Accuracy of a reflectance pulse oximeter in anesthetized horses

The accuracy of a reflectance pulse oximeter was determined in 22 anesthetized horses. Oximetric blood oxygen saturation was measured with the pulse oximeter probe attached to the mucosa of the mandible. Arterial blood oxygen saturation (SaO2) was calculated from arterial blood gas values and the equine blood oxygen dissociation curve. The mean +/- SD difference between oximetric blood oxygen saturation and SaO2 was -1.3 +/- 3.1% for values of SaO2 ranging from 80 to 100%. The difference between oximetric blood oxygen saturation and SaO2 was influenced by SaO2, the mean arterial blood pressure, and preanesthetic medication administered, but not by age, sex, or body weight of the horse, individual animal effect, anesthetic induction or maintenance agent, procedure performed, body position, mode of lung ventilation, time of sampling, arterial pH, or carbon dioxide tension.