Alarm system that processes both motion and vital signs using specific heuristic rules and thresholds

• US 8,594,776 B2
• Filed: 03/28/2012
• Issued: 11/26/2013
• Est. Priority Date: 05/20/2009
• Status: Active Grant

• Current Assignee: Sotera Wireless Incorporated
• Original Assignee: Sotera Wireless Incorporated
• Inventors: McCombie, Devin, Banet, Matt, Dhillon, Marshal, Moon, Jim
• Primary Examiner(s): Schaetzle, Kennedy
• Application Number:
  US13/432,976
• Publication Number:
  US 20120190949A1
• Time in Patent Office: 608 Days
• Field of Search: None
• US Class Current: 600/513
• CPC Class Codes: A61B 2562/0219 Inertial sensors, e.g. accelerometers, gyroscopes, tilt switches
• CPC Class Codes: A61B 5/0022 Monitoring a patient using a global network, e.g. telephone networks, internet
• CPC Class Codes: A61B 5/0059 using light, e.g. diagnosis by transillumination, diascopy, fluorescence A61B5/0093, A61B5/1455, A61B5/02416 and A61B5/0261 take precedence
• CPC Class Codes: A61B 5/01 Measuring temperature of body parts ; Diagnostic temperature sensing, e.g. for malignant or inflamed tissue clinical contact thermometers G01K13/20
• 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 5/02055 Simultaneously evaluating both cardiovascular condition and temperature
• 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 5/02416 using photoplethysmograph signals, e.g. generated by infrared radiation A61B5/14552 takes precedence
• CPC Class Codes: A61B 5/02438 with portable devices, e.g. worn by the patient
• CPC Class Codes: A61B 5/0245 by using sensing means generating electric signals, i.e. ECG signals
• CPC Class Codes: A61B 5/0816 Measuring devices for examining respiratory frequency measuring frequency of electric signals G01R23/00
• CPC Class Codes: A61B 5/11 Measuring movement of the entire body or parts thereof, e.g. head or hand tremor, mobility of a limb for measuring pulse A61B5/02 ;A61B5/1038 takes precedence; motion detection to correct for motion artifacts in physiological signals A61B5/721
• CPC Class Codes: A61B 5/1114 Tracking parts of the body
• 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 5/1123 Discriminating type of movement, e.g. walking or running A61B5/1116, A61B5/112 take precedence
• CPC Class Codes: A61B 5/145 : Measuring characteristics of blood in vivo, e.g. gas concentration, pH value; Measuring characteristics of body fluids or tissues, e.g. interstitial fluid, cerebral tissuemeasuring of blood pressure or blood flow A61B5/02; non-radiation detecting or locating of foreign bodies in blood A61B5/06
• 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 5/322 : Physical templates or devices for measuring ECG waveforms, e.g. electrocardiograph rulers or calipers by template matching A61B5/35
• CPC Class Codes: A61B 5/332 : Portable devices specially adapted therefor
• CPC Class Codes: A61B 5/349 : Detecting specific parameters of the electrocardiograph cycle
• CPC Class Codes: A61B 5/352 : Detecting R peaks, e.g. for synchronising diagnostic apparatus; Estimating R-R interval
• 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 5/7246 : using correlation, e.g. template matching or determination of similarity
• CPC Class Codes: A61B 5/7257 : using Fourier transforms
• CPC Class Codes: A61B 5/7278 : Artificial waveform generation or derivation, e.g. synthesising signals from measured signals A61B5/327 takes precedence
• CPC Class Codes: A61B 5/742 : using visual displays A61B5/339 takes precedence
• 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
• CPC Class Codes: G08B 21/0446 : worn on the body to detect changes of posture, e.g. a fall, inclination, acceleration, gait
• CPC Class Codes: G08B 21/0453 : worn on the body to detect health condition by physiological monitoring, e.g. electrocardiogram, temperature, breathing detecting, measuring or recording for diagnostic purposes A61B5/00
• CPC Class Codes: G16H 15/00 : ICT specially adapted for medical reports, e.g. generation or transmission thereof
• CPC Class Codes: G16H 50/20 : for computer-aided diagnosis, e.g. based on medical expert systems
• CPC Class Codes: G16H 50/50 : for simulation or modelling of medical disorders

