Alarm system that processes both motion and vital signs using specific heuristic rules and thresholds
Inventors
McCOMBIE, Devin • Banet, Matt • Dhillon, Marshal • Moon, Jim
Assignees
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Publication Number
US-11918321-B2
Publication Date
2024-03-05
Expiration Date
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.
Core Innovation
The invention provides a body-worn hospitalized patient monitoring system for monitoring a plurality of hospitalized patients. Each body-worn monitoring system is uniquely associated with a patient and includes a PPG sensor, an ECG sensor, and at least two three-axis accelerometers configured to model motion, activity level, and arm height using three time-dependent accelerometer waveforms from each three-axis accelerometer. A microprocessor continuously receives time-dependent photoplethysmogram waveforms, time-dependent ECG waveforms, and three time-dependent accelerometer waveforms, and determines on a continuous basis a heart rate value, a blood pressure value, an SpO2 value, and a motion parameter indicative of patient posture and motion.
Alarm determination is performed by collectively processing the heart rate value, the blood pressure value, the SpO2 value, and the motion parameter to determine an alarm rule indicating whether or not the patient requires attention. The system combines continuous vital-sign sensing with motion/activity-state classification and uses modified alarm thresholds and overriding rules to suppress motion-artifact-induced false alarms. The motion heuristics condition alarm behavior on activity state, including rules that modify or ignore vital-sign thresholds during convulsing and falling and that apply modified assumptions for walking.
The system models motion, activity level, and arm height for a patient based on three time-dependent accelerometer waveforms from each three-axis accelerometer. The accelerometers are used to determine gravitational vectors and to derive arm height parameters that relate elbow height and wrist height to height-dependent arm height parameters, and the model uses a DC portion of accelerometer waveforms to obtain the relevant accelerometer geometry for the patient. The arm height parameters are used to compute a correction factor and to calibrate or relate pulse transit time to blood pressure using height-dependent pressure terms, and the description includes experimental PTT versus arm-height data to support the height-dependent calibration or relationship for blood pressure determination.
Posture determination is performed using chest accelerometer DC values to define torso coordinate axes and to determine angles between gravity and the coordinate axes. Angles are compared to posture thresholds to classify a torso posture state, and remaining angles are compared to classify posture among posture states. The description further addresses patient-specific calibration and left/right arm-side orientation handling in relation to posture and motion parameters and alarm generation.
Claims Coverage
The provided claim set includes one independent claim and one dependent claim. The inventive features center on multi-sensor body-worn data acquisition for modeling motion, activity level, and arm height; continuous determination of heart rate, blood pressure, SpO2, and a motion parameter; alarm rule generation by collectively processing those values; and hospital-networked remote monitoring with user-selectable patient views, including a dependent claim adding a patient-location map view.
Multi-patient body-worn sensing for vital signs, motion, activity level, and arm height
A system for monitoring a plurality of hospitalized patients comprising a plurality of body-worn monitoring systems uniquely associated with patients, each including a PPG sensor, an ECG sensor, and at least two three-axis accelerometers configured to enable the modeling of motion, activity level, and arm height for the patient based on three time-dependent accelerometer waveforms from each three-axis accelerometer, and a microprocessor receiving on a continuous basis time-dependent photoplethysmogram and ECG waveforms and three time-dependent accelerometer waveforms to determine continuously a heart rate value, a blood pressure value, an SpO2 value, and a motion parameter indicative of patient posture and motion.
Collective alarm-rule processing using vital signs and motion parameter
A microprocessor configured to determine an alarm rule indicating whether or not the patient requires attention by collectively processing the heart rate value, the blood pressure value, the SpO2 value, and the motion parameter.
Hospital wireless network with remote monitor patient-attention display in user-selectable views
Each body-worn monitoring system configured to communicate over a wireless network within the hospital, and a remote monitor configured to receive on a continuous basis for each patient the heart rate value, the blood pressure value, the SpO2 value, the patient posture and motion, and the alarm rule, and to display in a first user-selectable view the heart rate value, the blood pressure value, the SpO2 value, an icon indicating patient posture and motion, and an icon indicating whether or not the patient requires attention, and in a second user-selectable view the heart rate value, the blood pressure value, the SpO2 value, the icon indicating patient posture and motion, the icon indicating whether or not the patient requires attention, and the time-dependent ECG waveform for a single patient.
Patient location display in a third user-selectable view on a hospital-area map
The dependent system adds a third user-selectable view in which the remote monitor displays the heart rate value, the blood pressure value, and the SpO2 value together with icons indicating patient posture and motion and whether or not the patient requires attention, and further displays each patient’s location on a hospital-area map.
Across the independent claim, the core coverage is a multi-patient hospital monitoring system using body-worn PPG, ECG, and accelerometer sensing to compute heart rate, blood pressure, and SpO2 together with a motion parameter, followed by alarm-rule determination by collectively processing those values, and remote monitoring that presents user-selectable views including patient posture and motion icons and attention icons and, for a selected patient, the time-dependent ECG waveform.
Stated Advantages
Suppresses motion-artifact-induced false alarms by combining continuous vital-sign sensing with motion/activity-state classification and using modified alarm thresholds and overriding rules conditioned on activity state.
Digitizing waveforms and using digital immunity to motion artifacts.
Documented Applications
Monitoring a plurality of hospitalized patients with body-worn monitoring systems and hospital-based remote monitoring views for patient attention and for displaying physiological and ECG information.
Displaying patient status for a single patient using a remote monitor second user-selectable view that includes the time-dependent ECG waveform.
Displaying each hospitalized patient’s location on a hospital-area map using a remote monitor third user-selectable view.
Monitoring a plurality of hospitalized patients using body-worn monitoring systems and a remote monitor within a hospital.
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