AUTOMATIC METHOD FOR MEASURING AND PROCESSING BLOOD PRESSURE
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Abstract
The present invention concerns an automatic method, as well as the related system and the tools allowing the same to be executed, for measuring and processing blood pressure starting from a detected pressure signal, the method operating in the time domain for discriminating whether the detected signal is an adequate measurement or not and, where it is not, time domain analysis automatically selects a low-pass filter to, possibly iteratively, apply to the detected pressure signal for having correct values and wave form of the blood pressure.
6 Citations
32 Claims
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1-13. -13. (canceled)
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14. Automatic method for measuring and processing blood pressure comprising the following steps:
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A. having a sampled detected pressure signal P(t) for one or more heart beats, each heart beat starting at an initial instant coinciding with the one of the initial diastolic pressure point and ending at a final instant coinciding with the one of the subsequent diastolic pressure point and comprising a dicrotic point, each beat having a systolic phase going from the initial diastolic point to the dicrotic point; and B. automatically analysing and discriminating morphology of the pressure signal P(t) sampled for each heart beat, determining instant and pressure value of one or more characteristic points of the pressure signal P(t) selected from the group comprising an initial diastolic pressure point, a systolic pressure point, a dicrotic point, and one or more resonance points, each one of which occurs in an instant wherein a second derivative d2P/dt2 of the pressure signal P(t) has a local maximum, at least one characteristic point of the pressure signal P(t) belonging to the systolic phase of the heart beat under consideration and being different from the initial diastolic pressure point; C. for each heart beat, determining an energy efficiency RES through the following sub-steps; C.1 determining a direct dynamic impedance Zd — D(t) for each one of said one or more characteristic points belonging to the systolic phase of the heart beat under consideration and different from the initial diastolic pressure point, said direct dynamic impedance Zd— D(t) being equal to the ratio between a value of the pressure signal P(t) at the characteristic point and the distance of the respective time instant from the initial instant of the heart beat under consideration, and determining an impedance ZD of a direct wave of pressure by summing with alternate signs the values of the direct dynamic impedances Zd— D(t) ordered according to a direct time order starting from the initial instant of the heart beat under consideration up to the dicrotic point instant, beginning to apply a positive sign to the direct dynamic impedance Zd— D(t) that is the first one in the direct time order;C.2 determining a reflected dynamic impedance Zd — R(t) for each one of said one or more characteristic points, said reflected dynamic impedance Zd— R(t) being equal to the ratio between a value of the pressure signal P(t) at the characteristic point and the distance of the respective time instant from the final instant of the heart beat under consideration, and determining an impedance ZR of reflected waves of pressure by summing with alternate signs the values of the reflected dynamic impedances Zd— R(t) ordered according to a reverse time order starting from the final instant down to the initial instant of the heart beat under consideration, beginning to apply a positive sign to the reflected dynamic impedance Zd— R(t) that is the first one in the reverse time order;C.3 determining said energy efficiency RES as ratio between the impedance ZD of the direct wave and the impedance ZR of the reflected waves;
RES=ZD/ZRD. for said energy efficiency RES determined in step C, checking whether a first derivative dP/dt of the pressure signal P(t) is lower than a first value Td of maximum threshold in the whole heart beat under consideration and whether the second derivative d2P/dt2 of the pressure signal P(t) is lower than a second value Td2 of maximum threshold in the whole heart beat under consideration, and in the case where the check has negative outcome making step E, otherwise, in the case where the check has positive outcome, making step F; E. selecting a cutoff frequency of a low-pass filter on the basis of said energy efficiency RES determined in step C, of the first derivative dP/dt and of the second derivative d2P/dt2 of the pressure signal P(t), and applying said low-pass filter to the pressure signal P(t), thus obtaining a new sampled pressure signal, and returning to execute the preceding steps starting from step B; F. outputting the pressure signal P(t) on which step B has been made for the last time. - View Dependent Claims (15, 16, 17, 18, 19, 20, 21, 22, 23, 26, 27, 28, 29, 30, 31, 32)
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24. Automatic apparatus for measuring and processing blood pressure comprising processing means capable to perform the steps of an automatic method for measuring and processing blood pressure comprising the following steps:
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A. having a sampled detected pressure signal P(t) for one or more heart beats, each heart beat starting at an initial instant coinciding with the one of the initial diastolic pressure point and ending at a final instant coinciding with the one of the subsequent diastolic pressure point and comprising a dicrotic point, each beat having a systolic phase going from the initial diastolic point to the dicrotic point; and B. automatically analysing and discriminating morphology of the pressure signal P(t) sampled for each heart beat, determining instant and pressure value of one or more characteristic points of the pressure signal P(t) selected from the group comprising an initial diastolic pressure point, a systolic pressure point, a dicrotic point, and one or more resonance points, each one of which occurs in an instant wherein a second derivative d2P/dt2 of the pressure signal P(t) has a local maximum, at least one characteristic point of the pressure signal P(t) belonging to the systolic phase of the heart beat under consideration and being different from the initial diastolic pressure point; C. for each heart beat, determining an energy efficiency RES through the following sub-steps; C.1 determining a direct dynamic impedance Zd — D(t) for each one of said one or more characteristic points belonging to the systolic phase of the heart beat under consideration and different from the initial diastolic pressure point, said direct dynamic impedance Zd— D(t) being equal to the ratio between a value of the pressure signal P(t) at the characteristic point and the distance of the respective time instant from the initial instant of the heart beat under consideration, and determining an impedance ZD of a direct wave of pressure by summing with alternate signs the values of the direct dynamic impedances Zd— D(t) ordered according to a direct time order starting from the