METHOD FOR MEASURING PATIENT MOTION, ACTIVITY LEVEL, AND POSTURE ALONG WITH PTT-BASED BLOOD PRESSURE

• US 20100298653A1
• Filed: 05/20/2009
• Published: 11/25/2010
• Est. Priority Date: 05/20/2009
• Status: Active Grant

• Current Assignee: Sotera Wireless Incorporated
• Original Assignee: Triage Wireless, Inc.
• Inventors: Dhillon, Marshal, McCombie, Devin, Banet, Matt
• Granted Patent: US 8,475,370 B2
• Time in Patent Office: Days
• US Class Current: 600/301
• CPC Class Codes: A61B 2560/0261 using hydrostatic pressure
• CPC Class Codes: A61B 2562/0219 Inertial sensors, e.g. accelerometers, gyroscopes, tilt switches
• CPC Class Codes: A61B 5/0002 Remote monitoring of patients using telemetry, e.g. transmission of vital signals via a communication network A61B5/07 takes precedence; transmission systems for measured values G08C; transmission H04B; transmission of digital information H04L; wireless communication networks H04W
• CPC Class Codes: A61B 5/0006 ECG or EEG signals
• CPC Class Codes: A61B 5/0024 for multiple sensor units attached to the patient, e.g. using a body or personal area network
• CPC Class Codes: A61B 5/0082 adapted for particular medical purposes
• CPC Class Codes: A61B 5/02028 Determining haemodynamic parameters not otherwise provided for, e.g. cardiac contractility or left ventricular ejection fraction
• CPC Class Codes: A61B 5/0205 Simultaneously evaluating both cardiovascular conditions and different types of body conditions, e.g. heart and respiratory condition
• CPC Class Codes: A61B 5/021 Measuring pressure in heart or blood vessels A61B5/0205 takes precedence
• CPC Class Codes: A61B 5/02125 of pulse wave propagation time
• CPC Class Codes: A61B 5/022 by applying pressure to close blood vessels, e.g. against the skin; Ophthalmodynamometers
• CPC Class Codes: A61B 5/02225 using the oscillometric method
• CPC Class Codes: A61B 5/02416 using photoplethysmograph signals, e.g. generated by infrared radiation A61B5/14552 takes precedence
• CPC Class Codes: A61B 5/0285 Measuring or recording phase velocity of blood waves
• 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 5/0816 Measuring devices for examining respiratory frequency measuring frequency of electric signals G01R23/00
• CPC Class Codes: A61B 5/1116 Determining posture transitions
• CPC Class Codes: A61B 5/1117 Fall detection
• CPC Class Codes: A61B 5/1118 Determining activity level
• CPC Class Codes: A61B 5/1122 of movement trajectories
• CPC Class Codes: A61B 5/1123 : Discriminating type of movement, e.g. walking or running A61B5/1116, A61B5/112 take precedence
• CPC Class Codes: A61B 5/14551 : for measuring blood gases
• CPC Class Codes: A61B 5/25 : Bioelectric electrodes therefor
• CPC Class Codes: A61B 5/282 : Holders for multiple electrodes for introduction into the body A61B5/287
• CPC Class Codes: A61B 5/30 : Input circuits therefor
• CPC Class Codes: A61B 5/316 : Modalities, i.e. specific diagnostic methods
• CPC Class Codes: A61B 5/318 : Heart-related electrical modalities, e.g. electrocardiography [ECG]
• CPC Class Codes: A61B 5/339 : Displays specially adapted therefor
• CPC Class Codes: A61B 5/349 : Detecting specific parameters of the electrocardiograph cycle
• CPC Class Codes: A61B 5/447 : specially adapted for aiding the prevention of ulcer or pressure sore development, i.e. before the ulcer or sore has developed
• CPC Class Codes: A61B 5/681 : Wristwatch-type devices
• CPC Class Codes: A61B 5/6823 : Trunk, e.g., chest, back, abdomen, hip
• CPC Class Codes: A61B 5/6824 : Arm or wrist
• CPC Class Codes: A61B 5/6826 : Finger
• CPC Class Codes: A61B 5/7207 : of noise induced by motion artifacts
• CPC Class Codes: A61B 5/7239 : using differentiation including higher order derivatives
• CPC Class Codes: A61B 5/7257 : using Fourier transforms
• CPC Class Codes: A61B 5/746 : Alarms related to a physiological condition, e.g. details of setting alarm thresholds or avoiding false alarms alarms per se G08B

