Evaluation of the reliability of pulse oximetry, at different attachment sites, to detect hypoxaemia in immobilized impala (Aepyceros melampus)

ABSTRACT

Objective

Evaluation of the reliability of pulse oximetry at four different attachment sites compared to haemoglobin oxygen saturation measured by a co-oximeter and calculated by a blood gas analyser in immobilized impala.

Study design

Randomized crossover study.

Animals

A total of 16 female impala.

Methods

Impala were immobilized with etorphine or thiafentanil alone, or etorphine in combination with a novel drug. Once immobilized, arterial blood samples were collected at 5 minute intervals for 30 minutes. Then oxygen was insufflated (5 L minute−1) intranasally at 40 minutes and additional samples were collected. A blood gas analyser was used to measure the arterial partial pressure of oxygen and calculate the oxygen haemoglobin saturation (cSaO2); a co-oximeter was used to measure the oxygen haemoglobin saturation (SaO2) in arterial blood. Pulse oximeter probes were attached: under the tail, to the pinna (ear) and buccal mucosa (cheek) and inside the rectum. Pulse oximeter readings [peripheral oxygen haemoglobin saturation (SpO2) and pulse quality] were recorded at each site and compared with SaO2 and cSaO2 using Bland-Altman and accuracy of the area root mean squares (Arms) methods to determine the efficacy. P value < 0.05 was considered significant.

Results

Pulse quality was ‘good’ at each attachment site. SpO2 measured under the tail was accurate and precise but only when SaO2values were above 90% (bias = 3, precision = 3, Arms = 4). The ear, cheek and rectal probes failed to give accurate or precise readings (ear: bias = −4, precision = 14, Arms = 15; cheek: bias = 12, precision = 11, Arms = 16; and rectum: bias = 5, precision = 12, Arms = 13).

Conclusion and clinical relevance

In order to obtain 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.

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