METHODS AND SYSTEMS FOR RECALIBRATING A BLOOD PRESSURE MONITOR WITH MEMORY

• US 20140364746A1
• Filed: 08/26/2014
• Published: 12/11/2014
• Est. Priority Date: 11/30/2010
• Status: Active Grant

• Current Assignee: Nellcor Puritan Bennett Ireland
• Original Assignee: Nellcor Puritan Bennett Ireland
• Inventors: Addison, Paul Stanley, Watson, James N.
• Granted Patent: US 9,289,136 B2
• Time in Patent Office: Days
• US Class Current: 600/480
• CPC Class Codes: A61B 2560/0223 of calibration, e.g. protocols for calibrating sensors
• CPC Class Codes: A61B 2560/0271 using a remote monitoring unit
• CPC Class Codes: A61B 5/02125 of pulse wave propagation time
• CPC Class Codes: A61B 5/02141 Details of apparatus construction, e.g. pump units or housings therefor, cuff pressurising systems, arrangements of fluid conduits or circuits A61B5/02233, A61B5/0235 take precedence
• CPC Class Codes: A61B 5/02416 using photoplethysmograph signals, e.g. generated by infrared radiation A61B5/14552 takes precedence
• CPC Class Codes: A61B 5/14551 for measuring blood gases
• CPC Class Codes: A61B 5/7221 Determining signal validity, reliability or quality A61B5/7207 and A61B5/7217 take precedence
• CPC Class Codes: A61B 5/7235 Details of waveform analysis A61B5/349 takes precedence
• CPC Class Codes: A61B 5/7239 using differentiation including higher order derivatives
• CPC Class Codes: G16H 40/40 for the management of medical equipment or devices, e.g. scheduling maintenance or upgrades
• CPC Class Codes: G16Z 99/00 Subject matter not provided for in other main groups of this subclass

Abstract

Systems and methods are provided for storing and recalling metrics associated with physiological signals. It may be determined that the value of a monitored physiological metric corresponds to a stored value. In such cases, a patient monitor may determine that a calibration is not desired. In some cases, a patient monitor may recall calibration parameters associated with the stored value if it determined that the stored value corresponds to the monitored metric value.

Claims

1. A system for determining blood pressure of a subject, the system comprising:

a signal input configured to receive from a sensing device a physiological signal indicative of an amount of light absorbed by a tissue of the subject;

a processor coupled to the signal input, wherein the processor is configured to;

monitor a metric derived at least in part from the physiological signal;

determine a first set of calibration parameters associated with a first value of the metric;

store the first set of calibration parameters and the associated first value of the metric;

determine a second set of calibration parameters associated with a second value of the metric;

store the second set of calibration parameters and the associated second value of the metric; and

determine a blood pressure of the subject based at least in part on the physiological signal, the metric, and at least one of the first and second sets of calibration parameters.

2. The system of claim 1, wherein the physiological signal comprises a photoplethysmograph (PPG) signal, and wherein the metric comprises at least one of a differential pulse transit time, a blood pressure, a heart rate, a PPG signal derivative, a PPG signal integral, a PPG signal moment, a PPG signal domain, a PPG signal range, a PPG signal peak value, a PPG signal morphology metric, a coefficient of a PPG signal transform, and a combination thereof.

3. The system of claim 1, further comprising a memory storage device coupled to the processor, wherein the first and second sets of calibration parameters and the associated first and second values of the metric are stored in the memory storage device.

4. The system of claim 1, wherein the processor is coupled to a memory storage device remote from the system, and wherein the first and second sets of calibration parameters and the associated first and second values of the metric are stored in the remote memory storage device.

5. The system of claim 1, wherein the processor is further configured to:

compare a current value of the metric to the first and second values of the metric to determine if the current value corresponds to the first or second value;

recall the associated first or second set of calibration parameters if the current value corresponds to the first or second value of the metric; and

determine the blood pressure based on the recalled set of calibration parameters.

6. The system of claim 5, wherein the processor is further configured to:

perform a calibration to determine a third set of calibration parameters associated with a third value of the metric if a current value of the metric does not correspond to at least one of the first and second values of the metric;

store the third set of calibration parameters and the associated third value of the metric; and

determine the blood pressure based on the third set of calibration parameters.

