Advanced Rescue Technology, October/November 2003
Thermal Imaging: It’s Not Just for Firefighting
By Jonathan Bastian
Bear with us and imagine, if you will: it’s about 03:00. Your ambulance just got back into quarters after another busy Saturday night. You and your partner are just hoping for a few hours of shut-eye before the end of your shift.
But, it’s not to be: you get toned out for yet another run. The dispatcher sends you and an engine company to a motor vehicle accident on the Bypass. This high-speed divided highway claims more lives than any other road in your area. As your driver starts up the ambulance, you think back on all the wrecks you’ve worked on this one road. Many of them involved severe injuries, extrications and fatalities, all due to curves, culverts and drivers’ carelessness.
About four minutes later, you arrive at the location that dispatch gave you. Yet, there is no car wreck. You and the police stand near the side of the road looking around, trying to determine where it could be. The dispatcher noted that the caller was specific: he saw the car lose control, cross the median and roll over right by this exit. You and the officers see and hear nothing that indicates a nearby accident.
Suddenly, the late-shift brain fog lifts for a split second, and you
ask the engine company officer about his thermal imager. He grabs it
out of the cab and turns it on. As you walk with the lieutenant along
the side of the road, he points down into a culvert, trying to show
you where he has found a large object emitting a lot of heat. It is
not visible from the road, due to the darkness and some bushes. As you
and your partner work your way down into the culvert, you find that
you’ve located the accident, and you immediately begin treating
the unconscious driver inside. The victim is alive, with some lacerations
and contusions. The extrication goes without difficulty, and the patient
is packaged and transported without incident.
You are accustomed to using technology that helps you assess and treat a patient; for the first time, technology has helped you find a patient.
What is a Thermal Imager?
A thermal imager (TI) is a device that detects the infrared energy (IR) that is emitted, reflected, or absorbed by everything on earth. The TI takes that information and creates an image on a screen that can be interpreted by its user. Just as your eye receives light, a thermal imager receives IR, or what humans normally perceive as heat. While your eye sees colors as a result of the energy it receives, the TI “sees” surface temperatures. Normally, the picture on the screen of the thermal imager displays the hottest objects as white, the coldest objects as black, and everything between in shades of gray. (One of the biggest misconceptions about thermal imagers is that they can see through objects. TIs only detect surface temperature differences.)
Firefighters have been using TIs since the early 1980s when the first
cameras were put in service in Europe. While the technology of thermal
imaging has changed over the years, these devices still create a picture
based on differences in relative surface temperatures. While the older
technology was crude and fragile, the newer technologies offer better
durability, better sensitivity and better overall imagery.
A TI is not the same as an image intensifier (“night vision” or “night scope”), because it does not amplify existing light. It responds only to IR. Image intensifiers should be familiar to anyone who watched news coverage of the recent military action in Iraq. These cameras produced the green images recorded at night. The black and white images that showed explosions just as white forms were images from a TI. The advantage of a TI is that it can perform when there is no light or when conditions (such as smoke or fog) reduce the vision that light normally allows. First responders can use a TI whenever their eyes cannot give them the information they desire.
Finding a Patient
The opening scenario provides an excellent example of how EMS personnel can benefit from the use of a TI. In this hypothetical situation, the TI helped to find the actual scene of the accident. A number of emergency personnel have used a TI to find victims ejected at MVAs, especially at night. Despite low-light conditions, the IR signature of an ejected victim should be visible to the TI and can assist firefighters and EMTs in performing a rapid and accurate search around a rollover accident.
Rescuers can also use the TI to help determine how many people were in a vehicle based on residual heat signatures that may have been left on the seats (of course, this residual heat signature is temporary and will fade over time). One fire department in Kentucky used a TI to find a victim whom responders did not even know existed. At the scene of a one-car MVA, EMS and fire personnel arrived and began treating the driver who was in the vehicle. A new member of the department, eager to help but lacking formal training, was told to survey the scene with the fire department’s TI. As he examined the interior of the vehicle, he noticed that the passenger seat was white on the TI, indicating warmth. Innocently, he asked why he could see a body outline in the seat. This prompted a short search, resulting in the discovery of another victim. The passenger had stumbled away from the vehicle in a daze, falling down an embankment and out of sight. Without the TI, rescuers would have unintentionally left the semi-conscious man lying in a ditch.
