To adapt the algorithm for the calculation of oxygen saturation to the blood characteristics
of the white rhinoceros by two different methods and to determine the accuracy of
conventional pulse oximetry measurements.
Adaptation of two mathematical models of the oxygen dissociation curve (ODC).
Twenty-five captive white rhinoceros (Ceratotherium simum), including 12 males and 13 females, aged 6–32 years.
During 33 anaesthetic events, 94 arterial blood gas samples with 72 simultaneous pulse
oximetry measurements were analysed. The calculation of oxygen saturation was adapted
to the characteristics of rhinoceros blood using two different methods. Firstly, a
mathematical model developed in 1984 and, secondly, an oxygen status algorithm (OSA)
produced by the same developer in 2005 were tested for their applicability for clinical
When arterial partial pressure of oxygen is >7.98 kPa (60 mmHg), oxygen saturation
exceeds 95%. At partial pressures of 6.12–6.52 kPa (46–49 mmHg) Method 1 determined
oxygen saturations of 92.5–95.3% and Method 2 oxygen saturations of 90.2–91.6%. Both
methods resulted in similar ODCs and accounted for the low p50 value of rhinoceros
blood. Method 1 provided better adaptation in respect to the physiological parameters
of the rhinoceros, especially with regard to the Bohr effect, than Method 2. Pulse
oximetry was an unreliable method of monitoring arterial oxygen saturation during
general anaesthesia in this species.
Adapting the oxygen saturation algorithm to consider the left shift of the ODC provides
a useful tool for monitoring oxygen status, especially as pulse oximetry is insufficiently
accurate. Experimental determination of the complete Hill curve is required to further
validate and optimize the algorithm for use in the white rhinoceros.
The method will facilitate the accurate interpretation of oxygen saturation calculated
by blood gas analysis in white rhinoceros.