BODY-WORN MONITOR FOR MEASURING RESPIRATION RATE

• US 20110066038A1
• Filed: 09/14/2009
• Published: 03/17/2011
• Est. Priority Date: 09/14/2009
• Status: Active Grant

• Current Assignee: Sotera Wireless Incorporated
• Original Assignee: Sotera Wireless Incorporated
• Inventors: BANET, Matt, DHILLON, Marshal, McCOMBIE, Devin
• Granted Patent: US 8,545,417 B2
• Time in Patent Office: Days
• US Class Current: 600/484
• 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 system for monitoring a patient'"'"'s respiratory rate, comprising:

a first sensor selected from the group consisting of;

i) an impedance pneumography sensor comprising at least two electrodes and an impedance pneumography processing circuit configured to process signals from the two electrodes to measure an impedance pneumography signal from the patient;

ii) an ECG sensor comprising at least two electrodes and an ECG processing circuit configured to process signals from the two electrodes to measure an ECG signal from the patient; and

iii) a PPG sensor comprising a light source, photodetector, and PPG processing circuit configured to process signals from the photodetector to measure a PPG signal from the patient;

a second sensor comprising a motion sensor configured to attach to the patient'"'"'s torso and measure a motion signal from the patient;

a processing system configured to be worn on the patient'"'"'s body and connect to the first sensor to receive a first signal representing at least one of the impedance pneumography, ECG, and PPG signals, and connect to the second sensor to receive a second signal representing the motion signal, the processing system configured to collectively process both the first and second signals to determine the patient'"'"'s respiration rate.

4. The system of claim 1, wherein the first sensor is an impedance pneumography sensor.

5. The system of claim 4, wherein the impedance pneumography signal comprises a first series of pulses, with each pulse in the first series representing a respiratory event.

6. The system of claim 5, wherein the motion signal comprises a second series of pulses, with each pulse in the second series representing a respiratory event.

7. The system of claim 6, wherein the processing system further comprises an algorithm configured to count each pulse in the first and second series of pulses to determine the patient'"'"'s respiratory rate.

8. The system of claim 7, wherein the algorithm is further configured to count each pulse in the first series of pulses to determine an initial value for respiratory rate, and then process the motion signal based on the initial value for respiratory rate to determine a final value for respiratory rate.

9. The system of claim 8, wherein the algorithm is further configured to digitally filter the motion signal based filter parameters determined from the initial value for respiratory rate.

10. The system of claim 7, wherein the algorithm is further configured to count each pulse in the second series of pulses to determine an initial value for respiratory rate, and then process the impedance pneumography signal based on the initial value for respiratory rate to determine a final value for respiratory rate.

11. The system of claim 10, wherein the algorithm is further configured to digitally filter the impedance pneumography signal based on the initial value for respiratory rate.

12. The system of claim 7, wherein the algorithm is further configured to calculate a mathematical average from the first and second series of pulses to determine the patient'"'"'s respiratory rate.

13. The system of claim 1, wherein the motion sensor is an accelerometer.

14. The system of claim 1, wherein the first sensor is an ECG sensor.

15. The system of claim 14, wherein the ECG signal comprises a first series of pulses with amplitudes characterized by a time-varying envelope, with a frequency of the envelope representing a respiratory rate.

16. The system of claim 15, wherein the motion signal comprises a second series of pulses, with each pulse in the second series representing a respiratory event.

17. The system of claim 16, wherein the processing system further comprises an algorithm configured to determine the respiratory rate by processing the frequency of the envelope and each pulse in the second series of pulses.

18. The system of claim 1, wherein the first sensor is a PPG sensor.

19. The system of claim 18, wherein the PPG signal comprises a first series of pulses with amplitudes characterized by a time-varying envelope, with a frequency of the envelope representing a respiratory rate.

20. The system of claim 19, wherein the motion signal comprises a second series of pulses, with each pulse in the second series representing a respiratory event.

21. The system of claim 20, wherein the processing system further comprises an algorithm configured to determine the respiratory rate by processing the frequency of the envelope and each pulse in the second series of pulses.

2. A system for determining respiration rate values for a patient, comprising:

a first sensor, configured to worn on the patient'"'"'s torso, comprising an impedance pneumography sensor;

a second sensor, configured to be worn on the patient'"'"'s torso, comprising an accelerometer;

a processing system, configured to be worn on the patient'"'"'s body and operably connect to the first and second sensors, the processing system configured to determine a respiration rate value by collectively processing signals from the first and second sensors.

3. A system for determining respiration rate values for a patient, comprising:

a first sensor, configured to worn on the patient'"'"'s torso, comprising at least one accelerometer for measuring a first signal representing movement of the patient'"'"'s torso due to respiratory events, and a second signal representing one of the patient'"'"'s posture and activity level;

a processing system, configured to be worn on the patient'"'"'s body and operably connect to the first sensor, the processing system configured to process the first signal to determine a value for the patient'"'"'s respiratory rate, and the second signal to determine one of the patient'"'"'s posture and activity level, with the value for respiration rate reported by the system modified by one of the posture and activity level determined from the second signal.