Method and apparatus for muscle function measurement
First Claim
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1. A method, comprising:
- sensing a pressure signal associated with a muscular contraction event via a chronically-implantable pressure sensor coupled to a chronically implanted medical device;
computing an instantaneous stiffness ratio waveform as a ratio of a first time derivative of the pressure signal to an instantaneous pressure metric within said IMD; and
deriving an index of muscle function from the instantaneous stiffness ratio waveform within said IMD,wherein the computing and deriving steps of said method are carried out within via operative circuitry wholly disposed within said IMD; and
wherein the index of muscle function comprises a peak of the stiffness ratio waveform.
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Abstract
The present invention provides an apparatus and method for monitoring muscle function based on an index derived from a pressure or force signal. The muscle function index is derived from an instantaneous muscle stiffness ratio computed as the ratio of the first time derivative of the pressure or force waveform to the corresponding instantaneous pressure or force. The instantaneous stiffness ratio, Ė/E(t), is in units of 1/sec and relates to the rate of strong bond formation and will be influenced by calcium handling properties of the muscle fibers and the intracellular calcium concentration. As such, an index derived from Ė/E(t) provides a measure of the inotropic status of the muscle.
24 Citations
21 Claims
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1. A method, comprising:
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sensing a pressure signal associated with a muscular contraction event via a chronically-implantable pressure sensor coupled to a chronically implanted medical device; computing an instantaneous stiffness ratio waveform as a ratio of a first time derivative of the pressure signal to an instantaneous pressure metric within said IMD; and deriving an index of muscle function from the instantaneous stiffness ratio waveform within said IMD, wherein the computing and deriving steps of said method are carried out within via operative circuitry wholly disposed within said IMD; and wherein the index of muscle function comprises a peak of the stiffness ratio waveform. - View Dependent Claims (2, 3, 4, 5)
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6. A method, comprising:
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sensing a force signal associated with a muscular contraction event, wherein the force signal is provided by a chronically-implantable sensor which is coupled to a chronically implanted medical device (IMD); computing an instantaneous stiffness ratio waveform as a ratio of a first time derivative of the force signal to an instantaneous force metric within the IMD; and deriving an index of muscle function from the stiffness ratio waveform within the IMD wherein the computing and deriving steps are performed via circuitry disposed within the. IMD; and wherein the index of muscle function comprises a peak of the stiffness ratio waveform. - View Dependent Claims (7, 8, 9, 10)
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11. A chronically implantable medical device (IMD), comprising:
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means for sensing a pressure signal associated with a muscular contraction event wherein the pressure signal is provided by a chronically-implantable sensor and said sensor couples to the (IMD); means within the IMD for computing an instantaneous stiffness ratio waveform as the ratio of the first time derivative of the pressure signal to the instantaneous pressure; and means within the IMD for deriving an index of muscle function as a feature of the instantaneous stiffness ratio waveform; and wherein the index of muscle function comprises a peak of the stiffness ratio waveform. - View Dependent Claims (12, 13, 14, 15, 16)
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17. A chronically implantable medical device (IMD), comprising:
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means for sensing a force signal associated with a muscular contraction event wherein the force signal is provided by a chronically-implantable sensor and said sensor couples to the (IMD); means within the IMD for computing an instantaneous stiffness ratio waveform as the ratio of the first time derivative of the force signal to instantaneous force; and
means within the IMD for deriving an index of muscle function as a feature of the instantaneous stiffness ratio waveform; andwherein the index of muscle function comprises a peak of the stiffness ratio waveform. - View Dependent Claims (18, 19, 20, 21)
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Specification