METHOD FOR GENERATING ALARMS/ALERTS BASED ON A PATIENT'S POSTURE AND VITAL SIGNS

• US 20100298661A1
• 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 10,555,676 B2
• Time in Patent Office: Days
• US Class Current: 600/301
• 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 method for generating an alarm while 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;

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

(h) generating an alarm by processing at least one of the patient'"'"'s posture and a parameter resulting from a comparison of the vital sign to a predetermined alarm criteria, wherein the alarm is indicated by a variance of the vital sign relative to the predetermined alarm criteria and is regulated according to the patient'"'"'s posture.

2. The method of claim 1, wherein step (h) further comprises processing both the patient'"'"'s posture and a parameter resulting from the comparison of the vital sign to the predetermined alarm criteria to generate the alarm.

3. The method of claim 1, wherein step (h) further comprises generating the alarm in response to a change in the patient'"'"'s posture.

4. The method of claim 3, wherein step (h) further comprises generating the alarm if the patient'"'"'s posture is standing up.

5. The method of claim 3, wherein step (h) further comprises generating the alarm if the patient'"'"'s posture changes from lying down to one of sitting and standing up.

6. The method of claim 3, wherein step (h) further comprises generating the alarm if the patient'"'"'s posture changes from one of standing up and sitting to lying down.

7. The method of claim 1, wherein step (e) further comprises analyzing three time-dependent motion waveforms, each corresponding to a unique axis, to determine the vector.

8. The method of claim 7, wherein step (f) further comprises comparing the vector to a coordinate space defined by three positional vectors, each indicating an orientation of the motion-detecting sensor on the patient.

9. The method of claim 8, wherein a first positional vector corresponds to a vertical axis in the coordinate space, a second positional vector corresponds to a horizontal axis in the coordinate space, and the third positional vector corresponds to a normal axis extending normal to the patient'"'"'s chest.

10. The method of claim 8, wherein the posture parameter is an angle.

11. The method of claim 10, wherein step (f) further comprises comparing the vector to the coordinate space to determine the angle between the vector and at least one of the three positional vectors.

12. The method of claim 11, wherein step (f) further comprises comparing the vector to the coordinate space to determine the angle between the vector and a vector corresponding to a vertical axis, or a property of the angle between the vector and the vector corresponding to the vertical axis.

13. The method of claim 12, wherein step (g) further comprises comparing the angle to a threshold value that is substantially equivalent to 45 degrees, and wherein the patient'"'"'s posture is estimated to be upright if the angle is less than the threshold value.

14. The method of claim 12, wherein step (g) further comprises comparing the angle to a threshold value that is substantially equivalent to 45 degrees, and wherein the patient'"'"'s posture is estimated to be lying down if the angle is greater than the threshold value.

15. The method of claim 14, wherein step (f) further comprises comparing the vector to the coordinate space to determine the angle between the vector and a vector corresponding to a normal axis extending normal to the patient'"'"'s chest, or a property of the angle between the vector and the vector corresponding to a normal axis extending normal to the patient'"'"'s chest.

16. The method of claim 15, wherein step (g) further comprises comparing the angle to a threshold value that is substantially equivalent to 35 degrees, and wherein the patient'"'"'s posture is estimated to be supine if the angle is less than the threshold value.

17. The method of claim 15, wherein step (g) further comprises comparing the angle to a threshold value that is substantially equivalent to 135 degrees, and wherein the patient'"'"'s posture is estimated to be prone if the angle is greater than the threshold value.

18. The method of claim 14, wherein step (f) further comprises comparing the vector to the coordinate space to determine the angle between the vector and a vector corresponding to a horizontal axis, or a property of the angle between the vector and the vector corresponding to the horizontal axis.

19. The method of claim 18, wherein step (g) further comprises comparing the angle to a threshold value that is substantially equivalent to 90 degrees, and wherein the patient'"'"'s posture is estimated to be lying on a first side if the angle is less than the threshold value.

20. The method of claim 18, wherein step (g) further comprises comparing the angle to a threshold value that is substantially equivalent to 90 degrees, and wherein the patient'"'"'s posture is estimated to be lying on a side opposite the first side if the angle is greater than the threshold value.

21. The method of claim 1, wherein step (c) further comprises detecting a set of time-dependent motion waveforms with at least one motion-detecting sensor positioned on the patient'"'"'s chest.

22. The method of claim 1, where the at least one motion-detecting sensor is an accelerometer.

23. The method of claim 1, wherein step (d) further comprises processing the first and second time-dependent physiological waveforms to calculate a time difference between a feature in the first time-dependent physiological waveform and a feature in the second time-dependent physiological waveform.

