Creating designs that measure impact

11 MARCH 2015

Inspired by element14’s ‘Sudden Impact’ Wearable Design Challenge, this is the second in a series of exclusive blog posts for MDT that will explore the challenges of creating wearable medical devices.

Author: Christian DeFeo, eSupplier and Innovation Manager, Newark element14

The Sudden Impact challenge is in full swing and our participants are continuing to support a multitude of different sports through a number of innovative device designs. Head injuries and internal trauma remain two of the most widely discussed topics amongst researchers and medical personnel, but how can design engineers measure the ‘impact’ of these injuries? How can ‘impact’ be defined and what are its limits? These are just some of the questions that our participants will need to answer before they even start trying to make their designs a reality.

Our Sudden Impact finalists come from all corners of the world and as such, one of their key tasks has been to ensure their designs meet their countries’ respective standards in defining and measuring injuries.
Challengers are quickly realising that before they can bring their ideas to life, their designs must be in line with scientific and medical regulations that ensure that all relayed diagnostics are accurate and unchanging – the latter being extremely important for the trainers and athletes who will be relying on the data from these handmade devices.
In other words, our design engineers need to make sure their solutions cannot provide users with false injury information; this information could lead to potentially serious consequences, particularly if an existing injury is not detected accurately.

Head Injury Criterion: Footballers and Skiers

German-born Hendrik Lipka’s design is targeted at skiers and footballers and has two key functions: monitoring an athlete’s heart rate during training and acting as a helmet-mounted impact monitor during competitions. Hendrik’s research for the device focused on the biological and medical sciences, and this is where he discovered the ‘Head Injury Criterion’, or ‘HIC’ as it is more commonly known. HIC is used to detect the effect and duration of acceleration and deceleration at the moment of impact with the head, and has become a popular way to test the durability and security of sports equipment and safety gear.
The HIC formula uses an acceleration curve to calculate an average acceleration during a specific period of time – this is usually 15ms but can range from as little as 3ms, all the way up to 36ms. A maximum value is then calculated using the overall time frame, in order to determine the impact of the force of acceleration to the head. Interestingly, different variables can be substituted into the formula to make it applicable to other parts of the body too. An example of a real life situation where the HIC formula could be used is to detect the sharp drop in acceleration when a footballer collides with a team player on the pitch.
However, while the HIC formula seems like a perfect fit for his design, Hendrik has admitted some difficulties with the theory. Analog Devices’ ADXL series accelerometer only captures 800 or 1600 measurements per second, making his preferred accuracy much more difficult to obtain. Ideally these measurements would occur every millisecond to better calculate sum totals in a specific time frame through simple multiplication and division.

As such, Hendrik’s main challenge is in programming his helmet to calculate acceleration fast and efficiently enough, without compromising on battery life.

Cumulative concussions and contact sports

Kas Lewis from Canada is another one of element14’s Sudden Impact finalists and proposed the idea of a multi-sport helmet that can monitor for heat strokes, heart attacks and concussions. While many helmets were suggested throughout the challenge, Kas’ stood out because of its ability to measure repeat injuries to the head, or ‘cumulative concussions’.
Although single impact injuries are thought to have a long lasting effect on the brain, it is generally agreed that cumulative concussions are far more dangerous as they do not allow the brain enough time to recover from one impact, before another follows. As such, the helmet Kas has designed is best suited to contact sports such as football, where injuries are rife and can have significant long-term consequences for the player.

Kas’ design will incorporate a temperature sensor to detect abnormal body temperatures, as well as two separate accelerometers to monitor the severity of individual concussions with a high degree of accuracy. The device will also be fully equipped with monitoring and reporting capabilities, using the CC3100 in conjunction with the MSP430F5529 to collect and upload real-time information to a cloud-based system such as Plot.ly.
However, like Hendrik, Kas faces a number of challenges as it is ‘still not fully clear in the scientific community how [the impact of cumulative concussions] should be measured’. Medical professionals have acknowledged that research is still ongoing in to how these traumas should be diagnosed and monitored.
When dealing with traditional concussions, we are aware of the main symptoms – such as memory loss, headaches – and the tools that can aid diagnostic testing – such as MRIs and X-rays. But there is not as of yet a clear set of characteristics of a cumulative concussion, therefore Kas needs to carefully consider whether simply monitoring the injury is sufficient.

The need for flexible designs

Designing technologies to meet the medical and health sectors’ criteria for impact and injury is an ongoing discussion amongst professionals and has been for many years. The challenges that Hendrik and Kas face are real examples of how these discussions need to happen if we are to enable engineers to tackle real-life problems with new and innovative designs.
However, until a universal medical consensus on a condition is reached, engineers’ designs need to be flexible and fluid, anticipating changes to medical standards that are as of yet unconfirmed. This is one of the difficult challenges that our Sudden Impact finalists’ designs will need to address and, in the next blog post, we will be exploring just how much this compromise is affecting the functionality of their devices.

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