BODY-WORN SYSTEM FOR MEASURING CONTINUOUS NON-INVASIVE BLOOD PRESSURE (cNIBP)

• US 20100160797A1
• Filed: 12/30/2009
• Published: 06/24/2010
• Est. Priority Date: 06/12/2007
• Status: Active Grant

• Current Assignee: Sotera Wireless Incorporated
• Original Assignee: Sotera Wireless Incorporated
• Inventors: BANET, Matt, DHILLON, Marshal, McCOMBIE, Devin
• Granted Patent: US 9,668,656 B2
• Time in Patent Office: Days
• US Class Current: 600/485
• CPC Class Codes: A61B 5/0022 Monitoring a patient using a global network, e.g. telephone networks, internet
• CPC Class Codes: A61B 5/02125 of pulse wave propagation time
• CPC Class Codes: A61B 5/02133 by using induced vibration of the blood vessel
• CPC Class Codes: A61B 5/0225 the pressure being controlled by electric signals, e.g. derived from Korotkoff sounds
• CPC Class Codes: A61B 5/02416 using photoplethysmograph signals, e.g. generated by infrared radiation A61B5/14552 takes precedence
• CPC Class Codes: A61B 5/0295 using plethysmography, i.e. measuring the variations in the volume of a body part as modified by the circulation of blood therethrough, e.g. impedance plethysmography
• CPC Class Codes: A61B 5/1118 Determining activity level
• 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 5/349 Detecting specific parameters of the electrocardiograph cycle
• CPC Class Codes: A61B 5/6824 Arm or wrist
• CPC Class Codes: A61B 5/721 using a separate sensor to detect motion or using motion information derived from signals other than the physiological signal to be measured
• CPC Class Codes: A61B 5/7239 using differentiation including higher order derivatives
• CPC Class Codes: A61B 5/742 using visual displays A61B5/339 takes precedence

Abstract

The present invention provides a technique for continuous measurement of blood pressure based on pulse transit time and which does not require any external calibration. This technique, referred to herein as the ‘Composite Method’, is carried out with a body-worn monitor that measures blood pressure and other vital signs, and wirelessly transmits them to a remote monitor. A network of body-worn sensors, typically placed on the patient'"'"'s right arm and chest, connect to the body-worn monitor and measure time-dependent ECG, PPG, accelerometer, and pressure waveforms. The disposable sensors can include a cuff that features an inflatable bladder coupled to a pressure sensor, three or more electrical sensors (e.g. electrodes), three or more accelerometers, a temperature sensor, and an optical sensor (e.g., a light source and photodiode) attached to the patient'"'"'s thumb.

Claims

1. A system for measuring a vital sign value from a patient, comprising:

(a) a first sensor configured to generate a first time-dependent signal indicative of one or more contractile properties of the patient'"'"'s heart;

(b) a second sensor configured to generate a second time-dependent signal indicative of one or more contractile properties of the patient'"'"'s heart, the second sensor comprising a radiation source configured to irradiate a portion of the patient, and a detector configured to detect radiation emitted from the radiation source after it passes through the portion of the patient, the detector comprising at least two pixel elements, each configured to generate a unique signal;

(c) a motion sensor configured to generate a motion signal indicative of movement of a region of the patient that the motion sensor is attached to; and

,

(d) a processing component configured to be worn on the patient'"'"'s body, the processing component programmed to;

(i) analyze a signal generated by a first pixel element;

(ii) analyze a signal generated by a second pixel element;

(iii) analyze the motion signal;

(iv) based on analysis of the motion signal, select a signal from at least one of the pixel elements characterized by a relatively low degree of motion corruption; and

(v) analyze the signal from (iv) to determine a vital sign value.

4. The system of claim 1, wherein the multi-pixel detector comprises at least a 3×

3 array of pixels.

5. The system of claim 4, wherein each pixel in the array of pixels comprises a photodetector.

6. The system of claim 5, wherein the second sensor is operably connected to a circuit configured to de-multiplex signals from the multi-pixel detector.

7. The system of claim 1, wherein the motion sensor is an accelerometer.

8. The system of claim 1, wherein the accelerometer is configured to generate a digital motion signal corresponding to each of the x, y, and z-axes.

9. The system of claim 1, wherein the processor is programmed to analyze the motion signal and a signal from each pixel element to determine the signal that has the lowest correlation to the motion signal, indicating that the signal is characterized by a relatively low degree of motion corruption.

10. The system of claim 1, wherein the processor is programmed to analyze the motion signal to determine a measurement period when patient movement is relatively low, and then measure a signal from each pixel element.

11. The system of claim 1, wherein the first sensor comprises an ECG circuit and at least two electrodes.

12. The system of claim 11, wherein the first time-dependent signal comprises an ECG signal.

13. The system of claim 12, wherein the signal selected from at least one of the pixel elements comprises a PPG signal.

14. The system of claim 13, wherein the processing component is programmed to determine an onset point in a portion comprised by the PPG signal.

15. The system of claim 14, wherein the processing component is programmed to determine a QRS complex comprised by the ECG signal.

16. The system of claim 15, wherein the processing component is programmed to determine a time difference between the QRS complex and the onset point.

17. The system of claim 16, wherein the processing component is programmed to calculate a blood pressure value from the time difference.

18. The system of claim 1, further comprising a transceiver configured to be worn on the patient'"'"'s arm that comprises the processing component.

19. The system of claim 18, wherein the transceiver comprises the motion sensor.

20. The system of claim 11, wherein the first sensor is configured to be worn on the patient'"'"'s chest.

21. The system of claim 1, wherein the second sensor is comprised by a flexible patch configured to be worn on the patient'"'"'s forehead.

2. A system for measuring a blood pressure value from a patient, comprising:

(a) a first sensor configured to generate a time-dependent electrical signal indicative of one or more contractile properties of the patient'"'"'s heart, the first sensor comprising an ECG circuit and at least two electrodes;

(b) a second sensor configured to generate a time-dependent optical signal indicative of one or more contractile properties of the patient'"'"'s heart, the second sensor comprising a radiation source configured to irradiate a portion of the patient, and a detector configured to detect radiation emitted from the radiation source after it passes through the portion of the patient, the detector comprising at least two pixel elements, each configured to generate a unique signal;

(c) a motion sensor configured to generate a motion signal indicative of movement of a region of the patient that the motion sensor is attached to; and

,

(d) a processing component configured to be worn on the patient'"'"'s body, the processing component programmed to;

(i) analyze a signal generated by a first pixel element;

(ii) analyze a signal generated by a second pixel element;

(iii) analyze the motion signal;

(iv) based on analysis of the motion signal, select a signal from at least one of the pixel elements characterized by a relatively low degree of motion corruption;

(v) analyze the signal from (iv) to determine a first feature;

(vi) analyze the time-dependent electrical signal to determine a second feature;

(vii) determine a time difference between the first and second features; and

(viii) determine a blood pressure value from the time difference.

3. A system for measuring a blood pressure value from a patient, comprising:

an ECG sensor configured to generate a time-dependent ECG signal;

an optical sensor featuring a radiation source and a multi-pixel radiation detector, with each pixel in the detector configured to detect radiation from the radiation source after it irradiates the patient to generate a unique signal;

a motion sensor attached to a region of the patient and configured to generate a motion signal indicative of movement of the region; and

a processing component programmed to analyze a signal from at least one pixel in the detector determined to have a relatively low degree of correlation with the motion signal to determine the blood pressure value.