Calculation of quality and its use in determination of indirect noninvasive blood pressure
First Claim
1. An automated sphygmomanometer apparatus, comprising:
- an inflatable and deflatable pressure cuff;
an inflating apparatus coupled to said cuff so as to selectively apply a medium under pressure to said cuff for inflating and pressurizing said cuff;
a cuff pressure sensor coupled to said cuff so as to sense cuff pressure including any blood pressure oscillations therein;
a deflating apparatus coupled to said cuff so as to selectively relieve pressure from said cuff; and
a programmed control device responsive to cuff pressure determination of said cuff pressure sensor, said control device programmed to control said inflating apparatus to inflate said cuff and said deflating apparatus to deflate said cuff during respective blood pressure determinations of a patient at predetermined intervals and to store oscillometric envelope data representing points of an oscillometric envelope defined by measured blood pressure oscillations, said control device further programmed to, to check the signal quality of said oscillometric envelope data, calculate the patient'"'"'s blood pressure from said oscillometric envelope data if the quality of the oscillometric envelope data is good, and to selectively display the calculated blood pressure in accordance with the signal quality of said oscillometric envelope data.
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Abstract
An automated sphygmomanometer which utilizes quality algorithms to stop any further analysis at various points during a blood pressure determination because of corrupted data. If the data is so corrupted that giving blood pressure numbers is inappropriate, this is recognized and the determination stopped. The quality algorithms make a decision to get more data with the hope of improving the blood pressure estimation. The request for data occurs both before and/or after a curve fitting process, if such a process is utilized. Some information is also provided to the cuff pressure control function about which pressure levels would be best for gathering the additional data. The quality algorithms are also used to make a decision as to whether it is appropriate to publish the blood pressure values obtained. Control parameters (weights) may be set within the blood pressure algorithm to help with other aspects of the NIBP algorithm and improve the quality of the final published numbers. The quality algorithms may also help the system to decide whether to publish any warnings when significant artifact is present.
70 Citations
31 Claims
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1. An automated sphygmomanometer apparatus, comprising:
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an inflatable and deflatable pressure cuff;
an inflating apparatus coupled to said cuff so as to selectively apply a medium under pressure to said cuff for inflating and pressurizing said cuff;
a cuff pressure sensor coupled to said cuff so as to sense cuff pressure including any blood pressure oscillations therein;
a deflating apparatus coupled to said cuff so as to selectively relieve pressure from said cuff; and
a programmed control device responsive to cuff pressure determination of said cuff pressure sensor, said control device programmed to control said inflating apparatus to inflate said cuff and said deflating apparatus to deflate said cuff during respective blood pressure determinations of a patient at predetermined intervals and to store oscillometric envelope data representing points of an oscillometric envelope defined by measured blood pressure oscillations, said control device further programmed to, to check the signal quality of said oscillometric envelope data, calculate the patient'"'"'s blood pressure from said oscillometric envelope data if the quality of the oscillometric envelope data is good, and to selectively display the calculated blood pressure in accordance with the signal quality of said oscillometric envelope data. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31)
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9. An apparatus as in claim 7, wherein said programmed control device checks the signal quality of said oscillometric envelope data by determining an intermediate complex quality number as a measure of a percentage of pressure steps whose best complexes are above an estimated noise level that is a root mean square (r.m.s.) error of all complexes in said newly acquired oscillometric envelope data.
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10. An apparatus as in claim 9, wherein said programmed control device bases said estimated noise level on a complex s.s.e. determined from the following equation:
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where; cij is complex data representing complex size from said newly acquired oscillometric envelope data;
“
i”
is an index used for envelope step data;
j is an index for the complexes at an envelope step pressure level;
pi represents step pressure; and
A, B, and C are Gaussian parameters for amplitude, mean, and deviation, respectively, used by said curve fit procedure.
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11. An apparatus as in claim 9, wherein said programmed control device checks the signal quality of said oscillometric envelope data by determining an intermediate step quality number as a measure of the variability of sizes of complexes at an envelope step pressure level.
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12. An apparatus as in claim 11, wherein said programmed control device determines said intermediate step quality number as a percentage of complexes out of all complexes received which has a ratio of an absolute difference between each complex to a best estimate of complex size for the cuff pressure at which the complex occurs which exceeds a threshold dependent upon said intermediate history quality number.
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13. An apparatus as in claim 11, wherein said programmed control device combines said intermediate history quality number, said intermediate envelope quality number, said intermediate complex quality number, and said intermediate step quality number in accordance with a weighting function to create an overall quality number representative of the signal quality of said oscillometric envelope data.
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14. An apparatus as in claim 13, wherein said programmed control device checks said calculated blood pressure and said overall quality number to determine if said calculated blood pressure and said overall quality number make physiological sense prior to displaying the calculated blood pressure.
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15. An apparatus as in claim 14, wherein said programmed control device compares said overall quality number to a first threshold, whereby said calculated blood pressure is displayed only if said first threshold is exceeded.
