Patent ID: 7917204

Claim:
A method for measuring an electrical bio-impedance of a patient with an implantable medical device comprising a voltage source that provides available voltage headroom, a current pulse generator that operates at an operating voltage, and at least one electrode configuration, said method comprising the steps of: in an electrical bio-impedance measurement session, generating, with said current pulse generator, at least one impedance measurement signal having at least one asymmetric multiphasic waveform comprised of a plurality of pulse phases each having a pulse phase amplitude, with respect to said operating voltage, and a pulse phase width, the respective pulse phase amplitudes collectively giving said waveform a waveform amplitude that is asymmetric with respect to said operating voltage, and said waveform having an overall DC component that is substantially equal to 0, and the symmetry of waveform amplitude allowing substantially all of said available voltage headroom to be used by said impedance measurement signal; applying said at least one impedance measurement signal with said waveform to said patient using said at least one electrode configuration; measuring at least one resulting impedance signal produced by the application of said at least one impedance measurement signal with said waveform; and determining at least one impedance value from the measured impedance signal.