S T A N F O R D M E D I C I N E
Volume 17 Number 3 FALL 2000
computer-based tools help anesthesiologists, radiologists and surgeons perfect their practices.
by evelyn strauss
Imagine boarding an airplane that will be flown by a pilot who graduated from flight school at the top of her class. You're one of her first passengers. * She aced every question on her certification boards. And she has worked with the very best pilots in the world, mentally cataloging how they handle tricky situations. Perhaps even more reassuring, she has logged hundreds of hours on a flight simulator that has trained her to handle the range of imaginable disasters.Your seatbelt seems practically superfluous. * Then imagine walking into a hospital, where very few surgeons have the had the benefit of training on simulators. If it makes you nervous, you're not alone -- many of the fledgling surgeons are apprehensive too. * When it comes to learning surgical skills "It's 'see one, do one, teach one,' " says Thomas M. Krummel, MD, the Emile Holman professor and chair of surgery. "That's a little bit tongue in cheek, but people really do practice an operation by doing it on a human being," he says. * The situation is changing with the growing ability of computers to simulate various aspects of human physiology and anatomy. "Just about every other high-hazard industry uses high-fidelity simulation for initial and continuing training of personnel," says David Gaba, MD, professor of anesthesiology. "The same thing is starting to come true for health care."
Beyond training, fully certified surgeons are using computer software programs that allow them to try out different approaches before making a single real incision. They map out their strategy -- like a flight plan -- in advance. This ability enhances their competence because they can navigate much trickier terrain than they could otherwise. Computers are even improving physicians' performance during procedures. They're helping surgeons to see, in real time, across physical barriers, effectively enabling them to fly safely in thick fog.
Stanford is way ahead in developing computer-based tools to assist in radiology and surgery, says Krummel. "Other people are working on similar things, but Stanford has more depth and breadth than any other institution in the world."
Just as aspiring commercial airline pilots must pass tests on flight simulators before they climb into a cockpit, aspiring medical students, surgeons or anesthesiologists will perform procedures on patient simulators to gain acceptance into medical school or residency training programs, predicts Krummel. Pre-meds will have to pass a practical MCAT run on a simulator, he forecasts. "The future of surgery is no longer blood and guts, it's bits and bytes."
Anyone could lay a Macy's mannequin on its back and pretend it's a patient. But Gaba's patient simulator not only looks human, it also acts human, at least in some respects. Eyelids open and shut, pupils dilate and constrict, and computerized lungs produce breath sounds. The simulator's heart beats, and its mathematical blood pumps through its body. "It calculates how much blood is flowing several hundred times per second," says Gaba. "It replicates to a reasonable degree what happens in a person."
Furthermore, the simulator "responds" to medical procedures. Special syringes hooked up to the mannequin allow the computer to monitor the amount of each drug trainees deliver to the "patient." Based on this data, the computer delivers reports on drugs' effects, continually updating them -- so as the drug level peaks, the effects peak, and as the drug is eliminated by the body, its effects recede.
This adult patient simulator has been used initially for training anesthesiologists, but Gaba and his team at Stanford, along with their colleagues at other universities, have adapted the tool and the curricula for other medical domains, including the intensive care unit, the emergency room, interventional radiology, the delivery room and neonatology.
In their program for anesthesiology residents, Gaba and his colleagues simulate an anesthetized patient who experiences a variety of medical complications -- a kink in his IV tubing, an allergic reaction to his medication, a heart attack. In the sessions, microphones and videotapes record what transpires. As part of ongoing research, the trainees even wear probes that measure their own heart rate.
Although they're dealing with a plastic mannequin, the trainees soon suspend disbelief. "When they're in the hot seat and things start to happen, they get totally sucked in," Gaba says. "We can tell from their voices and from their heart rates. And they swear."
Analysis is a critical part of the learning process. After the sessions, the participants review the videotapes and critique their performances. Debriefings last as long as or longer than the simulations themselves, says Gaba. The instructors provide guidance during the debriefing, but mostly the trainees critique themselves. "The debriefing is worth more than the simulations alone," Gaba says. "Using the simulators to practice nuts-and-bolts procedures is good, but the real impact on patient safety will come from what they teach about teamwork, leadership and crisis management."
