Patent Application
20060270949
The invention is in the field of monitoring methods and apparatus for ambulatory subjects.
In accordance with the statistics in some countries the population is ageing and it is projected that by the year 2051 those aged 65 years and over will constitute approximately one quarter of the total population.
Falls are one of the greatest risks facing this group and in the over 65 age group, accidents are the fifth highest cause of death, and approximately two thirds of accidents are falls. Falls also account for more than half of all injury-related hospital admissions in this group.
Falls and collapse are associated with functional decline, leading to disability, dependence and nursing home placement, even in cases where the fall did not cause injury. Up to half of all older people who fall or collapse without suffering injuries are unable to get up without assistance.
In the case of the elderly or infirm persons living alone, an inability to rise can lead to serious consequences of extreme distress, muscle damage, pneumonia, pressure sores, dehydration, hypothermia and mortality. Many such people become afraid and so restrict their daily activities and exercise, which in turn leads to a further reduction in health and wellbeing.
Some personal alarm systems provide such venerable people with an emergency button however this technology is rendered ineffective if the person is unable to press the button due to unconsciousness, injury or immobility.
Furthermore the ageing population and the related increasing prevalence of chronic disease are placing a large burden on the hospital system. There is a need to provide alternatives to hospital care for these patients.
One of the most important considerations in independent living is functional status; that is, the ability of a person to carry out routine daily tasks in his or her normal (home) environment. There are many different measurements that provide indication of functional status. These include, but are not limited to, the time taken to rise from sifting, postural sway when standing, walking speed, and step rate variability. Traditionally, these parameters have been measured in a dedicated laboratory in an expensive, time-consuming procedure, or they have been measured subjectively in the clinic or home using clinician observation or patient recall.
It is therefore an object of the invention to overcome some of the problems of the prior art or at least to provide a useful alternative.
One aspect of a preferred embodiment of the invention provides a monitoring apparatus for an ambulatory subject including:
Preferably the at least one designated performance threshold is determined by the processing unit from a plurality of previously determined instant ambulatory performance indicia.
Preferably the at least one event is initiated only if the determined instant ambulatory performance indicia is below or above the determined at least one designated performance threshold for a designated period of time.
Preferably the designated first period of time is determined from a plurality of previously determined instant ambulatory performance indicia.
Preferably the accelerometer simultaneously determines the acceleration of the subject in three orthogonal directions.
Preferably the portable monitor is configured to be mounted on an upright ambulatory such that one of the three orthogonal directions is in a vertical direction or within a designated angle of the vertical direction.
Preferably an initiated event is communicated by the apparatus to the remote receiver by wireless communication.
In another embodiment it is also preferred:
It is also further preferred:
Another aspect of the invention provides a method of monitoring an ambulatory subject including:
Preferably the at least one designated performance threshold is determined from a plurality of previously determined instant performance indicia, and the designated performance threshold can responsively and cooperatively adapt to statistical changes in previously determined instant performance indicia over time.
Preferably the event is initiated only if the determined instant ambulatory performance indicia is below or above the determined at least one designated performance threshold for a designated period of time.
Another aspect of the invention provides a monitoring apparatus for an ambulatory subject including:
In this aspect of the invention it is preferred:
Preferably the accelerometer simultaneously determines the acceleration of the subject in three orthogonal directions.
Preferably the portable monitor is mounted on an upright subject in an orientation so that one of the three orthogonal directions is in a vertical direction or within a designated angle of the vertical direction.
In another aspect the invention provides a method for detecting a person's inability to rise after a fall, collapse or other adverse event using a triaxial accelerometer included in a personal wearable ambulatory monitoring device. The first part of the procedure involves the detection of an inability to rise caused by a fall event. The first step in the method is sampling an output from the triaxial accelerometer that is indicative of body acceleration and body angle. The next step is to determine whether a fall has taken place by comparing the magnitude of the acceleration vector to an acceleration magnitude threshold for a period equal to a time duration threshold to determine the presence of an abnormal acceleration. If an abnormal acceleration is detected then the body angle is compared to a threshold value to identify a body state indicative of lying. A subsequent absence of movement is detected by comparing the magnitude of the acceleration vector to a second acceleration magnitude threshold. The second part of the procedure involves the detection of an inability to rise due to collapse or other adverse event. The first step in the method is sampling an output from the triaxial accelerometer that is indicative of body acceleration and body angle. The next step is to identify an inability to rise by comparing the magnitude of the acceleration vector to an acceleration magnitude threshold for a period equal to a time duration threshold to determine the absence of a normal amount of movement.
