Systems and methods for measuring respiration rate

Patent metadata

Field	Value
Publication number	US-2017150902-A1
Application number	US-201514954846-A
Country	US
Kind code	A1
Filing date	Nov 30, 2015
Priority date	Nov 30, 2015
Publication date	Jun 1, 2017
Grant date	—

Abstract

Systems and methods for generating a signal that indicates a respiration rate of a patient are provided. Differential sinusoidal current signals having a modulation frequency are generated. The differential current signals are passed between electrodes in contact with a patient's chest. A voltage signal is received based on the passing of the differential current signals between the electrodes. The voltage signal includes a sinusoidal voltage at the modulation frequency with an amplitude that varies based on the patient's respiration. An output signal including a low-frequency component and a high-frequency component is generated by multiplying the voltage signal by a sinusoidal signal. The sinusoidal signal has the modulation frequency. The output signal is filtered to remove the high-frequency component, and the filtered output signal includes a waveform with characteristics indicative of a respiration rate of the patient. Related apparatus, systems, techniques and articles are also described.

First claim

What is claimed is:

1 . A method for generating a signal that indicates a respiration rate of a patient, the method comprising:
generating differential current signals that each comprise a sinusoidal current having a modulation frequency; passing the differential current signals between electrodes in contact with a patient's chest; receiving a voltage signal based on the passing of the differential current signals between the electrodes, the voltage signal comprising a sinusoidal voltage at the modulation frequency with an amplitude that varies based on the patient's respiration; generating an output signal including a low-frequency component and a high-frequency component by multiplying the voltage signal by a sinusoidal signal having the modulation frequency and a constant amplitude; and filtering the output signal to remove the high-frequency component, the filtered output signal comprising a waveform with characteristics indicative of a respiration rate of the patient.

2 . The method of claim 1 , further comprising:
calculating the respiration rate of the patient based on the filtered output signal; and providing data characterizing the respiration rate.

3 . The method of claim 2 , wherein the providing of the data characterizing the respiration rate comprises:
storing the data; loading the data into a memory; displaying the data; or transmitting the data to a remote computing system.

4 . The method of claim 1 , wherein the differential current signals comprise a differential pair of signals 180 degrees out of phase with each other, and the voltage signal comprises a single-ended voltage signal, wherein generating the single-ended voltage signal comprises:
receiving first and second voltage signals based on the passing of the differential pair of signals between the electrodes, each of the first and second voltage signals corresponding to a respective signal of the differential pair, and the first and second voltage signals comprising sinusoidal voltages at the modulation frequency with amplitudes that vary based on the patient's respiration; and taking a difference between the first and second voltage signals to generate the single-ended voltage signal.

5 . The method of claim 1 , wherein the respiration rate of the patient, represented as a frequency, is one or more orders of magnitude lower than the modulation frequency.

6 . The method of claim 1 , wherein the sinusoidal signal is a voltage signal having the constant amplitude, and wherein the sinusoidal current signals have a second constant amplitude, the constant amplitude of the voltage signal being proportional to the second constant amplitude of the sinusoidal current signals.

7 . The method of claim 1 , further comprising:
performing additional filtering on the filtered output signal to remove a direct current (DC) bias from the filtered output signal.

8 . The method of claim 1 , wherein a frequency of the low-frequency component is one or more orders of magnitude lower than a frequency of the high-frequency component.

9 . A method for generating a signal that indicates a respiration rate of a patient, the method comprising:
receiving an amplitude-modulated (AM) signal with amplitude that varies based on a patient's respiration, the AM signal being based on a passing of a sinusoidal current signal between electrodes in contact with the patient's chest; and demodulating the AM signal using a multiplier, an output of the multiplier comprising a waveform with characteristics indicative of a respiration rate of the patient.

10 . The method of claim 9 , wherein the sinusoidal current signal and the AM signal have a same frequency, and wherein the demodulating of the AM signal comprises: multiplying, at the multiplier, the AM signal by a sinusoidal signal having the frequency and a constant amplitude.

11 . The method of claim 9 , further comprising:
calculating the respiration rate of the patient based on the output of the multiplier; and providing data characterizing the respiration rate.

12 . The method of claim 11 , wherein the providing of the data characterizing the respiration rate comprises:
storing the data in a memory; displaying the data; or transmitting the data to a remote computing system.

13 . A system for generating a signal that indicates a respiration rate of a patient, the system comprising:
a current source configured to generate differential current signals that each comprise a sinusoidal current having a modulation frequency, the differential current signals being passed between electrodes in contact with a patient's chest to generate a voltage signal, the voltage signal comprising a sinusoidal voltage at the modulation frequency with an amplitude that varies based on the patient's respiration; a signal source configured to generate a sinusoidal signal having the modulation frequency and a constant amplitude; a multiplier configured to generate an output signal including a low-frequency component and a high-frequency component by multiplying the voltage signal by the sinusoidal signal; and a filter configured to filter the output signal to remove the high-frequency component, the filtered output signal comprising a waveform with characteristics indicative of a respiration rate of the patient.

14 . The system of claim 13 , wherein the multiplier comprises a four-quadrant multiplier.

15 . The system of claim 13 , wherein the multiplier comprises a two-quadrant multiplier.

16 . The system of claim 13 , wherein the differential current signals comprise a differential pair of signals 180 degrees out of phase with each other, and the voltage signal comprises a single-ended voltage signal, the system further comprising:
a differential amplifier configured to receive first and second voltage signals based on the passing of the differential pair of signals between the electrodes, each of the first and second voltage signals corresponding to a respective signal of the differential pair, and the first and second voltage signals comprising sinusoidal voltages at the modulation frequency with amplitudes that vary based on the patient's respiration, wherein the differential amplifier generates the single-ended voltage signal by taking a difference between the first and second voltage signals.

17 . The system of claim 16 , wherein the differential amplifier comprises an instrumentation amplifier.

18 . The system of claim 13 , wherein the respiration rate of the patient, represented as a frequency, is one or more orders of magnitude lower than the modulation frequency.

19 . The system of claim 13 , wherein the sinusoidal signal is a voltage signal having the constant amplitude, and wherein the sinusoidal current signals have a second constant amplitude, the constant amplitude of the voltage signal being proportional to the second constant amplitude of the sinusoidal current signals.

20 . The system of claim 13 , further comprising:
a second filter configured to perform additional filtering on the filtered output signal to remove a direct current (DC) bias from the filtered output signal.

21 . The system of claim 13 , wherein a frequency of the low-frequency component is one or more orders of magnitude lower than a frequency of the high-frequency component.

22 . A patient monitoring device comprising:
a system for generating a signal that indicates a respiration rate of a patient, the system including:
a current source configured to g

Assignees

• Draeger Medical Systems Inc

Inventors

• Gay Thomas Edward

Classifications

• A61B5/113

  occurring during breathing · CPC title

• A61B5/0816 Primary

  Measuring devices for examining respiratory frequency (measuring frequency of electric signals G01R23/00) · CPC title

• A61B5/7225

  Details of analogue processing, e.g. isolation amplifier, gain or sensitivity adjustment, filtering, baseline or drift compensation (input circuits for detecting, measuring, or recording bioelectric or biomagnetic signals A61B5/30; specific diagnostic methods using bioelectric or biomagnetic signals A61B5/316) · CPC title

• A61B5/7203

  for noise prevention, reduction or removal · CPC title

• A61B5/085

  Measuring impedance of respiratory organs or lung elasticity · CPC title