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

• US 20100168589A1
• Filed: 12/30/2009
• Published: 07/01/2010
• Est. Priority Date: 06/12/2007
• Status: Active Grant

• Current Assignee: Sotera Wireless Incorporated (Foxconn Technology Co., Ltd.)
• Original Assignee: Sotera Wireless Incorporated (Foxconn Technology Co., Ltd.)
• Inventors: BANET, Matt, DHILLON, Marshal, McCOMBIE, Devin
• Granted Patent: US 8,808,188 B2
• Time in Patent Office: Days
• US Class Current: 600/490
• 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 5/33 specially adapted for cooperation with other devices
• 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 a pulse transit time 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 to determine a relationship between pulse transit time and blood pressure in the patient'"'"'s core region; and

iii) determine a blood pressure in the patient'"'"'s core region from a pulse transit time and the relationship between pulse transit time and blood pressure in the patient'"'"'s core region using a mathematical model representative of blood pressure in said core region.

4. The system of claim 1, wherein the first sensor is selected from the group consisting of an optical sensor, a pressure sensor, an electrical impedance sensor, an ECG waveform sensor, and a transducer.

5. The system of claim 4, wherein the second sensor is selected from the group consisting of an optical sensor, a pressure sensor, an electrical impedance sensor, an ECG waveform sensor, and a transducer.

6. The system of claim 5, wherein the first sensor is an optical sensor, the second sensor is an ECG waveform sensor, and the processing component is configured to determine the pulse transit time from a QRS complex in an ECG waveform and an onset point of an optical waveform.

7. The system of claim 1, wherein the processing component is configured to determine a relationship between pulse transit time and blood pressure in the patient'"'"'s femoral artery.

8. The system of claim 7, wherein the processing component is programmed to determine a relationship between pulse transit time and mean arterial pressure in the patient'"'"'s femoral artery.

9. The system of claim 8, wherein the relationship between pulse transit time and mean arterial pressure in the patient'"'"'s femoral artery is characterized by the following equation or a mathematical derivative thereof:

MAP_femoral=(m_femoral×

PTT)−

(m_femoral×

PTT_INDEX)+MAP_INDEX

wherein MAP_femoral represents blood pressure in the patient'"'"'s femoral artery, PTT represents pulse transit time measured from the first and second waveforms, PTT_INDEX represents a pulse transit time determined before PTT, m_femoral represents a mathematical slope representing a relationship between MAP_femoral and pulse transit time, and MAP_INDEX represents a mean arterial pressure determined from the time-dependent pressure waveform.

10. The system of claim 9, wherein the processing component is programmed to determine m_femoral by collectively processing the first, second, and pressure waveforms.

11. The system of claim 10, 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.

12. The system of claim 11, wherein the processing component is programmed to determine m_femoral by fitting the set of pulse transit time values to a linear equation.

13. The system of claim 9, wherein the processing component is programmed to determine a systolic blood pressure indicative of the patient'"'"'s femoral artery from MAP_femoral and a relationship between mean arterial pressure and systolic blood pressure determined from the time-dependent pressure waveform.

14. The system of claim 13, wherein the processing component is programmed to determine a systolic blood pressure indicative of the patient'"'"'s femoral artery from MAP_femoral, heart rate, and a relationship between mean arterial pressure and systolic blood pressure determined from the time-dependent pressure waveform.

15. The system of claim 9, wherein the processing component is programmed to determine a diastolic blood pressure indicative of the patient'"'"'s femoral artery from MAP_femoral and a relationship between mean arterial pressure and diastolic blood pressure determined from the time-dependent pressure waveform.

16. The system of claim 15, wherein the processing component is programmed to determine a diastolic blood pressure indicative of the patient'"'"'s femoral artery from MAP_femoral, heart rate, and a relationship between mean arterial pressure and diastolic blood pressure determined from the time-dependent pressure waveform.

17. The system of claim 8, wherein the relationship between pulse transit time and mean arterial pressure in the patient'"'"'s femoral artery is determined before the pressure-delivery system applies a variable pressure to the patient'"'"'s arm.

18. The system of claim 17, wherein the relationship between pulse transit time and mean arterial pressure in the patient'"'"'s femoral artery is described by a mathematical model determined from a group of patients.

19. The system of claim 17, wherein the relationship between pulse transit time and mean arterial pressure in the patient'"'"'s femoral artery is between 0.5 mmHg/ms and 1.5 mmHg/ms.

20. The system of claim 1, wherein the pressure delivery system is a pressurized cuff.

21. The system of claim 20, wherein the pressurized cuff is configured to be worn around the patient'"'"'s bicep.

2. 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;

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

an electrode system configured to attach to the patient and generate a time-dependent electrical waveform representing activity of the patient'"'"'s heart; and

,

a processing component programmed to;

i) determine a pulse transit time from a separation in time of a first feature of the time-dependent electrical waveform and a second feature of the time-dependent optical waveform;

ii) process the pressure, optical, and electrical waveforms to determine a relationship between pulse transit time and blood pressure in the patient'"'"'s core region; and

iii) determine a blood pressure in the patient'"'"'s core region from a pulse transit time and the relationship between pulse transit time and blood pressure in the patient'"'"'s core region using a mathematical model representative of blood pressure in said core region.

3. A system for measuring blood pressure, comprising:

an optical sensor configured to measure a first waveform from a patient;

an electrical sensor configured to measure a second waveform from the patient;

a processor configured to process the first and second waveforms with a mathematical system that models blood pressure in a femoral artery of the patient; and

a display system that displays a value representing blood pressure in the femoral artery of the patient.