Fig 1 shows an oximeter attached to a patient. The SpO₂ is 95% and pulse 84bpm. The trace shows a waveform with a regular pulse.

Question: What is the difference between the two traces?

Answer: The pulse waveform is erratic and not being well detected This patient may be moving or shivering. Hold the hand steady or wait until the patient has stopped shaking.

Shivering is a common problem in recovery, but not common in theatre. Check the patient carefully before deciding the oximeter is not correct.