Evaluation of accuracy of pulse oximetry in dogs

<jats:title>Summary</jats:title> <jats:p>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 (SaO<jats:sub>2</jats:sub>) measured directly with a multiwavelength spectrophotometer was compared with saturation estimated by pulse oximetry (SpO<jats:sub>2</jats:sub>). Linear regression analysis of the pooled data from 399 simultaneous measurements of SpO<jats:sub>2</jats:sub> and SaO<jats:sub>2</jats:sub> indicated a highly significant correlation of SpO<jats:sub>2</jats:sub> with SaO<jats:sub>2</jats:sub> (<jats:italic>r</jats:italic> = 0.97; <jats:italic>P</jats:italic> ≤ 0.0001). Although the mean difference (± <jats:sc>sd</jats:sc>) between SpO<jats:sub>2</jats:sub> and SaO<jats:sub>2</jats:sub> for pooled data was small (- 0.06 ± 6.8%), SpO<jats:sub>2</jats:sub> tended to underestimate high SaO<jats:sub>2</jats:sub> values (≥ 70%) and to overestimate low SaO<jats:sub>2 </jats:sub>values (< 70%). When SaO<jats:sub>2</jats:sub> values were ≥ 70%, the ear probe applied to the tail was less accurate (produced a significantly greater SpO<jats:sub>2</jats:sub>-SaO<jats:sub>2</jats:sub> difference) than the ear probe on the tongue, or the finger probe at either site. When SaO<jats:sub>2</jats:sub> values were ≤ 50%, the finger probe applied at the tail was more accurate (produced significantly smaller SpO<jats:sub>2</jats:sub>-SaO<jats:sub>2</jats:sub> differences) than the ear probe at either site. When SaO<jats:sub>2</jats:sub> values were ≤ 70%, high arterial carbon dioxide tension (≥ 60 mm of Hg) was associated with greater overestimation of SaO<jats:sub>2</jats:sub>.</jats:p>