Evaluation of accuracy of pulse oximetry in dogs

Abstract

Summary The accuracy of a pulse oximeter was evaluated over a wide range of arterial oxygen and carbon dioxide tensions, using 2 probes (finger probe and ear probe) and 2 monitoring sites (tongue and tail) in anesthetized dogs The arterial oxygen saturation of hemoglobin (SaO2) measured directly with a multiwavelength spectrophotometer was compared with saturation estimated by pulse oximetry (SpO2). Linear regression analysis of the pooled data from 399 simultaneous measurements of SpO2 and SaO2 indicated a highly significant correlation of SpO2 with SaO2 (r = 0.97; P ≤ 0.0001). Although the mean difference (± sd) between SpO2 and SaO2 for pooled data was small (- 0.06 ± 6.8%), SpO2 tended to underestimate high SaO2 values (≥ 70%) and to overestimate low SaO2 values (< 70%). When SaO2 values were ≥ 70%, the ear probe applied to the tail was less accurate (produced a significantly greater SpO2-SaO2 difference) than the ear probe on the tongue, or the finger probe at either site. When SaO2 values were ≤ 50%, the finger probe applied at the tail was more accurate (produced significantly smaller SpO2-SaO2 differences) than the ear probe at either site. When SaO2 values were ≤ 70%, high arterial carbon dioxide tension (≥ 60 mm of Hg) was associated with greater overestimation of SaO2.