Monitoring vital signs goes space-age
Fire departments, professional football teams and U.S. Army researchers are choosing ingestible and wearable telemetric sensors to wirelessly monitor the biometric data of humans working in harsh environments.
These telemetric sensors came to the forefront after the headline-making death of Minnesota Vikings lineman Korey Stringer on July 31, 2001, as a result of heat stroke, which occurs when a person’s body temperature rises to 106°F within 10 to 15 minutes, according to the Centers for Disease Control. It can lead to heart failure, permanent disability or even death, as seen in the Stringer case.
To prevent heat-related illnesses and loss of life, the Vikings adopted HQ’s CorTemp ingestible thermometer to record players’ core temperature before, during and after games. The vitamin-sized pill is a Class 2 medical device approved by the Food & Drug Administration, said Susan Smith, HQ’s marketing and sales manager. It transmits core body temperature readings in correlation with heart rate data at 262 kHz using near-field magnetic communications and offers an 18- to 24-inch transmission range. The data are collected by a recorder designed to be carried on the body or used as a hand-held reader to measure core body temperature within ± 0.1° C and heart rate within ± 0.1 beats per minute, Smith said.
The Philadelphia Eagles and the Jacksonville Jaguars also use CorTemp as a tool to track players’ core temperatures. Mike Ryan, head athletic trainer and physical therapist for the Jaguars, said the team has used the pill since 2004 to monitor players’ health during training camps and regular season games. Players spend approximately five hours per day running drills in ALLTEL Stadium during the July to August pre-season alone, leading to a risk for heat stroke, he said.
“In Florida we have 100 days of heat index over 100 degrees, and most of those are in the summer months,” he said. “The heat and humidity in Florida is obviously very difficult on players.”
Ryan scans each pill with the reader, registers them by player-number and then distributes the pills to players an hour before the team hits the field. His staff uses the hand-held reader to check players often because early intervention helps determine if players need to be sent to the Chill Zone, a large tented area with air conditioners and fans, Ryan said.
“It’s a way to get them out of the sun, cool them down, push fluids and put them in an ice bath, if necessary,” he said.
According to Michael F. Bergeron at the Department of Physical Therapy for the School of Allied Health Sciences Medical College of Georgia and the principle investigator on a CorTemp case study, the pill is effective but warned practitioners should provide at least a two-hour window before taking readings because the speed at which each individual’s digestive tract passes the pill through the stomach differs. He also recommended monitors are within 3 feet of players for accurate readings.
“Don’t buy every reading you get,” he said. “Sometimes I will get a 120°F reading, and I know I have to change my orientation around a player.”
NFL teams aren’t the only ones concerned with gauging core temperatures. The Victoria, Canada, Fire Department currently depends on an on-scene ambulance crew to take firefighters’ temperatures by ear before and after incidents to determine the cool-down time required before a firefighter can resume his or her duties. However, the results differ from a person’s true core temperature, making an ingestible sensor ideal for accurate readings, said Victoria Fire Department Assistant Chief Scott Woodburn.
On April 20, in conjunction with the University of Victoria, the fire department field-tested a different core temperature system, MiniMitter Respironics’ VitalSense Monitor and its ingestible capsule, on a select group of new academy cadets running live fire and rescue drills. The capsule contains a sensor that sends data via a low-power radio frequency transmission to the monitor, which can receive transmissions from multiple, miniature, wireless temperature sensors, according to the company.
“We found the VitalSense to be much more reliable and less temperamental to use,” said Lynneth Wolski, a University of Victoria professor of physical education who oversaw the drill. The system let her team simultaneously measure all components of physiological strain, she said.
The capsule was administered 20 minutes prior to the drills, Woodburn said. Selected cadets wore the recorders in the inside pocket of their bunker-gear jackets to wirelessly capture core temperature readings, while others were scanned using the device as a hand-held reader. The data were later downloaded to a PC and analyzed for heat exposure — which over time can lead to dire consequences, he said.
“A firefighter that’s overheated once, twice or more per year may have heart problems later in life, specifically heart attacks,” he said.
Considering approximately 45% of all firefighter on-duty deaths in the last 15 years were attributed to heart attacks, according to a report by the U.S. Fire Administration and the National Fire Protection Association, the sensor may help prevent long-term, heart-health risks, Woodburn said.
However, New York City Fire Department Chief Robert Ingram said using the pill for widespread deployment in the field is not realistic. Few departments check the temperature of firefighters pre- and post-incident due to time and personnel restraints, he said. When life is at risk, firefighter teams, especially those short on personnel, don’t have the time to distribute a pill and record temperature data, or do it consistently enough to be of value.
“The technology needs to transmit the data … automatically [to a command board] without having to have the personnel do it, or to slow down people from performing their life-saving actions,” he said.
The U.S. Army also is grappling with whether the widespread deployment of core temperature, telemetric sensors in the field is practical. Major William Latzka of the U.S. Army’s Research Institute of Environmental Medicine field-tested its prototype Warfighter Physiological Status Monitoring (WPSM) solution on personnel in May and June 2006. The wearable system consists of six components with imbedded sensors capable of concurrently transmitting physiological data, such as heart rate, fluid intake and movement. However, the system is currently being used only in non-combat drills for research purposes because of costs and availability, Latzka said.
The WPSM’s sensors play multiple roles. They can track a soldier’s location, monitor physiological signs, check man-down status and transmit the data to a transceiver latched to the subject’s belt. For example, the life-sign detection system is a 1 lb. chest belt that monitors heart rate, respiration and body position. The data it accumulates are transmitted to the transceiver, and then are sent to a portable radio or PDA. The information is transmitted over a range of one-half mile to two miles — depending on the radio — to a medic’s hand-held that illustrates the soldier’s health status: green (okay), yellow (look), red (look now), blue (unknown) or gray (absence of life signs over five minutes). It was developed to reduce combat mortality by wirelessly transmitting medical situational awareness data about soldiers’ health to hand-held devices or two-way radios, Latzka said.
“It’ll give medics a tool to assess the situation from a distance,” he said.
The data are transmitted over a low frequency to prevent interception, in order to protect soldiers’ locations on the battlefield, according to Latzka. However, the technology is adaptable.
“A lot of these things can be transmitted via Bluetooth, Wi-Fi or ZigBee to a receiver or to anything that can receive a Wi-Fi signal,” he said.
As with any new technology, cost and staff resources are issues. Few fire departments have budgets large enough for the sensors to be used for each and every firefighter responding to an incident, Woodburn said. Each CorTemp pill used by NFL teams costs an average of $30, Smith said. Data recorders from both CorTemp and MiniMitter Respironics average around $2000. And the U.S. Army’s life-sign detection system, only one part of the six-piece WPSM system, costs about $600 per unit.
“The costs are just too prohibitive to have one for every [first responder] out there,” Woodburn said.
