Determining a characteristic respiration rate

• US 9,220,440 B2
• Filed: 09/21/2009
• Issued: 12/29/2015
• Est. Priority Date: 09/21/2009
• Status: Active Grant

• Current Assignee: Nellcor Puritan Bennett Ireland
• Original Assignee: Nellcor Puritan Bennett Ireland
• Inventors: Addison, Paul Stanley, Watson, James Nicholas, McGonigle, Scott
• Primary Examiner(s): Kahelin, Michael
• Assistant Examiner(s): TRAN, THO Q
• Application Number:
  US12/563,836
• Publication Number:
  US 20110071406A1
• Time in Patent Office: 2,290 Days
• Field of Search: 600/483, 600/484, 600/300, 600/301, 600/529, 600/538, 607/6, 607/9, 607/20, 607/23, 607/25
• US Class Current: 1/1
• CPC Class Codes: A61B 5/0205 Simultaneously evaluating both cardiovascular conditions and different types of body conditions, e.g. heart and respiratory condition
• CPC Class Codes: A61B 5/0816 Measuring devices for examining respiratory frequency measuring frequency of electric signals G01R23/00
• CPC Class Codes: A61B 5/1455 using optical sensors, e.g. spectral photometrical oximeters
• CPC Class Codes: A61B 5/165 Evaluating the state of mind, e.g. depression, anxiety
• CPC Class Codes: A61B 5/7203 for noise prevention, reduction or removal
• CPC Class Codes: A61B 5/726 using Wavelet transforms
• 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 7/003 Detecting lung or respiration noise

Abstract

The present disclosure relates to monitoring a characteristic respiration rate of a patient based at least in part on a suitable time period that either precedes or follows a triggering event, such as a clinician/patient interaction, where the triggering event 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, monitoring the respiration rate 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 respiration rate. The patient signal used to derive a patient'"'"'s respiration rate may be of an oscillatory nature or may include oscillatory features that may be analyzed to derive a characteristic respiration rate.

Claims

1. A method for determining a characteristic respiration rate of a patient by a pulse oximeter, the method comprising:

receiving, using the pulse oximeter, a photoplethysmographic (PPG) signal derived from a pulse oximetry sensor, wherein the pulse oximetry sensor is configured to detect light attenuated by the patient;

determining, using the pulse oximeter, respiration rate values of the patient over time based at least in part on the PPG signal;

detecting, using the pulse oximeter, a first respiration rate event, wherein the first respiration rate event is detected based at least in part on a first deviation in the respiration rate values;

determining, using the pulse oximeter, a first altered portion of the respiration rate values based on the first respiration rate event;

determining, using the pulse oximeter, the characteristic respiration rate of the patient based at least in part on a selected portion of the respiration rate values, wherein;

the selected portion of the respiration rate values excludes the first altered portion of the respiration rate values;

the selected portion of the respiration rate values occurs earlier in time than the first altered portion of the respiration rate values;

the determining of the characteristic respiration rate is not based on the first altered portion of the respiration rate values; and

the characteristic respiration rate is determined to assess a clinical status of the patient; and

displaying, using an output of the pulse oximeter, the characteristic respiration rate.

2. The method of claim 1 further comprising:

determining, using the pulse oximeter, blood pressure values over time based at least in part on the PPG signal, wherein;

a first blood pressure value is determined based at least in part on a first blood pressure event; and

the first blood pressure event is detected based at least in part on a deviation in the blood pressure values;

identifying, using the pulse oximeter, a relaxation time based at least in part on the blood pressure values, wherein the relaxation time occurs later in time than the first blood pressure event; and

deriving, using the pulse oximeter, a characteristic blood pressure of the patient based at least in part on a blood pressure value at the relaxation time, wherein the characteristic blood pressure is continuously derived to assess the clinical status of the patient.

3. The method of claim 2, further comprising analyzing, using the pulse oximeter, at least one of the first blood pressure value, the characteristic blood pressure, and the relaxation time to assess the anxiety of the patient.

