Practice Makes Perfect

“Doc, I'm hit,” screams the Army rifleman as he sees a medic approach. Amid sounds of gunfire and grenades, the medic drops to the ground and begins treatment to stop the bleeding from the soldier's wounded arm.

Another day in Iraq or Afghanistan? No. In this scenario, the infantryman — though lifelike — is really a Combat Medical Training System (COMETS), now being developed by the Simulation Group of Boston's Center for Integration of Medicine and Innovative Technology (CIMIT). Designed to give combat medics the most realistic training possible short of treating a human, COMETS will simulate common battlefield procedures, including airway management, chest trauma and hemorrhage control. Moreover, the technology-laden mannequin will “live” or “die” depending on the skills of the attending medic.

In the field of medicine, where newcomers traditionally learn by watching experienced practitioners, simulation systems are beginning to revolutionize training. More and more surgical residents, dental school students, combat medics and other medical personnel are getting hands-on training much earlier, thanks to simulators that range from interactive mannequins to virtual-reality systems that mimic specific medical procedures.

“The practice-on-the-patient system worked for centuries, but we are at a crucial time in medical education,” says Dr. Steven Dawson, an interventional radiologist who heads the CIMIT Simulation Group, which is backed by $2.2 million in funding from the U.S. Army's Telemedicine and Advanced Technology Research Center (TATRC) and Research Area Directorate II, Combat Casualty Care. “Revolutions in computational mathematics, engineering and education are giving us more options.”

Built for the Battlefield

Alongside Dawson, a five-member staff of engineers, designers and computer scientists are working full-time on COMETS, with the goal of producing two full-body prototypes for an August 2009 conference on Advanced Technology Applications for Combat Casualty Care. While medical mannequins have been produced for many years by such companies as Laerdal and Medical Education Technology, the Simulation Group aims to design a system that sets new standards for portability, ruggedness and ease-of-use.

“When we got started on this project, there were no wireless systems on the market,” says Mark Ottensmeyer, a Ph.D. mechanical engineer working on COMETS. “We also want a system durable enough to stand up to dirt and mud and the rough treatment of 19-year-old medic trainees, so we needed to build a more rigid frame with more robust connectors between components. And since medic trainers rotate duty regularly, we don't want a system that takes them weeks to get up to speed.”

Designed to be a fully autonomous synthetic human, COMETS is pre-programmed to exhibit a specific injury. For example, a trainer will be able to attach a “wounded limb” to the mannequin, and the system is programmed to automatically recognize the injury and adjust the physiology, such as breathing and heartbeat.

“Writing the code to do the physiology is a major challenge,'' says Ottensmeyer. “How do you get sensor readings from fluid flow measurements representing blood loss or administering an IV? How do you make the heart rate and simulated blood pressure change when you place a tourniquet on an injured limb?”

The finished prototype will consist of a head, torso and detachable limbs on a stainless-steel frame. Actuators will move shoulders, hips and head to simulate how a body reacts in a conscious versus unconscious state. For example, two motors drive pitch and yaw motion in the head and the gain in the control loop can be programmed to make the head go limp to simulate unconsciousness. Similarly, the system's central processor can change stiffness in ball joints in the hips and shoulders.

The design team is experimenting with different grades of silicone rubber, such as those used in the special effects industry, to achieve realistic texture for skin and muscle tissue in areas treated by the medic.

System Control Center

For the mannequin's real time operating system, engineers have adopted a rugged, reconfigurable control and data acquisition system, which uses a visual programming language. The controller, featuring an industrial 200 MHz processor, links to an embedded FPGA and several input/output modules for communication with sensors and actuators. “This is where all of the physiology and data recording lives,” says Ottensmeyer. “Trainers will know what procedures were performed on the mannequin at a given time, as well as its condition. For example, you can tell how much blood was lost, when artificial respiration was done or whether a head was positioned properly in cases of fractured spine.”

To simulate heartbeat and pulse, based on changes in the mannequin's condition, the central processor triggers solenoid-driven electromechanical pulsation units that push up against the underside of the skin in such areas as the wrist and neck. For fluid handling, the torso holds a 1-lreservoir that can be programmed to pump simulated blood through synthetic veins and solenoid-controlled valves to an injured limb.

For voice, the system includes an audio amplifier in the head, which emits pre-recorded words and sounds — screams, moans, pleas for help — related to various physiological conditions. The mannequin will also recognize an RFID tag worn by the individual performing the treatment, triggering an appropriate vocal reaction like “Doc, save me.”

Other important innovations in COMETS include the system's power supply, consisting of a pair of hot-swappable, 23.1V battery packs that use a doped nano-phosphate chemistry developed by an MIT spin-off. “These batteries offer superior current delivery and allow both fast recharges and a very high number of recharges before they start to degrade,” says Ottensmeyer.

Finally, as medics move the mannequin from the site of the injury, wireless Ethernet lets the system upload the record of treatment modes and physiology changes to a display system to allow trainers and trainees to review treatment during an after-action review.

Among the biggest challenges in developing the system, which could also be used to train civilian first responders, is adapting components to fit a simulator the size of a human. “There are no convenient right angles to mount things to and you've got to squeeze in such components as batteries, computer controller, lung and chest wall actuators, motors for the head, audio amplifiers and more,” says Ottensmeyer. “So we need to find components that are compact yet deliver the required performance.”

Once the CIMIT research team develops a prototype acceptable to the Army, the responsibility for producing a commercial system will fall to established manufacturers who will license the technology. To make that transfer easier, the engineers are preparing 3-D CAD models or laser scans of all major components and are using commercial components as much as possible.

