Continuous Calibration of A Blood Pressure Measurement Device

• US 20150327785A1
• Filed: 05/18/2015
• Published: 11/19/2015
• Est. Priority Date: 05/19/2014
• Status: Active Grant

• Current Assignee: Philips Healthcare Informatics Incorporated (Koninklijke Philips N.V.)
• Original Assignee: Qualcomm, Inc.
• Inventors: Lading, Lars, Baek, David Boettcher
• Granted Patent: US 10,039,455 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: A61B 2560/0223 of calibration, e.g. protocols for calibrating sensors
• CPC Class Codes: A61B 2560/0238 Means for recording calibration data
• CPC Class Codes: A61B 2560/0242 adapted to measure environmental factors, e.g. temperature, pollution
• CPC Class Codes: A61B 2560/0247 for compensation or correction of the measured physiological value
• CPC Class Codes: A61B 2562/0214 Capacitive electrodes
• CPC Class Codes: A61B 2562/0219 Inertial sensors, e.g. accelerometers, gyroscopes, tilt switches
• CPC Class Codes: A61B 5/0059 using light, e.g. diagnosis by transillumination, diascopy, fluorescence A61B5/0093, A61B5/1455, A61B5/02416 and A61B5/0261 take precedence
• CPC Class Codes: A61B 5/0082 adapted for particular medical purposes
• CPC Class Codes: A61B 5/02007 Evaluating blood vessel condition, e.g. elasticity, compliance
• CPC Class Codes: A61B 5/021 Measuring pressure in heart or blood vessels A61B5/0205 takes precedence
• CPC Class Codes: A61B 5/02108 from analysis of pulse wave characteristics
• CPC Class Codes: A61B 5/02116 of pulse wave amplitude A61B5/02225 takes precedence
• CPC Class Codes: A61B 5/053 Measuring electrical impedance or conductance of a portion of the body
• CPC Class Codes: A61B 5/0535 Impedance plethysmography for measuring blood flow A61B5/0295
• CPC Class Codes: A61B 5/1075 for measuring dimensions by non-invasive methods, e.g. for determining thickness of tissue layer A61B8/0858 takes precedence
• CPC Class Codes: A61B 5/1126 using a particular sensing technique
• CPC Class Codes: A61B 5/6898 Portable consumer electronic devices, e.g. music players, telephones, tablet computers
• CPC Class Codes: A61B 5/725 using specific filters therefor, e.g. Kalman or adaptive filters A61B5/316 take precedence
• CPC Class Codes: A61B 5/726 using Wavelet transforms
• CPC Class Codes: A61B 5/7275 Determining trends in physiological measurement data; Predicting development of a medical condition based on physiological measurements, e.g. determining a risk factor
• CPC Class Codes: A61B 5/7278 : Artificial waveform generation or derivation, e.g. synthesising signals from measured signals A61B5/327 takes precedence
• CPC Class Codes: A61B 5/7282 : Event detection, e.g. detecting unique waveforms indicative of a medical condition A61B5/4094, A61B5/4818, A61B5/349, A61B5/0823 take precedence
• CPC Class Codes: A61B 5/7285 : for synchronising or triggering a physiological measurement or image acquisition with a physiological event or waveform, e.g. an ECG signal A61B6/5205, A61B6/541, A61B8/5207, A61B8/543 take precedence
• CPC Class Codes: A61B 8/04 : Measuring blood pressure

Abstract

Systems, methods, and devices of the various embodiments enable continuous non-invasive monitoring of blood pressure with a minimum of interference. The various embodiments may provide a method for adaptation for the calibration for continuous measurements of blood pressure, wherein the measured quantity may be related to an arterial lumen or arterial cross sectional area comprising calibrating the conversion for incremental variations of arterial properties and absolute value adaptation by exploitation of the exponential decay during the diastole. In various embodiments, continuous calibration of a non-interfering blood pressure measurement device may be initiated based on a change in mean arterial pressure being greater than a threshold value, such as a pressure value associated with an actual measured distension of a patient'"'"'s artery.