While a TI can help find missing victims, it can also confirm that all victims have been discovered. For example, if the TI shows that the front two seats exhibit heat impressions, yet the rear seats do not, emergency services personnel probably have only two victims. Rescuers may still benefit from a quick scene search, because the absence of additional heat signatures should not be considered as definitive proof that all victims have been discovered. For example, heat signatures would not be left behind by a small child who had been riding in an adult’s lap, or by a heavily clothed passenger whose body heat hadn’t been transmitted to the seat.
One October night, firefighters in the Abbotsford (Vancouver) Fire and Rescue Service received a report about a car running off a road into a drainage ditch just outside of Abbotsford. Firefighters identified the location of the partially submerged car, then scanned the vehicle with a TI. The image on the screen showed heat from the engine block, handprints leading off the roof of the car and a trail of footprints leading up the bank. A few minutes later, firefighters found the victim walking down the road. The thermal imager helped personnel verify that no one was remaining in the car, and it assisted them in finding the missing victim.
Locating patients is not limited to MVAs. The TI can assist in the search for lost children, walk-aways from long-term care facilities or other lost adults. Because the TI is looking for heat sources, the likelihood of success is greater when there is a more significant temperature difference between the environment and the missing person. These conditions also increase the effective range of the TI. For example, firefighters in St. Hilaire, Canada used a TI in search of a missing hiker one winter night. They received the report around 19:15 and initiated searches from the top and the base of the mountain. They searched in total darkness, with air temperatures hovering near 10ºF (-12ºC). Firefighters realized the futility of the effort and contacted a mutual aid department to request their TI. Within 15 minutes of the TI’s arrival, the victim was located from over 800 feet (245 m) away. Not only was the victim found much faster with the TI, but the rescuers themselves were at less risk from unseen hazards and environmental exposure.
Another example occurred in Copley, Ohio, when an elderly nursing home resident wandered away from the facility at approximately 19:00 on December 16, 2001. In wet weather with near-freezing temperatures, the man wore only a hospital gown and tennis shoes. Copley police officers and nursing home staff members searched unsuccessfully for 1_ hours, when officers remembered that the Copley Fire Department was equipped with TIs. Firefighters teamed up with the police department to conduct a search, scanning along the roadside with a TI. After just ten minutes, rescuers saw a heat signature about 75 feet from the road, where the man was found lying under thorny bushes in a backyard. Responders reportedly had walked past him several times in the dark, unable to find him. They believe the man would have died that night if he had not been located with the help of thermal imaging.
Finding Parts of a Patient
Grisly as they may seem, amputations are an everyday reality in EMS. In northern regions, the culprit may be a snow blower; in southern regions, a lawn mower. Across the US, machinery accidents happen at home and at work.
Regardless of the location and the culprit, amputated digits can pose significant challenges to EMTs and firefighters. The very nature of the equipment involved, as well as the small size of digits, frequently results in the body parts being thrown a distance from the victim. The search for amputated parts can be a long, tedious effort involving a large number of searchers crawling on their hands and knees. Such a search is a risk for rescuers, as they may unintentionally expose themselves to blood-borne pathogens or may risk injury from machinery and obstacles in the vicinity.
Because amputated digits generated their own heat, they will provide an IR signature for some period of time. (That time decreases depending on how cold the ambient environment is.) This IR signature, visible to the TI, can dramatically reduce the risks of a search as well as the overall time required to find the amputated parts. Photos 1 and 2 show simulated amputated fingers in metal shavings under a lathe. In the normal photo, the pink “fingers” are impossible to distinguish. The thermal image, however, clearly identifies where the heated “fingers” are partially buried in the shavings. While the primary advantage in this scenario is rescuer safety, imagine the time benefits if the search area was 800 square feet of machine shop floor, covered with similar shavings.
Photo 1: Metal shavings from a lathe hide “amputated fingers” from visible light. Photo courtesy of Bullard.
Photo 2: A thermal imager identifies two warm areas underneath the metal shavings (red circles added digitally for clarity). These are the “amputated fingers.” Photo courtesy of Bullard.
Similar time savings can be experienced when digits are amputated outdoors, and the searchers must scour a lawn or other large area. Obviously, time saved during the search translates directly into the increased probability of successful reattachment surgery.
Conclusion
While emergency services still view TIs primarily as firefighting tools, it is clear that they have a number of applications in the bulk of emergency responses. Whether you provide EMS as a member of a fire department or as a member of a third-party provider, you should consider requesting and using TIs whenever your eyes cannot give you the information you desire. Locating an MVA and any ejected victims, locating missing persons and locating amputated body parts are just a few examples of how thermal imaging can assist EMS providers. By no means is this list exhaustive; the uses of a thermal imager in the fire service or in EMS are limited only by your imagination.