System for calibrating a PTT-based blood pressure measurement using arm height

• US 9,307,915 B2
• Filed: 03/14/2014
• Issued: 04/12/2016
• Est. Priority Date: 05/20/2009
• Status: Active Grant

• Current Assignee: Sotera Wireless Incorporated
• Original Assignee: Sotera Wireless Incorporated
• Inventors: McCombie, Devin, Dhillon, Marshal, Banet, Matt
• Primary Examiner(s): EVANISKO, GEORGE ROBERT
• Application Number:
  US14/214,464
• Publication Number:
  US 20140200415A1
• Time in Patent Office: 760 Days
• US Class Current: 1/1
• 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 measuring vital signs from a patient, comprising:

(a) affixing to the patient'"'"'s lower arm a vital sign monitor, the vital sign monitor comprising a first housing enclosing a processing component, a transceiver which communicates with peripheral components using a Controller Area Network (CAN) protocol, and a first accelerometer configured to generate a first time-dependent digital motion waveform indicative of movement of the patient'"'"'s lower arm and to operably connect to the processing component to transmit the first time-dependent digital motion waveform via the CAN protocol;

(b) affixing to a finger of the patient a sensor configured to detect a time-dependent plethysmogram waveform and to operably connect to the processing component to transmit the time-dependent plethysmogram waveform to the processing component;

(c) affixing to the patient'"'"'s chest an integrated circuit operably connected to at least two electrodes, the intergrated circuit and electrodes configured to generate time-dependent digitized ECG waveforms and to operably connect to the processing component to transmit the digitized ECG waveforms to the processing component via the CAN protocol;

(d) affixing to the patient'"'"'s chest a second accelerometer configured to generate a second time-dependent digital motion waveform indicative of movement of the patient'"'"'s chest and to operably connect to the processing component to transmit the second time-dependent digital motion waveform to the processing component via the CAN protocol;

(e) affixing to the patient'"'"'s upper arm a third accelerometer configured to generate a third time-dependent digital motion waveform indicative of movement of the patient'"'"'s upper arm and to operably connect to the processing component to transmit the third time-dependent digital motion waveform to the processing component via the CAN protocol;

(f) synchronizing and processing with the processing component the time-dependent plethysmogram waveform, the time-dependent digitized ECG waveforms, the first time-dependent digital motion waveform, the second time-dependent digital motion waveform, and the third time-dependent digital motion waveform to determine (i) at least one vital sign calculated using the time-dependent plethysmogram waveform and the time-dependent ECG waveforms, and (ii) one or more motion parameters indicative of the patient'"'"'s posture, activity level, and degree of motion calculated using the first, second and third time-dependent digital motion waveforms.

2. The method of claim 1, wherein the second time-dependent digital motion waveform is transmitted to the processing component through a cable as a first digital data stream, and the third time-dependent digital motion waveform is transmitted to the processing component through said cable as a second digital data stream, wherein the first digital data stream is separately resolvable from the second digital data stream by the processing component.

3. The method of claim 2, wherein the time-dependent ECG waveforms are transmitted to the processing component through said cable as a third digital data stream separately resolvable from each of the first and second digital data streams.

4. The method of claim 1, wherein the at least two electrodes comprise at least three electrodes, and the integrated circuit is configured to operably connect to the at least three electrodes, with each electrode configured to detect an electrical signal from the patient'"'"'s body, and the integrated circuit configured to process the electrical signals detected by each electrode to generate the time-dependent ECG waveforms.

5. The method of claim 4, wherein the at least three electrodes comprise at least five electrodes, and the integrated circuit is configured to operably connect to the at least five electrodes, with each electrode configured to detect an electrical signal from the patient'"'"'s body, and the integrated circuit configured to process the electrical signals detected by each electrode to generate at least three separate time-dependent ECG waveforms.

6. The method of claim 5, wherein the at least five electrodes comprise at least twelve electrodes, and the integrated circuit is configured to operably connect to the at least twelve electrodes, with each electrode configured to detect an electrical signal from the patient'"'"'s body, and the integrated circuit configured to process the electrical signals detected by each electrode to generate at least five separate time-dependent ECG waveforms.

7. The method of claim 1, wherein the sensor configured to detect a time-dependent plethysmogram waveform is affixed to the base of the patient'"'"'s thumb.

8. The method of claim 1, wherein the vital sign calculated by the processing component is blood pressure.

9. The method of claim 1, wherein the one or more motion parameters distinguish between the following postures:

patient is upright, patient is supine, patient is prone, patient is on left side, and patient is on right side.

10. The method of claim 9, wherein the one or more motion parameters distinguish between the following activity levels:

sitting, standing, walking, running, resting, falling, lying down, and convulsing.

11. The method of claim 10, wherein the one or more motion parameters identify an activity level that indicates corruption of the time-dependent plethysmogram waveform and/or the time-dependent digitized ECG waveforms.