Apparatus and method for determining an approximation of the stroke volume and the cardiac output of the heart
First Claim
1. An apparatus for determining an approximate value for a stroke volume SV (in milliliter) of a subject'"'"'s heart, comprising a) means for measuring an electrical impedance Z(t) of a part of the subject'"'"'s body, wherein a value of said electrical impedance Z(t) changes with time t as a consequence of the beating of the heart;
- b) means for determining a base impedance Z0 as a part of said electrical impedance Z(t) which does not change significantly during a period of one cardiac cycle;
c) means for determining a peak magnitude of a temporal derivative of said electrical impedance Z(t), indicating an absolute maximum rate of change of said electrical impedance Z(t) during a systolic period of the cardiac cycle;
d) means for determining a left ventricular ejection time, TLVE;
e) means for determining the cardiac cycle period TRR of the heart; and
f) means for calculating said approximate value of the stroke volume SV wherein said calculating means is adapted to evaluate a formula wherein 0.15<
n<
0.8 and 0≦
m≦
1.5, and wherein VEFF is an approximate value of the subject'"'"'s volume of electrically participating tissue, and wherein C1 is a constant.
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Accused Products
Abstract
The invention relates to an apparatus and a method for determining an approximate value for the stroke volume and the cardiac output of a person'"'"'s heart. The apparatus and method employ a measured electrical impedance, or admittance, of a part of a person'"'"'s body, namely, the thorax. This part of a person'"'"'s body is chosen because its electrical impedance, or admittance, changes with time as a consequence of the periodic beating of the heart. Accordingly, the measured electrical admittance or impedance can provide information about the performance of the heart as a pump.
83 Citations
140 Claims
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1. An apparatus for determining an approximate value for a stroke volume SV (in milliliter) of a subject'"'"'s heart, comprising
a) means for measuring an electrical impedance Z(t) of a part of the subject'"'"'s body, wherein a value of said electrical impedance Z(t) changes with time t as a consequence of the beating of the heart; -
b) means for determining a base impedance Z0 as a part of said electrical impedance Z(t) which does not change significantly during a period of one cardiac cycle;
c) means for determining a peak magnitude of a temporal derivative of said electrical impedance Z(t), indicating an absolute maximum rate of change of said electrical impedance Z(t) during a systolic period of the cardiac cycle;
d) means for determining a left ventricular ejection time, TLVE;
e) means for determining the cardiac cycle period TRR of the heart; and
f) means for calculating said approximate value of the stroke volume SV wherein said calculating means is adapted to evaluate a formula wherein 0.15<
n<
0.8 and 0≦
m≦
1.5, and wherein VEFF is an approximate value of the subject'"'"'s volume of electrically participating tissue, and wherein C1 is a constant. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 35, 37, 39, 40)
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34. An apparatus for determining an approximate value for a stroke volume SV of a subject'"'"'s heart, comprising
a) a current source outputting an alternating current I(t) of predetermined amplitude to two electrodes; -
b) means for measuring a voltage U(t) caused by said alternating current between two electrodes; and
c) a processing unit receiving at least a signal representative of U(t), said processing unit being adapted to;
calculate an impedance Z(t) from the voltage U(t) and a value of the current I(t);
input Z(t) into a low-pass filter, an output of said low-pass filter being Z0;
input Z(t) into a high-pass filter, an output of said high-pass filter being Δ
Z(t);
calculate a peak magnitude determine a left ventricular ejection time TLVE from at least one of Z(t), Δ
Z(t) andby using predetermined criteria;
determine a cardiac cycle period TRR of the heart from at least one of Z(t), Δ
Z(t) andby using predetermined criteria;
calculate SV according to a formula wherein 0.15≦
n≦
0.8 and 0<
m≦
1.5, and wherein VEFF is an approximate value of the subject'"'"'s volume of electrically participating tissue, and wherein C1 is a constant.
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36. An apparatus for determining an approximate value for the stroke volume SV of a subject'"'"'s heart, comprising
a) a current source outputting an alternating current I(t) of predetermined amplitude to two electrodes; -
b) means for measuring a voltage U(t) caused by said alternating current between two electrodes;
c) means for measuring an electrocardiogram; and
d) a processing unit receiving at least a signal representative of U(t) and measured values of said electrocardiogram, said processing unit being adapted to;
calculate an impedance Z(t) from the voltage U(t) and a value of the current I(t);
input Z(t) into a low-pass filter, an output of said low-pass filter being Z0;
input Z(t) into a high-pass filter, an output of said high-pass filter being Δ
Z(t);
calculate a peak magnitude of determine a left ventricular ejection time TLVE from at least one of Z(t), Δ
Z(t) andby using predetermined criteria;
determine a cardiac cycle period TRR of the heart from the measured values of said electrocardiogram;
calculate SV according to a formula wherein 0.15<
n<
0.8 and 0<
m≦
1.5, and wherein VEFF is an approximate value of the subject'"'"'s volume of electrically participating tissue, and wherein C1 is a constant.
