System and method for monitoring cardiopulmonary fluid transfer rates using an implantable medical device
First Claim
1. A method for use with an implantable medical device for implant within a patient, said method comprising:
- determining, using a fluid perfusion transfer rate determination system, a fluid perfusion transfer rate representative of transfer of fluids from heart-to-lung within a patient; and
controlling, using a cardiopulmonary fluid transfer rate-based controller, at least one device function in response to the fluid perfusion transfer rate;
wherein determining a fluid perfusion transfer rate comprises;
measuring values representative of electrical admittance through at least a portion of the lungs;
identifying a first set of values measured while the patient is in a sleep posture;
determining a first exponential time-constant (k1) based on the first set of values; and
equating the first exponential time-constant (k1) with the rate of transfer of fluids from heart-to-lung within the patient;
wherein determining a first exponential time-constant (k1) comprises fitting a curve of the form;
Adm(u,t)=DC+A*(1−
u)*(1−
exp(−
k1*t))to the values measured, wherein “
DC”
represents a minimum detected admittance during the period, “
A”
represents a maximum detected admittance during the period minus DC, and u=0 for admittance data collected while the patient is in a sleep posture for a sufficient amount of time for admittance to increase significantly.
1 Assignment
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Accused Products
Abstract
Techniques are provided for use by a pacemaker or other implantable medical device for detecting and tracking trends in cardiopulmonary fluid transfer rates—such as heart-to-lung fluid perfusion rates and lung-to-lymphatic system fluid excretion rates—and for detecting heart failure, dyspnea or other cardiopulmonary conditions. In one example, the device periodically measures transthoracic admittance values. A first exponential time-constant (k1) is determined using curve-fitting from admittance values obtained while the patient is in a sleep posture. Time-constant k1 is representative of the fluid perfusion rate. A second exponential time-constant (k2) is determined based on admittance values obtained while the patient is standing/walking/sitting. The second exponential time-constant (k2) is representative of the fluid excretion rate from the lungs. The device then detects trends, if any, in the time-constants (or in “DC” baseline values) to detect or predict medical conditions such as an imminent heart failure exacerbation.
17 Citations
23 Claims
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1. A method for use with an implantable medical device for implant within a patient, said method comprising:
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determining, using a fluid perfusion transfer rate determination system, a fluid perfusion transfer rate representative of transfer of fluids from heart-to-lung within a patient; and controlling, using a cardiopulmonary fluid transfer rate-based controller, at least one device function in response to the fluid perfusion transfer rate; wherein determining a fluid perfusion transfer rate comprises; measuring values representative of electrical admittance through at least a portion of the lungs; identifying a first set of values measured while the patient is in a sleep posture; determining a first exponential time-constant (k1) based on the first set of values; and equating the first exponential time-constant (k1) with the rate of transfer of fluids from heart-to-lung within the patient; wherein determining a first exponential time-constant (k1) comprises fitting a curve of the form;
Adm(u,t)=DC+A*(1−
u)*(1−
exp(−
k1*t))to the values measured, wherein “
DC”
represents a minimum detected admittance during the period, “
A”
represents a maximum detected admittance during the period minus DC, and u=0 for admittance data collected while the patient is in a sleep posture for a sufficient amount of time for admittance to increase significantly. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A method for use with an implantable medical device for implant within a patient, said method comprising:
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determining, using a lymphatic fluid excretion rate determination system, a lymphatic fluid excretion rate representative of transfer of fluids from lung-to-lymphatic system; and controlling, using a cardiopulmonary fluid transfer rate-based controller, at least one device function in response to the lymphatic fluid excretion rate; wherein determining a lymphatic fluid excretion rate comprises; measuring values representative of electrical admittance through at least a portion of the lungs; identifying a second set of values measured while patient is not in a sleep posture; determining a second exponential time-constant (k2) based on the second set of values; and equating the second exponential time-constant (k2) with the rate of fluids from lung-to-lymphatic system within the patient; wherein determining the second exponential time-constants (k2) includes fitting a curve of the form;
Adm(u,t)=DC+A*u*exp(−
k2*t)to the values measured, wherein “
DC”
represents a minimum detected admittance during the period, “
A”
represents a maximum detected admittance during the period minus DC, and u=1 for admittance data collected during a subsequent time interval while the patient is not in a sleep posture for a sufficient amount of time for admittance to decrease significantly. - View Dependent Claims (11, 12, 13, 14)
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15. A method for use with an implantable medical device for implant within a patient, the method comprising:
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determining, using a cardiopulmonary fluid transfer rate determination system, a cardiopulmonary fluid transfer rate within the patient, wherein the cardiopulmonary fluid transfer rate includes both a fluid transfer rate from heart-to-lung and a fluid transfer rate from lung-to-lymphatic system; and controlling, using a cardiopulmonary fluid transfer rate-based controller, at least one device function in response to the cardiopulmonary fluid transfer rate; wherein determining the cardiopulmonary fluid transfer rates includes; measuring a set of values representative of electrical admittance through at least a portion of the lungs during at least one twenty-four hour period; determining a first exponential time-constant (k1) based on values detected while the patient is in a sleep posture; determining a second exponential time-constant (k2) based on values detected while the patient is not in a sleep posture; equating the first exponential time-constant (k1) with the rate of transfer of fluids from the heart-to-lung; and equating the second exponential time-constant (k2) with the rate of transfer of fluids from the lung-to-lymphatic system; wherein determining the first and second exponential time-constants (k1, k2) includes fitting a curve of the form;
