Posture and device orientation and calibration for implantable medical devices
First Claim
1. A method of determining the physical posture of a patient'"'"'s body, having an ideal Y axis, aligned with the superior-inferior body axis, an ideal Z axis aligned with the anterior-posterior body axis, and an ideal X axis aligned with the lateral-medial body said axis in relation to earth'"'"'s gravitational field comprising the steps of:
- implanting a multi-axis, solid state sensor in the patient'"'"'s body, said solid state sensor comprising X, Y, and Z accelerometers having X, Y, and Z device axes, respectively, orthogonally disposed to one another, which provide X, Y, and Z accelerometer output signals, respectively, of a magnitude and polarity dependent on the degree of alignment of the respective axis with earth'"'"'s gravitational field;
in a calibration mode following implantation;
measuring a first set of accelerometer output signals from said X, Y, and Z accelerometers while the patient is in a first body posture;
measuring a second set of accelerometer output signals from said X, Y, and Z accelerometers while the patient is in a second body posture orthogonal to said first body posture;
from said first and second sets of accelerometer output signals, deriving a pitch angle of the Y and Z device axes from the Y ideal axis and the Z ideal axis, respectively, due to rotation of the Y and Z device axes about the X device axis;
from said X and Z sets of accelerometer output signals, deriving a yaw angle of the X and Z device axes from the X ideal axis and the Z ideal axis, respectively, due to rotation of the X and Z device axes about the Y device axis; and
from said X and Y sets of accelerometer output signals, deriving a roll angle of the X and Y device axes from the X ideal axis and the Y ideal axis, respectively, due to rotation of the X and Y device axes about the Z device axis; and
in a normal operating mode, determining an unknown body posture of the patient by;
measuring the X, Y, and Z accelerometer output signals while the patient is in the unknown body posture;
correcting the measured X, Y, and Z accelerometer output signals employing the derived pitch, roll and yaw angles to derive corrected X, Y, and Z accelerometer output signals; and
determining the body posture of the patient employing the corrected X, Y, and Z accelerometer output signals.
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Abstract
A method of and apparatus for determining the physical posture of a patient'"'"'s body, having a superior-inferior body axis, an anterior-posterior body axis and a lateral-medial body axis, in relation to earth'"'"'s gravitational field. A medical device having first, second and, optionally, third accelerometers having sensitive axes mounted orthogonally within an implantable housing is adapted to be implanted with the sensitive axes nominally aligned with ideal X, Y and Z device axes correlated to patient body axes. Each accelerometer generates DC accelerometer signals having characteristic magnitudes and polarities on alignment of the sensitive axis with, against or normal to earth'"'"'s gravitational field and DC accelerometer signals of varying magnitudes and polarities when not so aligned. The actual pitch and roll angles of the sensitive axes of the accelerometers in the implanted IMD with respect to the true gravitational axes are determined and the yaw angles are determined or estimated. Corrected DC accelerometer output signals are derived from the pitch, roll and yaw angles and are compared to a set of stored thresholds for each body posture to determine the actual body posture. Storage of these comparisons or the raw signals themselves can be used for histogram data to provide theraputic or research benefits also described.