In another aspect of the invention it provides a method for monitoring a person's movement to detect an inability to rise due to a fall through using a triaxial accelerometer included in a personal monitoring system that consists of a receiver unit and a personal monitoring device, which communicates with the receiver units by means of wireless communication, and which is configured to be carried on the person and containing the triaxial accelerometer, including the steps of:
Preferably a severe fall is signalled via a communications network when a severe fall has taken place.
In another aspect the invention provides a method for monitoring a person's movement to detect an inability to rise due to a collapse or other adverse event using a triaxial accelerometer included in a personal monitoring system that consists of a receiver unit and a personal monitoring device, which communicates with the receiver units by means of wireless communication, and which is configured to be carried on the person and containing the triaxial accelerometer, including the steps of:
Preferably the method further includes the step of signalling the extended absence of movement via a communications network when no movement has occurred for the specified period.
In another aspect the invention provides longitudinal tracking of clinically significant parameters to detect early changes in functional status including but not limited to the onset of near falls and stumbles, clinically significant parameters are extracted from the data obtained from the triaxial accelerometer and stored in a database, deviations from the statistical normal values for each parameter are flagged, an alert is generated each time that a deviation is flagged, long term trends in the parameters are also flagged, and when a trend is detected in a parameter that exceeds a change threshold an alert is generated.
The invention will now be described by way of example only with reference to the following drawings in which:
It is to be noted where possible features common to the various embodiments illustrated in the figures are referred to in each drawing by a respective common feature number.
A preferred embodiment of a monitoring apparatus 1 for an ambulatory subject 2 in accordance with the invention will be described with general reference to FIGS. 1 to 6, and for description purposes the preferred embodiment will be described in the context of subject 2 being monitored by carer 11 being remote from subject 2, but in cooperative operable communication with apparatus 1 via receiver 5.
Apparatus 1 includes portable monitor 3 mountable on subject 2, mounted for example on belt 9 worn by subject 2 by a belt clip attached (not shown) to monitor 3.
Monitor 3 includes a three dimensional accelerometer to measure simultaneously instant acceleration vectors 4ax, 4ay, 4az of subject 2 in three different orthogonal directions X, Y, Z as shown in
Monitor 3 is arranged in relation to its mounting belt clip (not shown) so that its sensitive measurement axis in direction Z is orientated to be in a vertical direction 6 as shown in
Apparatus 1 further includes data processing and storage unit 7 for processing the measured simultaneous instant acceleration vectors 4ax 4ay 4az at different instants in time, initiating events for the attention of the carer according to the determinations of the data processing. Data processing and storage unit 7 also logs and stores the processed data for use and or reference by apparatus 1 and or carer 11 as required.
Events that are initiated by data processing and storage unit 7 are communicated to carer 11 for attention by data processing and storage unit 7 via the operationally cooperative pair of transmitter 10 and receiver 5. In this way remote supervisory monitoring of the ambulatory status and performance of subject 2 can be achieved by carer 11.
Data processing and storage unit 7 in
While the communication between data processing and storage unit 7 and remote receiver 5 are shown in
In another embodiment, monitor 3 identifies the methods of transmission that are available from its current location to data processing and storage unit 7. These may include, but are not limited to wireless network protocols, and mobile telephony protocols. The monitor 3 then selects the most appropriate method of transmission and transmits the data to the data processing and storage unit 7 using this method. If no method of transmission is available then the data are retained in monitor 3 unit until a method of transmission becomes available.