Simulators will presumably improve the safety of procedures because people will make errors in a virtual world without hurting anyone, "just as pilots can practice with flight simulators and crash," says Krummel. "When you look at aviation's track record, they were on an almost two-year run of not a single aviation fatality not too long ago. Compare that to the Institute of Medicine report released last fall. In medicine, we've got a 747 dropping out of the sky every three days." Simulators won't completely solve that problem, he says, but they will help.
With the simulators, trainees can confront a wide variety of situations. These include standard procedures as well as unusual events. "Pilots train for what to do on engine failure during take-off," says Gaba. "It doesn't happen often, but they need to know how to deal with it if it does." Furthermore, doctors-in-training can see a crisis through to the end -- an unlikely scenario in a real-life emergency. "In real crises, junior people get bumped out of the way and senior people take over," says Gaba.
Gaba's simulator has its limitations, of course. It can be adjusted to mimic, say, a prototypical pregnant woman, but "it can't be a specific pregnant woman," he says. "We don't design humans, we don't build them, and no one gives us an instruction manual." The device can't currently incorporate patient-specific data, in part because no one has untangled the complex set of events that occur in response to most drugs or other perturbations resulting from trauma and treatment. "You can't tell how someone is going to respond to morphine with imaging techniques such as MRI," says Gaba.
Eventually, however, physicians would like to incorporate patient-specific data, says Krummel, imagining his surgical simulator in the future. "At some point, you'll be able to practice not just a liver resection, but the liver resection you're going to do the next day," he says. And then, he imagines exploiting technology further. "The next day, we'll mount tools and sensors on robots and deliver the perfect operation." It might even be possible to cut and paste the best parts of different practice sessions. "When Steven Spielberg is making a movie, he shoots and re-shoots until he gets it just the way he wants. We'll do a part of the operation until we get it just the way we want, and then save that part."
He'd like to catalog these operations for trainees to watch -- and maybe even feel. "If you're learning how to play golf or tennis, the instructor will take your hands and show you what the swing feels like," he says. "You could put these devices in drive mode so people could feel what it's like to be Michael DeBakey [a famous cardiovascular surgeon]."
Simulators also provide a way for trainees to master and demonstrate practical skills in a systematic and standardized manner. "People usually learn based on random opportunity," says Krummel. "Whatever comes into the OR today is what you do. There's no organized curriculum." Krummel is developing a surgical simulator to systematically teach people techniques such as suturing, dissecting, and various scope-based procedures. It is composed of a series of virtual-reality devices that produce "touchable" three-dimensional images. Using force feedback technology, the device creates the illusion of performing a portion of a surgical procedure. Krummel envisions that his simulator will eventually recognize individual trainees and know their educational needs. A trainee would "check in" with a swipe of an ID card, he says. "A resident might select a particular procedure to practice or might say -- 'just put me on a quick rundown of surgical critical care or minimally invasive surgery' -- and away you'd go."
R2-D2 hasn't yet pulled scrubs over his dome and booties over his wheels, but the robot's computer cousins are already rolling into the operating room. Computer-imaging techniques are proving a boon to surgeons by providing them with enhanced vision. Michael Stephanides, MD, medical director of the National Biocomputation Center at Stanford, does not use a patient simulator, but a computer that has been fed MRI and CT scans from a real patient. With software developed by the center's technical director Kevin Montgomery, PhD, Stephanides plans specific operations. "We're taking the data that we get from patients' scans and doing 3-D reconstructions," he says. "That's routine these days in most centers, but we're taking it a step further and interacting with the images."
The software stacks up CT and MRI slices, creating a realistic version of a person's face, for example. "Then you can measure bone lengths and angles, make your cuts as you would in the operating room, and see if there are alternative ways of doing things," Stephanides says. "You walk to the operating room with a blueprint, which allows you to perform the surgery exactly the way you planned it. It cuts back on operating time and gives better results in terms of precision."
This tool has allowed Stephanides to tackle complicated challenges. For example, he reconstructed a large portion of Merced resident Susan Wendel's face. Her neurofibromatosis -- a benign tumor -- had deformed the right side of her face, forehead and nose. After more than 15 unsuccessful surgeries, she gave up. Her friends and family, however, urged her to seek medical intervention because the disfiguration kept getting worse. "I couldn't walk down the street without everyone turning their heads," she says. "I got Social Security because my looks were so bad. That was my only reason -- my looks. And believe me, Social Security is not easy to get. But they gave it to me right away."