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16. An apparatus as in claim 15, wherein said programmed control device further compares said overall quality number to a second threshold, greater than said first threshold, whereby said calculated blood pressure is displayed with a message warning of artifact if said overall quality number exceeds said first threshold but not said second threshold and displays said calculated blood pressure without said warning message if said overall quality number exceeds both said first and second thresholds.
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17. A method as in claim 13, wherein said signal quality checking step comprises the step of checking said calculated blood pressure and said overall quality number to determine if said calculated blood pressure and said overall quality number make physiological sense prior to displaying the calculated blood pressure.
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18. A method as in claim 17, wherein said signal quality checking step comprises the step of comparing said overall quality number to a first threshold, whereby said calculated blood pressure is displayed in said displaying step only if said first threshold is exceeded.
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19. A method as in claim 18, wherein said signal quality checking step further comprises the step of comparing said overall quality number to a second threshold, greater than said first threshold, and said displaying step comprises the steps of displaying said calculated blood pressure with a message warning of artifact if said overall quality number exceeds said first threshold but not said second threshold and displaying said calculated blood pressure without said warning message if said overall quality number exceeds both said first and second thresholds.
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21. A method as in claim 17, wherein said step of determining if said oscillometric envelope has said predetermined general bell shape is conducted prior to said blood pressure calculating step, and said blood pressure calculating step comprises the step of calculating the patient'"'"'s blood pressure using a curve fit procedure but only if said oscillometric envelope is determined to have said predetermined general bell shape.
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22. A method as in claim 21, wherein said signal quality checking step comprises the step of using blood pressure results determined during implementation of said curve fit procedure to said oscillometric envelope data to determine if the calculated blood pressures are in a reasonable physiological range and diastolic pressure <
- MAP <
systolic pressure.
- MAP <
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23. A method as in claim 22, wherein said signal quality checking step comprises the steps of comparing newly acquired oscillometric envelope data with stored oscillometric envelope data and determining an intermediate history quality number as a percentage of values of said newly acquired oscillometric envelope data that are within a predetermined range from values of said stored oscillometric envelope data.
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24. A method as in claim 23, wherein said signal quality checking step comprises the step of weighting more recent oscillometric envelope data more heavily than older oscillometric envelope data during said determination of said intermediate history quality number.
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25. A method as in claim 23, wherein said signal quality checking step comprises the step of determining an intermediate envelope quality number as a measure of how well curve fit data used by said curve fit procedure fits said newly acquired oscillometric envelope data.
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26. A method as in claim 25, wherein said step of determining said intermediate envelope quality number comprises the step of calculating the intermediate envelope quality number using the equation:
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Intermediate envelope quality=A*100/(A+sqrt(WEIGHT*Envelope s.s.e.)) where; A is a Gaussian parameter for amplitude used by said curve fit procedure;
WEIGHT has a value based on said intermediate history quality number; and
Envelope sum-squared error (s.s.e.) is found using the following equation;
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27. A method as in claim 25, wherein said signal quality checking step comprises the step of determining an intermediate complex quality number as a measure of a percentage of pressure steps whose best complexes are above an estimated noise level that is a root mean square (r.m.s.) error of all complexes in said newly acquired oscillometric envelope data.
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28. A method as in claim 27, wherein said step of determining said intermediate complex quality number comprises the step of calculating said estimated noise level based on a complex s.s.e. using the equation:
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where; cij is complex data representing complex size from said newly acquired oscillometric envelope data;
“
i”
is an index used for envelope step data; and
j is an index for the complexes at an envelope step pressure level;
pi represents step pressure; and
A, B, and C are Gaussian parameters for amplitude, mean, and deviation, respectively, used by said curve fit procedure.
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29. A method as in claim 27, wherein said signal quality checking step comprises the step of determining an intermediate step quality number as a measure of the variability of sizes of complexes at an envelope step pressure level.
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30. A method as in claim 29, wherein the step of determining said intermediate step quality number comprises the step of calculating a percentage of complexes out of all complexes received which has a ratio of an absolute difference between each complex to a best estimate of complex size for the cuff pressure at which the complex occurs which exceeds a threshold dependent upon said intermediate history quality number.
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31. A method as in claim 29, wherein said signal quality checking step comprises the step of combining said intermediate history quality number, said intermediate envelope quality number, said intermediate complex quality number, and said intermediate step quality number in accordance with a weighting function to create an overall quality number representative of the signal quality of said oscillometric envelope data.
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20. A method of measuring the blood pressure of a subject, comprising the steps of:
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obtaining from the subject a plurality of oscillometric data values including an amplitude from at least one complex taken at a plurality of pressure levels, said oscillometric data values representing points of an oscillometric envelope defined by measured blood pressure oscillations;
checking the signal quality of said oscillometric data values by determining if said oscillometric envelope has a predetermined general bell shape;
calculating the patient'"'"'s blood pressure from said oscillometric data values when the signal quality is determined to be good;
selectively displaying the calculated blood pressure in accordance with the signal quality of said oscillometric data values.
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Specification