699 Citations
68 Claims
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1. A method of determining the physical posture of a patient'"'"'s body, having an ideal Y axis, aligned with the superior-inferior body axis, an ideal Z axis aligned with the anterior-posterior body axis, and an ideal X axis aligned with the lateral-medial body said axis in relation to earth'"'"'s gravitational field comprising the steps of:
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implanting a multi-axis, solid state sensor in the patient'"'"'s body, said solid state sensor comprising X, Y, and Z accelerometers having X, Y, and Z device axes, respectively, orthogonally disposed to one another, which provide X, Y, and Z accelerometer output signals, respectively, of a magnitude and polarity dependent on the degree of alignment of the respective axis with earth'"'"'s gravitational field; in a calibration mode following implantation; measuring a first set of accelerometer output signals from said X, Y, and Z accelerometers while the patient is in a first body posture; measuring a second set of accelerometer output signals from said X, Y, and Z accelerometers while the patient is in a second body posture orthogonal to said first body posture; from said first and second sets of accelerometer output signals, deriving a pitch angle of the Y and Z device axes from the Y ideal axis and the Z ideal axis, respectively, due to rotation of the Y and Z device axes about the X device axis; from said X and Z sets of accelerometer output signals, deriving a yaw angle of the X and Z device axes from the X ideal axis and the Z ideal axis, respectively, due to rotation of the X and Z device axes about the Y device axis; and from said X and Y sets of accelerometer output signals, deriving a roll angle of the X and Y device axes from the X ideal axis and the Y ideal axis, respectively, due to rotation of the X and Y device axes about the Z device axis; and in a normal operating mode, determining an unknown body posture of the patient by; measuring the X, Y, and Z accelerometer output signals while the patient is in the unknown body posture; correcting the measured X, Y, and Z accelerometer output signals employing the derived pitch, roll and yaw angles to derive corrected X, Y, and Z accelerometer output signals; and determining the body posture of the patient employing the corrected X, Y, and Z accelerometer output signals. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 58, 59)
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13. A method of determining the physical posture of a patient'"'"'s body, having a superior-inferior body axis or ideal Y axis, an anterior-posterior body axis or ideal Z axis and a lateral-medial body axis or ideal X axis, in relation to earth'"'"'s gravitational field comprising the steps of:
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implanting a multi-axis, solid state sensor in the patient'"'"'s body, said solid state sensor comprising X, Y and Z DC accelerometers having X, Y and Z device axes, respectively, orthogonally disposed to one another, which provide X, Y and Z DC accelerometer output signals, respectively, of a magnitude and polarity dependent on the degree of alignment of the respective device axis with earth'"'"'s gravitational field; in a calibration mode following implantation; determining that the patient is in an upright body posture wherein said ideal Y axis is nominally into alignment with earth'"'"'s gravitational field and X and Z ideal axes are nominally normal to earth'"'"'s gravitational field; setting a yaw angle of the X and Z device axes from the ideal X or lateral-medial body axis and the ideal Z or anterior-posterior body axis, respectively, at a fixed value based on the assumption of minimal rotation of the X and Z device axes about the Y device axes after implantation; measuring at least one set of DC accelerometer output signals from the X, Y, and Z DC accelerometers in the assumed upright body posture; deriving a pitch angle of the Y and Z device axes from the ideal Y axis and the ideal Z axis, respectively, due to rotation of the Y and Z device axes a about the X device axis from the measured set of DC accelerometer output signals; and deriving a roll angle of the X and Y device axes from the ideal X axis and the ideal Y axis, respectively, due to rotation of the X and Y device axes about the device Z axis from the measured set of DC accelerometer output signals; and in a normal operating mode, determining an unknown posture of the patient by; measuring the X, Y, and Z DC accelerometer output signals; correcting the measured X, Y, and Z DC accelerometer output signals employing the stored pitch, roll and yaw angles to derive corrected X, Y, and Z DC accelerometer output signals; and determining the body posture of the patient employing the corrected X, Y, and Z DC accelerometer output signals. - View Dependent Claims (14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26)
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27. In an implantable medical device, a system for determining the body posture of a patient'"'"'s body having an ideal Y axis aligned with the superior-inferior body axis, an ideal Z axis aligned with the anterior-posterior body axis and an ideal X axis aligned with lateral-medial body axis, in relation to earth'"'"'s gravitational field comprising:
