SYSTEM FOR CALIBRATING A PTT-BASED BLOOD PRESSURE MEASUREMENT USING ARM HEIGHT

• US 20100298652A1
• 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 8,672,854 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 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.

2. The system of claim 1, wherein the processing component further comprises a display component.

4. The system of claim 1, wherein the processing component further comprises an audio component.

5. The system of claim 4, wherein the audio component renders audible instructions that instruct the patient to move an arm to the first arm position and then to the second arm position.

6. The system of claim 1, wherein the processing component is further configured to:

(i) detect when the patient'"'"'s arm is in the first position by processing at least one time-dependent motion waveform generated by each motion-detecting sensor; and

(ii) determine the first time difference and the first blood pressure value when the patient'"'"'s arm is in the first position.

7. The system of claim 6, wherein the processing component is further configured to:

(i) detect when the patient'"'"'s arm is in the second position by processing at least one time-dependent motion waveform generated by each motion-detecting sensor; and

(ii) determine the second time difference and the second blood pressure value when the patient'"'"'s arm is in the second position.

8. The system of claim 7, wherein the processing component is further configured to determine a third time difference between a feature present in each of the time-dependent waveform measured by the first sensor and a time-dependent electrical waveform after it determines the first and second time differences.

9. The system of claim 8, further comprising a pneumatic system comprising an inflatable cuff, a pump, and a pressure sensor, the inflatable cuff configured to attach to the patient'"'"'s arm and be inflated by the pump, and the pressure sensor configured to measure a time-dependent pressure waveform representing a pressure within the inflatable cuff.

10. The system of claim 9, wherein the pressure sensor is configured to measure a time-dependent pressure waveform representing a pressure within the inflatable cuff while the pump inflates the inflatable cuff.

11. The system of claim 9, further comprising a processor configured to process the time-dependent pressure waveform to calculate at least one cuff-based blood pressure value.

12. The system of claim 11, wherein the processing component is further configured to determine a blood pressure value by processing the third time difference, the blood pressure factor, and the cuff-based blood pressure value.

13. The system of claim 8, wherein the processing component is further configured to determine a blood pressure value by processing the third time difference and the blood pressure factor.

14. The system of claim 1, wherein a first motion-detecting sensor is positioned at a location on the patient'"'"'s body selected from a lower arm, wrist, hand, and finger.

15. The system of claim 14, wherein a second motion-detecting sensor is positioned at a location on the patient'"'"'s body selected from an upper arm, shoulder, and chest.

16. The system of claim 1, wherein the first sensor comprises an optical sensor comprising a source of electromagnetic radiation configured to irradiate tissue of the patient with radiation emitted therefrom, and a detector configured to detect one or more properties of the electromagnetic radiation after it irradiates said tissue, the optical sensor generating a time-dependent optical waveform indicative of volumetric changes in the irradiated tissue.

17. The system of claim 16, wherein the processing component is further configured to detect a time difference between a feature of the time-dependent optical waveform and a feature of the time-dependent electrical waveform.

18. A method of measuring blood pressure from a patient, comprising:

attaching a system according to one of claims 1-17 to a patient; and

determining a blood pressure value and at least one motion parameter using said processing component.

3. The system of claim 3, wherein the display component renders a graphic interface configured to instruct the patient to move an arm to the first arm position and then to the second arm position.

19. 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.

20. 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.

21. 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.

22. 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.

23. 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.