Design Criteria

When designing a wearable monitor of any kind, many criteria must be considered in order for the device to work most effectively. Ideally, a wearable motion monitor with an aim on identifying triggers for a stroke should focus on the following criteria:

1.  Accurately collects and assesses data in a quantifiable manner
2.  Report data in an easily readable format for both the patient and the doctor/advisor
3.  Does not interfere with and is not impacted by the user’s daily routine.

In a vacuum, each of these criteria are fairly easy to consider. However, this is not so simple when factoring everything at the same time. An ideal device for stroke rehabilitation must fulfill all of the above in order to provide good quality-of-life for the patient, as well as accurate and available results. Balancing all four of these criteria is the central challenge of creating a wearable motion monitor, and a more optimized balance ensures that the patient is able to make a more effective and efficient recovery.

Criteria 1: Collecting Data

The most important function of a wearable stroke monitor is its ability to accurately record the data of a patient, which is used to analyze potential causes of their stroke, impairments from a previous stroke, and their degree of improvement over time. Motion monitors may be tasked with recording multiple different types of data, including:

• Pulse
• Gait speed
• Nerve signaling
• Pressure
• Force

All of these measurements come with their own unique units, sensors, and methods of measurement within the body (Chen, Y.-H). In order to create the most accurate and efficient monitor, the requirements for the specific type of data recorded must be considered. Factors such as the rate of measurement, unit of measurement, and the measured fluctuation of data are all key factors in assessing a patient’s statistics, and multiple different types of sensors are often required for a complete analysis. For example: a sensor intended to track a user’s progression through motion therapy via their leg must measure the force of the ground imparted on the patient’s foot, the acceleration of the leg, and the pressure between the foot and the ground (Chen, Y.-H).

The app contains logs of the patient’s past data, and has an option to collect data from the sensor. When a data request is sent, the app will attempt to connect with the device via Bluetooth, collecting its stored data and presenting it graphically and ordering by time. It’s imperative that actual calculations and displays of the data are carried out via an external application, as this reduces the amount of programming and circuitry needed within the monitor itself. By removing the calculations and display from the monitor, we can afford to make it less expensive to manufacture and also reduce the size of the monitor itself, enhancing its concealability and ease of use.

Criteria 2: Reporting Data

The device must motivate the patient to continue their stroke rehabilitation journey. The process of stroke recovery is arduous, and patients often require plentiful support from their loved ones. Aside from this aspect, the device should function to intrinsically motivate the patient by adapting to their preferences as to what variation of feedback they prefer. For instance, if a patient prefers auditory feedback, there should be auditory electronic positive affirmations from the device as to encourage further engagement with their rehabilitation exercises. Other forms of feedback for the device includes positive text messages to appeal to visual preferences, and vibration patterns to appeal to tactile preferences.

The method in which the resultant data from the device is evaluated must also be optimized. One such method that is used involves the assignment of each patient with a similar neurotypical individual of same age and sex (Demers). This data is used to project movement metrics that the stroke patient should strive to achieve. However, even if age and sex are matched to the stroke rehabilitation patient, the metrics that the patient should achieve may differ slightly. This is due to differences in body compositions, previous health conditions, and patient availability to engage with their recovery plan. In order to address these myriad complications, an algorithm can be created in order to produce movement metrics that align more accurately with what a patient should work to reach. In order to further encourage patient motivation, these metrics can be set to be daily or weekly goals to gamify the process of recovery.

Criteria 3: User Lifestyle

The user’s lifestyle must also be considered when designing a product of this nature. As the product will be attached to the user at all times for the period of therapy, it is important that the product itself and its components are both comfortable and easy to work with. Some of these specific details include, but are not limited to:

• Weight: The product should try to be as light as possible to reduce strain on the user.
• Material: The product should feel comfortable and satisfying to wear.
• Motion: The product should not limit a user’s range of motion, or strive to limit it as little as possible
• Size: The product should be concealable in some form if the patient chooses, either through size, color, or placement.

 

In terms of criteria that the patient will directly interact with, tracked movement involving the device should be intuitive and rewarding. The patient will be able to use the device remotely at their leisure. Consequently,  the device interface must be accessible, especially to the elderly who may lack technological knowledge.

Since the patient is expected wear the device at all times and engages with their prescribed movements throughout the entirety of the day, the device should not be cumbersome for the patient. More specifically, the device must interface comfortably with the patient. If the device breaks, there should be an obvious and painless method to remove and replace the device. The device should be light, to create further difficulty with the patient’s movement. To prevent allergic reactions to device materials, the device should be constructed from hypoallergenic materials: similarly, the device packaging should display the materials the device is constructed from to properly inform the user to avoid allergic reactions.

Another factor to consider as apart of the patient’s lifestyle is when the patient is required to perform their rehabilitation movements as recommended by their physician. An advantage of using a wearable device in tandem with a rehabilitation program is that the patient can largely determine when they would prefer to do their rehabilitation exercises. Accordingly, in order to minimize the external social perception of the rehabilitation device it is important for the device to measure passive movements as opposed to active movements while in public. Wearable medical devices that require passive movements are noted to contribute to the patient being less conspicuous than medical devices that require active movements. (Dunne, 2014) For instance, movements such as walking or going up stairs can be considered passive movements that can be tracked by the stroke rehabilitation device. While in public, the device itself should not mandate additional movement that would render the patient conspicuous to any extent that could discourage the patient from continuing to wear the device. While the patient’s rehabilitation program will contain active movements for the patient to push their capabilities of their impaired lower limb, these active movements can be performed at home. The patient will likely already struggle to perform some extent of basic mobility in public. To maximize patient comfort, and by extension time the patient spends wearing the device, active movements should be reserved for patient selected time intervals while still tracking passive patient movement in public as they go about their day.

 

Limitations and Challenges

While it is easy to assess each of the design criteria in a vacuum, combining all of them together is prone to cause friction. For example: Part of making a motion monitor smaller may include reducing the size of the display. However, this causes the display of the device to be less accessible. When improving one criteria, there is often an opposite reaction from another.

How do we remedy this?

• Further developing the components of the device can fulfill multiple criteria at once. If a sensor is made smaller, the device itself can become smaller without compromising readings.
• Inventing new ways of display: for instance, if a device is made smaller, rely on a different method of display, such as sound.
• Using multiple different methods of display or feedback at the same time can allow the sensor to do more things at once without compromising size.