Analysis scripts and supplementary files: Blood colour can be used to assess arterial blood oxygenation in immobilised impala (Aepyceros melampus)

Background To determine the relationship between arterial blood colour (CIE L*a*b*) and blood oxygenation [functional oxyhaemoglobin saturation (SaO2) and fractional oxyhaemoglobin saturation (FO2Hb)], and if arterial blood colour can be used to predict arterial blood oxygenation.

Methods A prospective randomised crossover study where 11 female impala were immobilised with potent opioids. Arterial blood was collected anaerobically into heparinised syringes and analysed immediately using spectrocolourimetry and co-oximetry. Data were analysed by modelling the relationship between predicted CIE L*a*b* components and SaO2 and FO2Hb, and assessing the subjective ordering of the resulting colour palette by 20 observers using a modified version of the Farnsworth-Munsell hue test.

Results The second-order polynomial (quadratic) model produced the best fit for all three CIE L*a*b* components for SaO2 and FO2Hb. The regression models were used to generate predicted CIE L*a*b* co-ordinates over a range of SaO2 and FO2Hb percentages (15 to 95%). The resulting colour palettes were correctly ordered by all observers, in the SaO2 and FO2Hb ranges of 45 to 95% saturation.

Conclusions An association between the blood colour components (CIE L*a*b*) and SaO2 and FO2Hb exists and arterial blood colour can be used to reliably estimate arterial blood oxygenation of impala.