Method and apparatus for monitored biphasic cardiac impedance sensing
First Claim
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1. A cardiac stimulation apparatus comprising:
- a stimulator for producing a stimulating pulse to stimulate a patient'"'"'s heart;
an impedance measuring circuit for measuring impedance within the patient'"'"'s body, said impedance measuring circuit includinga signal generator for producing a biphasic current 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 the patient'"'"'s body, andmeans for determining impedance from said pulse pair;
means responsive to said impedance measuring circuit for controlling said stimulator;
a monitor comprising a test load for selectively receiving said pulse pair and means for comparing said first and second pulses when applied across said test load; and
means responsive to said monitor for controlling said impedance measuring circuit.
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Abstract
A method and apparatus for monitoring balanced biphasic current pulses used for measuring impedance in cardiac stimulators involves detecting imbalances between the pulses of opposite polarity. Such imbalances are potentially harmful to cardiac stimulator users. By converting the two different pulse phases into potentials, a determination can be made as to whether adequately balanced pulses are being generated. If an imbalance is detected, corrective action can be taken quickly enough to avoid harmful effects to the stimulator user.
110 Citations
26 Claims
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1. A cardiac stimulation apparatus comprising:
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a stimulator for producing a stimulating pulse to stimulate a patient'"'"'s heart; an impedance measuring circuit for measuring impedance within the patient'"'"'s body, said impedance measuring circuit including a signal generator for producing a biphasic current 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 the patient'"'"'s body, and means for determining impedance from said pulse pair; means responsive to said impedance measuring circuit for controlling said stimulator; a monitor comprising a test load for selectively receiving said pulse pair and means for comparing said first and second pulses when applied across said test load; and means responsive to said monitor for controlling said impedance measuring circuit. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. An impedance measuring apparatus for use in controlling a cardiac stimulator apparatus, said measuring apparatus comprising:
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a circuit for generating biphasic current pulse pairs; means for applying said pulse pairs to a portion of said patient'"'"'s body; means for determining impedance of said portion of said patient'"'"'s body from said applied pulse pairs; and monitor means connected to said circuit for determining whether each of said current pulse pairs is substantially electrically balanced. - View Dependent Claims (14, 15, 16, 17)
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18. A method for cardiac stimulation comprising the steps of:
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stimulating the patient'"'"'s heart; measuring impedance within the patient'"'"'s body, said measuring step including the steps of producing a biphasic current 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 and transmitting said pulse pairs through a connection to at least a portion of the patient'"'"'s body; controlling the stimulating of the patient'"'"'s heart as a function of said measure impedance; monitoring at least some of said first and second pulses to determine whether said pulse pairs are not substantially electrically balanced; and adjusting said current pulse pairs in response to said determination. - View Dependent Claims (19, 20, 21, 22, 23, 24, 25, 26)
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Specification