Claims

1. A method for continuous calibration of a blood pressure measurement device, comprising:

determining, by a processor, whether a change in a measurement of an artery of a patient as measured by a non-interfering blood pressure measurement device and elevation of the non-interfering blood pressure measurement device occurred between two observation times;

determining, by the processor, whether a change in pulse rate has occurred between the two observation times in response to determining that a change in a measurement of the artery as measured by the non-interfering blood pressure measurement device and elevation of the non-interfering blood pressure measurement device occurred between two observation times;

determining, by the processor, an incremental variation between the two observation times in response to determining that no change in pulse rate occurred between the two observation times;

determining, by the processor, a coefficient fitting an exponentially decaying function representing an exponential decay of a portion of a diastolic phase to diastolic parts of measured pulses between the two observation times;

determining, by the processor, a current mean arterial pressure based at least in part on the exponentially decaying function and the incremental variation between the two observation times;

determining, by the processor, whether a change in mean arterial pressure is greater than a threshold value based on a comparison of the determined current mean arterial pressure and a previously determined mean arterial pressure; and

calibrating, by the processor, the non-interfering blood pressure measurement device in response to determining that the change in mean arterial pressure is greater than the threshold value.

2. The method of claim 1, wherein determining, by the processor, the current mean arterial pressure based at least in part on the exponentially decaying function and the incremental variation between the two observation times comprises:

determining, by the processor, a diastolic pressure based on the exponentially decaying function and the incremental variation between the two observation times;

determining, by the processor, a pulse pressure based at least in part on an exponential stress-strain function and the incremental variation between the two observation times;

determining, by the processor, a systolic blood pressure based on the determined diastolic pressure and the determined pulse pressure; and

determining, by the processor, a mean arterial pressure based on a mean of the pulse pressures from a start of a systole to an end of a diastole scaled with the incremental variation and a bias correction term.

3. The method of claim 1, wherein the measurement of the artery relates to a distension of the artery and is measured by the non-interfering blood pressure measurement device by one or more of bioimpedance, impedance plethysmography, photoplethsmography, ultrasound, and surface pressure sensing.

4. The method of claim 1, wherein the threshold value is a pressure value associated with an actual measured distension of the artery of the patient.

5. The method of claim 1, wherein calibrating the non-interfering blood pressure measurement device includes updating calibration values stored in a memory based on the change in mean arterial pressure and the change in the measurement of the artery.

6. The method of claim 1, wherein determining, by the processor, whether a change in pulse rate has occurred between the two observation times comprises localizing, by the processor, the pulses by one or more of:

determining a zero crossing of a high-pass filter demodulated signal;

localizing maximum pulse gradients;

localizing the pulses based on a quantity related to the maximum and minimum of each pulse;

and wavelet filtering to extract shape and time information.

7. A device, comprising:

a processor in communication with a non-interfering blood pressure measurement device, wherein the processor is configured with processor executable instructions to perform operations to;

determine whether a change in a measurement of an artery of a patient as measured by the non-interfering blood pressure measurement device and elevation of the non-interfering blood pressure measurement device occurred between two observation times;

determine whether a change in pulse rate has occurred between the two observation times in response to determining that a change in a measurement of the artery as measured by the non-interfering blood pressure measurement device and elevation of the non-interfering blood pressure measurement device occurred between two observation times;

determine an incremental variation between the two observation times in response to determining that no change in pulse rate occurred between the two observation times;

determine a coefficient fitting an exponentially decaying function representing an exponential decay of a portion of a diastolic phase to diastolic parts of measured pulses between the two observation times;

determine a current mean arterial pressure based at least in part on the exponentially decaying function and the incremental variation between the two observation times;

determine whether a change in mean arterial pressure is greater than a threshold value based on a comparison of the determined current mean arterial pressure and a previously determined mean arterial pressure; and

calibrate the non-interfering blood pressure measurement device in response to determining that the change in mean arterial pressure is greater than the threshold value.

8. The device of claim 7, wherein the processor is configured with processor executable instructions to perform operations to determine the current mean arterial pressure based at least in part on the exponentially decaying function and the incremental variation between the two observation times by:

determining a diastolic pressure based on the exponentially decaying function and the incremental variation between the two observation times;

determining a pulse pressure based at least in part on an exponential stress-strain function and the incremental variation between the two observation times;

determining a systolic blood pressure based on the determined diastolic pressure and the determined pulse pressure; and

determining a mean arterial pressure based on a mean of the pulse pressures from a start of a systole to an end of a diastole scaled with the incremental variation and a bias correction term.