Abstract

The invention provides a system and method for measuring vital signs (e.g. SYS, DIA, SpO2, heart rate, and respiratory rate) and motion (e.g. activity level, posture, degree of motion, and arm height) from a patient. The system features: (i) first and second sensors configured to independently generate time-dependent waveforms indicative of one or more contractile properties of the patient'"'"'s heart; and (ii) at least three motion-detecting sensors positioned on the forearm, upper arm, and a body location other than the forearm or upper arm of the patient. Each motion-detecting sensor generates at least one time-dependent motion waveform indicative of motion of the location on the patient'"'"'s body to which it is affixed. A processing component, typically worn on the patient'"'"'s body and featuring a microprocessor, receives the time-dependent waveforms generated by the different sensors and processes them to determine: (i) a pulse transit time calculated using a time difference between features in two separate time-dependent waveforms, (ii) a blood pressure value calculated from the time difference, and (iii) a motion parameter calculated from at least one motion waveform.

Claims

1. A method for monitoring a patient, comprising the following steps:

(a) detecting a first time-dependent physiological waveform indicative of one or more contractile properties of the patient'"'"'s heart with a first sensor comprising a first detector configured to be worn on the patient'"'"'s body;

(b) detecting a second time-dependent physiological waveform indicative of one or more contractile properties of the patient'"'"'s heart with a second sensor comprising a second detector configured to be worn on the patient'"'"'s body;

(c) detecting sets of time-dependent motion waveforms with at least two motion-detecting sensors positioned on different locations on the patient'"'"'s body, wherein each motion-detecting sensor detects a set of motion waveforms indicative of motion of the location on the patient'"'"'s body to which the motion-detecting sensor is affixed;

(d) processing the first and second time-dependent physiological waveforms to determine at least one vital sign from the patient;

(e) analyzing at least a portion of each set of time-dependent motion waveforms, or a mathematical derivative thereof, to determine a motion parameter;

(f) processing the motion parameter to determine a probability that the patient is undergoing a specific activity state; and

(g) estimating the patient'"'"'s activity state based on the probability.

2. The method of claim 1, wherein step (e) further comprises calculating a mathematical transform of at least one motion waveform to determine a frequency-dependent motion waveform.

3. The method of claim 2, wherein step (e) further comprises calculating a power spectrum of at least one motion waveform.

4. The method of claim 3, wherein step (e) further comprises calculating an amplitude of at least one frequency component of the power spectrum, or a mathematical derivative thereof, to determine the motion parameter.

5. The method of claim 1, wherein step (e) further comprises analyzing a time-dependent variation of least one motion waveform.

6. The method of claim 5, wherein step (e) further comprises calculating a standard deviation of at least one motion waveform to determine the motion parameter.

7. The method of claim 5, wherein step (e) further comprises calculating a mathematical derivative of at least one motion waveform to determine the motion parameter.

8. The method of claim 5, wherein step (e) further comprises comparing at least a portion of the motion waveform to a mathematical function.

9. The method of claim 4, wherein step (e) further comprises determining a logit variable z, or a mathematical derivative thereof, wherein z is defined as:

z=b₀+b₁x₁+b₂x₂+ . . . +b_mx_m

wherein b₀, b₁, b₂, and b_m, are predetermined constants related to motion, and at least one of x₀, x₁, x₂, and x_m, is a motion parameter determined from an amplitude of at least one frequency component of the power spectrum.

10. The method of claim 9, wherein step (f) further comprises processing the logit variable z, or a mathematical derivative thereof, with a mathematical function to determine the probability that the patient is undergoing a specific activity state.

11. The method of claim 10, wherein step (f) further comprises processing the logit variable z, or a mathematical derivative thereof, with a probability function P, or a mathematical derivative thereof, wherein P is defined as:

12. The method of claim 11, wherein step (g) further comprises comparing P, or a mathematical derivative thereof, to a predetermined threshold value to estimate the patient'"'"'s activity state.

