Poor signal

Pulse oximeters need a strong regular pulse in the finger (or ear etc) that the probe is on.

A common problem is that people can have cold hands and feet, and have only a very weak pulse. In this case a pulse oximeter may display a reading but it might not be accurate. Some pulse oximeters have a means of indicating how strong the signal is they are receiving and it is important to check this. A still weaker signal may mean the pulse oximeter is not able to work at all.

An irregular signal can also cause problems for a pulse oximeter trying to determine oxygen saturation. This can be caused by an irregular heart beat or by the patient moving, shivering or fitting.

Poor positioning of the probe can cause inaccurate readings due to various problems. This can be a particular problem with very small fingers and very large ones. Make sure the probe is well on the finger.

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page last modified: 22/05/2005
Pulse oximetry
What is oxygen saturation?
What does it mean?
How does it work?
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