Abstract

Two cetaceans experienced inappropriate air accumulation; pneumothorax occurred in a 36 year-old female bottlenose dolphin (Tursiops truncatus gilli), and a 26-year old killer whale (Orcinus orca) developed subcutaneous emphysema.

The bottlenose dolphin initially presented with excessive positive buoyancy, diving difficulty, and corking upon ascent. She became dyspneic after being lifted from the water and placed on a foam pad for thoracic ultrasound and radiographs. Once returned to the water the respiratory parameters returned to normal. The examination revealed pneumothorax with no obvious etiology. Over a period of approximately 4 months the pneumothorax resolved as evidenced by normalization of buoyancy and diving behavior.

The killer whale developed subcutaneous emphysema while on treatment for chronic pneumonia. She first presented with gas trapped within the subglossal region. The gas was easily suctioned through a 1.2 mm x 40 mm (1 ½ ", 18-gauge) needle inserted into the base of the swelling. Within 36 hours the gas returned, followed by the development of a diffuse fluctuant swelling over the back between the leading edge of the dorsal fin and the blowhole. Thereafter, the whale demonstrated difficulty diving to the bottom of the 3.7 m deep pool and corking to the surface upon ascent. To remove the subcutaneous accumulation of gas, we placed a 2.1 mm x 140 mm (5.25", 14 g) needle into the subcutaneous space and aspirated approximately 46 l of gas. Approximately 24 hours later the gas rapidly returned to the subglossal region and subcutaneous space. A second aspiration yielded over 100 l of gas. Within 12 hours, the subcutaneous emphysema returned. Due to the rapid recurrence of the condition and the innocuous nature of subcutaneous emphysema, further aspiration attempts were discontinued. Over a period of 2 to 3 weeks the gas accumulation dissipated, finally disappearing by 4 weeks.

A definitive etiology was never identified in either case. In domestic species pneumothorax can result from a primary pulmonary leak or rupture of the mediastinal pleura. Pneumomediastinum results from airway or alveolar rupture where air is transmitted from the air space or airway to the interstitium, tracking toward the hilum, and ultimately filling the mediastinum. It may occur as a sole event or in combination with pneumothorax.