BODY-WORN MONITOR FOR MEASURING RESPIRATION RATE

• US 20110066008A1
• Filed: 09/14/2009
• Published: 03/17/2011
• Est. Priority Date: 09/14/2009
• Status: Abandoned Application

• Current Assignee: Sotera Wireless Incorporated
• Original Assignee: Sotera Wireless Incorporated
• Inventors: Dhillon, Marshal, McCombie, Devin, Banet, Matt
• Application Number:
  US12/559,430
• Publication Number:
  US 20110066008A1
• Time in Patent Office: Days
• US Class Current: 600/301
• CPC Class Codes: A61B 2562/0219 Inertial sensors, e.g. accelerometers, gyroscopes, tilt switches
• CPC Class Codes: A61B 5/0002 Remote monitoring of patients using telemetry, e.g. transmission of vital signals via a communication network A61B5/07 takes precedence; transmission systems for measured values G08C; transmission H04B; transmission of digital information H04L; wireless communication networks H04W
• 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 5/02416 using photoplethysmograph signals, e.g. generated by infrared radiation A61B5/14552 takes precedence
• CPC Class Codes: A61B 5/0535 Impedance plethysmography for measuring blood flow A61B5/0295
• CPC Class Codes: A61B 5/0809 by impedance pneumography
• CPC Class Codes: A61B 5/0816 Measuring devices for examining respiratory frequency measuring frequency of electric signals G01R23/00
• CPC Class Codes: A61B 5/1116 Determining posture transitions
• CPC Class Codes: A61B 5/1118 Determining activity level
• CPC Class Codes: A61B 5/113 occurring during breathing
• CPC Class Codes: A61B 5/318 Heart-related electrical modalities, e.g. electrocardiography [ECG]
• CPC Class Codes: A61B 5/681 Wristwatch-type devices
• CPC Class Codes: A61B 5/6823 Trunk, e.g., chest, back, abdomen, hip
• CPC Class Codes: A61B 5/6824 Arm or wrist
• CPC Class Codes: A61B 5/6826 Finger
• CPC Class Codes: A61B 5/721 using a separate sensor to detect motion or using motion information derived from signals other than the physiological signal to be measured
• CPC Class Codes: A61B 5/7239 using differentiation including higher order derivatives
• CPC Class Codes: A61B 5/746 Alarms related to a physiological condition, e.g. details of setting alarm thresholds or avoiding false alarms alarms per se G08B

Abstract

The invention provides a multi-sensor system that uses an algorithm based on adaptive filtering to monitor a patient'"'"'s respiratory rate. The system features a first sensor selected from the following group: i) an impedance pneumography sensor featuring at least two electrodes and a processing circuit configured to measure an impedance pneumography signal; ii) an ECG sensor featuring at least two electrodes and an ECG processing circuit configured to measure an ECG signal; and iii) a PPG sensor featuring a light source, photodetector, and PPG processing circuit configured to measure a PPG signal. Each of these sensors measures a time-dependent signal which is sensitive to respiratory rate and, during operation, is processed to determine an initial respiratory rate value. An adaptive digital filter is determined from the initial respiratory rate. The system features a second sensor (e.g. a digital 3-axis accelerometer) that attaches to the patient'"'"'s torso and measures an ACC signal indicating movement of the chest or abdomen that is also sensitive to respiratory rate. This second signal is processed with the adaptive filter to determine a final value for respiratory rate.

Claims

1. A method for monitoring a patient, comprising:

(a) measuring a first time-dependent signal by detecting a modulated electrical current passing through the patient'"'"'s torso;

(b) measuring a second time-dependent signal by detecting respiration-induced movements in the patient'"'"'s torso with at least one motion sensor;

(c) measuring a time-dependent motion signal with at least one motion sensor;

(d) processing the time-dependent motion signal to determine at least one of the patient'"'"'s posture and activity state;

(e) processing both the first and second time-dependent signals to determine a respiration rate value for the patient; and

,

(f) suppressing an alarm based on the respiration rate value due to at least one of the patient'"'"'s posture and activity state.

3. The method of claim 1, wherein step (e) further comprises processing one of the patient'"'"'s posture, activity state, and degree of motion in combination with a parameter resulting from the comparison of the respiration rate value to the predetermined alarm criteria to suppress the alarm.

