Accuracy of a reflectance pulse oximeter in anesthetized horses.

This study investigates the accuracy of a reflectance pulse oximeter, a device used to measure blood oxygen saturation, in anesthetized horses. The researchers found that the device’s readings were generally close to the calculated arterial blood oxygen saturation, with certain factors like blood saturation level, mean arterial blood pressure, and pre-anesthetic medication influencing the difference.

Research Objectives

• The primary aim of this study was to determine the accuracy of a reflectance pulse oximeter in anesthetized horses.
• The researchers measured the oximetric blood oxygen saturation using a pulse oximeter probe attached to the horse’s mandible (lower jaw) mucosa.
• They then calculated the arterial blood oxygen saturation (SaO2) using arterial blood gas values and the equine blood oxygen dissociation curve as a benchmark.

Research Findings

• The average difference between oximetric blood oxygen saturation and SaO2 was -1.3 ± 3.1% for SaO2 values ranging from 80 to 100%. This means the pulse oximeter’s readings were, on average, slightly lower than the calculated SaO2, but still reasonably close.
• The difference between the two measurements was influenced by the SaO2 level, the mean arterial blood pressure and whether pre-anesthetic medication was administered.

Factors not influencing the Result

• The study found that the age, sex, and body weight of the horse did not notably impact the difference between oximetric blood oxygen saturation and SaO2.
• Other factors, such as the individual animal effect, anesthetic induction or maintenance agent, the medical procedure performed, the body position of the horse, and the mode of lung ventilation, were also found not to significantly affect the results.
• Similarly, the time of sampling, arterial pH (a measure of acidity or alkalinity), and carbon dioxide tension (pressure) did not significantly impact the oximeter’s accuracy.