Implantable blood oxygen sensor and method of use

An implantable oxygen sensor and lead used with an implantable rate-responsive pacing system;

• said pacing system including timing means for generating timing signals and for defining a pacing interval, and pulse generator means for generating stimulating pulses at appropriate times within said pacing interval;
• said timing means including control circuits for automatically adjusting the pacing interval of said pacing system as a function of the oxygen content of body blood sensed by said oxygen sensor, said implantable oxygen sensor and lead comprising:
• means responsive to a drive signal for emitting a measuring signal into said body blood, said measuring signal being of a type that is affected by the oxygen content of said blood;
• means for receiving the measuring signal after it has been emitted into said body blood and affected by the oxygen content thereof;
• lead means for delivering the stimulation pulses from the pulse generator to a desired body location;
• an implantable hermetically sealed case within said lead means wherein said emitting means and receiving means are housed;
• control means for generating said drive signal;
• and
• processing means coupled to said receiving means for processing the receiving measuring signal and for generating an output signal indicative of the oxygen content of said blood.

A hermetically sealed, implantable medical sensor used to sense a desired parameter associated with body tissue, including body fluids, in which said medical sensor is implanted, said sensor comprising:

• a hollow tube having sealed window means therein;
• a substrate inserted into said tube;
• light-emitting diode means placed on said substrate for emitting light of a prescribed frequency range in response to a drive signal, said light-emitting diode means being positioned on said substrate so as to permit at least a portion of said light to pass through said window means, contact body tissue outside of said window means, and reflect back through said window means;
• phototransistor means placed on said substrate for receiving light of a prescribed frequency range received through said window means, and for generating an output signal having characteristics that vary as a function of at least one parameter of the light received through said window means;
• connection means for connecting said light-emitting diode means and said phototransistor means is a desired circuit configuration, and for connecting a first terminal to said light-emitting diode means, and for connecting a second terminal to said phototransistor means;
• sealing means sealably secured to each end of said tube for sealing said substrate, light-emitting diode means, phototransistor means, and connection means within said tube, said sealing means including feedthrough means for making electrical contact from a point external said tube with said first and second terminals;
• means for generating said drive signal and applying it through said first and second terminals to said light-emitting diode means;
• and
• means for monitoring through said first and second terminals the output signal generated by said phototransistor means, and for processing said signal to provide a sensor signal indicative of said at least one parameter of the light received through said window means, said sensor signal thereby providing a measure of a desired characteristic of said body tissue as measured by the manner in which said at least one parameter of light is affected by coming in contact with said body tissue.

A method of using a medical sensor that includes light-emitting diode means for emitting a light pulse that is directed to a desired type of organic material to be analyzed, which light pulse is then received by phototransistor means, a desired property of said organic material being determinable in accordance with the manner in which at least one detectable property of the light pulse is affected by the organic material;

• said method comprising the steps of:
• (a) exciting said light-emitting diode means with a first drive current for a first period of time;
• (b) exciting said light-emitting diode means with a second drive current for a second period of time immediately subsequent said first period of time;
• (c) monitoring the light pulses received by said phototransistor means during said first and second periods of time to determine the change in said light pulses as a result of having come in contact with the organic material;
• and
• (d) processing the amount of change identified in step (c) to determine a desired property of the organic material.