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

• US 20100160795A1
• 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 9,215,986 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 monitoring a blood pressure value from a patient, comprising:

(a) a sensor comprising;

a first radiation source configured to emit optical radiation at a first wavelength;

a second radiation source configured to emit optical radiation at a second wavelength;

a photodetector configured to detect radiation emitted by the first radiation source after it passes through a portion of the patient to generate a first signal, and radiation emitted by the second radiation source after it passes through a portion of the patient to generate a second signal; and

a housing comprising the first and second radiation sources and the photodetector; and

,

(b) a processing component configured to be worn on the patient'"'"'s body and operably connected to the sensor to receive the first and second signals, the processing component programmed to;

i) collectively process the first and second signals to generate a processed signal;

ii) process the processed signal with a digital filter to generate a filtered signal;

iii) analyze the filtered signal to determine a feature related to blood pressure; and

iv) analyze the feature related to blood pressure to determine the blood pressure value.

6. The system of claim 1, wherein the first radiation source emits an optical wavelength between 800-1000 nm.

7. The system of claim 6, wherein the second radiation source emits an optical wavelength between 590-700 nm.

8. The system of claim 1, wherein the processing component is programmed to collectively process the first and second signals by subtracting one signal from the other to generate the processed signal.

9. The system of claim 8, wherein the processing component is programmed to process the processed signal with a digital bandpass filter to generate the filtered signal.

10. The system of claim 9, wherein the processing component is programmed to process the processed signal with a digital bandpass filter characterized by a passband between 0.01-5.0 Hz to generate the filtered signal.

11. The system of claim 1, wherein the processing component is programmed to collectively process the first and second signals by dividing one signal into the other to generate the processed signal.

12. The system of claim 11, wherein the processing component is programmed to process the processed signal with a digital bandpass filter to generate the filtered signal.

13. The system of claim 12, wherein the processing component is programmed to process the processed signal with a digital bandpass filter characterized by a passband between 0.01-5.0 Hz to generate the filtered signal.

14. The system of claim 1, wherein the processing component is programmed to analyze the filtered signal to determine an onset point representing the feature related to blood pressure.

15. The system of claim 14, further comprising a second sensor comprising an ECG circuit and at least two electrodes, the second sensor configured to detect electrical signals from the patient and process them to generate a third signal.

16. The system of claim 15, wherein the processing component is further configured to receive the third signal, and is programmed to determine a QRS component from the third signal.

17. The system of claim 16, wherein the processing component is programmed to determine a time difference between the onset point and a feature of the QRS component, and then process the time difference to determine the blood pressure value.

18. The system of claim 1, further comprising a motion sensor configured to attach to a portion of patient, the motion sensor configured to generate a motion signal indicative of motion of the portion to which the motion sensor is attached.

19. The system of claim 18, wherein the processing component is programmed to analyze the motion signal to determine if at least one of the first and second signals is corrupted by motion.

20. The system of claim 19, wherein, if at least one of the first and second signals is corrupted by motion, the processing component is programmed to:

i) collectively process the first and second signals to generate the processed signal; and

ii) process the processed signal with the digital filter to generate the filtered signal.

21. The system of claim 18, wherein the motion sensor is an accelerometer.

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

(a) a sensor comprising;

a first radiation source configured to emit optical radiation at a first wavelength;

a second radiation source configured to emit optical radiation at a second wavelength;

a photodetector configured to detect radiation emitted by the first radiation source after it passes through a portion of the patient to generate a first signal, and radiation emitted by the second radiation source after it passes through a portion of the patient to generate a second signal; and

a housing comprising the first and second radiation sources and the photodetector; and

,

(b) a processing component configured to be worn on the patient'"'"'s body and connected to the sensor to receive the first and second signals, the processing component programmed to;

i) process the first and second signals with a digital filter to generate first and second filtered signals;

ii) collectively process the first and second filtered signals to generate a processed signal;

iii) analyze the processed signal to determine a feature related to blood pressure; and

iv) analyze the feature related to blood pressure to determine the blood pressure value.

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

(a) a first sensor comprising;

a first radiation source configured to emit optical radiation at a first wavelength;

a second radiation source configured to emit optical radiation at a second wavelength; and

a photodetector configured to detect radiation emitted by the first radiation source after it passes through a portion of the patient to generate a first signal, and radiation emitted by the second radiation source after it passes through a portion of the patient to generate a second signal;

(b) a second sensor comprising;

an ECG circuit and at least two electrodes, the second sensor configured to detect electrical signals from the patient and process them to generate a third signal; and

,

(c) a processing component configured to be worn on the patient'"'"'s body and connected to the first sensor to receive the first and second signals, and to the second sensor to receive the third signal, the processing component programmed to;

i) collectively process the first and second signals by either subtracting one signal from the other or dividing one signal into the other to generate a processed signal;

ii) process the processed signal with a digital filter to generate a filtered signal;

iii) analyze the filtered signal to determine a first time-dependent feature;

iv) analyze the third signal or a processed version thereof to determine a second time-dependent feature;

v) analyze the first and second time-dependent features to determine a time difference; and

vi) analyze the time difference to determine the blood pressure value.

4. A system for determining blood pressure values for a patient, comprising:

(a) a first sensor comprising;

a first and second light source and a photodetector, and configured to measure a first signal corresponding to the first light source and a second signal corresponding to the second light source; and

(b) a processing component configured to be worn on the patient'"'"'s body and operably connected to the first sensor and comprising;

a motion sensor for detecting a motion signal and an input port for receiving the first and second signals, the processing component programmed to determine blood pressure values by collectively processing the motion signal and a third signal resulting from combining and then digitally filtering the first and second signals.

5. A system for determining blood pressure values for a patient, comprising:

(a) a first sensor comprising;

a first and second light source and a photodetector, and configured to measure a first signal corresponding to the first light source and a second signal corresponding to the second light source;

(b) a second sensor comprising;

an ECG circuit and at least two electrodes configured to measure a third signal;

(c) a processing component configured to be worn on the patient'"'"'s body and operably connected to the first and second sensors, the processing component programmed to determine blood pressure values by collectively processing the third signal and a fourth signal resulting from combining and then digitally filtering the first and second signals.