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Rate responsive cardiac pacemaker with biphasic impedance sensing and method

  • US 5,507,785 A
  • Filed: 12/21/1994
  • Issued: 04/16/1996
  • Est. Priority Date: 12/21/1994
  • Status: Expired due to Term
First Claim
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1. A cardiac stimulation apparatus comprisingmeans for stimulating a patient'"'"'s heart;

  • means for measuring impedance within the patient'"'"'s body, said impedance measuring means includingmeans for producing a constant current biphasic pulse pair, said pulse pair having a first pulse having current flowing in a first direction and a second pulse having current flowing in a second direction, means for electrically transmitting said pulse pair through at least a portion of said patient'"'"'s body,means for detecting a first voltage associated with said first pulse across at least a part of said patient'"'"'s body,means for producing a first signal proportional to said first voltage,means for detecting a second voltage associated with said second pulse across at least a part of said patient'"'"'s body,means for producing a second signal proportional to said second voltage, andmeans for producing a combined signal from said first and second signals,means for deriving a metabolic demand parameter from said combined signal; and

    means for adjusting said means for stimulating said patient'"'"'s heart in relation to said metabolic demand parameter.

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