Abstract

The invention provides a body-worn monitor that measures a patient'"'"'s vital signs (e.g. blood pressure, SpO2, heart rate, respiratory rate, and temperature) while simultaneously characterizing their activity state (e.g. resting, walking, convulsing, falling). The body-worn monitor processes this information to minimize corruption of the vital signs by motion-related artifacts. A software framework generates alarms/alerts based on threshold values that are either preset or determined in real time. The framework additionally includes a series of ‘heuristic’ rules that take the patient'"'"'s activity state and motion into account, and process the vital signs accordingly. These rules, for example, indicate that a walking patient is likely breathing and has a regular heart rate, even if their motion-corrupted vital signs suggest otherwise.

Claims

1. A system for processing at least one vital sign from a patient and generating an alarm, the system comprising:

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

a second sensor comprising a second detector configured to be worn on the patient and to detect a second time-dependent physiological waveform indicative of one or more contractile properties of the patient'"'"'s heart;

a first three axis motion-detecting sensor configured to be positioned on an arm of the patient at the wrist and to generate three time-dependent motion waveforms indicative of movement of the wrist;

a second three axis motion-detecting sensor configured to be positioned on the arm at the upper arm and to generate three time-dependent motion waveforms indicative of movement of the upper arm;

a third three axis motion-detecting sensor configured to be positioned on the chest of the patient and to generate three time-dependent motion waveforms indicative of movements of the chest;

a first processing component configured to be worn on the patient'"'"'s body and to receive the first time-dependent physiological waveform, the second time-dependent physiological waveform, the three time-dependent motion waveforms indicative of movement of the wrist, the three time-dependent motion waveforms indicative of movement of the upper arm, and the three time-dependent motion waveforms indicative of movement of the chest and determine therefrom;

(i) a coordinate space defined by a first vector defining a vertical axis for the patient'"'"'s chest, a second vector defining a horizontal axis for the patient'"'"'s chest, and the third vector defining an axis extending normal from the patient'"'"'s chest,

(ii) a fourth vector defining an axis extending along the upper arm,

(ii) a fifth vector defining an axis extending along the lower arm,

(iii) motion of the patient'"'"'s torso,

(iv) posture of the patient,

(v) motion of the patient'"'"'s upper arm,

(vi) motion of the patient'"'"'s lower arm,

(vii) relative height of the patient'"'"'s upper and lower arm,

(viii) at least one vital sign calculated using at least one of the first and second time- dependent physiological waveforms, and

(ix) an activity state of the patient; and

a second processing component configured to receive the at least one vital sign and motion parameter and determine therefrom;

(i) a first alarm condition, calculated by comparing the at least one vital sign to an alarm threshold;

(ii) a second alarm condition, calculated from the motion, posture and activity state of the patient; and

(iii) an alarm rule, determined by collectively processing the first and second alarm conditions with an alarm algorithm, the alarm rule indicating whether or not the system generates an alarm.

2. The system of claim 1, wherein the alarm rule comprises generating the alarm if the motion of the patient indicates that the patient is falling or convulsing.

3. The system of claim 1, wherein the alarm threshold is set at a first value if the motion and activity state of the patient indicate that the patient is walking, and a second value if the motion and activity state of the patient indicate that the patient is at rest.

4. The system of claim 1, wherein the first time-dependent physiological waveform is an ECG waveform.

5. The system of claim 4, wherein the second time-dependent physiological waveform is an optical waveform.

6. The system of claim 5, wherein the first processing component is further configured to:

(x) calculate a time difference between a feature in the ECG waveform and a feature in the optical waveform; and

(xi) determine a blood pressure value from the time difference.

7. The system of claim 1, wherein both the first and second time-dependent physiological waveforms are selected from a group consisting of an optical waveform, an acoustic waveform, an ECG waveform, and a pressure waveform.

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

(x) calculate a time difference between a feature in the first time-dependent physiological waveform and a feature in the second time-dependent physiological waveform; and

(xi) determine a blood pressure value from the time difference.