Volume 46, Issue 3 p. 207-212
Free Access

Potential errors in pulse oximetry

II. Effects of changes in saturation and signal quality*

R. K. WEBB

R. K. WEBB

R.K. Webb, MB, BS, FFARACS, Senior Staff Specialist, A.C. Ralston, BSc, BAppSc, Medical Physicist, W.B. Runciman, Bsc(Med), MB, BCh, FFARACS, PhD, Professor and Head of Department of Anaesthesia and Intensive Care, Royal Adelaide Hospital, North Terrace, Adelaide, South Australia, Australia 5000.

Search for more papers by this author
A. C. RALSTON

A. C. RALSTON

R.K. Webb, MB, BS, FFARACS, Senior Staff Specialist, A.C. Ralston, BSc, BAppSc, Medical Physicist, W.B. Runciman, Bsc(Med), MB, BCh, FFARACS, PhD, Professor and Head of Department of Anaesthesia and Intensive Care, Royal Adelaide Hospital, North Terrace, Adelaide, South Australia, Australia 5000.

Search for more papers by this author
W. B. RUNCIMAN

Corresponding Author

W. B. RUNCIMAN

R.K. Webb, MB, BS, FFARACS, Senior Staff Specialist, A.C. Ralston, BSc, BAppSc, Medical Physicist, W.B. Runciman, Bsc(Med), MB, BCh, FFARACS, PhD, Professor and Head of Department of Anaesthesia and Intensive Care, Royal Adelaide Hospital, North Terrace, Adelaide, South Australia, Australia 5000.

should be addressed to Professor W.B. Runciman please.Search for more papers by this author
First published: March 1991
Citations: 124
*

Combined study with Australian Patient Safety Foundation, GPO Box 400, Adelaide, South Australia, Australia 5001.

Summary

The published studies of pulse oximeter performance under conditions of normal, high and low saturation, exercise, poor signal quality and cardiac arrhythmia are reviewed. Most pulse oximeters have an absolute mean error of less than 2% at normal saturation and perfusion; two-thirds have a standard deviation (SD) of less than 2%, and the remainder an SD of less than 3%. Some pulse oximeters tend to read 100% with fractional saturations of 97–98%. Pulse oximeters may be suitable hyperoxic alarms for neonates if the alarm limit chosen is directly validated for each device. Pulse oximeters are poorly calibrated at low saturations and are generally less accurate and less precise than at normal saturations; nearly 30% of 244 values reviewed were in error by more than 5% at saturations of less than 80%. Ear, nose and forehead probes respond more rapidly to rapid desaturation than finger probes, but are generally less accurate and less precise. Ear oximetry may be inaccurate during exercise. Low signal quality can result in failure to present a saturation reading, but data given with low signal quality warning messages are generally no less accurate than those without. Cardiac arrhythmias do not decrease accuracy of pulse oximeters so long as saturation readings are steady.