Body-worn system for measuring continuous non-invasive blood pressure (cNIBP)

• US 9,215,986 B2
• Filed: 12/30/2009
• Issued: 12/22/2015
• 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
• Primary Examiner(s): Natnithithadha, Navin
• Assistant Examiner(s): WEARE, MEREDITH H
• Application Number:
  US12/650,383
• Publication Number:
  US 20100160795A1
• Time in Patent Office: 2,183 Days
• Field of Search: 600/480, 600/485, 600500-507
• US Class Current: 1/1
• 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 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 photoplethysmogram waveform, and radiation emitted by the second radiation source after it passes through a portion of the patient to generate a second photoplethysmogram waveform;

(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 photoplethysmogram waveforms, and to the second sensor to receive the third signal, the processing component programmed to;

i) collectively process the first and second photoplethysmogram waveforms by dividing one photoplethysmogram waveform into the other photoplethysmogram waveform 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.

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

3. The system of claim 2, wherein the second radiation source emits an optical wavelength between 590-700 nm.

4. The system of claim 1, 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.

5. 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.

6. The system of claim 5, wherein the processing component is further configured to receive the third signal, and is programmed to determine a QRS component from the third signal.

7. The system of claim 6, 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.

8. 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.

9. The system of claim 8, wherein the motion sensor is an accelerometer.