13. The method of claim 5, wherein step (e) further comprises determining a logit variable z, or a mathematical derivative thereof, wherein z is defined as:

z=b₀+b₁x₁+b₂x₂+ . . . +b_mx_m

wherein b₀, b₁, b₂, and b_m, are predetermined constants related to motion, and at least one of x₀, x₁, x₂, and x_m, is a motion parameter determined from a time-dependent variation of least one motion waveform.

14. The method of claim 13, wherein step (f) further comprises processing the logit variable z, or a mathematical derivative thereof, with a mathematical function to determine the probability that the patient is undergoing a specific activity state.

15. The method of claim 14, wherein step (f) further comprises processing the logit variable z, or a mathematical derivative thereof, with a probability function P, or a mathematical derivative thereof, wherein P is defined as:

16. The method of claim 15, wherein step (g) further comprises comparing P, or a mathematical derivative thereof, to a predetermined threshold value to estimate the patient'"'"'s activity state.

17. The method of claim 1, wherein step (g) further comprises estimating an activity state selected from the group consisting of resting, moving, sitting, standing, walking, running, falling, lying down, and convulsing.

18. The method of claim 1, wherein step (d) further comprises determining at least one vital sign by calculating a time difference between a feature in the first time-dependent physiological waveform and a feature in the second time-dependent physiological waveform.

19. The method of claim 18, wherein step (d) further comprises calculating a blood pressure from the time difference.

20. The method of claim 13, wherein the first time-dependent physiological waveform is an electrical waveform, and step (a) further comprises detecting the electrical waveform with at least two electrodes attached to the patient and operably connected to an electrical circuit.

21. The method of claim 20, wherein the second time-dependent physiological waveform is an optical waveform, and step (b) further comprises detecting the optical waveform with an optical sensor comprising a light source and a photodiode.

22. The method of claim 11, wherein each of the first and second time-dependent physiological waveforms are selected from a group consisting of an optical waveform, an electrical waveform, an acoustic waveform, and a pressure waveform.

23. The method of claim 22, wherein steps (a) and (b) each further comprise detecting a time-dependent physiological waveform with a sensor selected from a group consisting of:

(i) an optical sensor comprising a light source and a photodiode;

(ii) an electrical sensor comprising at least two electrodes operably connected to an electrical circuit;

(iii) an acoustic sensor comprising a microphone; and

(iv) a pressure sensor comprising a transducer.

24. A system for measuring vital signs from a patient, comprising:

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

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

(c) at least three motion-detecting sensors positioned on the forearm, upper arm, and a body location other than the forearm or upper arm of the patient, each of said motion-detecting sensors generating at least one time-dependent motion waveform indicative of motion of the location on the patient'"'"'s body to which the motion-detecting sensor is affixed;

(d) a processing component configured to be worn on the patient'"'"'s body and comprising a microprocessor, said processing component configured to receive the first time-dependent waveform, the second time-dependent waveform, and the at least one time-dependent motion waveform generated by each motion-detecting sensor and determine therefrom;

(i) a pulse transit time calculated using a time difference between a time-dependent feature in each of the first and second time-dependent waveforms, (ii) a blood pressure value calculated using said time difference, and (iii) at least one motion parameter selected from the patient'"'"'s posture, activity level, and degree of motion calculated using at least one motion waveform generated by each of said motion-detecting sensors; and

(e) a wireless communication system configured to be worn on the patient'"'"'s body and operably connect to the processing component, the wireless system configured to wirelessly transmit the blood pressure value and at least one motion parameter determined by the processing component to a remote receiver.

25. A system for measuring vital signs from a patient, comprising:

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

(b) a cable system comprising;

an electrical sensor comprising;

at least two electrodes configured to detect electrical signals from the patient'"'"'s body and operably connect to an electrical circuit configured to process the detected electrical signals, the electrical sensor generating a time-dependent electrical waveform indicative of one or more contractile properties of the patient'"'"'s heart, and,

at least two motion-detecting sensors, each of said motion-detecting sensors generating at least one time-dependent motion waveform indicative of motion of the location on the patient'"'"'s body to which the motion-detecting sensor is affixed; and

,

(c) a processing component configured to be worn on the patient'"'"'s body and comprising a microprocessor and one or more electrical connectors for operably connecting the microprocessor to the sensor and the cable system, said processing component configured to receive the time-dependent electrical waveform, the time-dependent physiological waveform, and the at least one time-dependent motion waveform generated by each motion-detecting sensor and determine therefrom;

(i) at least one vital sign calculated using at least one of the time-dependent physiological waveform and the time-dependent electrical waveform, and (ii) at least one motion parameter selected from the patient'"'"'s posture, activity level, arm height, and degree of motion calculated using at least one time-dependent motion waveform generated by each of said motion-detecting sensors.