In another embodiment monitor 3 may also include a geographical positioning system (GPS) and in the case of an event being initiated the GPS coordinates of monitor 3 can be communicated to receiver 5 with the event which provides the location of subject 2.
Data processing and storage unit 7 includes a suite of data processing models (generally not shown) each processing model representative of a different ambulatory performance indicia of interest to carer 11 for the proper remote supervisory ambulatory monitoring of subject 2.
The data input in to each of the processing models is from the instant acceleration vectors 4ax, 4ay, 4az representative of the movement dynamics of subject 2 measured by portable monitor 3. The processing model inputs may be one vector 4ax, 4ay, 4az component or a combination of vector 4ax, 4ay, 4az components.
Other inputs to the processing models include inputs calculated by the processing models themselves from one or more vector 4ax, 4ay, 4i az component inputs. Such calculated processing model inputs include calculated performance threshold magnitudes for the ambulatory performance indicia, calculated instant body angle Θ.
An output of each processing model is one instant ambulatory performance indicia of subject 2 determined from the instant acceleration vectors 4ax, 4ay, 4az and the requirements of the processing model.
The calculated instant ambulatory performance indicia is logged and stored in data processing and storage unit 7 for further use and or reference by apparatus 1 and or carer 11 as required.
Another output of each processing model is calculated performance threshold magnitudes for the corresponding ambulatory performance indicia.
Such performance threshold magnitudes are calculated from the ambulatory performance indicia logged and stored during the absence of adverse events and the ambulatory performance indicia logged and stored provide a convenient and in-situ reference to calculate suitable performance threshold magnitudes for the ambulatory performance indicia. Such performance threshold magnitude calculations maybe based on for example, statistical techniques like data averaging by calculating root means square values of sampled historical data. The performance threshold magnitude calculations for a specific processing model is done by the processing model itself based on ambulatory performance indicia determined by the model itself.
The performance threshold magnitudes for the ambulatory performance indicia once calculated are then used as calculated inputs into the respective processing model to provide a reference to the processing model to initiate an event which is another calculated type output of the processing model.
An event is initiated when the instant ambulatory performance indicia is above or below the respective threshold for a designated period of time, which may be one instant or longer, as required by the processing model. The initiated event if required by the processing model is then communicated by apparatus 1 to carer 11 for attention.
Furthermore the processing model is adapted so that the performance threshold magnitudes inputted to the processing model are updated by the processing model itself as the calculated thresholds magnitudes vary with time. In this way the threshold magnitudes used by the processing model adapt to the longer term ambulatory performance changes in subject 2 which are reflected in the changes in the calculated threshold magnitudes over time.
Of course the apparatus 1 provides for performance threshold magnitudes to be inputted by human intervention into the processing model as required.
A calculated output of the processing model is the calculated instant body angle Θ of subject 2 shown in
The calculated instant body angle Θ of subject 2 is useful parameter and is used as a calculated input in the processing model to help discriminate between different ambulatory activities, subject dispositions, and transitions between different dispositions.
The instant body angle Θ of subject 2 as shown in
By way of example, one useful ambulatory performance indicia of subject 2 of interest to carer 11 would be whether subject 2 indicates an absence of normal movement for a prolonged period of time which can be indicative of an inability of subject 2 to rise due to some adverse event. A schematic model of this is illustrated in a general way in
The ambulatory performance indicia may be characterised by designating an acceleration threshold magnitude which is representative of a minimum expected level of movement in subject 2 under non adverse or normal conditions, for example during sleep.
In this example the instant magnitude of the sum of the instant acceleration vectors 4ax, 4ay, 4az, is measured my monitor 3 and the root mean square value of the instant magnitude is calculated every minute and compared to the designated acceleration threshold magnitude. If the root means square value of the instant magnitude remains below the designated acceleration threshold magnitude for a designated period of time, for example 6 hours then this state of affairs would be of concern to carer 11 and consequently an event is initiated by the apparatus 1 representative of this state of affairs and communicated to carer 11 for their attention and or action as required.
