A Comparison of 2 Pluse Oximeters in Dogs

Readings from 2 veterinary pulse oximeters (SDI Vet-Ox #4402 and Nellcor N-20V) were compared in 6 isoflurane-anesthetized dogs. Simultaneous readings Of S_p0₂were recorded from 2 sites (toe and ear) over a range of inspired oxygen concentrations (15-100%), and compared to directly measured S_aO₂ readings. Greater variability of readings was obtained from the Vet-Ox, which failed to give readings 25% of the time. The bias (mean S_aO₂-S_p0₂) and precision (SD of bias) were calculated from the data for each oximeter. For the Vet-Ox, bias (precision) from the toe was +4.O (5.2) and from the ear +1.7 (2.2). The bias (precision) for N-20V readings from the toe was +1.6 (1.5) and from the ear +0.7 (1.5). Generally, both oximeters tended to underestimate S_aO₂; however, both overestimated at the lowest P_a0₂ values. Pearscn cowelation coeefficients were 0.81 for the Vet-Ox and 0.94 for the N-20V for the combined data, including value from probes placed on the toe and ear at all inspired oxygen concentrations. In the two locatiom from which readings were obtained, the 2 units performed quite differently.