Systems and methods to monitor repositioning of a patient
A patient monitoring system to help manage a patient that is at risk of forming one or more pressure ulcers is disclosed. The system includes a patient-worn wireless sensor that senses the patient's orientation and wirelessly transmits information indicative of the sensed orientation to a patient monitor. The patient monitor receives, stores, and processes the transmitted information. It also displays and transmits information indicative of the patient's orientation to help caregivers manage the patient's risk of formation of one or more pressure ulcers. The patient monitor detects patient turns from one position to another. The system can identify the present orientation of the patient and determine how long the patient has been in the present orientation. If the patient remains in an orientation beyond a predefined duration, the system can notify the patient and/or caretakers that the patient is due to be repositioned.
1. A system for monitoring an orientation of a patient to reduce a risk of the patient developing a pressure ulcer, the system comprising:
a sensor configured to attach to the patient, the sensor including an accelerometer, a processor, and a first wireless transceiver, said accelerometer configured to measure an acceleration of the patient with respect to a roll axis and a pitch axis, said roll axis corresponding to a longitudinal axis extending along a length of the patient's body and said pitch axis corresponding to an axis aligned with the patient's hips, said sensor configured to output a signal responsive to the acceleration measured by the accelerometer, said acceleration indicative of a possible change in the orientation of said patient when said sensor is worn by said patient; and
a patient monitor comprising a signal processor, a memory device, a storage device, and a second wireless transceiver, said second wireless transceiver configured to receive said signal from said first wireless transceiver of said sensor and said signal processor configured to process said received signal to determine whether said possible change corresponds to an actual change in said orientation and, when said actual change has occurred, said signal processor further configured to record a patient turn event, to compare said patient turn event with a patient turn protocol, and when said possible change is not said actual change and no patient turn event occurs according to the patient turn protocol, said patient monitor is configured to notify a caregiver of a patient turn protocol violation;
wherein said signal processor is configured to determine whether said possible change corresponds to said actual change by:
receiving a first set of information responsive to the acceleration of the patient with respect to the roll axis over a first time period;
receiving a second set of information responsive to the acceleration of the patient with respect to the pitch axis over the first time period;
processing said first and second sets of information responsive to the acceleration of the patient with respect to the roll axis and the pitch axis to form a time window of patient orientation history over the first time period, said time window comprising a first plurality of orientation values corresponding to the roll axis and a second plurality of orientation values corresponding to the pitch axis;
dividing said time window of patient orientation history into a plurality of segments, each of the plurality of segments comprising a portion of the first plurality of orientation values and a portion of the second plurality of orientation values;
determining, for each of the plurality of segments, a segment value indicative of said patient's orientation during the segment to reduce an impact of noise in the time window associated with false indications of patient turn events, wherein the segment value is a vector including a first component representative of the portion of the first plurality of orientation values that are within the segment and a second component representative of the portion of the second plurality of orientation values that are within the segment; and
determining a difference between each one of said plurality of segment values and another one of said plurality of segment values and comparing said difference to a threshold, wherein said signal processor is configured to record said patient turn event based at least on said comparison;
wherein said first component comprises a median of the portion of the first plurality of orientation values that are within the segment and wherein said second component comprises a median of the portion of the second plurality of orientation values that are within the segment, and wherein said medians are in units of degrees ranging from −180 degrees to +180 degrees.
2. The system of claim 1 , wherein said signal processor of said patient monitor is further configured to reset a patient orientation duration timer when said processor records said patient turn event.
3. The system of claim 1 , comprising a third wireless transceiver, said third wireless transceiver configured to receive said signal from said sensor and to transmit said signal to said patient monitor.
4. The system of claim 3 , comprising a power supply for said third wireless transceiver different from a power supply for said sensor or said patient monitor.
5. The system of claim 1 , wherein said sensor further comprises a gyroscope configured to measure an angular velocity of the patient with respect to the roll axis and the pitch axis.
6. The system of claim 1 , wherein said sensor further comprises an acoustic sensor.
7. The system of claim 1 , wherein said sensor further comprises a temperature sensor.
8. The system of claim 1 , wherein said sensor further comprises an ECG sensor.
9. The system of claim 1 , wherein said sensor further comprises one or more of an acoustic sensor, a temperature sensor, and an ECG sensor.
10. The system of claim 1 , wherein said patient monitor is further configured to determine measurements of one or more of the following parameters: an angular velocity, a magnetic field, a respiration rate, a temperature, an impedance value, a moisture value, an oximetry value and an electrocardiogram.
11. The system of claim 1 , wherein said determining the difference between each one of said plurality of segment values and another one of said plurality of segment values comprises determining a first difference between said first components of each one of said plurality of segment values and another one of said plurality of segment values and a second difference between said second components of each one of said plurality of segment values and another one of said plurality of segment values.
12. A method of determining a patient turn event based on a patient's recent orientation history with a patient-worn sensor, the patient-worn sensor comprising an accelerometer, a processor, and a first wireless transceiver, said method comprising:
receiving, with a patient monitor, a first set of acceleration data from the patient-worn sensor over a first time period, said first set of acceleration data responsive to a roll axis corresponding to a longitudinal axis extending along a length of the patient's body;
receiving, with the patient monitor, a second set of acceleration data from the patient-worn sensor over the first time period, said second set of acceleration data responsive to a pitch axis corresponding to an axis aligned with the patient's hips;
processing said first and second sets of acceleration data responsive to the acceleration of the patient with respect to the roll axis and the pitch axis over the first time period to form a time window of patient orientation history, said time window comprising a first plurality of orientation values corresponding to the roll axis and a second plurality of orientation values corresponding to the pitch axis;
dividing said time window into a plurality of segments to reduce an impact of noise in the time window associated with false indications of patient turn events, each of the plurality of segments comprising a portion of the first plurality of orientation values and a portion of the second plurality of orientation values;
determining, for each of the plurality of segments within said time window:
a segment vector, the segment vector comprising a first component and a second component, the first component being a median of the portion of the first plurality of orientation values within the segment, the second component being a median of the portion of the second plurality of orientation values within the segment;
determining differences between each one of the segment vectors of the plurality of segments and each of the other segment vectors of the plurality of segments; and
identifying the patient turn event based on comparisons of said differences with one or more thresholds.
13. The method of claim 12 , wherein the step of determining differences between each one of the segment vectors of the plurality of segments and each of the other segment vectors of the plurality of segments comprises determining:
differences between the first components of each of the segment vectors of the plurality of segments and the first components of each of the other segment vectors of the plurality of segments; and
differences between the second components of each of the segment vectors of the plurality of segments and the second components of each of the other segment vectors of the plurality of segments.
14. The method of claim 13 , wherein said identifying the patient turn event based on said comparisons of said differences with the one or more thresholds comprises:
comparing each of the differences between the first components of the segment vectors to a first threshold, said first threshold indicative of an orientation change about the roll axis; and
comparing each of the differences between the second components of the segment vectors to a second threshold, said second threshold indicative of an orientation change about the pitch axis.
15. The method of claim 14 , wherein the first threshold is 45 degrees.
16. The method of claim 15 , wherein the second threshold is 45 degrees.