CONTACTLESS RESPIRATION MONITORING OF A PATIENT

• US 20110112425A1
• Filed: 05/04/2009
• Published: 05/12/2011
• Est. Priority Date: 05/09/2008
• Status: Active Grant

• Current Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Original Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Inventors: Muhlsteff, Jens, Morren, Geert G.G., Pinter, Robert
• Granted Patent: US 8,870,785 B2
• Time in Patent Office: Days
• US Class Current: 600/534
• CPC Class Codes: A61B 5/05 Detecting, measuring or recording for diagnosis by means of electric currents or magnetic fields; Measuring using microwaves or radio waves impedance plethysmography A61B5/0295; measuring movement of the entire body or parts thereof A61B5/11; detecting, measuring or recording bioelectric or biomagnetic signals of the body or parts thereof A61B5/24
• CPC Class Codes: A61B 5/0507 using microwaves or terahertz waves
• 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 5/7239 using differentiation including higher order derivatives
• CPC Class Codes: G01S 13/583 using transmission of continuous unmodulated waves, amplitude-, frequency-, or phase-modulated waves and based upon the Doppler effect resulting from movement of targets
• CPC Class Codes: G01S 13/88 Radar or analogous systems specially adapted for specific applications electromagnetic prospecting or detecting of objects, e.g. near-field detection, G01V3/00
• CPC Class Codes: G01S 7/352 Receivers

Abstract

The invention relates to a method for detection of respiration of a patient comprising the following steps: emitting an electromagnetic signal towards the patient; receiving a reflected electromagnetic signal reflected from the patient; converting the reflected electromagnetic signal, yielding a first signal; phase-shifting the reflected electromagnetic signal and converting the phase-shifted reflected electromagnetic signal, yielding a second signal; determining a first vector being defined by the time derivatives of the first signal and the second signal, for a common first point in time; determining a second and vector being defined by the time derivatives of the first signal and the second signal, for a common second point in time; and calculating the scalar product of the normalized first vector and the normalized second vector as an indicator value for a change from expiration to inspiration of the patient or vice versa. A change from expiration to inspiration of the patient or vice versa is preferably indicated if the indicator value is below a threshold value, preferably below a value of 0. In this way, a possibility for contactless remote respiration monitoring of a patient based on the Doppler radar principle is provided which is reliable and easy to handle.

Claims

1. A method for detection of respiration of a patient comprising the following steps:

emitting an electromagnetic signal towards the patient;

receiving a reflected electromagnetic signal reflected from the patient;

converting the reflected electromagnetic signal, yielding a first signal;

phase-shifting the reflected electromagnetic signal and converting the phase-shifted reflected electromagnetic signal, yielding a second signal;

determining a first vector being defined by the time derivatives of the first signal and the second signal, for a common first point in time;

determining a second vector being defined by the time derivatives of the first signal and the second signal, for a common second point in time; and

calculating the scalar product of the normalized first vector and the normalized second vector as an indicator value for a change from expiration to inspiration of the patient or vice versa.

2. The method according to claim 1, wherein for determining the first point in time and the second point in time for building the first vector and the second vector, respectively, characteristic points in time defined by specific criteria fulfilled simultaneously in the first signal and the second signal are determined.

3. The method according to claim 2, wherein the specific criteria is a detected zero-crossing of the time derivative of the first signal or the second signal, respectively.

4. The method according to claim 1, wherein the indicator value is compared with a predefined threshold value.

5. The method according to claim 4, wherein the predefined threshold value is 0.

6. The method according to claim 4, wherein a change from expiration to inspiration of the patient or vice versa is indicated if the indicator value is below the threshold value.

7. The method according to claim 1, wherein the first vector, the second vector and the scalar product of the normalized first vector and the normalized second vector as an indicator value for a change from expiration to inspiration of the patient or vice versa are consecutively determined, preferably in predefined time periods.

8. The method according to claim 1, wherein the vorticity {right arrow over (V)} for two different points in time T₁ and T₂, respectively, are calculated by {right arrow over (V)}₁=−

{right arrow over (r)}₁×

({right arrow over (M)}₁(T₁)−

{right arrow over (r)}₁) and {right arrow over (V)}₂=−

{right arrow over (r)}₂×

({right arrow over (M)}₂(T₂)−

{right arrow over (r)}₂), wherein {right arrow over (r)}₁ is the first vector, {right arrow over (r)}₂ is the second vector, and {right arrow over (M)}₁ and {right arrow over (M)}₂ are vectors built from the time derivatives of the first signal and the second signal at times T₁ and T₂, respectively.

9. The method according to claim 1, wherein the respiration rate is indicated.

10. A device for contactless respiration monitoring of a patient, comprising

a two-channel Doppler radar sensor for receiving a reflected electromagnetic signal reflected from the patient, wherein

the two-channel Doppler radar sensor is adapted for converting the reflected electromagnetic signal, yielding a first signal and for phase-shifting the reflected electromagnetic signal and converting the phase-shifted reflected electromagnetic signal, yielding a second signal;

wherein

a calculating unit is provided which is adapted for determining a first vector being defined by the time derivatives of the first signal and the second signal, for a common first point in time, determining a second vector being defined by the time derivatives of the first signal and the second signal, for a common second point in time, and calculating the scalar product of the normalized first vector and the normalized second vector as an indicator value for a change from expiration to inspiration of the patient or vice versa.

11. The device according to claim 10, wherein the calculating unit is adapted for comparing the indicator value with a predefined threshold value and for indicating a change from expiration to inspiration of the patient or vice versa is indicated if the indicator value is below the threshold value.

12. The device according to claim 10, wherein a display for displaying the respiration rate based on indicated changes from expiration to inspiration of the patient or vice versa is provided.