Accuracy of pulse oximetry in the intensive care unit

Intensive Care Med. 2001 Oct;27(10):1606-13. doi: 10.1007/s001340101064.


Objective: Pulse oximetry (SpO2) is a standard monitoring device in intensive care units (ICUs), currently used to guide therapeutic interventions. Few studies have evaluated the accuracy of SpO2 in critically ill patients. Our objective was to compare pulse oximetry with arterial oxygen saturation (SaO2) in such patients, and to examine the effect of several factors on this relationship.

Design: Observational prospective study.

Setting: A 26-bed medical ICU in a university hospital.

Patients: One hundred two consecutive patients admitted to the ICU in whom one or serial arterial blood gas analyses (ABGs) were performed and a reliable pulse oximeter signal was present.

Interventions: For each ABG, we collected SaO2, SpO2, the type of pulse oximeter, the mode of ventilation and requirement for vasoactive drugs.

Measurements and results: Three hundred twenty-three data points were collected. The mean difference between SpO2 and SaO2 was -0.02% and standard deviation of the differences was 2.1%. From one sample to another, the fluctuations in SpO2 to arterial saturation difference indicated that SaO2 could not be reliably predicted from SpO2 after a single ABG. Subgroup analysis showed that the accuracy of SpO2 appeared to be influenced by the type of oximeter, the presence of hypoxemia and the requirement for vasoactive drugs. Finally, high SpO2 thresholds were necessary to detect significant hypoxemia with good sensitivity.

Conclusion: Large SpO2 to SaO2 differences may occur in critically ill patients with poor reproducibility of SpO2. A SpO2 above 94% appears necessary to ensure a SaO2 of 90%.

Publication types

  • Comparative Study
  • Validation Study

MeSH terms

  • Bias
  • Blood Gas Analysis / instrumentation
  • Blood Gas Analysis / methods
  • Blood Gas Analysis / standards
  • Confounding Factors, Epidemiologic
  • Critical Care / methods
  • Critical Care / standards*
  • Hospitals, University
  • Humans
  • Hypoxia / blood*
  • Hypoxia / diagnosis*
  • Intensive Care Units*
  • Linear Models
  • Monitoring, Physiologic / instrumentation
  • Monitoring, Physiologic / methods
  • Monitoring, Physiologic / standards*
  • Oximetry / instrumentation
  • Oximetry / methods
  • Oximetry / standards*
  • Oxygen / blood*
  • Prospective Studies
  • Respiration, Artificial / methods
  • Sensitivity and Specificity
  • Vasoconstrictor Agents / therapeutic use
  • Vasodilator Agents / therapeutic use


  • Vasoconstrictor Agents
  • Vasodilator Agents
  • Oxygen