Pulse oximeters: For health care providers

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• Pulse oximetry limitations
• What we recommend

Pulse oximetry limitations

Arterial blood gas (ABG) testing is considered the gold standard in measuring blood oxygenation. Pulse oximeters offer convenience because they do not require a blood sample and can be easily measured at the bedside. However, pulse oximeter measurements are an estimate and are less accurate than ABG measurements.

This means there is always a risk that a pulse oximeter reading may be different from the actual blood oxygenation level. This difference may be clinically significant.

Recent reports have identified that pulse oximeter readings can be less accurate in people with dark skin. These reports describe a bias toward occult hypoxemia. Occult hypoxemia is when the estimated blood gas value measured by a pulse oximeter reads higher than the arterial blood gas measurement of oxygen saturation.

Reports have also indicated that pulse oximeter readings may be less accurate as true oxygen saturation decreases.

Regulated pulse oximeters typically give readings within 2% to 4% of ABG but can be less accurate due to many real-world factors, such as:

• how the oximeter was used
  • incorrect sensor
  • incorrectly applied sensor (for example, tightness, fit and location)
  • improper finger placement
  • excessive movement
• physical traits and medical conditions
  • acidosis
  • jaundice
  • low perfusion
  • severe anemia
  • venous congestion
  • cardiac arrest or shock
  • use of intravascular dyes
  • dysfunctional hemoglobin
  • elevated levels of bilirubin
  • venous pulsation or pulse quality
  • low blood pressure (hypotension)
  • low body temperature (hypothermia)
  • hypoxia or very low oxygen saturation
  • finger nails (wearing polish, artificial nails, very long nails)
  • finger size (due to a mismatch between finger and sensor size)
• the environment in which the reading was taken
  • excessive light
  • extreme moisture (use of sanitizers, rain)
  • cold (warm hands give optimal performance)
  • presence of electromagnetic or electrosurgical sources

What we recommend

Even with these limitations, pulse oximeters are useful clinically. To support decision-making, consider taking measurements at different locations or finding a trend to assess oxygenation with a pulse oximeter more accurately.

When there are conflicting signs of hypoxia or doubt in the pulse oximeter reading:

• blood-gas measurements may be considered to accurately establish oxygenation
• if blood-gas measurements are not possible or practical, assume the reading is inaccurate and take a precautionary approach to clinical management of the patient

Review the device labelling for information on:

• the accuracy of your device
• how to properly take a pulse oximeter reading with your device
• how to calibrate your device and maintain device calibration

It’s important to be aware of the limitations with using pulse oximeters so you can take action before an adverse event happens.

You should contact the manufacturer if:

• there’s a technical problem with the device
• you’re concerned about your device’s performance

Check that your device is licensed in Canada:

• Medical devices active licences search

Report adverse events:

• Consumer Medical Device Report Form

Report a medical device problem:

• Hospital
• Health care provider