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Cardiac cycle synchronized sampling of impedance signal

  • US 8,880,171 B2
  • Filed: 02/13/2014
  • Issued: 11/04/2014
  • Est. Priority Date: 07/02/2003
  • Status: Active Grant
First Claim
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1. A system comprising implantable device, the implantable medical device including:

  • an intrinsic cardiac signal sensor;

    an impedance measurement circuit configured to apply a specified current to a transthoracic region of a subject and to sample a transthoracic voltage resulting from the specified current wherein the impedance measurement circuit is configured to measure the transthoracic voltage using a transthoracic measurement vector; and

    a processor, coupled to the intrinsic cardiac signal sensor and the impedance measurement circuit, the processor configured to;

    initiate, for first impedance vector, sampling of a transthoracic voltage signal synchronous to an occurrence of a fiducial marker in a sensed intrinsic cardiac signal to preserve a respiratory component of the transthoracic signal and to determine lung ventilation using the respiratory component of the transthoracic voltage signal, wherein the sampling attenuates or removes variation with cardiac stroke volume from the transthoracic voltage signal; and

    initiate, for at least a second impedance vector, sampling of a transthoracic voltage signal synchronous to an occurrence of a fiducial marker in a sensed intrinsic cardiac signal.

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