Determining a characteristic physiological parameter

• US 9,198,582 B2
• Filed: 06/30/2009
• Issued: 12/01/2015
• Est. Priority Date: 06/30/2009
• Status: Active Grant

• Current Assignee: Nellcor Puritan Bennett Ireland
• Original Assignee: Nellcor Puritan Bennett Ireland
• Inventors: Watson, James N., Addison, Paul Stanley, Sethi, Rakesh
• Primary Examiner(s): Natnithithadha, Navin
• Assistant Examiner(s): WEARE, MEREDITH H
• Application Number:
  US12/495,529
• Publication Number:
  US 20100331724A1
• Time in Patent Office: 2,345 Days
• Field of Search: 600/481, 600485-503
• US Class Current: 1/1
• CPC Class Codes: A61B 5/021 Measuring pressure in heart or blood vessels A61B5/0205 takes precedence
• CPC Class Codes: A61B 5/0215 by means inserted into the body catheters A61M25/00
• CPC Class Codes: A61B 5/022 by applying pressure to close blood vessels, e.g. against the skin; Ophthalmodynamometers
• CPC Class Codes: A61B 5/02416 using photoplethysmograph signals, e.g. generated by infrared radiation A61B5/14552 takes precedence
• CPC Class Codes: A61B 5/0816 Measuring devices for examining respiratory frequency measuring frequency of electric signals G01R23/00
• CPC Class Codes: A61B 5/14551 for measuring blood gases
• CPC Class Codes: A61B 5/16 Devices for psychotechnics using teaching or educational appliances G09B1/00 - G09B7/00; Testing reaction times ; Devices for evaluating the psychological state
• CPC Class Codes: A61B 5/165 Evaluating the state of mind, e.g. depression, anxiety
• CPC Class Codes: A61B 5/6816 Ear lobe
• CPC Class Codes: A61B 5/6826 Finger
• CPC Class Codes: A61B 5/6829 Foot or ankle
• CPC Class Codes: A61B 5/6838 Clamps or clips
• CPC Class Codes: A61B 5/726 using Wavelet transforms

Abstract

The present disclosure relates to monitoring a characteristic physiological parameter of a patient during a suitable time period that either precedes or follows a triggering event, such as a clinician/patient interaction, that may negatively impact the physiological parameter. In some embodiments, physiological parameter values falling between one or more pre-set thresholds may be used to derive the characteristic physiological parameter. In some embodiments, tracking the physiological parameter may provide additional information about the patient'"'"'s status. In some embodiments, confidence measures may be associated with, or may be used to analyze features of the patient signal to derive information about, the characteristic physiological parameter. The patient signal used to derive a patient'"'"'s physiological parameter may be of an oscillatory nature or may include oscillatory features that may be analyzed to derive a characteristic blood pressure or a characteristic respiration rate.

Claims

1. A method for determining a characteristic value of a physiological parameter of a patient in a clinical setting, the method comprising:

monitoring, using a processor, values of the physiological parameter of the patient across a first time period and a second time period that is subsequent to the first time period based at least in part on a signal obtained from a patient sensor, wherein the first time period does not overlap with the second time period and wherein the first time period and the second time period are defined by the occurrence of a physiological event caused by the clinical setting;

identifying, using a processor, the physiological event based on the values of the physiological parameter in the first time period and based on the patient being in the clinical setting;

determining, using a processor, the characteristic value of the physiological parameter of the patient based on the values of the physiological parameter in the second time period wherein the characteristic value of the physiological parameter is determined to assess a clinical status of the patient, wherein the physiological parameter is a blood pressure, wherein the physiological event is a blood pressure event, and wherein the characteristic value of the physiological parameter is a characteristic value of blood pressure;

determining, using a processor, an initial value of the blood pressure based at least in part on a value of the blood pressure in the first time period; and

identifying, using a processor, an endpoint defined by a relaxation time following the blood pressure event, wherein the determining the characteristic value of the blood pressure is based at least in part on a value of the blood pressure after the endpoint and wherein the relaxation time is identified based at least in part on a slope of the values of the blood pressure across the second time period reaching a threshold value.

2. The method of claim 1 wherein the characteristic value of the blood pressure is continuously determined.

3. The method of claim 1, further comprising generating at least one confidence measure associated with the characteristic value of the blood pressure.

