ACCURACY OF 2 PULSE OXIMETERS AT LOW ARTERIAL HEMOGLOBIN-OXYGEN SATURATION

Objective: To evaluate the performance of two pulse oximeters in the m easurement of arterial hemoglobin saturation in hypoxemic children. De sign: Prospective, repeated measures observational study. Setting: A 1 6-bed pediatric intensive care unit in a children's tertiary hospital. Patients: Sixty-six patients with arterial saturation of <90%. Interv entions: Three arterial blood samples were taken from each subject dur ing a 48 hr period. Pulse oximeter measurements of arterial saturation were compared with arterial saturation determined by cooximetry. Meas urements and Main Results: Arterial saturation was measured using one or both pulse oximeters (Spo(2)) and compared with the arterial hemogl obin saturation determined by cooximetry (Sao(2)). Sixty-two subjects were studied, using the Ohmeda pulse oximeter giving 185 data points ( 78 with saturations <75% [defined by the average of pulse oximeter and cooximeter]) 53 subjects were studied, using the Hewlett-Packard puls e oximeter yielding 155 data points (60 with saturations <75%). Spo(2) ranged from 24% to 94%. Bias and precision of the Ohmeda pulse oximet er were -2.8% and 4.8% >75% and -0.8% and 8.0% <75%. Bias and precisio n of the Hewlett-Packard pulse oximeter were -0.5% and 5.1% >75% and 0 .4% and 4.6% <75%. Intrapatient regression coefficient (r) for the dif ferences between pulse oximeter and cooximeter was 0.58 for the Ohmeda and 0.59 for the Hewlett-Packard. Regression coeffi cients for predic ting change in cooximeter value given a change in the Ohmeda pulse oxi meter were 0.59 and 0.71 <75% and >75%, respectively. Similar coeffici ents for the Hewlett-Packard pulse oximeter were 0.50 and 0.70, respec tively. Conclusion: The performance of the Ohmeda pulse oximeter deter iorated below an Spo(2) of 75%. The Hewlett-Packard pulse oximeter per formed consistently above and below an Spo(2) of 75%, The ability of b oth pulse oximeters to reliably predict change in Sao(2) based on chan ge in pulse oximetry was limited. We recommend measurement of Pao(2) o r Sao(2) for important clinical decisions.