Adm(u,t)=DC+A*(1−
u)*(1−
exp(−
k1*t))+A*u*exp(−
k2*t)to the values measured throughout the twenty-four hour period, wherein “
DC”
represents a minimum detected admittance during the period, “
A”
represents a maximum detected admittance during the period minus DC, and u=0 for admittance data collected while the patient is in a sleep posture for a sufficient amount of time for admittance to increase significantly and u=1 for admittance data collected during a subsequent time interval while the patient is not in a sleep posture for a sufficient amount of time for admittance to decrease significantly. - View Dependent Claims (16, 17, 18, 19, 20)
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21. A system for use with an implantable medical device for implant within a patient, the system comprising:
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a fluid perfusion transfer rate determination system operative to determine a fluid perfusion transfer rate representative of transfer of fluids from heart-to-lung within a patient; and a cardiopulmonary fluid transfer rate-based controller operative to control at least one device function based on to the fluid perfusion transfer rate; wherein the fluid perfusion transfer rate determination system is operative to; measure values representative of electrical admittance through at least a portion of the lungs; identify a first set of values measured while the patient is in a sleep posture; determine a first exponential time-constant (k1) based on the first set of values; and equate the first exponential time-constant (k1) with the rate of transfer of fluids from heart-to-lung within the patient; wherein to determine a first exponential time-constant (k1), the fluid perfusion transfer rate determination system is further operative to fit a curve of the form;
Adm(u,t)=DC+A*(1−
u)*(1−
exp(−
k1*t))to the values measured, wherein “
DC”
represents a minimum detected admittance during the period, “
A”
represents a maximum detected admittance during the period minus DC, and u=0 for admittance data collected while the patient is in a sleep posture for a sufficient amount of time for admittance to increase significantly.
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22. A system for use with an implantable medical device for implant within a patient, said system comprising:
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a lymphatic fluid excretion rate determination system operative to determine a lymphatic fluid excretion rate representative of transfer of fluids from lung-to-lymphatic system within the patient; and a cardiopulmonary fluid transfer rate-based controller operative to control at least one device function based on the lymphatic fluid excretion rate; wherein the lymphatic fluid excretion rate determination system is operative to; measure values representative of electrical admittance through at least a portion of the lungs; identify a second set of values measured while patient is not in a sleep posture; determine a second exponential time-constant (k2) based on the second set of values; and equate the second exponential time-constant (k2) with the rate of fluids from lung-to-lymphatic system within the patient; wherein, to determine a second exponential time-constant (k2), the lymphatic fluid excretion rate determination system is further operative to fit a curve of the form;
Adm(u,t)=DC+A*u*exp(−
k2*t)to the values measured, wherein “
DC”
represents a minimum detected admittance during the period, “
A”
represents a maximum detected admittance during the period minus DC, and u=1 for admittance data collected during a subsequent time interval while the patient is not in a sleep posture for a sufficient amount of time for admittance to decrease significantly.
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23. A system for use with an implantable medical device for implant within a patient, said system comprising:
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a cardiopulmonary fluid transfer rate determination system operative to determine at least one of a fluid transfer rate from heart-to-lung and a fluid transfer rate from lung-to-lymphatic system; and a cardiopulmonary fluid transfer rate-based controller operative to control at least one device function based on a cardiopulmonary fluid transfer rate wherein the cardiopulmonary fluid transfer rate determination system is operative to; measure a set of values representative of electrical admittance through at least a portion of the lungs during at least one twenty-four hour period; determine a first exponential time-constant (k1) based on values detected while the patient is in a sleep posture; determine a second exponential time-constant (k2) based on values detected while the patient is not in a sleep posture; equate the first exponential time-constant (k1) with the rate of transfer of fluids from the heart-to-lung; and equate the second exponential time-constant (k2) with the rate of transfer of fluids from the lung-to-lymphatic system; wherein, to determine the first and second exponential time-constants (k1, k2), the cardiopulmonary fluid transfer rate determination system is further operative to fit a curve of the form;
Adm(u,t)=DC+A*(1−
u)*(1−
exp(−
k1*t))+A*u*exp(−
k2*t)to the values measured throughout the twenty-four hour period, wherein “
DC”
represents a minimum detected admittance during the period, “
A”
represents a maximum detected admittance during the period minus DC, and u=0 for admittance data collected while the patient is in a sleep posture for a sufficient amount of time for admittance to increase significantly and u=1 for admittance data collected during a subsequent time interval while the patient is not in a sleep posture for a sufficient amount of time for admittance to decrease significantly.
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Specification