RESUMO
OBJECTIVE: Evaluation of five pulse oximeters in dogs, cats and horses with sensors placed at five sites and hemoglobin saturation at three plateaus. STUDY DESIGN: Prospective randomized multispecies experimental trial. ANIMALS: Five healthy dogs, cats and horses. METHODS: Animals were anesthetized and instrumented with ECG leads and arterial catheters. Five pulse oximeters (Nellcor Puritan Bennett-395, NPB-190, NPB-290, NPB-40 and Surgi-Vet V3304) with sensors at five sites were studied in a 5 x 5 Latin square design. Ten readings (SpO2) were taken at each of three hemoglobin saturation plateaus (98, 85 and 72%) in each animal. Arterial samples were drawn concurrently and hemoglobin saturation was measured with a co-oximeter. Accuracy of saturation measurements was calculated as the root mean squared difference (RMSD), a composite of bias and precision, for each model tested in each species. RESULTS: Accuracy varied widely. In dogs, the RMSD for the NPB-395, NPB-190, NPB-290, NPB-40 and V3304 were 2.7, 2.2, 2.4, 1.7 and 2.7% respectively. Failure to produce readings for the NPB-395, NPB-190, NPB-290, NPB-40 and V3304 were 0, 0, 0.7, 0, and 20%, respectively. The Pearson correlation coefficients for the tongue, toe, ear, lip and prepuce or vulva were 0.95, 0.97, 0.69, 0.87 and 0.95, respectively. In horses, the RMSD for the NPB-395, NPB-190, NPB-290, NPB-40 and V3304 were 3.1, 3.0, 4.7, 3.3 and 2.1%, respectively while rates of failure to produce readings were 10, 21, 0, 17 and 60%, respectively. The Pearson correlation coefficients for the tongue, nostril, ear, lip and prepuce or vulva were 0.98, 0.94, 0.88, 0.93 and 0.94, respectively. In cats, the RMSD for all data for the NPB-395, NPB-190, NPB-290, NPB-40 and V3304 were 5.9, 5.6, 7.9, 7.9 and 10.7%, respectively while failure rates were 0, 0.7, 0, 20 and 32%, respectively. The correlation coefficients for the tongue, rear paw, ear, lip and front paw were 0.54, 0.79,.0.64, 0.49 and 0.57, respectively. For saturations above 90% in cats, the RMSD for the NPB-395, NPB-190, NPB-290, NPB-40 and V3304 were 2.6, 4.4, 4.0, 3.5 and 4.8%, respectively, while failure rates were 0, 1.7, 0, 25 and 43%, respectively. CONCLUSIONS AND CLINICAL RELEVANCE: Accuracy and failure rates (failure to produce a reading) varied widely from model to model and from species to species. Generally, among the models tested in the clinically relevant range (90-100%) RMSD ranged from 2-5% while failure rates were highest in the V3304.