24. The method of claim 23, wherein step (d) further comprises calculating a blood pressure from the time difference.

25. The method of claim 23, 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.

26. The method of claim 25, 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.

27. The method of claim 23, 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.

28. The method of claim 27, 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.

29. 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 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 detect a second time-dependent physiological waveform indicative of one or more contractile properties of the patient'"'"'s heart;

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

a first processing component configured to receive the time-dependent physiological and motion waveforms and determine therefrom;

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

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

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

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;

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;

detecting sets of time-dependent motion waveforms with at least two motion-detecting sensors positioned on locations selected from a forearm, upper arm, and a body location other than the forearm or upper arm of the patient, wherein each set of motion waveforms is indicative of motion of the location on the patient'"'"'s body to which it is affixed;

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

analyzing at least a portion of the sets of time-dependent motion waveforms with a motion-determining algorithm to determine if the patient is in an activity state selected from the group of resting, moving, sitting, standing, walking, running, falling, lying down, and convulsing; and

generating an alarm by processing the patient'"'"'s activity state and comparing the vital sign to a predetermined alarm criteria corresponding to the activity state.

31. A system for continuously monitoring a plurality of patients, the system comprising:

a patient monitor configured to be worn on the body of each of the plurality of patients, each patient monitor comprising;

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

at least two motion-detecting sensors positioned on locations selected from a forearm, upper arm, and a body location other than the forearm or upper arm of the patient, each of the motion-detecting sensors generating at least one motion waveform indicative of motion of a body location onto which the motion-detecting sensor is affixed;

a location sensor comprising a wireless component and a location processing component, the location processing component configured to receive a signal from the wireless component and process this signal to determine a physical location of the patient to which the location sensor is attached;

a processing component configured to receive the time-dependent physiological and motion waveforms and determine therefrom;

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

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

(iii) an alarm parameter calculated from the at least one of the vital sign and motion parameter; and

,

a wireless transceiver configured to wirelessly transmit the vital sign, motion parameter, location of the patient, and alarm parameter through a wireless system; and

,

a remote computer system comprising a display and an interface to the wireless system, the interface configured to receive from the wireless system a vital sign, motion parameter, location of the patient, and alarm parameter corresponding to each of the plurality of patients comprising a patient monitor, and the display configured to render a user interface that describes at least one of a vital sign, motion parameter, location of the patient, and alarm parameter for each patient of the plurality of patients comprising a patient monitor.

32. A system for continuously monitoring a patient, the system configured to be worn on the patient'"'"'s body and comprising:

an optical sensor comprising a first light source, a second light source, and a light detector, the optical sensor configured to detect a first time-dependent optical waveform from radiation generated by the first light source, and a second time-dependent optical waveform from radiation generated by the second light source, wherein both the first and second time-dependent optical waveforms are indicative of one or more contractile properties of the patient'"'"'s heart;

an electrical sensor comprising at least two electrodes and an electrical circuit, wherein each electrode is configured to attach to separate locations on the patient and measure an electrical signal, and the electrical circuit is configured to receive and process an electrical signal from each electrode to generate a first time-dependent electrical waveform indicative of one or more contractile properties of the patient'"'"'s heart and a second time-dependent electrical waveform indicative of a respiratory rate;

at least two motion-detecting sensors positioned on two separate locations on the body of the patient, the locations selected from a forearm, upper arm, chest, and hand of the patient, wherein each of the motion-detecting sensors generates at least one motion waveform indicative of motion of a body location onto which the motion-detecting sensor is affixed; and

a processing component configured to receive the first and second time-dependent optical waveforms, the first and second time-dependent electrical waveforms, and the motion waveforms, and determine therefrom;

(i) a time difference between a feature in one of the first and second time-dependent optical waveforms and a feature in one of the first and second electrical waveforms;

(ii) a blood pressure value calculated from the time difference;

iii) an SpO2 value calculated from both the first and second time-dependent optical waveforms;

(iii) a heart rate calculated from at least one of the time-dependent electrical waveforms;

(iv) a respiratory rate calculated from the second time-dependent electrical waveform;

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

(vi) an alarm parameter calculated from at least one of the blood pressure value, SpO2 value, heart rate, respiratory rate, and the motion parameter.

33. 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 worn on the patient'"'"'s body and configured 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 worn on the patient'"'"'s body and configured to detect a second time-dependent physiological waveform indicative of one or more contractile properties of the patient'"'"'s heart;

a first motion-detecting sensor positioned on a first location on the patient'"'"'s body, the motion-detecting sensor configured to generate a first set of motion waveforms indicative of motion of the location on the patient'"'"'s body to which it is affixed;

a processing component configured to be worn on the patient'"'"'s body, the processing component comprising;

a second motion-detecting sensor positioned on a second location on the patient'"'"'s body, the second motion-detecting sensor configured to generate a second set of motion waveforms indicative of motion of the location on the patient'"'"'s body to which the processing component is affixed; and

a microprocessor configured to receive the time-dependent physiological waveforms and at least of portion of the first and second set of motion waveforms and determine therefrom;

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

(ii) at least one motion parameter selected from the patient'"'"'s posture, activity state, and degree of motion, the motion parameter calculated by comparing at least one of the following components to a predetermined threshold value;

(a) a component calculated from a time-dependent waveform generated by the motion-detecting sensor;

(b) a component calculated from a frequency-dependent waveform calculated from the time-dependent waveform; and

(c) a component determined from an ROC curve; and

(iii) an alarm, determined by collectively processing the at least one vital sign and the motion parameter with an alarm algorithm.