A variable pitch oxygen saturation indicator designed for use in the magnetic resonance environment

Many commercially available pulse oximeters have a variable pitch blood oxygen saturation indicator, which emits a 'beep' between 175 Hz and 675 Hz with each heart beat. The frequency of this beep is dependent on the blood oxygenation measured by the oximeter, higher frequencies corresponding to higher blood saturation percentages. This is a useful feature for an anaesthetist, rapidly communicating potentially life-threatening situations in an easily detectable manner. Most available oximeters with an audio output feature are vulnerable to the effects of magnetic resonance scanning. In this article an add-on module is described for generating a beep to indicate the blood oxygen saturation which has been specifically designed to operate in the MR environment.