Patent ID: 7136704

Claim:
An implantable cardiac stimulation system comprising: a cardiac stimulation lead adapted to be in contact with a patient's blood stream and selected cardiac sites, said stimulation lead having at least one electrical conductor; and a stimulation device comprising: a processor; an oxygen monitoring circuit electrically coupled to said at least one electrical conductor and in contact with the patient's blood stream, said oxygen monitoring circuit configured to monitor the oxygen concentration of the patient's blood; a cardiac stimulation pulse generator coupled and responsive to the processor and configured to deliver cardiac stimulation pulses via the cardiac stimulation lead to the selected cardiac sites; an oxygen monitoring pulse generator coupled to the processor and configured to generate a biphasic pulse train for application to the at least one electrical conductor between consecutive cardiac stimulation pulses, the pulse train defining a data frame having a pre-determined number of bits including parameter information bits, wherein upon the occurrence of the biphasic pulse train, the oxygen monitoring circuit interrogates the patient's blood during an interval between consecutive cardiac stimulation pulses to measure the blood oxygen concentration utilizing respective ones of the pulse train bits for carrying commands and parameter information between the processor and oxygen monitoring circuit.