Abstract:
Pulse oximetry is a cost-effective and a simple way to continuously monitor oxygenation of haemoglobin (SpO2) in humans and animals. Although pulse oximetry has been used extensively in wildlife, its efficacy and accuracy has not been validated. We aimed to establish, in immobilized impala, whether pulse oximetry is a reliable method to measure oxygenation of haemoglobin and aimed to determine which attachment site gives the most accurate measures. Sixteen healthy female impala were immobilized with etorphine or thiafentanil alone, or with a serotonin-agonist drug. Arterial blood samples were collected from the auricular artery at 5 minutes intervals during immobilization. At 40 minutes of immobilization, intranasal oxygen insufflation was provided to the impala at 5 L minute-1 flow rate to increase arterial oxygenation. A blood gas analyser was used to measure PaO2 (partial pressure of arterial oxygen) and calculate cSaO2 (calculated arterial haemoglobin oxygen saturation) and a co-oximeter was used to measure SaO2 (gold standard measure of arterial haemoglobin oxygen saturation) from arterial blood. Pulse oximeter probes were attached at four sites; namely under the tail, ear, rectum, and cheek. Pulse oximeter readings (SpO2 and pulse quality) were recorded at each site and compared with SaO2 and cSaO2 using Bland-Altman and accuracy root mean squares (Arms) methods to determine the efficacy. The pulse quality measured was generally good at each attachment site. Pulse oximetry measured under the tail was accurate and precise but only when SaO2 values were above 90% (bias = 3.03, precision = 3.15, Arms = 4.32). For the ear probe placement, overall bias and precision were high indicating that pulse oximetry was inaccurate (bias = -3.9) and imprecise (precision = 14.2). The cheek and rectal probe placement failed to give accurate or precise readings (cheek: bias = 11.63, precision = 10.86, Arms = 15.82 and rectum: bias = 4.9, precision = 12.02, Arms = 12.90). In order to get accurate and precise pulse oximetry readings in immobilized impala, probes must be placed under the tail and SaO2 must be above 90%. Since SaO2 values are usually low in immobilized impala, pulse oximeter readings should be interpreted with caution.
