BODY-WORN MONITOR FOR MEASURING RESPIRATORY RATE

• US 20110257553A1
• Filed: 04/19/2010
• Published: 10/20/2011
• Est. Priority Date: 04/19/2010
• Status: Active Grant

• Current Assignee: Sotera Wireless Incorporated
• Original Assignee: Sotera Wireless Incorporated
• Inventors: BANET, Matt, DHILLON, Marshal, McCOMBIE, Devin
• Granted Patent: US 9,173,593 B2
• Time in Patent Office: Days
• US Class Current: 600/536
• CPC Class Codes: A61B 2562/0219 Inertial sensors, e.g. accelerometers, gyroscopes, tilt switches
• 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 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 at least one motion signal with a motion sensor connected to the patient, the at least one motion signal corresponding to motion of a portion of the patient'"'"'s body to which the motion sensor is attached;

(c) analyzing the motion signal to determine a motion parameter; and

(d) based on the motion parameter, selecting one of the following algorithms to process at least one of the motion and impedance pneumography signals to determine the patient'"'"'s respiratory rate;

i) a first algorithm comprising a step for counting breathing-induced pulses in the impedance pneumography signal to determine respiratory rate; and

ii) a second algorithm comprising collectively processing both the motion signal and impedance pneumography signal to determine a digital filter, and then processing one of the motion signal and impedance pneumography signal with the digital filter to determine respiratory rate.

5. The method of claim 1, wherein the motion parameter is a degree of the patient'"'"'s motion.

6. The method of claim 5, wherein step (c) further comprises selecting the first algorithm if the degree of the patient'"'"'s motion is below a pre-determined threshold value.

7. The method of claim 5, wherein step (c) further comprises selecting the second algorithm if the degree of the patient'"'"'s motion is above a pre-determined threshold value.

8. The method of claim 1, wherein the motion parameter is an activity level.

9. The method of claim 8, wherein step (c) further comprises selecting the first algorithm if the activity level is resting.

10. The method of claim 8, wherein step (c) further comprises selecting the second algorithm if the activity level is one of walking, moving, or running.

11. The method of claim 1, wherein the motion parameter is a posture.

12. The method of claim 11, wherein step (c) further comprises selecting the first algorithm if the posture is laying down.

13. The method of claim 11, wherein step (c) further comprises selecting the second algorithm if the posture is one of standing up.

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 at least one motion signal with a motion sensor connected to the patient, the at least one motion signal corresponding to motion of a portion of the patient'"'"'s body to which the motion sensor is attached;

(c) analyzing the motion signal to determine a motion parameter; and

(d) based on the motion parameter, selecting one of the following algorithms to process at least one of the motion and impedance pneumography signals to determine the patient'"'"'s respiratory rate;

i) a first algorithm comprising a step for counting breathing-induced pulses in the impedance pneumography signal to determine respiratory rate; and

ii) a second algorithm comprising transforming both the motion signal and impedance pneumography signal into frequency-domain signals, and then collectively processing the frequency-domain signals to determine respiratory rate.

14. The method of claim 2, wherein the motion parameter is a degree of the patient'"'"'s motion.

15. The method of claim 14, wherein step (c) further comprises selecting the first algorithm if the degree of the patient'"'"'s motion is below a pre-determined threshold value.

16. The method of claim 14, wherein step (c) further comprises selecting the second algorithm if the degree of the patient'"'"'s motion is above a pre-determined threshold value.

17. The method of claim 2, wherein the motion parameter is an activity level.

18. The method of claim 17, wherein step (c) further comprises selecting the first algorithm if the activity level is resting.

19. The method of claim 17, wherein step (c) further comprises selecting the second algorithm if the activity level is one of walking, moving, or running.

20. The method of claim 2, wherein the motion parameter is a posture.

21. The method of claim 20, wherein step (c) further comprises selecting the first algorithm if the posture is laying down.

22. The method of claim 21, wherein step (c) further comprises selecting the second algorithm if the posture is one of standing up.

3. 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 at least one motion signal with a motion sensor connected to the patient, the at least one motion signal corresponding to motion of a portion of the patient'"'"'s body to which the motion sensor is attached;

(c) analyzing the motion signal to determine a motion parameter; and

(d) based on the motion parameter, selecting one of the following algorithms to process both the motion and impedance pneumography signals to determine the patient'"'"'s respiratory rate;

i) a first algorithm comprising collectively processing both the motion signal and impedance pneumography signal to determine a digital filter, and then processing one of the motion signal and impedance pneumography signal with the digital filter to determine respiratory rate; and

ii) a second algorithm comprising transforming both the motion signal and impedance pneumography signal into frequency-domain signals, and then collectively processing the frequency-domain signals to determine respiratory rate.

4. A method for determining a respiratory rate value from a patient, comprising the following steps:

(a) measuring at least one electrical signal affected by at least one of respiratory rate and motion with a first sensor;

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

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

(d) based on the motion parameter, selecting at least one of the following algorithms to determine the respiratory rate value;

i) a first algorithm that counts breathing-induced pulses in the electrical signal;

ii) a second algorithm that processes the electrical signal with an adaptive filter generated by collectively processing the electrical signal and the motion signal; and

iii) a third algorithm that collectively processes frequency-dependent spectra of both the motion and electrical signals.