Stephanides was much more aggressive than her previous surgeons. "He had to cut my nose off," Wendel says. Although she must undergo additional operations to complete the reconstruction, the major surgeries are over and she is impressed with the results. "People walk right by me now. It looks like I was just in a little car accident or something."
To create extra tissue for the surgery, Stephanides implanted saline pouches under Wendel's forehead. Injecting liquid every week forced her body to grow new skin. Then he planned with the computer exactly how he would use the newly formed tissue to reconstruct her nose and right upper brow, trying different ways of slicing and twisting her forehead to create a new nose. He wanted to keep it attached at the bridge so it would retain its blood supply until it healed. When the time came for the real event, he had prepared a sterile aluminum template that guided him through cutting a piece of Wendel's forehead skin in exactly the right shape needed to make a new nose.
Wendel represents just one of 40 or 50 surgeries that were charted using these computer tools, says Montgomery. They're especially helpful in situations where surgeons create one part of the body from another. "You can use this technology to fabricate the missing part more precisely," says Stephanides. He applied the software toward rebuilding a whole jaw for a cancer patient who had to have that and part of her tongue removed. To make the jaw, Stephanides used the fibula, a bone in the leg used for lateral stability, which is considered a spare part. (Usually patients walk with no difficulty after this surgery.) "The problem is it's a straight stick and you want to rebuild a 3-D jaw," says Montgomery.
Stephanides took a scan of her jaw before removing it. He measured the distances and angles and unfolded the structure on the computer. He manipulated the fibula on the monitor and came up with the necessary cuts that would allow him to turn that linear bone into a jaw. "We printed out the templates and took them into the OR," says Montgomery. "Mike actually laid them on the woman's fibula and used them to cut the exact shapes."
Montgomery says they're currently working on a head-mounted computer display for use during surgery. It "looks like oversized sunglasses," he says, and it contains a tracking device that tells the computer where the surgeon is looking. Right now, they're using it as "virtual hanging windows over the patient -- so all the information a surgeon needs is easily available. The surgeon no longer has to leave the patient's side, walk across the room to the lightbox, memorize the CT or X-ray film and then return to the surgery. " With the display, "the information is all there, right in front of you while you're working on the patient," Montgomery says.
Eventually, it should be possible to incorporate data gathered during an operation as well as from scans generated in advance. Already, surgeons perform endoscopic surgery, in which they insert tools and a camera into a person's body and maneuver with the help of real-time visual information. But endoscopes often deliver sub-optimal views because a piece of tissue obscures the lens or fluid fogs it. Physicians are working to enhance the power of endoscopic procedures by using tools other than cameras to provide information. X-rays and sonograms would allow surgeons to see through physical barriers and provide crucial information about, for example, the advantages of cutting a centimeter to the left or right, depending on what's on the other side. "It's like pointing a camcorder at a wall when you want to look into the adjacent room," says Shahidi.
These devices address another major limitation of endoscopic procedures: disorientation. Endoscopic surgeons must learn to operate on a patient while looking at a video screen -- and the view can be confusing at first. Sometimes "right" on the screen might not be "right" on the patient and "left" on the screen might not really be "left." To circumvent that problem, Shahidi has developed a system that uses a computer to assure that the patient and the screen image share the same orientation. Similar systems that incorporate real-time X-rays and sonograms are on their way to FDA approval. This scenario requires that the system deliver information very quickly, says Shahidi. "A surgeon's not going to wait 20 minutes before making a cut." Although these tools aren't yet standard, they will be, he predicts. "In the future, it will be considered barbaric if you had to open a guy 10 to 20 cm to put your hands in and see what you're doing," he says.
When these tools are honed and high-precision minimally invasive surgery is typical, "everyone wins," says Shahidi. "The patient has much less pain and goes home and back to work sooner. Insurance companies win big time because the patient doesn't have to stay in the hospital for ten days. There's much less chance of complications or of having to do it again. Surgeons love it because it makes them perform much better."
And that sounds like friendlier skies in the operating room. SM