Simultaneous comparison of three noninvasive oximeters in healthy volunteers

Noninvasive monitoring of arterial hemoglobin oxygen saturation (SaO2) from the Nellcor N-100 and the Ohmeda-Biox 3700 pulse oximeters were compared with SaO2 measured simultaneously by the Hewlett-Packard 47201A ear oximeter. A total of 868 pairs of data points ranging in saturation from 55-100% were obtained from 31 healthy adult volunteers of different ages, sex, skin pigmentation, height, weight, hematocrit, and smoking habits. Steady state and rapidly changing hypoxic conditions were achieved by varying the inspired O2 concentration between 10 and 100%. Measurements were analyzed by means of linear regression. The equations for the best fitted linear regression line between the Nellcor and the Ohmeda-Biox pulse oximeters as compared to the reference Hewlett-Packard ear oximeter readings were Y = 0.92X + 7.45 and Y = 1.10X - 10.73, respectively. Our study showed that despite a very close correlation among these three oximeters (r = 0.98), when compared to the Hewlett-Packard ear oximeter, the Nellcor pulse oximeter overestimates SaO2 by 2-4%, whereas the Ohmeda-Biox pulse oximeter underestimates SaO2 by 3-6% for SaO2 levels between 70 and 55%.