This prospective laboratory investigation was done to compare the accuracy of a 3rd (Dolphin Voyager) versus 1st generation pulse oximeter (Nellcor N-180). Eight adult dogs were included.
In anesthetized dogs, arterial oxygen saturation (SpO2) was recorded simultaneously with each pulse oximeter.
The oxygen fraction in inspired gas (FiO2) was successively reduced from 1.00 to 0.09, with re-saturation (FiO2 0.40) after each breathe-down step.
After each 3-minute FiO2 plateau, SpO2 and pulse rate (PR) were compared with the fractional arterial saturation (SaO2) and PR determined by co-oximetry and invasive blood pressure monitoring, respectively.
Data analysis included Bland-Altman (B¨CA) plots, Lin`s concordance correlation factor (¦Ñc), and linear regression models.
Results: Over a SaO2 range of 33¨C99%, the overall bias (mean SpO2 − SaO2), precision (SD of bias), and accuracy (Arms) for the Dolphin Voyager and Nellcor N-180 were 4.3%, 4.4%, and 6.1%, and 3.2%, 3.0%, and 4.3%, respectively.
Bias increased at SaO2 < 90%, more so with the Dolphin Voyager (from 1.6% to 8.6%) than Nellcor N-180 (from 3.2% to 4.5%).
The SpO2 readings correlated significantly with SaO2 for both the Dolphin Voyager (¦Ñc = 0.94) and Nellcor N-180 (¦Ñc = 0.97) (p < 0.001).
Regarding PR, bias, precision, and accuracy (Arms) for the Dolphin Voyager and Nellcor N-180 were −0.5, 4.6, and 4.6 and 1.38, 4.3, and 4.5 beats minute1, respectively. Significant correlation existed between pulse oximeter and directly measured PR (Dolphin Voyager: ¦Ñc = 0.98; Nellcor N-180: ¦Ñc = 0.99) (p < 0.001).
Conclusions and clinical relevance: In anesthetized dogs with adequate hemodynamic function, both instruments record SaO2 relatively accurately over a wide range of normal saturation values. However, there is an increasing overestimation at SaO2 < 90%, particularly with the Dolphin Voyager, indicating that 3rd generation pulse oximeters may not perform better than older instruments.
The 5.4-fold increase in bias with the Dolphin Voyager at SaO2 < 90% stresses the importance of a 93¨C94% SpO2 threshold to ensure an arterial saturation of ¡Ã90%.
In contrast, PR monitoring with both devices is very reliable.
Source: Burns, Patrick M, Driessen, Bernd, Boston, Ray & Gunther, Robert A (2006): Accuracy of a third (Dolphin Voyager) versus first generation pulse oximeter (Nellcor N-180) in predicting arterial oxygen saturation and pulse rate in the anesthetized dog. In: Veterinary Anaesthesia and Analgesia 33 (5), 281-295.
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