initial instant of the heart beat under consideration up to the dicrotic point instant, beginning to apply a positive sign to the direct dynamic impedance Zd— D(t) that is the first one in the direct time order;C.2 determining a reflected dynamic impedance Zd — R(t) for each one of said one or more characteristic points, said reflected dynamic impedance Zd— R(t) being equal to the ratio between a value of the pressure signal P(t) at the characteristic point and the distance of the respective time instant from the final instant of the heart beat under consideration, and determining an impedance ZR of reflected waves of pressure by summing with alternate signs the values of the reflected dynamic impedances Zd— R(t) ordered according to a reverse time order starting from the final instant down to the initial instant of the heart beat under consideration, beginning to apply a positive sign to the reflected dynamic impedance Zd— R(t) that is the first one in the reverse time order;C.3 determining said energy efficiency RES as ratio between the impedance ZD of the direct wave and the impedance ZR of the reflected waves;
RES=ZD/ZRD. for said energy efficiency RES determined in step C, checking whether a first derivative dP/dt of the pressure signal P(t) is lower than a first value Td of maximum threshold in the whole heart beat under consideration and whether the second derivative d2P/dt2 of the pressure signal P(t) is lower than a second value Td2 of maximum threshold in the whole heart beat under consideration, and in the case where the check has negative outcome making step E, otherwise, in the case where the check has positive outcome, making step F; E. selecting a cutoff frequency of a low-pass filter on the basis of said energy efficiency RES determined in step C, of the first derivative dP/dt and of the second derivative d2P/dt2 of the pressure signal P(t), and applying said low-pass filter to the pressure signal P(t), thus obtaining a new sampled pressure signal, and returning to execute the preceding steps starting from step B; F. outputting the pressure signal P(t) on which step B has been made for the last time.
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25. Computer-readable memory medium, having a program stored therein, wherein the program is adapted to perform, when operating on processing means of an apparatus, the following steps of an automatic method for measuring and processing blood pressure:
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the following steps; A. having a sampled detected pressure signal P(t) for one or more heart beats, each heart beat starting at an initial instant coinciding with the one of the initial diastolic pressure point and ending at a final instant coinciding with the one of the subsequent diastolic pressure point and comprising a dicrotic point, each beat having a systolic phase going from the initial diastolic point to the dicrotic point; and B. automatically analysing and discriminating morphology of the pressure signal P(t) sampled for each heart beat, determining instant and pressure value of one or more characteristic points of the pressure signal P(t) selected from the group comprising an initial diastolic pressure point, a systolic pressure point, a dicrotic point, and one or more resonance points, each one of which occurs in an instant wherein a second derivative d2P/dt2 of the pressure signal P(t) has a local maximum, at least one characteristic point of the pressure signal P(t) belonging to the systolic phase of the heart beat under consideration and being different from the initial diastolic pressure point; C. for each heart beat, determining an energy efficiency RES through the following sub-steps; C.1 determining a direct dynamic impedance Zd — D(t) for each one of said one or more characteristic points belonging to the systolic phase of the heart beat under consideration and different from the initial diastolic pressure point, said direct dynamic impedance Zd— D(t) being equal to the ratio between a value of the pressure signal P(t) at the characteristic point and the distance of the respective time instant from the initial instant of the heart beat under consideration, and determining an impedance ZD of a direct wave of pressure by summing with alternate signs the values of the direct dynamic impedances Zd— D(t) ordered according to a direct time order starting from the initial instant of the heart beat under consideration up to the dicrotic point instant, beginning to apply a positive sign to the direct dynamic impedance Zd— D(t) that is the first one in the direct time order;C.2 determining a reflected dynamic impedance Zd — R(t) for each one of said one or more characteristic points, said reflected dynamic impedance Zd— R(t) being equal to the ratio between a value of the pressure signal P(t) at the characteristic point and the distance of the respective time instant from the final instant of the heart beat under consideration, and determining an impedance ZR of reflected waves of pressure by summing with alternate signs the values of the reflected dynamic impedances Zd— R(t) ordered according to a reverse time order starting from the final instant down to the initial instant of the heart beat under consideration, beginning to apply a positive sign to the reflected dynamic impedance Zd— R(t) that is the first one in the reverse time order;C.3 determining said energy efficiency RES as ratio between the impedance ZD of the direct wave and the impedance ZR of the reflected waves;
RES=ZD/ZRD. for said energy efficiency RES determined in step C, checking whether a first derivative dP/dt of the pressure signal P(t) is lower than a first value Td of maximum threshold in the whole heart beat under consideration and whether the second derivative d2P/dt2 of the pressure signal P(t) is lower than a second value Td2 of maximum threshold in the whole heart beat under consideration, and in the case where the check has negative outcome making step E, otherwise, in the case where the check has positive outcome, making step F; E. selecting a cutoff frequency of a low-pass filter on the basis of said energy efficiency RES determined in step C, of the first derivative dP/dt and of the second derivative d2P/dt2 of the pressure signal P(t), and applying said low-pass filter to the pressure signal P(t), thus obtaining a new sampled pressure signal, and returning to execute the preceding steps starting from step B; F. outputting the pressure signal P(t) on which step B has been made for the last time.
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Specification
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Current AssigneeSalvatore Romano
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Original AssigneeSalvatore Romano
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InventorsRomano, Salvatore
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Application NumberUS13/818,985Publication NumberTime in Patent OfficeDaysField of SearchUS Class Current600/485CPC Class CodesA61B 5/02108 from analysis of pulse wave...A61B 5/02125 of pulse wave propagation timeA61B 5/0215 by means inserted into the ...A61B 5/7239 using differentiation inclu...A61B 5/725 using specific filters ther...A61B 5/742 using visual displays A61B5...