4. The method of claim 1, wherein the first respiration rate event is detected based at least in part on the first altered portion of the respiration rate values reaching a threshold value.

5. The method of claim 1 wherein the first respiration rate event is detected based at least in part on the slope of the respiration rate values reaching a threshold value.

6. The method of claim 1 wherein the characteristic respiration rate is determined based at least in part on an average value of the selected portion, an average value of the selected portion with at least one outlying value of the selected portion removed, a weighted average value of the selected portion, a median value of the selected portion, and/or the mode value of the selected portion, and/or combinations thereof.

7. The method of claim 1 further comprising:

detecting, using the pulse oximeter, a second respiration rate event, wherein;

the second respiration rate event is detected based at least in part on a second deviation in the respiration rate values; and

the second respiration rate event precedes in time the first respiration rate event;

determining, using the pulse oximeter, a second altered portion of the respiration rate values based on the second respiration rate event; and

determining, using the pulse oximeter, the characteristic respiration rate of the patient based at least in part on another selected portion of the respiration rate values that excludes the first altered portion and the second altered portion of the respiration rate values.

8. The method of claim 1, wherein determining the characteristic respiration rate further comprises analyzing the oscillation of a portion of the PPG signal from which the selected portion of the respiration rate values that excludes the first altered portion of the respiration rate values is determined.

9. The method of claim 1, further comprising:

transforming, using the pulse oximeter, a portion of the PPG signal from which the selected portion of the respiration rate values that excludes the first altered portion of the respiration rate values is determined into a transformed signal using a wavelet transform;

generating, using the pulse oximeter, a scalogram based at least in part on the transformed signal;

identifying, using the pulse oximeter, a band on the scalogram;

extracting ridge information from the band;

generating, using the pulse oximeter, at least one confidence measure based at least in part on the ridge information; and

determining, using the pulse oximeter, the characteristic respiration rate based at least in part on the scalogram and the at least one confidence measure.

10. The method of claim 9, further comprising:

selecting, using the pulse oximeter, a region of the scalogram;

summing, using the pulse oximeter, amplitudes for each scale in the region;

generating, using the pulse oximeter, the at least one confidence measure based at least in part on the ridge information and the summed amplitudes; and

determining, using the pulse oximeter, the characteristic respiration rate based at least in part on the scalogram and the at least one confidence measure.

11. A system for determining a characteristic respiration rate of a patient, the system comprising:

a pulse oximetry sensor configured to generate a photoplethysmographic (PPG) signal, wherein the pulse oximetry sensor is configured to detect light attenuated by the patient;

a pulse oximeter coupled to the pulse oximetry sensor, wherein the pulse oximeter is configured to;

determine respiration rate values of the patient over time based at least in part on the PPG signal;

detect a first respiration rate event, wherein the first respiration rate event is detected based at least in part on a first deviation in the respiration rate values;

determine a first altered portion of the respiration rate values based on the first respiration rate event; and

determine the characteristic respiration rate of the patient based at least in part on a selected portion of the respiration rate values, wherein;

the selected portion of the respiration rate values excludes the first altered portion of the respiration rate values;

the selected portion of the respiration rate values occurs earlier in time than the first altered portion of the respiration rate values; and

the characteristic respiration rate is not determined based on the first altered portion of the respiration rate values; and

an output coupled to the pulse oximeter, wherein the output is configured to display the characteristic respiration rate.

12. The system of claim 11 wherein:

the pulse oximeter is further configured to;

determine blood pressure values over time based at least in part on the PPG signal, wherein a first blood pressure value is determined based at least in part on a first blood pressure event and wherein the first blood pressure event is detected based at least in part on a deviation in the blood pressure values;

identify a relaxation time based at least in part on the blood pressure values, wherein the relaxation time occurs later in time than the first blood pressure event; and

derive a characteristic blood pressure of the patient based at least in part on a blood pressure value at the relaxation time, wherein the characteristic blood pressure is continuously derived to assess the clinical status of the patient; and

the output is further configured to display the characteristic blood pressure.

