A method and apparatus is provided for protecting a patient during a radio frequency medical procedure. A detector includes an input receiving electrical impulses representing at least one patient parameter to be monitored from at least one shielded sensor connected to the patient. The detector detects at least one of (a) a voltage associated with parasitic current generated during a radio frequency medical procedure and (b) a current generated during a radio frequency medical procedure. A control circuit is coupled to the detector and compares at least one of (a) the detected voltage with a threshold voltage value and (b) the detected current with a threshold current value. A switch is coupled between the detector and the control circuit. In response to a control signal generated by the control circuit, the switch selectively switches between a conductive state and a non conductive state. The conductive state maintains a low impedance at the at least one shielded sensor and maintains the shield of the at least one shielded sensor in an effective state when at least one of (a) the detected voltage is below the threshold voltage value and (b) the detected current is below the threshold current value. The non-conductive state provides a high impedance at the at least one shielded sensor and causes the shield of the at least one shielded sensor to become ineffective when at least one of (a) the detected voltage is equal to or greater than the threshold voltage value and (b) the detected current is equal to or greater than the threshold current.