9. The device of claim 7, wherein the measurement of the artery relates to a distension of the artery and is measured by the non-interfering blood pressure measurement device by one or more of bioimpedance, impedance plethysmography, photoplethsmography, ultrasound, and surface pressure sensing.

10. The device of claim 7, wherein the threshold value is a pressure value associated with an actual measured distension of the artery of the patient.

11. The device of claim 7, wherein the processor is configured with processor executable instructions to perform operations to calibrate the non-interfering blood pressure measurement device by updating calibration values stored in a memory based on the change in mean arterial pressure and the change in the measurement of the artery.

12. The device of claim 7, wherein the processor is configured with processor executable instructions to perform operations to determine whether a change in pulse rate has occurred between the two observation times by localizing the pulses by one or more of:

determining a zero crossing of a high-pass filter demodulated signal;

localizing maximum pulse gradients;

localizing the pulses based on a quantity related to the maximum and minimum of each pulse; and

wavelet filtering to extract shape and time information.

13. A non-interfering blood pressure measurement device, comprising:

an arterial measurement sensor;

an elevation sensor; and

a processor connected to the arterial measurement sensor and elevation sensor, wherein the processor is configured with processor executable instructions to perform operations to;

determine whether a change in a measurement of an artery of a patient as measured by the arterial measurement sensor and elevation of the non-interfering blood pressure measurement device as measured by the elevation sensor occurred between two observation times;

determine whether a change in pulse rate has occurred between the two observation times in response to determining that a change in a measurement of the artery as measured by the arterial measurement sensor and elevation of the non-interfering blood pressure measurement device as measured by the elevation sensor occurred between two observation times;

determine an incremental variation between the two observation times in response to determining that no change in pulse rate occurred between the two observation times;

determine a coefficient fitting an exponentially decaying function representing an exponential decay of a portion of a diastolic phase to diastolic parts of measured pulses between the two observation times;

determine a current mean arterial pressure based at least in part on the exponentially decaying function and the incremental variation between the two observation times;

determine whether a change in mean arterial pressure is greater than a threshold value based on a comparison of the determined current mean arterial pressure and a previously determined mean arterial pressure; and

calibrate the arterial measurement sensor and elevation sensor in response to determining that the change in mean arterial pressure is greater than the threshold value.

14. The non-interfering blood pressure measurement device of claim 13, wherein the processor is configured with processor executable instructions to perform operations to determine the current mean arterial pressure based at least in part on the exponentially decaying function and the incremental variation between the two observation times by:

determining a diastolic pressure based on the exponentially decaying function and the incremental variation between the two observation times;

determining a pulse pressure based at least in part on an exponential stress-strain function and the incremental variation between the two observation times;

determining a systolic blood pressure based on the determined diastolic pressure and the determined pulse pressure; and

determining a mean arterial pressure based on a mean of the pulse pressures from a start of a systole to an end of a diastole scaled with the incremental variation and a bias correction term.

15. The non-interfering blood pressure measurement device of claim 13, wherein the measurement of the artery relates to a distension of the artery and is measured by the non-interfering blood pressure measurement device by one or more of bioimpedance, impedance plethysmography, photoplethsmography, ultrasound, and surface pressure sensing.

16. The non-interfering blood pressure measurement device of claim 13, wherein the threshold value is a pressure value associated with an actual measured distension of an the artery of the patient.

17. The non-interfering blood pressure measurement device of claim 13, wherein the processor is configured with processor executable instructions to perform operations to calibrate the arterial measurement sensor and elevation sensor by updating calibration values stored in a memory based on the change in mean arterial pressure and the change in the measurement of the artery.

18. The non-interfering blood pressure measurement device of claim 13, wherein the processor is configured with processor executable instructions to perform operations to determine whether a change in pulse rate has occurred between the two observation times by localizing the pulses by one or more of:

determining a zero crossing of a high-pass filter demodulated signal;

localizing maximum pulse gradients;

localizing the pulses based on a quantity related to the maximum and minimum of each pulse; and

wavelet filtering to extract shape and time information.

