Bottlenose dolphins take rapid breaths that begin with an explosive exhalation and are followed by a deep inhalation. The dolphin then holds its breath while it swims, forages, interacts with others, and then returns to the surface of the water for another breath. These deep breaths are held for up to several minutes at a time. Dolphins also use more of their lung volume than humans for each breath, being as efficient as possible while they are at the surface to breathe.
So now imagine that the air is polluted. What happens when a dolphin takes deep, full breaths of polluted air, and then holds that breath while it swims, forages, or interacts with others? With their deep, prolonged breath holds, and the fact that dolphins don’t have noses or nasal turbinates to filter air, we would expect even more contamination to reach their lungs than in a human breathing the same air. While their respiratory adaptations serve them well for diving and living in the ocean, they may also make them more vulnerable to lung injury and infection.
To evaluate lung health in a live dolphin, ultrasound is a valuable diagnostic tool that offers a rapid assessment. The dolphin body is well-suited for ultrasound, as their skin is smooth and hairless, so doesn’t require any preparation before conducting the exam. Current ultrasound units are powerful enough to penetrate the blubber of a dolphin and rugged enough to use on a salty research vessel. Exams can either be performed in-water or on the deck of the research vessel.
Determining what is ‘normal’ for a wild dolphin would be challenging if we didn’t have decades of experience working with animals in human care. By providing long-term health care to dolphins and routinely performing ultrasound examinations to monitor their well-being, we have characterized variations of normal conditions in the lung and defined disease states. This information now serves as a reference point for interpreting ultrasound results from wild dolphins, and helps us understand how lung health may be impacted in the face of an environmental disaster, long-term contamination, or infectious disease outbreak.
Since 2011, we have been collecting standardized pulmonary (lung) ultrasound data on Sarasota Bay dolphins. Pulmonary abnormalities detected are divided into the following categories: (1) pleural effusion, or fluid surrounding the lungs; (2) superficial pulmonary nodules, or <2cm round/ovoid foci of non-aerated lung; (3) pulmonary masses, or 2cm or greater well-defined areas of non-aerated lung; (4) alveolar-interstitial syndrome, or evidence of reduced air in the lung and replacement of air with cellular infiltrate, and (5) pulmonary consolidation, where fluid or cellular infiltrate is occupying the alveolar spaces in the lungs. During the exam, numerous images are captured to document the findings in each dolphin’s lungs. After the field exam is performed and abnormalities recorded, our sonographer (CRS)-radiologist (MI) team goes through each animal’s data set and then assigns an overall lung score: normal, mild, moderate, or severe. To date, the vast majority of Sarasota Bay dolphins evaluated have been assigned either normal or mild lung disease scores, and no dolphins have received a severe lung disease score. We will continue to collect lung ultrasound data for each animal as a critical part of their medical record, as well as further develop this baseline of essential data for comparisons to other populations of bottlenose dolphins to study the impact of environmental factors on lung health.
This article was published on page 12-13 in the November 2014 issue of Nicks n Notches