Determining A Characteristic Respiration Rate

• US 20110071406A1
• Filed: 09/21/2009
• Published: 03/24/2011
• Est. Priority Date: 09/21/2009
• Status: Active Grant

• Current Assignee: Nellcor Puritan Bennett Ireland
• Original Assignee: Nellcor Puritan Bennett Ireland
• Inventors: McGonigle, Scott, Addison, Paul Stanley, Watson, James Nicholas
• Granted Patent: US 9,220,440 B2
• Time in Patent Office: Days
• US Class Current: 600/484
• 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, the method comprising:

determining a respiration rate of the patient based at least in part on a signal obtained from a patient sensor;

detecting a first respiration rate event, wherein the first respiration rate event is detected based at least in part on a first altered portion of the respiration rate; and

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

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

the selected portion of the respiration rate occurs before the first altered portion of the respiration rate; and

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

2. The method of claim 1 further comprising:

determining a blood pressure based at least in part on the 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 an altered portion of the blood pressure;

identifying a relaxation time based at least in part on the blood pressure, wherein the relaxation time occurs after the first blood pressure event; and

deriving a characteristic blood pressure of the patient based at least in part on the blood pressure 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, wherein the first blood pressure value, the characteristic blood pressure, and the relaxation time are analyzed at least in part 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 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 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 a second respiration rate event that alters the respiration rate of the patient, wherein;

the second respiration rate event is detected based at least in part on a second altered portion of the respiration rate; and

the second respiration rate event precedes the first respiration rate event; and

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

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

9. The method of claim 1, further comprising:

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

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

identifying a band on the scalogram;

extracting ridge information from the band;

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

determining 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 a region of the scalogram;

summing amplitudes for each scale in the region; and

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

determining 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:

an input signal generator for generating a signal;

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

determine a respiration rate of the patient based at least in part on the signal;

detect a first respiration rate event, wherein the first respiration rate event is detected based at least in part on a first altered portion of the respiration rate; and

determine the characteristic respiration rate of the patient based at least in part on a selected portion of the respiration rate that excludes the first altered portion of the respiration rate, wherein;

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

the selected portion of the respiration rate occurs before the first altered portion of the respiration rate; and

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

12. The system of claim 11 wherein:

the processor is further configured to;

derive a blood pressure based at least in part on the 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 an altered portion of the blood pressure;

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

derive a characteristic blood pressure of the patient based at least in part on the blood pressure 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 processor is further configured to analyze at least in part the first blood pressure value, the characteristic blood pressure, and/or the relaxation time to assess the anxiety of the patient.

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

define the selected portion of the respiration rate as the portion of the respiration rate that excludes the first altered portion of the respiration rate; 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 processor is further configured to:

detect a second respiration rate event that alters the respiration rate of the patient, wherein;

the second respiration rate event is detected based at least in part on a second altered portion of the respiration rate; and

the second respiration rate event precedes the first respiration rate event; and

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

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

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

transform a portion of the signal from which the selected portion of the respiration rate that excludes the first altered portion of the respiration rate 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 processor is further configured to:

select a region of the scalogram;

sum amplitudes for each scale in the region; and

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 computer-readable medium for use in determining a characteristic respiration rate of a patient, the computer-readable medium having computer program instructions recorded thereon for:

determining a respiration rate of the patient based at least in part on a signal obtained from a patient sensor;

detecting a first respiration rate event, wherein the first respiration rate event is detected based at least in part on a first altered portion of the respiration rate; and

determining the characteristic respiration rate of the patient based at least in part on a selected portion of the respiration rate that excludes the first altered portion of the respiration rate, wherein;

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

the selected portion of the respiration rate occurs before the first altered portion of the respiration rate; and

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

20. The computer-readable medium of claim 19, having further computer program instructions recorded thereon for:

deriving a blood pressure based at least in part on the 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 an altered portion of the blood pressure;

identifying a relaxation time based at least in part on the blood pressure, wherein the relaxation time occurs after the first blood pressure event; and

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