Preventing Heat Stroke

FAYETTEVILLE, Ark. — Biological engineering students at the University of Arkansas have developed a wireless biosensor that can accurately record and monitor a football player’s body temperature in real time while the player is active. The prototype designed by students in the College of Engineering contributes to research into a commercial product that could prevent death due to heat stroke.

“Deaths due to heat stroke are preventable with new technology,” said Tom Costello, associate professor of biological and agricultural engineering. “Trainers and coaches on the sideline need to know whose body temperature is creeping up there (to a dangerous level). Once you have that information, you can pull the player off the field, hydrate, and give the body a chance to lose some of that heat and cool down.”

Matt Graham, left, and John Leach

For their senior design project, Costello’s students -- Matt Graham, John Leach and James McCarty -- designed and built a system prototype that, with modifications, could provide potentially life-saving information to coaches and trainers. The system wirelessly gathers and monitors body temperature and communicates information on many players in real time. To the player practicing or participating in a game, the system would be transparent in that it would not compromise safety or affect comfort and performance.

The complete system includes a thermocouple temperature sensor, a transmitter, two amplifiers and a base-station receiver connected to a laptop with user-interface software. As part of the project, Graham, Leach and McCarty exhaustively researched each component to find commercial products that were compatible with each other and most appropriate for their design. For example, they considered many types of sensors -- thermistors, infrared sensors and liquid crystal thermometry -- before settling on thermocouples, which they found to be superior in response time, size, durability, expense and quality of data produced.

The students embedded the wireless system in a Schutt football helmet, which was loaned by the UA Men’s Athletics Department. The sensor adheres to a dense pad, which touches the surface of the player’s forehead and records the body’s temperature from the temporal artery. The sensor sends an analog signal to the transmitter, which converts the signal into digital data. The amplifiers increase voltage from the sensor to enable it to provide linear, higher-resolution data, which allows the researchers to measure temperature within a tenth of a degree Fahrenheit, the medical industry standard.

The connected components communicate with a base-station receiver, which transfers data into a laptop computer. The system has a transmission distance of approximately 1,000 feet, which would work in the largest football stadiums.

User-friendly software provides basic information that can be viewed in raw form or graphic format. From the software’s main page, each player’s name serves as a link to a reference page that includes heat stress notes and a history chart. This page also includes buttons that enable the user to set a player’s baseline temperature and changes in threshold temperature. The software allows the user to monitor temperatures of many players simultaneously. Most importantly, based on each player’s threshold, a temperature-alert page automatically pops up and supercedes all other windows if a player has reached his threshold.

Graham said software changes are easy and could facilitate many types of communication. For example, if a trainer or support person is not available to monitor the software, the alert page could be programmed to sound an alarm, call a cell phone or send a text message.  

 Supervised by Costello, the students shepherded their project through many design iterations and rigorously tested the final prototype on subjects in a resting position and during physical exertion and exercise. In the latter tests, subjects donned the helmet and ran one mile on a level surface in an indoor track facility. Temperatures gathered by the prototype during the exercise phase were compared to oral, tympanic membrane and temporal artery readings immediately after the subject stopped running. The system recorded accurate temperature readings in real time while subjects were running. The researchers did not test the system in a helmet-impact environment.

The students won second place at the Open Gunlogson National Student Environmental Design Competition in Portland, Ore., July 10.  The event was part of the annual international meeting of the American Society of Agricultural and Biological Engineers. Only the top three teams from schools nationwide were invited to present their designs.

Each year, heat stroke claims the life of at least one high school, collegiate or professional football player. Formal practices hadn’t even begun this year when a 15-year-old student in Rockdale County, Ga., died as a result of heat stroke following a voluntary workout in preparation for the start of the football season. The problem is that coaches, trainers and the players themselves do not know when the body’s core temperature has reached a critical threshold, despite physiological signs such as dizziness and blurred vision.

Heat exhaustion can occur when internal body temperature increases to 100.4 degrees; if it reaches 104.9 degrees, a person may suffer a potentially fatal heat stroke. Football players are especially vulnerable to heat exhaustion and stroke for several reasons. Their bodies struggle to cool down because they are practicing in temperatures that are as hot as or hotter than the body’s temperature. Protective gear, especially helmets -- the human body releases 60 percent of its heat though the head -- prevents the body from efficiently releasing heat so it can cool down.