Apparatus and method for determining a physiological parameter
First Claim
1. Apparatus for determining at least one physiological parameter of a patient, said apparatus comprising:
- a sensor device adapted to provide readings of an blood variable of said patient,memory means for storing said readings as a curve representing said variable over time t,evaluation means adapted to determine a mean value from said curve and to determine said at least one physiological parameter using said mean value,whereinsaid evaluation means are further adaptedto determine at least one of a spectral density S(ω
) of said curve and a variance of said blood variable,to determine at least one model parameter representing an effective value of a heart beat using said mean value and at least one of said spectral density S(ω
) and said variance, said effective value being selected from an effective amplitude Aeff of said heart beat, an effective duration deff of said heart beat and an effective area Feff under said heart beat, andto determine said at least one physiological parameter using at least one said model parameter.
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Accused Products
Abstract
An apparatus for determining a physiological parameter of a patient, such as cardiac output, comprises a sensor device providing readings of a blood variable, memory means storing the readings as a curve over time, evaluation means determining a mean value from the curve and determining the physiological parameter using the mean value is provided. The evaluation means determine a spectral density of the curve and/or a variance. The evaluation means also determine at least one model parameter representing an effective value of a heart beat using the mean value and the spectral density and/or variance. The effective value is selected from an effective amplitude of the heart beat, an effective duration of the heart beat and an effective area under the heart beat. The physiological parameter is determined using at least one of the model parameters.
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Citations
39 Claims
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1. Apparatus for determining at least one physiological parameter of a patient, said apparatus comprising:
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a sensor device adapted to provide readings of an blood variable of said patient, memory means for storing said readings as a curve representing said variable over time t, evaluation means adapted to determine a mean value from said curve and to determine said at least one physiological parameter using said mean value, wherein said evaluation means are further adapted to determine at least one of a spectral density S(ω
) of said curve and a variance of said blood variable,to determine at least one model parameter representing an effective value of a heart beat using said mean value and at least one of said spectral density S(ω
) and said variance, said effective value being selected from an effective amplitude Aeff of said heart beat, an effective duration deff of said heart beat and an effective area Feff under said heart beat, andto determine said at least one physiological parameter using at least one said model parameter. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19)
wherein said memory means are adapted to record said physical quantity measured over the course of time at said second location as a dilution curve, and said evaluation unit is adapted to determine a comparative value of at least one of said physiological parameters from said dilution curve using dilution algorithms. -
15. Apparatus according to claim 13, wherein said evaluation unit is adapted to use said comparative value for calibration.
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16. Apparatus according to claim 15, wherein calibration includes determining, using said comparative value, correction parameter α
- used in determining said model parameter, said correction parameter α
assuming values greater than or equal to 1, said values being the higher the less the patient'"'"'s heart frequency deviates from a rhythmic condition.
- used in determining said model parameter, said correction parameter α
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17. Apparatus according to claim 13, wherein said evaluation unit is adapted to reject and re-calculate said physiological parameter, if the difference between the determined physiological parameter and the respective comparative value exceeds a threshold value.
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18. Apparatus according to claim 1, wherein said sensor device includes a pressure sensor device, said blood variable is an arterial blood pressure, said curve representing said variable over time is a pressure curve P(t) over time t, and said mean value is a mean arterial blood pressure <
- P>
.
- P>
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19. Apparatus according to claim 1, wherein said sensor device includes a plethysmography and/or pulse-oximetry sensor setup.
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20. Method for determining at least one physiological parameter of a patient, said method comprising the steps of:
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importing readings of a blood variable of said patient, storing said readings as a curve representing said blood variable over time t, determining a mean value from said curve and determining at least one physiological parameter using said mean value wherein said method further includes determining at least one of a spectral density S(ω
) of said curve and a variance of said blood variable,determining at least one model parameter representing an effective value of a heart beat using said mean value and at least one of said spectral density S(ω
) and said variance, said effective value being selected from an effective amplitude Aeff of said heart beat, an effective duration deff of said heart beat and an effective area Feff under said heart beat, anddetermining said at least one physiological parameter using at least one said model parameter. - View Dependent Claims (21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38)
wherein, said measurement readings of said physical quantity at said second location of the blood circulation of said patient are recorded as a dilution curve, and said comparative value of at least one of said physiological parameters is determined from said dilution curve using dilution algorithms. -
34. Method according to claim 32, wherein said comparative value is used for calibration.
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35. Method according to claim 34, wherein calibration includes determining, using said comparative value, correction parameter α
- used in determining said model parameter, said correction parameter α
assuming values greater than or equal to 1, said values being the higher the less the patient'"'"'s heart frequency deviates from a rhythmic condition.
- used in determining said model parameter, said correction parameter α
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36. Method according to claim 32, wherein said physiological parameter is rejected and re-calculated, if the difference between the determined physiological parameter and the respective comparative value exceeds a threshold value.
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37. Method according to claim 20, wherein said blood variable is an arterial blood pressure, said curve representing said variable over time t is a pressure curve P(t) over time t, and said mean value is a mean arterial blood pressure <
- P>
.
- P>
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38. Method according to claim 20, wherein said imported readings are readings obtained through plethysmographic and/or pulsoximetric measurement techniques.
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39. Physical storage medium having stored thereon a computer program which, when executed on a computer system, causes the computer system to perform a method for determining at least one physiological parameter of a patient, said method comprising the steps of:
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importing readings of a blood variable of said patient, storing said readings as a curve representing said blood variable over time t, determining a mean value from said curve and determining at least one physiological parameter using said mean value wherein said method further includes determining at least one of a spectral density S(ω
) of said curve and a variance of said blood variable,determining at least one model parameter representing an effective value of a heart beat using said mean value and at least one of said spectral density S(ω
) and said variance <
(δ
P)2>
, said effective value being selected from an effective amplitude Aeff of said heart beat, an effective duration deff of said heart beat and an effective area Feff under said heart beat, anddetermining said at least one physiological parameter using at least one said model parameter.
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Specification