19. A device, comprising:

means for determining whether a change in a measurement of an artery of a patient as measured by a non-interfering blood pressure measurement device and elevation of the non-interfering blood pressure measurement device occurred between two observation times;

means for determining whether a change in pulse rate has occurred between the two observation times in response to determining that a change in a measurement of the artery as measured by the non-interfering blood pressure measurement device and elevation of the non-interfering blood pressure measurement device occurred between two observation times;

means for determining an incremental variation between the two observation times in response to determining that no change in pulse rate occurred between the two observation times;

means for determining a coefficient fitting an exponentially decaying function representing an exponential decay of a portion of a diastolic phase to diastolic parts of measured pulses between the two observation times;

means for determining a current mean arterial pressure based at least in part on the exponentially decaying function and the incremental variation between the two observation times;

means for determining whether a change in mean arterial pressure is greater than a threshold value based on a comparison of the determined current mean arterial pressure and a previously determined mean arterial pressure; and

means for calibrating the non-interfering blood pressure measurement device in response to determining that the change in mean arterial pressure is greater than the threshold value.

20. The device of claim 19, wherein means for determining the current mean arterial pressure based at least in part on the exponentially decaying function and the incremental variation between the two observation times comprises:

means for determining a diastolic pressure based on the exponentially decaying function and the incremental variation between the two observation times;

means for determining a pulse pressure based at least in part on an exponential stress-strain function and the incremental variation between the two observation times;

means for determining a systolic blood pressure based on the determined diastolic pressure and the determined pulse pressure; and

means for determining a mean arterial pressure based on a mean of the pulse pressures from a start of a systole to an end of a diastole scaled with the incremental variation and a bias correction term.

21. The device of claim 19, wherein the measurement of the artery relates to a distension of the artery and is measured by the non-interfering blood pressure measurement device by one or more of bioimpedance, impedance plethysmography, photoplethsmography, ultrasound, and surface pressure sensing.

22. The device of claim 19, wherein the threshold value is a pressure value associated with an actual measured distension of an the artery of the patient.

23. The device of claim 19, wherein means for calibrating the non-interfering blood pressure measurement device includes means for updating calibration values stored in a memory based on the change in mean arterial pressure and the change in the measurement of the artery.

24. The device of claim 19, wherein means for determining whether a change in pulse rate has occurred between the two observation times comprises means for localizing the pulses by one or more of:

determining a zero crossing of a high-pass filter demodulated signal;

localizing maximum pulse gradients;

localizing the pulses based on a quantity related to the maximum and minimum of each pulse; and

wavelet filtering to extract shape and time information.

25. A non-transitory processor readable medium having stored thereon processor executable instructions configured to cause a processor to perform operations comprising:

determining whether a change in pulse rate has occurred between the two observation times in response to determining that a change in a measurement of an artery of a patient as measured by a non-interfering blood pressure measurement device and elevation of the non-interfering blood pressure measurement device occurred between two observation times;

determining an incremental variation between the two observation times in response to determining that no change in pulse rate occurred between the two observation times;

determining a coefficient fitting an exponentially decaying function with an additive bias representing an exponential decay of a portion of a diastolic phase to diastolic parts of measured pulses between the two observation times;

determining a current mean arterial pressure based at least in part on the exponentially decaying function and the incremental variation between the two observation times;

determining whether a change in mean arterial pressure is greater than a threshold value based on a comparison of the determined current mean arterial pressure and a previously determined mean arterial pressure; and

means for calibrating the non-interfering blood pressure measurement device in response to determining that the change in mean arterial pressure is greater than the threshold value.

26. The non-transitory processor readable medium of claim 25, wherein the stored processor readable instructions are configured to cause a processor to perform operations such that determining the current mean arterial pressure based at least in part on the exponentially decaying function and the incremental variation between the two observation times comprises:

determining a diastolic pressure based on the exponentially decaying function and the incremental variation between the two observation times;

determining a pulse pressure based at least in part on an exponential stress-strain function and the incremental variation between the two observation times;

determining a systolic blood pressure based on the determined diastolic pressure and the determined pulse pressure; and

determining a mean arterial pressure based on a mean of the pulse pressures from a start of a systole to an end of a diastole scaled with the incremental variation and a bias correction term.

