Abstract:
BACKGROUND: Monitoring blood oxygenation is essential in immobilised rhinoceros, which are susceptible to opioid induced hypoxaemia. This study assessed the reliability, clinical performance and trending ability of the Nonin
PalmSAT 2500 A pulse oximeter’s and the Masimo Radical-7 pulse co-oximeter’s dual-wavelength technology, with
their probes placed at two measurement sites, the inner surface of the third-eyelid and the scarified ear pinna of
immobilised white rhinoceroses. Eight white rhinoceros were immobilised with etorphine-based drug combinations
and given butorphanol after 12 min, and oxygen after 40 min, of recumbency. The Nonin and Masimo devices, with
dual-wavelength probes attached to the third-eyelid and ear recorded arterial peripheral oxygen-haemoglobin
saturation (SpO2) at pre-determined time points, concurrently with measurements of arterial oxygen-haemoglobin
saturation (SaO2), from drawn blood samples, by a benchtop AVOXimeter 4000 co-oximeter (reference method).
Reliability of the Nonin and Masimo devices was evaluated using the Bland-Altman and the area root mean squares
(ARMS) methods. Clinical performance of the devices was evaluated for their ability to accurately detect clinical
hypoxemia using receiver operating characteristic (ROC) curves and measures of sensitivity, specificity, and positive
and negative predictive values. Trending ability of the devices was assessed by calculating concordance rates from
four-quadrant plots.
RESULTS: Only the Nonin device with transflectance probe attached to the third-eyelid provided reliable SpO2
measurements across the 70 to 100% saturation range (bias −1%, precision 4%, ARMS 4%). Nonin and Masimo
devices with transflectance probes attached to the third-eyelid both had high clinical performance at detecting
clinical hypoxaemia [area under the ROC curves (AUC): 0.93 and 0.90, respectively]. However, the Nonin and
Masimo devices with transmission probes attached to the ear were unreliable and provided only moderate clinical performance. Both Nonin and Masimo devices, at both measurement sites, had concordance rates lower than the
recommended threshold of ≥90%, indicating poor trending ability.
CONCLUSIONS: The overall assessment of reliability, clinical performance and trending ability indicate that the Nonin
device with transflectance probe attached to the third-eyelid is best suited for monitoring of blood oxygenation in
immobilised rhinoceros. The immobilisation procedure may have affected cardiovascular function to an extent that it
limited the devices’ performance.