A Family of Simulators

One commercial manufacturer that has already established a long track record — with more than 3,000 simulators in use — is Florida-based Medical Education Technologies Inc. (METI). Many of these systems, including the HPS and iStan simulators, offer capabilities that rival those envisioned for COMETS.

The $65,000 wireless iStan system, developed in part through a collaboration with the Army, comes in several patient models, such as “iGranny” and “iTruck Driver.” Through mathematical modeling, the simulators can embody the physiology of a healthy 25 year old or an overweight middle-aged patient. The mannequins can simulate 14 different medical scenarios, such as angina with cardiac arrest or pneumonia with septic shock. Moreover, iStan is programmed to react appropriately when a particular simulated drug is administered.

These realistic capabilities, including systems to simulate breathing, pulse, heartbeat, speech and blood loss, have been fueling an annual growth rate for METI of 30 percent. “Until recently, the medical community has been learning on human beings or animals, but ethically the world is increasingly moving away from that,” says Carlos Moreno, METI's vice president of engineering.

Instead, more medical societies and hospital residency programs are advocating medical practitioners demonstrate skills on simulators before treating patients. In Spain, for example, newly trained anesthesiologists used METI's HPS simulator at a professional conference attended by prospective employers to prove their skills in administering anesthetics.

Tracing its roots to the Anesthesiology Dept. of the University of Florida's medical school, METI developed a family of mannequin simulators for adults, babies and children, including models designed for specific medical settings, such as emergency care. The company continuously adds new training modules to meet the changing needs of medical curriculum.

“Much like the auto companies, we've developed a basic platform or architecture that includes such components as servo and stepper motors, compressors, fluid pumps, sensors, actuators and proprietary materials,” says Moreno. “Where possible, we try to share key components, such as the electronics for actuators. To some extent, it's plug-and-play.”

But there's always the challenge of meeting the special requirements of new systems. For the HPS mannequin, for example, adding the capability to administer an anesthetic gas meant replicating in the mannequin the lung volume of an adult. It also required new flow control and gas analyzer components, both for identifying the gas that the simulator inhales and conveying that information to the software that runs the physiological models.

“The medical simulation field is still very young,” says Moreno, “so you can't walk into a library and find tons of research papers. Almost everything we do is plowing new ground.”

Teeth to Temporal Bones

Rather than simulate the functioning of an entire body, other companies are fashioning systems to train medical personnel in specific medical procedures.

Israel-based Image Navigation has sold 350 DentSim units to some 25 medical schools around the world, including the University of Minnesota, Virginia Commonwealth, the University of Pennsylvania and Case Western Reserve. The system includes an off-the-shell simulator, supplied by such companies as KaVo and A-dec and consisting of torso, head and ancillary dental equipment.

Onto this equipment, Image Navigation adapts the DentSim, which includes a special tracking system that records a student's treatment methods, such as filling a cavity, and rates it versus ideal practice for that procedure. The system features special DentSim software, a CPU, two infrared CCD cameras and infrared tracking LEDs mounted on the dental handpiece and the jaw of the mannequin.

In a typical procedure, software for a specific dental procedure is loaded into the system and the student then inserts an artificial tooth into the mannequin. As the student works on the tooth, DentSim records the identical results on a virtual tooth for later evaluation by the student and the instructor.

“Once the session is complete, all you do is click on an evaluation button to get immediate 3-D volumetric analysis,” says Udi Doan, the company's vice president for North America. “And we guarantee accuracy to 150 microns.”

DentSim now tracks more than 100 procedures and will soon be adding modules for dental implants. Reports from schools show the system sharply reduced the time it takes for students to master key physical dexterity skills. “Simulators aren't just for airline pilots,” says Doan. “In medical and dental training, simulators let you learn and make mistakes in a safe environment.”

Other companies rely on haptics, proprietary software and computer graphics to design virtual reality simulators for a growing number of medical procedures. SensAble Technologies, a Boston-area company, produces haptic devices that harness motors, cable drives and optical encoders to create force feedback for medical simulation. The technology is now employed in more than a dozen applications, ranging from a simulator that mimics a temporal bone drilling procedure for ear surgery to a “haptic cow” used to train veterinary students.

“Many simulators have been in the research stage for years but are now starting to reach the commercial market,” says David Chen, chief technology officer for SensAble, who cites a growing appreciation in the medical community for simulator-based training.

Typical of SensAble's customers is Touch of Life Technologies (TolTech), which introduced its knee arthroscopic surgery VR simulator in March in partnership with the American Academy of Orthopaedic Surgeons. The simulator builds on research at the University of Colorado Medical School, a participant in the National Library of Medicine's Visible Human Project to develop anatomically detailed 3-D images of the human body.

During a training session with the TolTech system, an individual uses one hand to manipulate a surgical instrument mounted on the end of the haptic device and the other to hold the arthroscope. Besides experiencing the force feedback while moving the surgical probe, the operator also views two monitors. One monitor is the Virtual Mentor, which displays the essential steps in the surgical procedure, evaluates the skills of the trainee and even gives vocal warnings. The second monitor displays the arthroscopic view of the simulated surgery, such as an ACL repair, as it takes place, including high-resolution 3-D anatomical images.

Victor Spitzer, TolTech president and an anatomy instructor at the University of Colorado, emphasizes the importance of the system's software, developed by electrical engineer Karl Reinig. “The SensAble haptics allow you to apply any force and Karl did an excellent job through software of creating the feel of human tissue,” says Spitzer. In 2009, TolTech will unveil two more VR systems — one for simulating a needle for injecting drugs into joints, the other to simulate administering a nerve block.

“Medical simulators are clearly a growth industry,” says Spitzer. “Potential users include not only medical students or residents in medical specialties, but also experienced doctors who need to upgrade their skills and practice new procedures.”