Abstract
Hypothesis: Pulse oximetry is an accurate, noninvasive assay of oxygen saturation percentage (SaO 2) in acutely severe anemia (less than 5 g/dL). Design: A paired comparison of SaO 2 by pulse oximetry (SpO 2) and arterial blood gas analysis (SaO 2) in patients with either acute gastrointestinal bleeding or blunt trauma with hematocrit of less than 20%. Setting: An academic emergency department in a tertiary referral hospital with a Level I trauma center. Participants: Seventeen nonhypoxic patients were identified with initial hematocrit of less than 20% over a 9-month period. Measurements and main results: Determination of SaO 2 by pulse oximetry and arterial blood analysis was not statistically significantly different ( P <.05) over a range of hemoglobin levels from 2.3 to 8.7 g/dL. The observed mean difference between SpO 2 and SaO 2 was 0.53±0.23% (mean±SEM; n=17). The 95% confidence interval associated with this difference score ranged from 0.044 to 1.014. Conclusion: Despite reports that pulse oximetry is inaccurate below a hemoglobin concentration of 5 g/dL, our study suggested that this technology is accurate and reliable at 2.3 g/dL for nonhypoxic SaO 2 values (SaO 2 of more than 93%). The anemic endpoint where pulse oximetry either becomes inaccurate or simply fails to work has not been determined. Pulse oximetry overestimates SaO 2 on average by 0.53% over a range of hemoglobin concentrations from 2.3 to 8.7 g/dL. [Jay GD, Hughes L, Renzi FP: Pulse oximetry is accurate in acute anemia from hemorrhage. Ann Emerg Med July 1994;24:32-35.]
Published Version
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