Fingertip Pulse Oximeter Testing – Small Devices, Big Questions About Accuracy
They're small, inexpensive, easy to use and commonly found in GP practices, medical clinics, Age Care and other healthcare environments.
Fingertip pulse oximeters are small, inexpensive, easy to use and commonly found in GP practices, medical clinics and other healthcare environments. But how accurate are they? Fingertip pulse oximeter testing plays an important role in identifying devices that may not be performing as expected.
But how do you know those numbers are correct?
At ClinicCheck, part of NZ Test Group, our experience carrying out annual biomedical equipment inspections has shown that these seemingly simple devices don't always perform as expected.
And when healthcare professionals rely on those readings to help assess a patient, accuracy matters.
What Does a Fingertip Pulse Oximeter Measure?
A fingertip pulse oximeter provides two important measurements:
SpO₂ (oxygen saturation): An estimate of the percentage of haemoglobin in arterial blood carrying oxygen.
Pulse rate: The number of heartbeats per minute.
The device uses light transmitted through the finger to estimate oxygen saturation and detect changes associated with the pulse.
Unlike a blood test, a pulse oximeter is non-invasive and provides a reading within seconds.
However, the number displayed is an estimate, not a direct measurement of blood oxygen levels.
Can a Pulse Oximeter Give an Incorrect Reading?
Yes, and that's an important consideration for anyone using these devices.
A pulse oximeter can display a number that looks perfectly reasonable without necessarily providing an accurate measurement.
Readings can be affected by several factors, including:
Poor circulation or cold fingers.
Patient movement during measurement.
Incorrect finger positioning.
Nail polish or artificial nails.
Ambient light interfering with the sensor.
Device condition, sensor performance or internal faults.
Skin pigmentation can also affect the accuracy of some pulse oximeters, with research identifying a risk of oxygen saturation being overestimated in certain patients.
These factors demonstrate why a displayed reading should always be considered alongside the patient's clinical condition.
But there's another question worth asking.
What happens when the problem isn't the patient or the measurement conditions, but the pulse oximeter itself?
What Have We Found During Annual Equipment Inspections?
During routine annual biomedical equipment inspections, ClinicCheck has identified fingertip pulse oximeters that did not meet the applicable verification requirements.
These findings are particularly interesting because the devices may appear to be operating normally.
They switch on, display an oxygen saturation percentage, and show a pulse rate.
To someone using the device, there may be no obvious indication that further investigation is needed.
This highlights an important distinction:
A pulse oximeter displaying a reading is not necessarily the same as a pulse oximeter providing a reading within its specified accuracy limits.
Our experience reinforces the value of including these small medical devices in an appropriate equipment management and verification programme.
How Are Fingertip Pulse Oximeters Tested?
Depending on the device and the available verification equipment, a biomedical technician may use a suitable SpO₂ simulator or pulse oximeter testing system to assess aspects of the device's performance.
Testing may include checking:
The device's response to simulated oxygen saturation conditions.
Displayed pulse rate against a known simulated value.
Consistency and stability of readings.
General operation, display condition and battery performance.
Results against the manufacturer's applicable specifications and verification procedures.
An important point is that not all SpO₂ simulators or test methods can establish the complete clinical accuracy of a pulse oximeter.
Some systems are intended for functional checks or repeatability assessments rather than full accuracy validation.
The verification method must therefore be appropriate for the particular device and the claims being made about its performance.
Why Does Annual Verification Matter?
Fingertip pulse oximeters are often relatively inexpensive compared with larger medical devices.
That can make them easy to overlook.
However, their purchase price does not determine their clinical importance.
A small fingertip oximeter may be used during patient assessments, respiratory examinations or routine observations.
A misleading oxygen saturation reading could influence how a patient's condition is interpreted.
Under an appropriate medical equipment management programme, inspection and verification can help identify devices requiring further investigation, repair or replacement.
AS/NZS 3551:2012 – Management programs for medical equipment provides a framework for managing medical equipment throughout its service life, including inspection, maintenance, testing and documentation.
The appropriate inspection and verification arrangements should consider the equipment, its intended use, manufacturer recommendations and clinical risk.
What Should Happen When a Pulse Oximeter Fails Verification?
When a fingertip pulse oximeter does not meet the applicable verification criteria, the result should be investigated and documented.
Depending on the findings, this may involve confirming the test method, checking the device's condition, reviewing manufacturer specifications or arranging further assessment.
Where a device cannot be demonstrated to meet the requirements for its intended clinical use, it should not simply be returned to service.
For some inexpensive fingertip oximeters, replacement may be more practical than repair.
The important point is that a device should not be considered satisfactory simply because it turns on and displays numbers.
Small Device, Important Responsibility
Fingertip pulse oximeters are a useful and convenient clinical tool.
But their simplicity can create a false sense of confidence.
Our experience at ClinicCheck has demonstrated that faults or unacceptable verification results can be found even in devices that appear to operate normally.
Regular equipment management, appropriate performance checks and awareness of measurement limitations all contribute to safer clinical practice.
Because when it comes to medical equipment, small doesn't mean unimportant.
How ClinicCheck Can Help
ClinicCheck, part of NZ Test Group, provides biomedical equipment inspection and verification services throughout New Zealand.
Our work includes medical equipment covered by AS/NZS 3551:2012, helping healthcare providers manage equipment performance, safety and compliance.
Whether it's a fingertip pulse oximeter, blood pressure monitor, ECG machine or other medical device, our focus is on providing practical, independent equipment verification.
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