A pulse oximeter probe is a small peg-like or adhesive device that is used to measure the oxygen saturation of your blood (an indication of how effectively you are breathing) in hospitals and other clinical settings.
It is usually attached to a finger, but in some situations it will be attached to an ear or toe (there are site specific probes used for this). There are also different sized probes used for children and babies.
The NHS has issued a safety alert warning that if an incorrect pulse oximeter probe is used, or it is used in the wrong place it can give a reading 50% lower or 30% higher than the actual value.
Adult finger oximeter probes should not be attached an ear.
Oximeter probes for babies and children should not be used on adults, and when used on babies should be selected according to the patient’s weight.
If an oximeter probe intended for the finger is attached to the ear (or vice versa), or a probe intended for an adult is attached to a baby or a child (or vice versa), it can produce a reading up to 50% lower or 30% higher than the real value. The clinical implication of an inaccurately high reading […] is that staff may be falsely reassured about a patient’s condition, when in reality the patient is deteriorating, or may make an inappropriate intervention when in fact a patient is stable or improving. — NHS
The warning was issued after studies found many clinical staff were unaware finger probes can give misleading results if attached to ears. And that many probes do not have clear indications as to where they should be used once removed from packaging.
They found that this posed a potentially high risk of harm to patients.
A PDF copy of the alert can be found here.