Pulse oximeter

You may hear some of the following terms:

  • SpO2 = This is an indirect measurement of O2 in the blood, usually using and Oximeter device on the patients fingertip. It provides an estimate of the blood O2 in a capillary below the nail. Abnormal SpO2 is below 95% without pre-existing lung condition.
    Those with a pre-existing lung condition may have lower normal values e.g. abnormal SpO2 may be less than 92%.
  • SaO2 = This is a direct measurement of the O2 in the arterial blood gases. It measures the percentage of the oxyhaemoglobin. Normal levels should be between 95 to 100%.
  • Haemoglobin = Haemoglobin is a red protein responsible for transporting oxygen in the blood it can be in two states oxygenated or deoxygenated.


  • Harper J. Post-anaesthesia care unit nurses' knowledge of pulse oximeter. J Nurses Staff‘ Dev 2004; 20(4):177-180
  • AttinM, CardinS, DeeV, DoeringL, DunnD, EricksonVetaI. An educational project to improve knowledge related to pulse oximeter. Am J Crit Care 2002; 11(6):529-534.