4. The method of claim 3, wherein step (e) further comprises suppressing the alarm if the patient'"'"'s posture is standing up.

5. The method of claim 3, wherein step (e) further comprises suppressing the alarm if the patient'"'"'s posture changes from lying down to one of sitting and standing up.

6. The method of claim 3, wherein step (e) further comprises suppressing the alarm if the patient'"'"'s posture changes from one of standing upright and sitting to lying down.

7. The method of claim 1, wherein step (d) further comprises analyzing three time-dependent motion signals, each corresponding to a unique axis, to determine at least one of the patient'"'"'s posture and activity state.

8. The method of claim 7, wherein step (d) further comprises determining a vector from components of the three time-dependent motion signals.

9. The method of claim 7, wherein step (d) further comprises comparing the vector to a coordinate space defined by three positional vectors, each indicating an orientation of the motion-detecting sensor on the patient.

10. The method of claim 9, wherein a first positional vector corresponds to a vertical axis in the coordinate space, a second positional vector corresponds to a horizontal axis in the coordinate space, and the third positional vector corresponds to a normal axis extending normal to the patient'"'"'s chest.

11. The method of claim 10, wherein step (d) further comprises determining an angle associated with the vector.

12. The method of claim 11, wherein step (d) further comprises comparing the vector to the coordinate space to determine the angle between the vector and at least one of the three positional vectors.

13. The method of claim 11, wherein step (d) further comprises comparing the vector to the coordinate space to determine the angle between the vector and a vector corresponding to a vertical axis, or a property of the angle between the vector and the vector corresponding to the vertical axis.

14. The method of claim 13, wherein step (d) further comprises comparing the angle to a threshold value that is substantially equivalent to 45 degrees, and wherein the patient'"'"'s posture is estimated to be upright if the angle is less than the threshold value.

15. The method of claim 13, wherein step (d) further comprises comparing the angle to a threshold value that is substantially equivalent to 45 degrees, and wherein the patient'"'"'s posture is estimated to be lying down if the angle is greater than the threshold value.

16. The method of claim 15, wherein step (d) further comprises comparing the vector to the coordinate space to determine the angle between the vector and a vector corresponding to a normal axis extending normal to the patient'"'"'s chest, or a property of the angle between the vector and the vector corresponding to a normal axis extending normal to the patient'"'"'s chest.

17. The method of claim 16, wherein step (d) further comprises comparing the angle to a threshold value that is substantially equivalent to 35 degrees, and wherein the patient'"'"'s posture is estimated to be supine if the angle is less than the threshold value.

18. The method of claim 16, wherein step (d) further comprises comparing the angle to a threshold value that is substantially equivalent to 135 degrees, and wherein the patient'"'"'s posture is estimated to be prone if the angle is greater than the threshold value.

19. The method of claim 15, wherein step (d) further comprises comparing the vector to the coordinate space to determine the angle between the vector and a vector corresponding to a horizontal axis, or a property of the angle between the vector and the vector corresponding to the horizontal axis.

20. The method of claim 19, wherein step (h) further comprises comparing the angle to a threshold value that is substantially equivalent to 90 degrees, and wherein the patient'"'"'s posture is estimated to be lying on a first side if the angle is less than the threshold value.

21. The method of claim 19, wherein step (h) further comprises comparing the angle to a threshold value that is substantially equivalent to 90 degrees, and wherein the patient'"'"'s posture is estimated to be lying on a side opposite the first side if the angle is greater than the threshold value.

22. The method of claim 1, wherein step (c) further comprises detecting a set of time-dependent motion signals with at least one motion-detecting sensor positioned on the patient'"'"'s chest.

23. The method of claim 1, where the at least one motion-detecting sensor is an accelerometer.

2. A method for determining a respiration rate value for a patient, comprising:

(a) measuring at least one electrical signal affected by respiration rate with a first sensor;

(b) measuring a first motion signal affected by respiration rate with a second sensor;

(c) measuring a second motion signal affected by the patient'"'"'s posture with a motion sensor;

(d) collectively processing the electrical signal and first motion signal to determine a respiration rate value for the patient;

(e) processing the motion signal to determine at least of one of the patient'"'"'s posture, activity state, and degree of motion; and

(f) suppressing an alarm based on the respiration rate value due to at least one of the patient'"'"'s posture, activity state, and degree of motion.