13. The system of claim 12, wherein the pulse oximeter is further configured to analyze at least one of the first blood pressure value, the characteristic blood pressure, and the relaxation time to assess the anxiety of the patient.

14. The system of claim 11 wherein the pulse oximeter is further configured to:

define the selected portion of the respiration rate values as the portion of the respiration rate values that excludes the first altered portion of the respiration rate values; and

determine the characteristic respiration rate based at least in part on the group consisting of an average value of the selected portion, an average value of the selected portion with at least one outlying value of the selected portion removed, a weighted average value of the selected portion, a median value of the selected portion, and/or the mode value of the selected portion, and/or combinations thereof.

15. The system of claim 11, wherein the pulse oximeter is further configured to:

detect a second respiration rate event, wherein;

the second respiration rate event is detected based at least in part on a second deviation in the respiration rate values; and

the second respiration rate event precedes in time the first respiration rate event;

determine a second altered portion of the respiration rate values based on the second respiration rate event; and

determine the characteristic respiration rate of the patient based at least in part on another selected portion of the respiration rate values that excludes the first altered portion and the second altered portion of the respiration rate values.

16. The system of claim 11, wherein the pulse oximeter is further configured to determine the characteristic respiration rate based at least in part on the oscillation of a portion of the PPG signal from which the selected portion of the respiration rate values that excludes the first altered portion of the respiration rate values is determined.

17. The system of claim 11, wherein the pulse oximeter is further configured to:

transform a portion of the PPG signal from which the selected portion of the respiration rate values that excludes the first altered portion of the respiration rate values is determined into a transformed signal using a wavelet transform;

generate a scalogram based at least in part on the transformed signal;

identify a band on the scalogram;

extract ridge information from the band;

generate at least one confidence measure based at least in part on the ridge information; and

determine the characteristic respiration rate based at least in part on the scalogram and the at least one confidence measure.

18. The system of claim 17, wherein the pulse oximeter is further configured to:

select a region of the scalogram;

sum amplitudes for each scale in the region;

generate the at least one confidence measure based at least in part on the ridge information and the summed amplitudes; and

determine the characteristic respiration rate based at least in part on the scalogram and the at least one confidence measure.

19. A non-transitory computer-readable medium for use in determining a characteristic respiration rate of a patient, the computer-readable medium comprising:

computer program instructions recorded thereon for causing a pulse oximeter to;

receive a photoplethysmographic (PPG) signal derived from a pulse oximetry sensor, wherein the pulse oximetry sensor is configured to detect light attenuated by the patient;

determine respiration rate values of the patient over time based at least in part on the PPG signal obtained from a patient sensor;

detect a first respiration rate event, wherein the first respiration rate event is detected based at least in part on a deviation in the respiration rate values;

detect a first altered portion of the respiration rate values based on the first respiration rate event;

determine the characteristic respiration rate of the patient based at least in part on a selected portion of the respiration rate values, wherein;

the selected portion of the respiration rate values excludes the first altered portion of the respiration rate values;

the selected portion of the respiration rate values occurs earlier in time than the first altered portion of the respiration rate values;

the determining of the characteristic respiration rate is not based on the first altered portion of the respiration rate values; and

the characteristic respiration rate is determined to assess a clinical status of the patient; and

configure an output to display the characteristic respiration rate.

20. The non-transitory computer-readable medium of claim 19, further comprising computer program instructions recorded thereon for causing the pulse oximeter to:

determine values over time based at least in part on the PPG signal obtained from the patient sensor, wherein;

a first blood pressure value is determined based at least in part on a first blood pressure event; and

the first blood pressure event is detected based at least in part on a deviation in the blood pressure values;

identify a relaxation time based at least in part on the blood pressure values, wherein the relaxation time occurs later in time than the first blood pressure event; and

derive a characteristic blood pressure of the patient based at least in part on a blood pressure value at a relaxation time, wherein the characteristic blood pressure is continuously derived to assess the clinical status of the patient.