Skip to main content

Effect of anemia on pulse oximeter accuracy at low saturation


A retrospective evaluation of simultaneous tests of oximeters of various manufacturers in volunteer subjects disclosed greater errors at low saturations in subjects with low hemoglobin (Hb) concentrations. Forty-three pulse oximcters of 12 manufacturers studied over a period of 10 months showed that, at a mean arterial oxygen saturation (SaO2) level of 54.5%, as Hb concentration fell, average pulse oximeter (SpO2) bias increased approximately linearly from 0 at Hb > 14 g/dl to about -14% at 8 < Hb < 9 g/dl. At SaO2 = 53.6%, the mean bias (SaO2-SpO2) of 13 oximcters of 5 manufacturers averaged -15.0% (n = 43) in a subject with Hb = 8 g/dl, but -6.4% (n = 390) in nonanemic subjects. The additional bias in the anemic subject increased with desaturation. It was 0.13% at SaO2 = 98.5% (n = 13), -1.31% at 87.5% (n = 38), -2.71% at 75.1% (n = 38), -5.18% at 61.3% (n = 26), and -9.95% at 53.6% (n = 41); n is the product of the number of oximeters and number of tests in each saturation range. The instruments that showed the greatest errors at low saturations in nonanemic subjects also showed the greatest additional errors associated with anemia (the range between manufacturers of anemic incremental error at about 53% being from -3.2 to -14.5%) and conformed well to the relationship bias (anemic) = 1.35 × bias (normal)-8.18% (r = 0.94; Sy·x = 3.3%). The error due to anemia was zero at 97% SaO2 and became evident when SaO2 fell below 75%.

This is a preview of subscription content, access via your institution.


  1. Lee SE, Tremper KK, Barker SJ. Effects of anemia on pulse oximetry and continuous mixed venous oxygen saturation monitoring in dogs. Anesth Analg 1988;67;S130

    Google Scholar 

  2. Severinghaus JW, Naifeh KH. Accuracy of response of six pulse oximeters to profound brief steady hypoxia. Anesthesiology 1987;67:551–558

    PubMed  Article  CAS  Google Scholar 

  3. Severinghaus JW, Naifeh KH, Koh SO. Errors in 14 pulse oximeters during profound hypoxia. J Clin Monit 1989;5:72–81

    PubMed  Article  CAS  Google Scholar 

Download references

Author information

Authors and Affiliations


Rights and permissions

Reprints and Permissions

About this article

Cite this article

Severinghaus, J.W., Koh, S.O. Effect of anemia on pulse oximeter accuracy at low saturation. J Clin Monitor Comput 6, 85–88 (1990).

Download citation

  • Received:

  • Revised:

  • Accepted:

  • Issue Date:

  • DOI:

Key words

  • Measurement techniques: pulse oximetry
  • Blood: anemia
  • Equipment: pulse oximeters
  • Oxygen: saturation
  • Hypoxia