4. The method of claim 1, wherein a difference between the initial value of the blood pressure value and the characteristic value of the blood pressure is analyzed at least in part to indicate a stress of the patient.

5. The method of claim 4, wherein the difference between the initial value of the blood pressure value and the characteristic value of the blood pressure is normalized by one of a group consisting of the initial value of the blood pressure, the characteristic value of the blood pressure, and a weighted mean of the initial value of the blood pressure and the characteristic value of the blood pressure.

6. The method of claim 1, wherein the relaxation time is analyzed at least in part to indicate an ability of the patient to respond to stressful situations.

7. The method of claim 6, wherein the relaxation time is normalized by a mean value of an relaxation time of a representative patient population.

8. A system for determining a characteristic value of a physiological parameter of a patient in a clinical setting, the system comprising:

an input signal generator for generating a signal;

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

monitor values of the physiological parameter of the patient across a first time period and a second time period that is subsequent to the first time period based at least in part on the signal, wherein the first time period does not overlap with the second time period and wherein the first time period and the second time period are defined by the occurrence of a physiological event caused by the clinical setting;

identify the physiological event based on the values of the physiological parameter in the first time period and based on the patient being in the clinical setting;

determine the characteristic value of the physiological parameter of the patient based on the values of the physiological parameter in the second time period, wherein the characteristic value of the physiological parameter is determined to assess a clinical status of the patient, wherein the physiological parameter is a blood pressure, wherein the physiological event is a blood pressure event, and wherein the characteristic value of the physiological parameter is a characteristic value of blood pressure;

determine an initial value of the blood pressure based at least in part on a value of the blood pressure in the first time period; and

identify an endpoint defined by a relaxation time following the blood pressure event, wherein the processor is configured to determine the characteristic value of the blood pressure based at least in part on a value of the blood pressure after the endpoint and wherein the relaxation time is identified based at least in part on a slope of the values of the blood pressure across the second time period reaching a threshold value; and

an output coupled to the processor, wherein the output is configured to display the characteristic value of the blood pressure.

9. The system of claim 8 wherein the characteristic value of the blood pressure is continuously determined.

10. The system of claim 8, wherein the processor is further configured to generate at least one confidence measure associated with the characteristic value of the blood pressure.

11. The system of claim 8 wherein the processor is further configured to analyze at least in part the difference between the initial value of the blood pressure value and the characteristic value of the blood pressure to indicate a stress of the patient.

12. The system of claim 11 wherein the processor is further configured to normalize the difference between the initial value of the blood pressure value and the characteristic value of the blood pressure by one of a group consisting of the initial value of the blood pressure, the characteristic value of the blood pressure, and a weighted mean of the initial value of the blood pressure and the characteristic value of the blood pressure.

13. The system of claim 8, wherein the processor is further configured to analyze at least in part the relaxation time to indicate an ability of the patient to respond to stressful situations.

14. The system of claim 13, wherein the processor is further configured to normalize the relaxation time by a mean value of the relaxation time of a representative patient population.

15. A non-transitory computer-readable medium for use in determining a characteristic value of a physiological parameter of a patient in a clinical setting, the computer-readable medium having computer program instructions recorded thereon for:

monitoring values of the physiological parameter of the patient across a first time period and a second time period that is subsequent to the first time period, based at least in part on a signal obtained from a patient sensor, wherein the first time period does not overlap with the second time period and wherein the first time period and the second time period are defined by the occurrence of a physiological event caused by the clinical setting;

identifying the physiological event based on the values of the physiological parameter in the first time period and based on the patient being in the clinical setting;

determining the characteristic value of the physiological parameter of the patient based on the values of the physiological parameter in the second time period wherein the characteristic value of the physiological parameter is determined to assess a clinical status of the patient, wherein the physiological parameter is a blood pressure, wherein the physiological event is a blood pressure event, and wherein the characteristic value of the physiological parameter is a characteristic value of blood pressure;

determining an initial value of the blood pressure based at least in part on a value of the blood pressure in the first time period; and

identifying, using a processor, an endpoint defined by a relaxation time following the blood pressure event, wherein the determining the characteristic value of the blood pressure is based at least in part on a value of the blood pressure after the endpoint and wherein the relaxation time is identified based at least in part on a slope of the values of the blood pressure across the second time period reaching a threshold value.