EFFECT OF SKIN PIGMENTATION ON PULSE OXIMETRY ACCURACY IN THE EMERGENCY DEPARTMENT

Objective: To determine whether pulse oximeter (PO) accuracy and signa l quality are affected by level of skin pigmentation. Methods: Observa tional study in a community hospital ED. Consecutive adult patients un dergoing arterial blood gas determination were enrolled into the study . Skin pigmentation was determined by comparison with standardized col or swatches under controlled lighting; assigned values were used to st ratify patients into 3 groups (light, intermediate, and dark) using pr edetermined criteria. Simultaneous with arterial blood sampling, staff recorded PO reading of O-2 saturation using the Nellcor D-25 oximeter . PO values were compared with criterion standard values measured usin g a 4-wavelength spectrophotometer or co-oximeter. PO signal quality a lso was recorded. Bias (the mean difference between PO and co-oximeter -measured values of hemoglobin saturation) and precision (the standard deviation of the bias) were calculated. Groups were compared using on e-way ANOVA, Bartlett's test for variances, and chi(2) test. Results: O-2 saturation data were obtained for 284 patients. Bias values did no t differ between the 3 skin pigment groups (p = 0.79). Precision was o f borderline significance (p = 0.05), but there was no dose-response r elation between skin pigmentation and precision. Study personnel repor ted suboptimal PO function most often among patients in the dark group (p = 0.003), but this finding was of no clinical significance. PO sig nal failure was rare (<1% of all patients). Conclusions: Although seve ral prior studies suggest the contrary, this study found that skin pig mentation does not affect the bias or precision of pulse oximetry. Fur thermore, skin pigmentation has no clinically significant effect on PO signal quality.