BODY-WORN MONITOR FOR MEASURING RESPIRATORY RATE

• US 20110257552A1
• Filed: 04/19/2010
• Published: 10/20/2011
• Est. Priority Date: 04/19/2010
• Status: Active Grant

• Current Assignee: Sotera Wireless Incorporated (Foxconn Technology Co., Ltd.)
• Original Assignee: Sotera Wireless Incorporated (Foxconn Technology Co., Ltd.)
• Inventors: BANET, Matt, DHILLON, Marshal, McCOMBIE, Devin
• Granted Patent: US 9,339,209 B2
• Time in Patent Office: Days
• US Class Current: 600/534
• 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 5/0008 Temperature signals
• 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 5/0809 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 5/113 occurring during breathing
• CPC Class Codes: A61B 5/14551 for measuring blood gases
• CPC Class Codes: A61B 5/318 Heart-related electrical modalities, e.g. electrocardiography [ECG]
• CPC Class Codes: A61B 5/7239 using differentiation including higher order derivatives
• CPC Class Codes: A61B 5/7257 using Fourier transforms

Abstract

The invention provides a system for measuring respiratory rate (RR) from a patient. The system includes an impedance pneumography (IP) sensor, connected to at least two electrodes, and a processing system that receives and processes signals from the electrodes to measure an IP signal. A motion sensor (e.g. an accelerometer) measures at least one motion signal (e.g. an ACC waveform) describing movement of a portion of the patient'"'"'s body to which it is attached. The processing system receives the IP and motion signals, and processes them to determine, respectfully, frequency-domain IP and motion spectra. Both spectra are then collectively processed to remove motion components from the IP spectrum and determine RR. For example, during the processing, an algorithm determines motion frequency components from the frequency-domain motion spectrum, and then using a digital filter removes these, or parameters calculated therefrom, from the IP spectrum.

Claims

1. A method for measuring respiratory rate from a patient, comprising the following steps:

(a) measuring a first impedance pneumography signal from the patient with an impedance pneumography sensor connected to at least two electrodes, the first impedance pneumography signal representing a time-dependent capacitance change in the patient'"'"'s torso;

(b) measuring a first motion signal with a motion sensor connected to the patient, the first motion signal corresponding to motion of a portion of the patient'"'"'s body to which the motion sensor is attached;

(c) collectively processing the first motion signal and the first impedance pneumography signal to determine a set of coefficients associated with a digital adaptive filter;

(d) storing the set of coefficients in a computer memory;

(e) measuring a second impedance pneumography signal from the patient with the impedance pneumography sensor;

(f) measuring a second motion signal with the motion sensor;

(g) analyzing the second motion signal to determine a motion parameter;

(h) when the motion parameter exceeds a pre-determined threshold, processing the set of coefficients and the second impedance pneumography signal to determine a processed impedance pneumography signal; and

,

(i) analyzing the processed impedance pneumography signal to determine the respiratory rate.

4. The method of claim 1, wherein the digital adaptive filter is calculated from an impulse response function.

5. The method of claim 4, wherein the impulse response function is calculated from one of a finite impulse response function and an autoregressive moving average model.

6. The method of claim 5, wherein an order of the digital adaptive filter calculated from the impulse response function is between 20 and 30.

7. The method of claim 5, wherein an order of the digital adaptive filter calculated from the autoregressive moving average model is between 1 and 5.

8. The method of claim 1, wherein step (c) further comprises formulating the set of coefficients as a column vector.

9. The method of claim 8, wherein step (h) further comprises processing the column vector or a mathematical derivative thereof with the second impedance pneumography signal to determine a processed impedance pneumography signal.

10. The method of claim 9, wherein step (i) further comprises taking a mathematical derivative of the processed impedance pneumography signal.

11. The method of claim 9, where step (i) further comprises counting pulses in the processed impedance pneumography signal or a mathematical derivative thereof.

2. A method for measuring respiratory rate from a patient, comprising the following steps:

(a) measuring an impedance pneumography signal from the patient with an impedance pneumography sensor connected to at least two electrodes, the impedance pneumography signal representing a time-dependent capacitance change in the patient'"'"'s torso;

(b) measuring a motion signal with a motion sensor connected to the patient, the motion signal corresponding to motion of a portion of the patient'"'"'s body to which the motion sensor is attached;

(c) collectively processing the motion signal and the impedance pneumography signal to determine a set of coefficients associated with a digital adaptive filter;

(d) analyzing the motion signal to determine a motion parameter;

(e) when the motion parameter exceeds a pre-determined threshold, processing the set of coefficients and the impedance pneumography signal to determine a processed impedance pneumography signal; and

,

(f) analyzing the processed impedance pneumography signal to determine the respiratory rate.

12. The method of claim 2, wherein the digital adaptive filter is calculated from an impulse response function.

13. The method of claim 12, wherein the impulse response function is calculated from one of a finite impulse response function and an autoregressive moving average model.

14. The method of claim 13, wherein an order of the digital adaptive filter calculated from the impulse response function is between 20 and 30.

15. The method of claim 13, wherein an order of the digital adaptive filter calculated from the autoregressive moving average model is between 1 and 5.

16. The method of claim 2, wherein step (c) further comprises formulating the set of coefficients as a column vector.

17. The method of claim 16, wherein step (e) further comprises processing the column vector or a mathematical derivative thereof with the impedance pneumography signal to determine a processed impedance pneumography signal.

18. The method of claim 17, wherein step (f) further comprises taking a mathematical derivative of the processed impedance pneumography signal.

19. The method of claim 17, where step (f) further comprises counting pulses in the processed impedance pneumography signal or a mathematical derivative thereof.

3. A system for determining respiratory 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 respiratory rate value by processing a signal from the second sensor with an adaptive digital filter determined from a signal from the first and second sensors.