BODY-WORN MONITOR FOR MEASURING RESPIRATORY RATE

• US 20110257554A1
• 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 8,747,330 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 with a first microprocessor located on the patient'"'"'s body to determine a motion parameter;

(d) analyzing the motion parameter with the first microprocessor, and in response transmitting the impedance pneumography signal and the motion signal to a second microprocessor positioned at a different location than the first microprocessor;

(e) using the second microprocessor, collectively processing both the motion signal and impedance pneumography signal to determine coefficients corresponding to a digital filter;

(f) transmitting the coefficients from the second microprocessor to the first microprocessor;

(g) using the first microprocessor, processing one of the motion signal and impedance pneumography signal with the coefficients to determine a digitally filtered waveform; and

(h) using the first microprocessor, analyzing the digitally filtered waveform to determine a respiratory rate.

5. The method of claim 1, wherein the first microprocessor is located on the patient'"'"'s wrist.

6. The method of claim 1, wherein step (d) further comprises serially transmitting the impedance pneumography signal and the motion signal from the first microprocessor to the second microprocessor.

7. The method of claim 6, wherein the second microprocessor is located on the patient'"'"'s torso.

8. The method of claim 1, wherein step (d) further comprises wirelessly transmitting the impedance pneumography signal and the motion signal from the first microprocessor to the second microprocessor.

9. The method of claim 8, wherein the second microprocessor is located on a remote server.

10. The method of claim 1, wherein step (e) further comprises analyzing the motion signal to determine a set of components corresponding to the patient'"'"'s motion, and then generating coefficients which are optimized to remove the components corresponding to the patient'"'"'s motion when implemented in a digital filter that processes the impedance pneumography signal.

11. The method of claim 1, further comprising storing the coefficients in a computer memory associated with the first microprocessor.

12. The method of claim 11, further comprising measuring a new impedance pneumography signal, and then processing the new impedance pneumography signal with the coefficients stored in the computer memory to determine a new digitally filtered waveform.

13. The method of claim 12, further comprising analyzing the new digitally filtered waveform with the first microprocessor to determine a respiratory rate.

19. The method of claim 1, wherein step (f) further comprises determining motion components from the frequency-based transform of the motion signal, removing the motion components, or components calculated therefrom, from the frequency-based transform of the impedance pneumography signal, and then analyzing the resultant signal to determine the patient'"'"'s respiratory rate.

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 with a first microprocessor located on the patient'"'"'s body to determine a motion parameter;

(d) analyzing the motion parameter with the first microprocessor, and in response transmitting the impedance pneumography signal and the motion signal to a second microprocessor positioned at a different location than the first microprocessor;

(e) using the second microprocessor, calculating a frequency-based transform of both the impedance pneumography signal and the motion signal;

(f) using the second microprocessor, collectively analyzing frequency-based transforms of both the impedance pneumography signal and the motion signal to determine a value for respiratory rate; and

(g) transmitting the value for respiratory rate from the second microprocessor to the first microprocessor.

14. The method of claim 2, wherein the first microprocessor is located on the patient'"'"'s wrist.

15. The method of claim 2, wherein step (d) further comprises serially transmitting the impedance pneumography signal and the motion signal from the first microprocessor to the second microprocessor.

16. The method of claim 15, wherein the second microprocessor is located on the patient'"'"'s torso.

17. The method of claim 2, wherein step (d) further comprises wirelessly transmitting the impedance pneumography signal and the motion signal from the first microprocessor to the second microprocessor.

18. The method of claim 17, wherein the second microprocessor is located on a remote server.

3. 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 with a first microprocessor located on the patient'"'"'s body to determine a motion parameter;

(d) based on the motion parameter, transmitting digital versions of the electrical signal and the motion signal to a second microprocessor;

(e) analyzing the digital versions of the electrical signal and the motion signal with the second microprocessor to determine a value for respiratory rate; and

(f) transmitting the value for respiratory rate from the second microprocessor to the first microprocessor.

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 with a first microprocessor located on the patient'"'"'s body to determine a motion parameter;

(d) based on the motion parameter, transmitting digital versions of the electrical signal and the motion signal to a second microprocessor;

(e) analyzing the digital versions of the electrical signal and the motion signal with the second microprocessor to determine coefficients used to calculate a value for respiratory rate;

(f) transmitting the coefficients used to calculate a value for respiratory rate from the second microprocessor to the first microprocessor; and

(g) processing the coefficients used to calculate a value for respiratory rate and the digital version of the electrical signal to determine the value for respiratory rate.