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

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

(b) an electrical sensor comprising;

at least two electrodes configured to detect electrical signals from the patient'"'"'s body, and an electrical circuit operably connected to the electrodes and configured to process the detected electrical signals, the electrical sensor generating a time-dependent electrical waveform indicative of one or more contractile properties of the patient'"'"'s heart;

(c) at least two motion-detecting sensors positioned on separate locations on the patient'"'"'s body, each of said motion-detecting sensors generating at least one time-dependent motion waveform indicative of motion of the location on the patient'"'"'s body to which the motion-detecting sensor is affixed; and

,

(d) a processing component configured to be worn on the patient'"'"'s body and comprising a microprocessor, said processing component configured to receive the first time-dependent waveform, the time-dependent electrical waveform, and the at least one time-dependent motion waveform generated by each motion-detecting sensor, and to determine;

(i) a first arm position from one or more of the time-dependent motion waveforms acquired in a first arm position;

(ii) a first time difference between a feature present in each of a first time-dependent waveform and a first time-dependent electrical waveform acquired in the first arm position;

(iii) a second arm position from one or more of the time-dependent motion waveforms acquired in a second arm position;

(iv) a second time difference between a feature present in each of a second time-dependent waveform and a second time-dependent electrical waveform acquired in the second arm position;

(v) a first blood pressure value calculated at the first arm position;

(vi) a second blood pressure value calculated at the second arm position;

(vii) a blood pressure factor calculated using the first blood pressure value and the first time difference or a property derived therefrom, together with the second blood pressure value and the second time difference or a property derived therefrom.

27. A system for measuring vital signs from a patient, comprising:

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

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

(c) at least two motion-detecting sensors positioned on a location selected from a forearm, upper arm, and a body location other than the forearm or upper arm of the patient, each of said motion-detecting sensors generating at least one time-dependent motion waveform indicative of motion of the location on the patient'"'"'s body to which the motion-detecting sensor is affixed; and

,

(d) a processing component configured to be worn on the patient'"'"'s body and comprising a microprocessor, said processing component configured to receive the first time-dependent waveform, the second time-dependent waveform, and the at least one time-dependent motion waveform generated by each motion-detecting sensor and determine therefrom;

(i) one or more vital signs calculated using the first and second time-dependent waveforms;

(ii) at least one motion parameter selected from the patient'"'"'s posture, activity level, arm height, and degree of motion and calculated using at least one motion waveform generated by each of said motion-detecting sensors; and

(iii) at least one alarm condition calculated using one or more of the vital signs and at least one motion parameter, wherein an alarm condition indicated by a variance in one or more of the vital signs is regulated according to one or more motion parameters.

28. A method for monitoring vital signs and posture of a patient, the method comprising the following steps:

(a) detecting a first time-dependent physiological waveform indicative of one or more contractile properties of the patient'"'"'s heart with a first sensor comprising a first detector configured to be worn on the patient'"'"'s body;

(b) detecting a second time-dependent physiological waveform indicative of one or more contractile properties of the patient'"'"'s heart with a second sensor comprising a second detector configured to be worn on the patient'"'"'s body;

(c) detecting a set of time-dependent motion waveforms with at least one motion-detecting sensor positioned on the patient'"'"'s torso, wherein the one motion-detecting sensor detects a set of motion waveforms indicative of motion of the patient'"'"'s torso;

(d) processing the first and second time-dependent physiological waveforms to determine at least one vital sign from the patient;

(e) analyzing at least a portion of the set of time-dependent motion waveforms, or a mathematical derivative thereof, to determine a vector corresponding to motion of the patient'"'"'s torso;

(f) comparing the vector to a coordinate space representative of how the motion-detecting sensor is oriented on the patient to determine a posture parameter; and

(g) comparing the posture parameter to a threshold value to estimate the patient'"'"'s posture.