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a multi-axis, solid state sensor, comprising X, Y and Z DC accelerometers having X, Y and Z device axes, respectively, orthogonally disposed to one another, which provide X, Y and Z DC accelerometer output signals, respectively, of a magnitude and polarity dependent on the degree of alignment of the respective device axis with earth'"'"'s gravitational field, the multi-axis, solid state sensor associated with the implantable medical device and adapted to be implanted in the patient'"'"'s body so that the X device axis is nominally aligned with the lateral-medial body axis, the Y device axis is nominally aligned with the superior-inferior body axis, and the Z device axis is nominally aligned with the anterior-posterior body axis; means for correcting for deviations in alignment of the X device axis from the ideal X axis or lateral-medial body axis, the Y device axis from the ideal Y axis or superior-inferior body axis, and the Z device axis from the ideal Z axis or anterior-posterior body axis following implantation of the medical device comprising; means for measuring a first set of DC accelerometer output signals from said X, Y and Z DC accelerometers while the patient is in a first body posture such that the Y device axis is nominally in alignment with earth'"'"'s gravitational field and the X and Z device axes are nominally normal to earth'"'"'s gravitational field; means for measuring a second set of DC accelerometer output signals from said X, Y and Z DC accelerometers while the patient is in a second body posture orthogonal to said first body posture wherein one of the X or Z device axes is generally in alignment with earth'"'"'s gravitational field and the other of the X and Z device axes and the Y device axis are nominally normal to earth'"'"'s gravitational field; means for deriving a pitch angle of the Y and Z device axes from the Y and Z ideal axis respectively, due to rotation of the Y and Z device axes about the X device axis from said first and second sets of DC accelerometer output signals; means for deriving a yaw angle of the X and Z device axes from the ideal X and Z axis, respectively, due to rotation of the X and Z device axes about the Y device axis from said first and second sets of DC accelerometer output signals; and means for deriving a roll angle of the X and Y device axes from the ideal X and Y axis, respectively, due to rotation of the X and Y device axes about the Z device axis from said first and second sets of DC accelerometer output signals; and in a normal operating mode, means operable for determining an unknown body posture of the patient comprising; means for measuring the X, Y and Z DC accelerometer output signals while the patient is in the unknown body posture; means for correcting the measured X, Y, and Z DC accelerometer output signals employing the derived pitch, roll and yaw angles to derive corrected X, Y and Z DC accelerometer output signals; and means for determining the body posture of the patient employing the corrected X, Y and Z DC accelerometer output signals. - View Dependent Claims (28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 65, 66, 67, 68)
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39. An implantable medical device employing a system of determining the body posture of a patient'"'"'s body, having an ideal Y axis or superior-inferior body axis, an ideal Z axis or anterior-posterior body axis and an ideal X-axis or lateral-medial body axis, in relation to earth'"'"'s gravitational field, comprising:
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a multi-axis, solid state sensor, comprising X, Y and DC accelerometers having X, Y and Z device axes, respectively, orthogonally disposed to one another, which provide X, Y and Z DC accelerometer output signals, respectively, of a magnitude and polarity dependent on the degree of alignment of the respective device axis with earth'"'"'s gravitational field, the multi-axis, solid state sensor associated with the implantable medical device and adapted to be implanted in the patient'"'"'s body so that the X device axis is nominally aligned with the lateral-medial body axis, means operable assuming a minimal deviation of the yaw angle or the rotation of the X and Z device axis around the Y device axis at the site of implantation for correcting for deviations in alignment of the actual device axes from the ideal device axes, means for determining that the patient is in an upright body posture wherein said Y device axis is nominally aligned with earth'"'"'s gravitational field and X and Z device axes are nominally normal to earth'"'"'s gravitational field; means for setting a yaw angle of the X and Z device axes from the ideal X and, respectively, at a fixed value based on the assumption of minimal rotation of the X and Z device axes around the Y device axis means for measuring at least one set of DC accelerometer output signals from the X, Y, and Z DC accelerometers while the patient is in the assumed upright body posture; means for deriving a pitch angle of the Y and Z device axes from the ideal Y and Z device respectively, due to rotation of the Y and Z device axes about the X device axis from the measured set of DC accelerometer output signals; and means for deriving a roll angle of the X and Y device axes from the ideal X and Y axes, respectively, due to rotation of the X and Y device axes about the Z device axis from the measured set of DC accelerometer output signals; and in a normal operating mode, means for determining an unknown posture of the patient comprising; means for measuring the X, Y and Z DC accelerometer output signals; means for correcting the measured X, Y and Z DC accelerometer output signals employing the stored pitch, roll and yaw angles to derive corrected X, Y and Z DC accelerometer output signals; and means for determining the body posture of the patient employing the corrected X, Y and Z DC accelerometer output signals. - View Dependent Claims (40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52)
