On 14 August, the University of Pretoria’s scientists from the Faculty of Veterinary Science demonstrated that the pulse oximeter can be used more effectively to monitor the blood oxygen levels of the endangered rhinoceros while it is under anaesthesia and immobilised.
According to Healthline, pulse oximetry is a “noninvasive test that measures the oxygen saturation level of your blood”. It can quickly identify minor changes in oxygen levels. These levels indicate how well blood is able to carry oxygen to the limbs and other areas furthest from the heart.
The use of a pulse oximeter is a response to protecting rhinos from poachers. According to Rhinos.org, just over
15 000 rhinoceroses remain in South Africa and just under
10 000 rhinos have fallen prey to poaching since 2007. During dehorning or relocation, the mammal needs to be immobilised, and its lungs and heart may not respond well to the potent immobilising drugs. Dr Thembeka Mtetwa explained, “The drugs can negatively affect the cardio-respiratory function of the rhino. This can cause blood oxygen to drop to dangerously low levels.” Thus, monitoring the fluctuating levels is critical for making important decisions such as whether to administer medication to stimulate breathing or to give oxygen to the rhino.
A team of UP’s veterinary scientists were faced with the challenge of identifying a reliable means of monitoring the mammals’ blood oxygen levels. This team consisted of Dr Mtetwa, Prof. Leith Meyer (a wildlife vet and physiologist), experimental physiologist Prof. Ned Snelling, wildlife vet Dr Peter Buss of SANParks, wildlife veterinarian Dr Annette Roug, and ecophysiologist Dr Ashleigh Donaldson. They tested the reliability of different pulse oximeters at various attachment points on the body of an immobilised rhino and discovered that the rhino’s third eyelid is an efficient, reliable site to attach the pulse oximeter.
Dr Mtetwa stated, “The third eyelid is a crescent-shaped fold of the outer eye structure which forms a thin, semi-transparent ‘blinking’ membrane over the rhino’s eye.” The UP scientists explained that, in humans, the third eyelid is the little, barely noticeable pink structure snuggled in the corner of the eye; it is vestigial and has no function. They further indicated, “In rhinos, it is much larger, and it contains lots of small blood vessels. It’s also quite noticeable in dogs, cats, and other animals. It functions to protect and clear the eye of foreign bodies when it closes, and to help keep the eye moist.”
Prof. Meyer was the one to come up with the unique idea to test the feasibility of placing the pulse oximeter on the third eyelid. Prof. Meyer explained, “The colour, moisture, and capillary refill time of the external mucous membranes of the body are good indicators of hydration, circulation, and the overall health of the animal, and are typically good sites to place a pulse oximeter probe.” Prof. Snelling added, “The great thing about the rhino’s third eyelid is that it is relatively thin. It has lots of blood vessels close to the surface, and it’s easy for vets and vet nurses to access it.”
Before the latest veterinary innovation, scientists and vets would monitor the blood oxygen levels of immobilised rhinos with blood gas analysers and pulse oximeters – which are designed for humans, not for rhinos – without any certainty of their reliability. Dr Mtetwa expressed that the pulse oximeter provides a real-time reading of the oxygen levels in the blood of the endangered mammal.