The designated acceleration threshold magnitude may be set by a reference to previous instant acceleration vector 4ax, 4ay, 4az data that has been logged and stored for subject 2 gathered during specific sleep tasks given to subject 2 under non adverse conditions, or gathered from subject 2 normal sleeping routine.
That is for example the root mean square of the instant magnitude of the sum of the instant acceleration vectors 4ax, 4ay, 4az is calculated over a period during which subject 2 is known to be in normal sleep, and that root mean square value is used as the designated acceleration threshold magnitude in the processing model for the ambulatory performance indicia of interest.
Preferably the designated acceleration threshold magnitude in the processing model is adapted to contingently vary over time as the calculated root mean square of the instant magnitude of the sum of the instant acceleration vectors 4ax, 4ay, 4az value during normal sleep changes over time as the normal sleeping patterns of movements of subject 2 changes.
In this way the processing model is adaptive to the changing sleeping conditions of subject 2 but can discriminate relatively short term variances which may indicate an adverse event such as an absence of normal movement for a prolonged period of time which can be indicative of subject 2 inability to rise due to the adverse event.
By way of another example, another useful ambulatory performance indicia of subject 2 of interest to carer 11 would be whether subject 2 fails to get up after an abnormally high movement which can be indicative of subject 2 inability to rise after a severe fall or collapse. A schematic model of this is illustrated in a general way in
The ambulatory performance indicia may be characterised by designating several threshold magnitudes.
A first acceleration threshold magnitude is designated which is representative of a minimum expected level of movement in subject 2 under non adverse conditions for when subject 2 is going from a disposition of lying down to a disposition of getting up.
A second acceleration threshold magnitude is designated which is representative of a maximum expected level of movement in subject 2 under non adverse conditions for when subject 2 is going from a disposition of being upright to a disposition of lying down. For example a nominal value maybe 1.8 g where g is the acceleration due to gravity, approx. 9.81 m.s−2.
Both these thresholds may be set by a reference to previous instant acceleration vector 4ax, 4ay, 4az data that has been logged and stored for subject 2 gathered during specific getting up lying, down tasks given to subject 2 under non adverse conditions, or gathered from subject 2 normal daily routine.
A body angle threshold is designated where for convenient reference the body angle Θ as shown in
The body angle threshold being representative of an angle when subject 2 is considered to no longer be upright, for example a body angle in excess of 60 degrees (form the vertical) may be deemed to be no longer upright.
In this example the sum of the simultaneously determined instant acceleration vectors 4ax, 4ay, 4az are processed into an instantaneous polar acceleration vector with polar coordinates and the magnitude of this polar acceleration vector is compared to the second acceleration threshold magnitude.
If the magnitude of this instant polar acceleration vector is greater than the second acceleration threshold magnitude for a minimum designated period of time then an abnormally large acceleration has been detected. In that case calculate the instant body angle Θ of subject 2 from the determined instant acceleration vectors 4ax, 4ay, 4az, as described previously herein.
If the body angle body angle Θ of subject 2 is less than the designated body angle threshold then the previously detected abnormally large acceleration is deemed to have been attributable to a stumble or knock rather than a potential fall.
However if the instant body angle body angle Θ of subject 2 is more than the designated body angle threshold then the previously detected abnormally large acceleration is deemed to have been attributable to a fall and if the instant body angle body angle Θ of subject 2 remains more than the designated body angle threshold for more than a minimum designated period of time, then it is deemed that subject 2 is unable to get up unaided from the laying disposition perhaps a result of a debilitating fall, and a corresponding event is communicated to the carer 11 for attention.
However if the if the instant body angle body angle Θ of subject 2 does not remain more than the designated body angle threshold for more than a minimum designated period of time, then it is deemed that subject 2 was able to get up from the laying disposition and immediate assistance may not be required.
In a preferred alternative after the fall has been determined if the magnitude of the instant polar acceleration vector remains below the designated first acceleration threshold magnitude for a minimum designated period of time, then it is deemed that subject 2 is unable to get up unaided from the laying disposition perhaps a result of a debilitating fall, and a corresponding event is communicated to the carer 11 for attention.
