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Apparatus for in vivo intracardial of a measured signal corresponding to the physical activity of a subject and a heart pacemaker having a stimulation rate controlled thereby

  • US 5,218,961 A
  • Filed: 09/17/1991
  • Issued: 06/15/1993
  • Est. Priority Date: 09/28/1990
  • Status: Expired due to Term
First Claim
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1. An apparatus for in vivo intracardial acquisition of a measured signal corresponding to the level of physical activity of a subject, said apparatus comprising:

  • first means for converting an electrical test signal into a first electrical signal component dependent on the blood oxygen content of said subject, the degree of dependence being dependent on the value of said test signal;

    second means for converting said electrical test signal into a second electrical signal component dependent on the blood temperature of said subject, the degree of dependence being dependent on the value of said test signal;

    said first means and said second means for converting being electrically combined in a circuit having only two terminals;

    control circuitry coupled to said two terminals including drive circuit means for supplying said test signal to said first and second means for converting, and further including measuring means for generating a measured signal which includes said first and second signal components depending on blood oxygen content and blood temperature;

    said test signal having a range of values including a first value below which said measured signal is significantly more dependent on blood temperature than on blood oxygen content and including a second value at which said measured signal is significantly more dependent on blood oxygen content than on blood temperature; and

    means for adjusting said test signal to a value within said range including said first value and said second value.

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