated with other chest abnormalities like pulmonary contusions or hemothorax (Shaw et al 2003).
Diagnosis of pneumothorax is usually done by auscultation combined with a history of a recent trauma. Every traumatized patient should receive chest films for blunt trauma evaluation. However the radiographs should only be taken in an animal that is not in acute respiratory distress. Decompression by thoracoenthesis should always be performed before going to radiology. Radiography is used to confirm the diagnosis (Shaw et al 2003). Signs include elevation of the cardiac silhouette from the sternum, collapse of the lung lobes, and absence of vascular markings out to the periphery of the thorax.
Anatomy of Pneumothorax The lungs are surrounded by two “sacks”, the visceral and parietal pleura. The visceral pleura covers the outer surface of the lungs, and the parietal pleura lines the chest wall. These “sacks” are in close contact, but there is a small space between them, the intrapleural space. The intrapleural space is normally filled with a small amount of fluid that serves as a lubricant for the lungs to prevent friction during the normal motion of breathing (Shaw et al 2003). This fluid is the only substance that should be in the intrapleural space.......