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53. A method of determining the physical posture of a patient'"'"'s body, having an ideal Y axis, an Z axis, and an ideal X axis, in relation to earth'"'"'s gravitational field comprising the steps of:
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implanting a multi-axis, solid state sensor, comprising X, Y and Z DC accelerometers having X, Y and Z device axes, respectively, which respond to earth'"'"'s gravitational field to provide X, Y and Z respective DC accelerometer signals of a magnitude and polarity dependent on the degree of alignment therewith, in the patient'"'"'s body so that said X, Y and Z device axes are generally aligned with said lateral-medial, superior-inferior, and anterior-posterior body axes, respectively; in a calibration mode wherein the patient is in at least one known or assumed body posture; deriving a pitch angle of the Y and Z axes from the ideal Y and Z device axes respectively, due to rotation of the Y and Z device axes about the X device axis; deriving a yaw angle of the X and Z device axes from the ideal X and Z axes, respectively, due to rotation of the X and Z device axes about the Y device axes; and deriving a roll angle of the X and Y device axes from the ideal X and Y axes, respectively, due to rotation of the X and Y device axes about the Z device axis; and in a normal operating mode; measuring X, Y and Z measured DC accelerometer signals from said X, Y and Z DC accelerometers, respectively, in an unknown body posture that the patient assumes; correcting the measured X, Y and Z DC accelerometer signals to compensate for derived pitch, roll and yaw angles resulting from mis-alignment of said X, Y and Z device axes with said ideal X, Y and axes, respectively; and determining the body posture of the patient from the corrected X, Y and Z DC accelerometer signals. - View Dependent Claims (54, 55, 56, 57)
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60. An implantable medical device having a system for determining the physical posture of a patient'"'"'s body, having an ideal Y axis, an ideal Z axis and an ideal X axis, in relation to earth'"'"'s gravitational field comprising:
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a multi-axis, solid state sensor, comprising X, Y and Z DC accelerometers having X, Y and Z device axes, respectively, orthogonally disposed to one another, which provide X, Y and Z DC accelerometer output signals, respectively, of a magnitude and polarity dependent on the degree of alignment of the respective device axis with the earth'"'"'s gravitational field, the multi-axis, solid state sensor associated with the implantable medical device and adapted to be implanted in the patient'"'"'s body so that the X device axis is nominally aligned with the lateral-medial body axis, the Y device axis is nominally aligned with the superior-inferior body axis, and the Z device axis is nominally aligned with the anterior-posterior body axis; means for correcting for deviations in alignment of the X device axis from the ideal X axis or lateral-medial body axis, the Y device axis from the ideal Y axis or superior-inferior body axis, and the Z device axis from the ideal Z axis or anterior-posterior body axis following implantation of the medical device comprising; means operable in a calibration mode with the patient in at least one known or assumed body posture for deriving a pitch angle of the Y and Z device axes from the ideal Y and Z axes, respectively, due to rotation of the Y and Z device axes about the X device axis in the implantation step; means operable in the calibration mode with the patient in at least one known or assumed body posture for deriving a yaw angle of the X and Z device axes from the ideal X and Z axes, respectively, due to rotation of the X and Z device axes about the Y device axis in the implantation step; and means operable in the calibration mode with the patient in at least one known or assumed body posture for deriving a roll angle of the X and Y device axes from the ideal X and Y axes, respectively, due to rotation of the X and Y axes about the Z device axis in the implantation step; means operable in a normal operating mode when the patient assumes an unknown body posture for deriving X, Y and Z measured DC accelerometer signals from said X, Y and Z DC accelerometers, respectively; means for correcting the measured X, Y and Z DC accelerometer signals for determined pitch, roll and yaw angular deviations resulting from mis-alignment of said X, Y and Z device axes with said ideal X, Y and Z axes, respectively; and means for determining the body posture of the patient from the corrected X, Y and Z DC accelerometer signals. - View Dependent Claims (61, 62, 63, 64)
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Specification