7. The system of claim 5, wherein comparing the current value of the metric to the first and second values of the metric further comprises:

determining a difference between the current value and the first value of the metric;

determining a difference between the current value and the second value of the metric; and

comparing the differences to a threshold to determine if the current value corresponds to at least one of the first and second values.

8. The system of claim 5, wherein the comparing the current value of the metric to the first and second values of the metric further comprises using a pattern recognition technique.

9. The system of claim 1, wherein the determining the blood pressure of the subject further comprises:

selecting one of the first set of calibration parameters and the second set of calibration parameters based on a current value of the metric; and

determining the blood pressure of the subject based on the selected calibration parameter set and the physiological signal.

10. The system of claim 1, wherein the processor is further configured to:

generate a database comprising the first and second values of the metric and the associated first and second sets of calibration parameters; and

append subsequently obtained additional values of the metric and associated additional sets of calibration parameters to the database.

11. The system of claim 1, wherein the metric comprises a first metric, and wherein the processor is further configured to:

monitor a second metric derived at least in part from the physiological signal;

determine additional sets of calibration parameters associated with subsequently obtained additional values of the second metric;

store the additional sets of calibration parameters and associated additional values; and

determine the blood pressure of the subject based at least in part on the physiological signal, at least one of the first metric and the second metric, and at least one of the first, second, and additional sets of calibration parameters.

12. A method for determining blood pressure of a subject, the method comprising:

receiving a photoplethysmograph (PPG) signal from a pulse oximetry sensor;

monitoring, using a processor coupled to the pulse oximetry sensor, a metric derived, by the processor, at least in part from the PPG signal;

determining, using the processor, a first set of calibration parameters associated with a first value of the metric;

storing, to a memory storage device coupled to the processor, the first set of calibration parameters and the associated first value of the metric;

determining, using the processor, a second set of calibration parameters associated with a second value of the metric;

storing, to the memory storage device, the second set of calibration parameters and the associated second value of the metric;

determining, using the processor, the blood pressure of the subject based at least in part on the physiological signal, the metric, and at least one of the first and second sets of calibration parameters; and

outputting, to a display device coupled to the processor, the determined blood pressure of the subject.

13. The method of claim 12, wherein the metric comprises at least one of a differential pulse transit time, a blood pressure, a heart rate, a PPG signal derivative, a PPG signal integral, a PPG signal moment, a PPG signal domain, a PPG signal range, a PPG signal peak value, a PPG signal morphology metric, a coefficient of a PPG signal transform, and a combination thereof.

14. The method of claim 12, wherein the memory storage device is remote from the processor.

15. The method of claim 12, wherein the determining the blood pressure of the subject further comprises:

comparing, using the processor, a current value of the metric to the first and second values of the metric to determine if the current value corresponds to the first or second value;

recalling, from the memory storage device, the associated first or second set of calibration parameters if the current value corresponds to the first or second value of the metric; and

determining, using the processor, the blood pressure based on the recalled set of calibration parameters.

16. The method of claim 15, further comprising:

performing, using a calibration device coupled to the processor, a calibration to determine a third set of calibration parameters associated with a third value of the metric if the current value of the metric does not correspond to at least one of the first and second values of the metric;

storing, to the memory storage device, the third set of calibration parameters and the associated third value of the metric; and

determining, using the processor, the blood pressure based on the third set of calibration parameters.

17. The method of claim 15, wherein the comparing the current value of the metric to the first and second values of the metric further comprises:

determining a difference between the current value and the first value of the metric;

determining a difference between the current value and the second value of the metric; and

comparing the differences to a threshold to determine if the current value corresponds to at least one of the first and second values.

18. The method of claim 15, wherein the comparing the current value of the metric to the first and second values of the metric further comprises using a pattern recognition technique.

19. The method of claim 12, wherein the determining the blood pressure of the subject further comprises:

selecting one of the first set of calibration parameters and the second set of calibration parameters based on a current value of the metric; and

determining the blood pressure of the subject based on the selected calibration parameter set and the physiological signal.

20. The method of claim 12, further comprising:

generating, in the memory storage device, a database comprising the first and second values of the metric and the associated first and second sets of calibration parameters; and

appending subsequently obtained additional values of the metric and associated additional sets of calibration parameters to the database.

21. The method of claim 20, further comprising:

searching the database for values corresponding to a current value of the metric;

recalling, from the database, a set of calibration parameters associated with the value corresponding to the current value of the metric; and

determining, using the processor, the blood pressure based on the associated set of calibration parameters.