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

• US 8,808,188 B2
• Filed: 12/30/2009
• Issued: 08/19/2014
• 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:
  US12/650,354
• Publication Number:
  US 20100168589A1
• Time in Patent Office: 1,693 Days
• Field of Search: 600/481, 600485-525
• 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 patient'"'"'s blood pressure, the system comprising:

a pressure-delivery system for applying a variable pressure to the patient'"'"'s arm;

a pressure sensor for measuring a time-dependent pressure waveform representing the pressure applied to the patient'"'"'s arm;

a first sensor configured to attach to the patient and generate a first time-dependent waveform representing a flow of blood within the patient;

a second sensor configured to attach to the patient and generate a second time-dependent waveform representing contractile properties of the patient'"'"'s heart; and

,

a processing component programmed to;

i) determine an index pulse transit time (PTT_index) from a separation in time of a first feature of the first time-dependent waveform and a second feature of the second time-dependent waveform;

ii) process the pressure, first, and second waveforms as pressure is applied by the pressure-delivery system and determine therefrom a patient-specific slope (m_femoral) representing a relationship between pulse transit time and mean arterial blood pressure in the patient'"'"'s femoral artery;

iii) determine a mean arterial pressure value (MAP_INDEX) from a peak pulse amplitude in the time-dependent pressure waveform; and

iv) determine a mean blood pressure value in the patient'"'"'s femoral artery (MAP_femoral) from a pulse transit time measured from the first and second waveforms (PTT) according to the equation MAP_femoral=(m_femoral×

PTT)−

(m_femoral×

PTT_INDEX)+MAP_INDEX, wherein PTT_INDEX represents a pulse transit time determined before PTT.

2. The system of claim 1, wherein the processing component is programmed to determine m_femoral by collectively processing the first, second, and pressure waveforms.

3. The system of claim 2, wherein the processing component is programmed to determine m_femoral by processing a set of pulse transit time values measured while time-dependent pressure is applied to the patient'"'"'s arm.

4. The system of claim 3, wherein the processing component is programmed to determine m_femoral by fitting the set of pulse transit time values to a linear equation.