Case Studies in Physiology: Ventilation and perfusion in a giraffe-does size matter?

The trachea in the giraffe is long but narrow, and dead space ventilation is considered to be of approximately the same size as in other mammals. Less is known about the matching between ventilation and lung blood flow. The lungs in the giraffe are large, up to 1 m high and 0.7 m wide, and this may cause considerable ventilation/perfusion (VA/Q) mismatch due to the influence of gravitational forces, which could lead to hypoxemia. We studied a young giraffe under anesthesia using the multiple inert gas elimination technique to analyze the VA/Q distribution and arterial oxygenation and compared the results with those obtained in other species of different sizes, including humans. VA/Q distribution was broad but unimodal, and the shunt of blood flow through nonventilated lung regions was essentially absent, suggesting no lung collapse. The VA/Q match was as good as in the similarly sized horse and was even comparable to that in smaller sized animals, including rabbit and rat. The match was also similar to that in anesthetized humans. Arterial oxygenation was essentially similar in all studied species. The findings suggest that the efficiency of VA/Q matching is independent of lung size in the studied mammals that vary in weight from less than 1 to more than 400 kg.

Polar bear Ursus maritimus hearing measured with auditory evoked potentials.

While there has been recent concern about the effects of sound on marine mammals, including polar bears, there are no data available measuring the hearing of any bear. The in-air hearing of three polar bears was measured using evoked auditory potentials obtained while tone pips were played to three individually anaesthetized bears at the Kolmården Djurpark. Hearing was tested in half-octave steps from 1 to 22.5 kHz. Measurements were not obtainable at 1 kHz and best sensitivity was found in the range from 11.2-22.5 kHz. Considering the tone pips were short and background noise measurements were available, absolute measurements were estimated based on an assumed mammalian integration time of 300 ms. These data show sensitive hearing in the polar bear over a wide frequency range and should cause those concerned with the introduction of anthropogenic noise into the polar bear's environment to operate with caution.

Survey of tuberculin testing in Swedish zoos.

Tuberculin test results from 214 animals in three Swedish zoos, tested between the years 1993 and 2000, were compiled from a questionnaire sent out to zoo veterinarians. Comparative testing with bovine and avian tuberculin was used on various sites of injection. A total of five skin test reactors were found: three cotton-top tamarins (Saguinus oedipus) in one zoo and two tapirs (Tapirus terrestris) in another zoo. Postmortem culture from one of the tapirs revealed growth of Mycobacterium tuberculosis, and a stamping out policy was adopted in the herd. Tuberculosis in the primates was ruled out by further investigations. Zoo veterinarians should try to adopt a common scheme for the regular testing of zoo animals to improve the diagnostic ability and comparison of results between institutions.