27. The non-transitory processor readable medium of claim 25, wherein the stored processor readable instructions are configured to cause a processor to perform operations such that the measurement of the artery relates to a distension of the artery and is measured by the non-interfering blood pressure measurement device by one or more of bioimpedance, impedance plethysmography, photoplethsmography, ultrasound, and surface pressure sensing.

28. The non-transitory processor readable medium of claim 25, wherein the stored processor readable instructions are configured to cause a processor to perform operations such that the threshold value is a pressure value associated with an actual measured distension of the artery of the patient.

29. The non-transitory processor readable medium of claim 25, wherein the stored processor readable instructions are configured to cause a processor to perform operations such that calibrating the non-interfering blood pressure measurement device includes updating calibration values stored in a memory based on the change in mean arterial pressure and the change in the measurement of the artery.

30. The non-transitory processor readable medium of claim 25, wherein the stored processor readable instructions are configured to cause a processor to perform operations such that determining whether a change in pulse rate has occurred between the two observation times comprises localizing the pulses by one or more of:

determining a zero crossing of a high-pass filter demodulated signal;

localizing maximum pulse gradients;

localizing the pulses based on a quantity related to the maximum and minimum of each pulse; and

wavelet filtering to extract shape and time information.

31. A system, comprising:

a non-interfering blood pressure measurement device; and

a computing device, comprising a processor in communication with the non-interfering blood pressure measurement device, wherein the processor is configured with processor executable instructions to perform operations to

determine whether a change in a measurement of an artery of a patient as measured by the non-interfering blood pressure measurement device and elevation of the non-interfering blood pressure measurement device occurred between two observation times;

determine whether a change in pulse rate has occurred between the two observation times in response to determining that a change in a measurement of the artery as measured by the non-interfering blood pressure measurement device and elevation of the non-interfering blood pressure measurement device occurred between two observation times;

determine an incremental variation between the two observation times in response to determining that no change in pulse rate occurred between the two observation times;

determine a coefficient fitting an exponentially decaying function with an additive bias representing an exponential decay of a portion of a diastolic phase to diastolic parts of measured pulses between the two observation times;

determine a current mean arterial pressure based at least in part on the exponentially decaying function and the incremental variation between the two observation times;

determine whether a change in mean arterial pressure is greater than a threshold value based on a comparison of the determined current mean arterial pressure and a previously determined mean arterial pressure; and

calibrate the non-interfering blood pressure measurement device in response to determining that the change in mean arterial pressure is greater than the threshold value.

32. The system of claim 31, wherein the processor is configured with processor executable instructions to perform operations to determine the current mean arterial pressure based at least in part on the exponentially decaying function and the incremental variation between the two observation times by:

determining a diastolic pressure based on the exponentially decaying function and the incremental variation between the two observation times;

determining a pulse pressure based at least in part on an exponential stress-strain function and the incremental variation between the two observation times;

determining a systolic blood pressure based on the determined diastolic pressure and the determined pulse pressure; and

determining a mean arterial pressure based on a mean of the pulse pressures from a start of a systole to an end of a diastole scaled with the incremental variation and a bias correction term.

33. The system of claim 31, wherein the measurement of the artery relates to a distension of the artery and is measured by the non-interfering blood pressure measurement device by one or more of bioimpedance, impedance plethysmography, photoplethsmography, ultrasound, and surface pressure sensing.

34. The system of claim 31, wherein the threshold value is a pressure value associated with an actual measured distension of the artery of the patient.

35. The system of claim 31, wherein the processor is configured with processor executable instructions to perform operations to calibrate the non-interfering blood pressure measurement device by updating calibration values stored in a memory based on the change in mean arterial pressure and the change in the measurement of the artery.

36. The system of claim 31, wherein the processor is configured with processor executable instructions to perform operations to determine whether a change in pulse rate has occurred between the two observation times by localizing the pulses by one or more of:

determining a zero crossing of a high-pass filter demodulated signal;

localizing maximum pulse gradients;

localizing the pulses based on a quantity related to the maximum and minimum of each pulse; and

wavelet filtering to extract shape and time information.