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38. An apparatus for determining an approximate value for a stroke volume SV of a subject'"'"'s heart, comprising
a) a current source outputting an alternating current I(t) of predetermined amplitude to two electrodes; -
b) means for measuring a voltage U(t) caused by said alternating current between two electrodes;
c) means for measuring an electrocardiogram and means for calculating a cardiac cycle period TRR of the heart from measured values of said electrocardiogram;
d) a processing unit receiving at least a signal representative of U(t) and a signal representative of TRR, said processing unit being adapted to;
calculate an impedance Z(t) from the voltage U(t) and a value of the current I(t);
input Z(t) into a low-pass filter, an output of said low-pass filter being Z0;
input Z(t) into a high-pass filter, an output of said high-pass filter being Δ
Z(t);
calculate a peak magnitude determine a left ventricular ejection time TLVE from at least one of Z(t), Δ
Z(t) andby using predetermined criteria;
calculate SV according to a formula wherein 0.15<
n<
0.8 and 0<
m≦
1.5, and wherein VEFF is an approximate value of the subject'"'"'s volume of electrically participating tissue, and wherein C1 is a constant.
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41. An apparatus for determining an approximate value for a stroke volume SV of a subject'"'"'s heart, comprising
a) a current source outputting an alternating current I(t) of predetermined amplitude to two electrodes; -
b) means for measuring a voltage U(t) caused by said alternating current between two electrodes;
c) a processor unit receiving at least a signal representative of U(t), said processing unit being adapted to;
calculate an impedance Z(t) from the voltage U(t) and a value of the current I(t);
input Z(t) into a low-pass filter, an output of said low-pass filter being Z0;
input Z(t) into a high-pass filter, an output of said high-pass filter being Δ
Z(t);
calculate a peak magnitude determine a left ventricular ejection time TLVE from at least one of Z(t), Δ
Z(t) andby using predetermined criteria;
calculate SV according to a formula wherein 0.15<
n<
0.8, and wherein VEFF is an approximate value of the subject'"'"'s volume of electrically participating tissue, and wherein C1 is a constant.
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42. A method of determining an approximate value for a stroke volume SV of a subject'"'"'s heart, comprising the steps of:
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a) measuring an impedance Z(t) of a part of the subject'"'"'s body, wherein a value of said impedance Z(t) changes with time t as a consequence of the beating of the heart;
b) determining a mean impedance Z0;
c) determining a peak magnitude of a derivative of said impedance Z(t) over the time t by using the measured impedance Z(t) for at least a systolic period of one cardiac cycle;
d) determining a left ventricular ejection time, TLVE; and
e) determining a cardiac cycle period TRR of the heart;
f) calculating an approximate value of the stroke volume according to a formula wherein 0.15<
n<
0.8 and 0<
m≦
1.5, and wherein VEFF is an approximate value of the subject'"'"'s volume of electrically participating tissue, and wherein C1 is a constant. - View Dependent Claims (43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70)
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71. An apparatus for determining an approximate value for a stroke volume SV (in milliliter) of a subject'"'"'s heart, comprising
a) means for measuring an electrical admittance Y(t) of a part of the subject'"'"'s body, wherein a value of said electrical admittance Y(t) changes with time t as a consequence of the beating of the heart; -
b) means for determining a base admittance Y0 as a part of said electrical admittance Y(t) which does not change significantly during a period of one cardiac cycle;
c) means for determining a peak magnitude of a temporal derivative of said electrical admittance Y(t) , indicating an absolute maximum rate of change of said electrical admittance Y(t) during a systolic period of the cardiac cycle;
d) means for determining a left ventricular ejection time, TLVE;
e) means for determining the cardiac cycle period TRR of the heart; and
f) means for calculating said approximate value of the stroke volume SV wherein said calculating means is adapted to evaluate a formula wherein 0.15≦
n≦
0.8 and 0≦
m≦
1.5, and wherein VEFF is an approximate value of the subject'"'"'s volume of electrically participating tissue, and wherein C1 is a constant. - View Dependent Claims (72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100, 101, 102, 103)
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104. An apparatus for determining an approximate value for a stroke volume SV of a subject'"'"'s heart, comprising
a) a current source outputting an alternating current I(t) of predetermined amplitude to two electrodes; -
b) means for measuring a voltage U(t) caused by said alternating current between two electrodes; and
c) a processing unit receiving at least a signal representative of U(t), said processing unit being adapted to;
calculate an admittance Y(t) from the voltage U(t) and a value of the current I(t);
input Y(t) into a low-pass filter, an output of said low-pass filter being Y0;
input Y(t) into a high-pass filter, an output of said high-pass filter being Δ
