SYSTEMS AND METHODS FOR CONTINUOUS NON-INVASIVE BLOOD PRESSURE MONITORING

• US 20110021929A1
• Filed: 07/27/2009
• Published: 01/27/2011
• Est. Priority Date: 07/27/2009
• Status: Abandoned Application

• Current Assignee: Nellcor Puritan Bennett Ireland
• Original Assignee: Nellcor Puritan Bennett Ireland
• Inventors: Watson, James, Sethi, Rakesh, Addison, Paul Stanly
• Application Number:
  US12/509,790
• Publication Number:
  US 20110021929A1
• Time in Patent Office: Days
• US Class Current: 600/485
• CPC Class Codes: A61B 5/021 Measuring pressure in heart or blood vessels A61B5/0205 takes precedence
• CPC Class Codes: A61B 5/02125 of pulse wave propagation time

Abstract

Systems and methods are disclosed herein for continuous non-invasive blood pressure (CNIBP) monitoring. Multiple reference blood pressure values may be obtained using a calibration device. These multiple reference blood pressure values may be used as calibration points for determining a relationship between the blood pressure of a patient and photoplethysmograph (PPG) signals.

Claims

1. A system for monitoring blood pressure of a patient, the system comprising:

a signal generator for generating at least two PPG signals from at least two respective sensors attached to the patient;

a processor coupled to the signal generator, wherein the processor is capable of;

determining at least two reference blood pressure values based at least in part on a calibration device coupled to the patient and to the processor, and

updating a relationship between blood pressure of the patient and the at least two PPG signals based at least in part on the at least two reference blood pressure values,

calculating a blood pressure value based at least in part on the updated relationship; and

an output device coupled to the processor.

2. The system of claim 1, wherein the processor is further capable of:

identifying at least two points in the at least two PPG signals, wherein the at least two points occur after the reference blood pressure value is obtained;

determining a time difference between the at least two points; and

calculating the blood pressure value based at least in part on the time difference and the updated relationship.

3. The system of claim 2, wherein the relationship is

P=a+b·

ln(T)

or a mathematical equivalent thereof, wherein P is the blood pressure value, T is the time difference, and a and b are constants determined based at least in part on the at least two reference blood pressure values.

4. The system of claim 1, wherein the processor is further capable of identifying a reference blood pressure value as an outlier.

5. The system of claim 4, wherein the processor is further capable of determining a new reference blood pressure value to verify the outlier.

6. The system of claim 1, wherein the processor is further capable of:

associating weighting factors with the at least two reference blood pressure values; and

updating the relationship based at least in part on the at least two reference blood pressure values and the weighting factors.

7. The system of claim 1, wherein the processor is further capable of:

identifying a blood pressure event;

determining at least two further reference blood pressure values after the blood pressure event occurs;

resetting the relationship between blood pressure of the patient and the at least two PPG signals; and

updating the relationship based at least in part on the at least two further reference blood pressure values.

8. The system of claim 7, wherein the blood pressure event is a change in vascular compliance.

9. The system of claim 7, wherein the blood pressure event is a blood pressure change that exceeds a threshold stored in the processor.

10. A method for monitoring blood pressure of a patient, the method comprising:

determining using a processor at least two reference blood pressure values based at least in part on a calibration device coupled to the patient and to the processor;

obtaining at least two PPG signals from at least two respective sensors attached to the patient;

updating a relationship between blood pressure of the patient and the at least two PPG signals based at least in part on the at least two reference blood pressure values; and

calculating a blood pressure value based at least in part on the updated relationship.

11. The method of claim 10, further comprising:

identifying at least two points in the at least two PPG signals, wherein the at least two points occur after the at least two reference blood pressure values are obtained;

determining a time difference between the at least two points; and

calculating the blood pressure value based at least in part on the time difference and the updated relationship.

12. The method of claim 10, wherein the relationship is

P=a+b·

ln(T)

or a mathematical equivalent thereof, where P is the blood pressure value, T is the time difference, and a and b are constants determined based at least in part on the at least two reference blood pressure values.

13. The method of claim 10, further comprising identifying a blood pressure value as an outlier.

14. The method of claim 13, further comprising determining a new reference blood pressure value to verify the outlier.

15. The method of claim 10, further comprising:

associating weighting factors with the at least two reference blood pressure values; and

updating the relationship based at least in part on the at least two reference blood pressure values and the weighting factors.

16. The method of claim 10, further comprising:

identifying a blood pressure event;

determining at least two further reference blood pressure values after the blood pressure event occurs;

resetting the relationship between blood pressure of the patient and the at least two PPG signals; and

updating the relationship based at least in part on the at least two further reference blood pressure values.

17. The method of claim 16, wherein the blood pressure event is a change in vascular compliance.

18. The method of claim 16, wherein the blood pressure event is a blood pressure change that exceeds a threshold stored in the processor.

19. A computer-readable medium for use in monitoring blood pressure of a patient, the computer-readable medium having computer program instructions recorded thereon for:

determining at least two reference blood pressure values based at least in part on a calibration device coupled to the patient;

obtaining at least two PPG signals from at least two respective sensors attached to the patient;

updating a relationship between blood pressure of the patient and the at least two PPG signals based at least in part on the at least two reference blood pressure values; and

calculating a blood pressure value based at least in part on the updated relationship.