By way of another example, other useful ambulatory performance indicia of subject 2 of interest to carer 11 would be indicia which are representative of the functional status of subject 2. Advantageously monitoring apparatus 1 provides for the longitudinally monitoring of the functional status of subject 2 with automated alarm generation when deterioration in functional status of subject 1 is detected.
For example movements such as sitting down into a chair, rising from a chair, lying down, standing up from lying and walking are all important for basic assessment of functional status. Additional or different movements may be monitored if they provide useful information relevant to a particular subject. As an example, monitoring tremor may be useful if subject 2 suffers from Parkinson's disease.
Relevant ambulatory performance indicia to these activities can be determined from the data provided by monitor 3 using modelling techniques. However before these performance indicia can be determined from the determined instant acceleration vectors 4ax, 4ay, 4z, the subject's movement must be identified and classified to determine which model or algorithm can be applied to determine the ambulatory performance indicia.
Whether the subject 2 is engaged in activity or rest ca be determined from the instant acceleration vectors 4ax, 4ay, 4az, for example by sampling the magnitude of the acceleration vectors 4ax, 4ay, 4az, at 40 Hz and then filtering the measured instant acceleration vectors 4ax, 4ay, 4az samples with a high pass filter with a 3 dB cut-off between 0.1 and 0.5 Hz. The resultant magnitude of this filtered sample is representative of whether subject 2 is engaged in activity or is at rest. The algorithm disclosed by Mathie et al. which is incorporated herein by reference [Mathie, M. J., Coster, A. C. F., Lovell, N. H. and Celler, B. G. (2003). Detection of daily physical activities using a triaxial accelerometer, Medical and Biological Engineering and Computing] may be used for this purpose.
Once movements are identified, movement relevant performance indicia sensitive to functional status of subject 2 can be determined from the determined instant acceleration vectors 4ax, 4ay, 4az by the appropriate corresponding algorithms and models.
For example:
In addition, general measures of movement, such as metabolic energy expenditure, can also be computed from the signals obtained from the triaxial accelerometer as metabolic energy expenditure is linearly related to the sum of the integrals of the magnitudes of the three orthogonal acceleration signals.
The data from the monitor 1 is transmitted to data processing and storage unit 7 and the sensitive relevant movement performance indicia are stored. These indicia are tracked longitudinally. Each time new data are received the data processing and storage unit 7 compares the new data to the existing data.
The data processing and storage unit 7 also examines the time-trend produced by the pre-existing data and the new data for example as illustrated in
The generated alarm is communicated to a carer 11, clinician, emergency call centre, and/or to the subject 2 using an appropriate telecommunications technology, including, but not limited to, telephone, facsimile, email, text message system on mobile telephone network, or an Internet alert message.
The threshold and alarm values are set so that genuine deterioration in functional ability is detected. The intent is to detect deterioration early in the process so that preventative interventions can occur to prevent morbidity. The threshold values are subject 2 specific.
During the first few weeks of use of the apparatus 1 by subject 2 the alarms are de-activated and the thresholds automatically adapt, based on the data obtained from subject 2. Following this, the thresholds are fixed by the apparatus 1, although they can still be changed manually and the alarms are enabled.
In another preferred embodiment of the invention the subect wears a triaxial accelerometer on the waist and data are sampled from the triaxial accelerometer by a microprocessor in the monitoring device and stored in a buffer in the monitoring device and the data are processed according to process 1 and process 2 following and illustrated in (
Process 1
In these embodiments alerts and alarms preferably are raised in the following manner:
The invention has been described by way of example only with reference to preferred embodiments which is not intended to introduce limitations on the scope of the invention. It will be appreciated by persons skilled in the art that alternative embodiments exist even though they may not have been described herein which remain within the scope and spirit of the invention as broadly described herein.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2003904336 | Aug 2003 | AU | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/AU04/01081 | 8/13/2004 | WO | 2/15/2006 |
| Number | Date | Country | |
|---|---|---|---|
| 60514969 | Oct 2003 | US |