Y(t);
calculate a peak magnitude determine a left ventricular ejection time TLVE from at least one of Y(t), Δ
Y(t) andby using predetermined criteria;
determine a cardiac cycle period TRR of the heart from at least one of Y(t), Δ
Y(t) andby using predetermined criteria;
calculate SV according to a formula wherein 0.15≦
n≦
0.8 and 0<
m<
1.5, and wherein VEFF is an approximate value of the subject'"'"'s volume of electrically participating tissue, and wherein C1 is a constant. - View Dependent Claims (105)
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106. An apparatus for determining an approximate value for the stroke volume SV of a subject'"'"'s heart, comprising
a) a current source outputting an alternating current I(t) of predetermined amplitude to two electrodes; -
b) means for measuring a voltage U(t) caused by said alternating current between two electrodes;
c) means for measuring an electrocardiogram; and
d) a processing unit receiving at least a signal representative of U(t) and measured values of said electrocardiogram, said processing unit being adapted to;
calculate an admittance Y(t) from the voltage U(t) and a value of the current I(t);
input Y(t) into a low-pass filter, an output of said low-pass filter being Y0;
input Y(t) into a high-pass filter, an output of said high-pass filter being Δ
Y(t);
calculate a peak magnitude determine a left ventricular ejection time TLVE from at least one of Y(t), Δ
Y(t) andby using predetermined criteria;
determine a cardiac cycle period TRR of the heart from the measured values of said electrocardiogram;
calculate SV according to a formula wherein 0.15<
n<
0.8 and 0<
m<
1.5, and wherein VEFF is an approximate value of the subject'"'"'s volume of electrically participating tissue, and wherein C1 is a constant. - View Dependent Claims (107)
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108. An apparatus for determining an approximate value for a stroke volume SV of a subject'"'"'s heart, comprising
a) a current source outputting an alternating current I(t) of predetermined amplitude to two electrodes; -
b) means for measuring a voltage U(t) caused by said alternating current between two electrodes;
c) means for measuring an electrocardiogram and means for calculating a cardiac cycle period TRR of the heart from measured values of said electrocardiogram;
d) a processing unit receiving at least a signal representative of U(t) and a signal representative of TRR, said processing unit being adapted to;
calculate an admittance Y(t) from the voltage U(t) and a value of the current I(t);
input Y(t) into a low-pass filter, an output of said low-pass filter being Y0;
input Y(t) into a high-pass filter, an output of said high-pass filter being Δ
Y(t);
calculate a peak magnitude determine a left ventricular ejection time TLVE from at least one of Y(t), Δ
Y(t) andby using predetermined criteria;
calculate SV according to a formula wherein 0.15<
n<
0.8 and 0<
m<
1.5, and wherein VEFF is an approximate value of the subject'"'"'s volume of electrically participating tissue, and wherein C1 is a constant. - View Dependent Claims (109, 110)
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111. An apparatus for determining an approximate value for a stroke volume SV of a subject'"'"'s heart, comprising
a) a current source outputting an alternating current I(t) of predetermined amplitude to two electrodes; -
b) means for measuring a voltage U(t) caused by said alternating current between two electrodes;
c) a processor unit receiving at least a signal representative of U(t), said processing unit being adapted to;
calculate an admittance Y(t) from the voltage U(t) and a value of the current I(t);
input Y(t) into a low-pass filter, an output of said low-pass filter being Y0;
input Y(t) into a high-pass filter, an output of said high-pass filter being Δ
Y(t);
calculate a peak magnitude determine a left ventricular ejection time TLVE from at least one of Y(t), Δ
Y(t) andby using predetermined criteria;
calculate SV according to a formula wherein 0.15<
n<
0.8, and wherein VEFF is an approximate value of the subject'"'"'s volume of electrically participating tissue, and wherein C1 is a constant. - View Dependent Claims (113, 114, 115, 116, 117, 118, 119, 120, 121, 122, 123, 124, 125, 126, 127, 128, 129, 130, 131, 132, 133, 134, 135, 136, 137, 138, 139, 140)
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112. A method of determining an approximate value for a stroke volume SV of a subject'"'"'s heart, comprising the steps of:
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a) measuring an admittance Y(t) of a part of the subject'"'"'s body, wherein a value of said admittance Y(t) changes with time t as a consequence of the beating of the heart;
b) determining a mean admittance Y0;
c) determining a peak magnitude of a derivative of said admittance Y(t) over the time t by using the measured admittance Y(t) for at least a systolic period of one cardiac cycle;
d) determining a left ventricular ejection time, TLVE; and
e) determining a cardiac cycle period TRR of the heart;
f) calculating an approximate value of the stroke volume according to a formula wherein 0.15<
n<
0.8 and 0<
m≦
1.5, and wherein VEFF is an approximate value of the subject'"'"'s volume of electrically participating tissue, and wherein C1 is a constant.
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Specification