Abstract

Pneumonia is major cause of morbidity and mortality in dolphins. The success of treatment depends on rapid interference. However overt clinical signs only develop when the respiratory organs are severely affected and laboratory tests on a blood sample can be misleadingly normal during a life threatening pneumonia. Capnography is a non-invasive technique that measures the concentration of CO2 in airway gases. In a capnogram this CO2 concentration is plotted either against time or expired volume. A bronchopneumonia that results in sequential emptying of fast and slow alveoli will change the shape of a time capnogram.

This study investigated the possibility of applying this technique to dolphins (Tursiops truncatus) The capnograph used was a CO2 SMO plus model 8100 (Novametrix Medical Systems). The animals were desensitised to a human anaesthesiology mask and were trained to exhale on command into the mask. The CO2 sensor was placed in one of two bifurcating arms, which were connected to the mask. One hundred and twenty nine series were taken from 15 adult Tursiops truncatus. A series consisted of six to fifteen breaths. Although the respiratory cycle of dolphins is much faster than of humans, the shapes of human and dolphin capnograms were similar.

During the tests one animal became ill. She had decreased food intake (10 £ 3 kg fish daily intake, weekly average) increased breathing frequency (13 £ 17 breaths per five minutes, weekly average). Bronchoscopy showed severely inflamed mucosa and purulent secretion. The time capnogram had a characteristic change of shape. The end expiratory CO2 concentration increased. After two weeks of antibiotic treatment (8 mg/kg Clindamycin BID) the shape of the capnogram and the end expiratory CO2 concentration started to return to pre disease states.

Air leaking from the mask and disturbance of the CO2 sensor by moisture made it difficult to obtain curves for evaluation. However these tests show it is possible to perform capnography on dolphins. The technique seems promising for use in screening, diagnosis, monitoring and disease management. Further research should aim at establishing normal values, inter and intra individual variation and refinement of the technique.