An occasional series on inventors and inventions
Never let it be said that Vancouver biomedical engineer James McEwen isn't prudent.
As an avid downhill skier and recent convert to the horrors and hazards of snowboarding, Dr. McEwen took the precaution of inventing a medical device that makes surgery far safer, in the event he mangles a limb while hurtling down a mountain at breakneck speeds.
"It's a way of feeding the orthopedic system. Now I can see my inventions in use when I come back with a popped anterior cruciate ligament or something," Dr. McEwen says with a laugh.
All kidding aside, Dr. McEwen is actually a saviour, rather than a sacrificer, of body limbs.
His invention, the microprocessor-controlled automatic tourniquet system, is used during an estimated 15,000-20,000 surgical procedures a day around the world. Now a standard tool in virtually all major hospitals, the device is primarily used to keep blood out of surgical fields.
The system is significantly more reliable and safer than its predecessors, but it works much like surgical tourniquets of the past, whether those were leather and brass contraptions from Roman times, tightly cinched belts in the American Civil war, bicycle tires and pneumatic pumps in the early 1900s -- or, more recently, mechanical tourniquets that applied pressure to a limb in occasionally excessive quantities, causing damage to underlying tissue, nerves and blood vessels.
Tourniquets have long been an essential condition of limb surgery, Dr. McEwen notes. "Without a tourniquet, someone has said that surgery on limbs would be like trying to repair a watch in an inkwell. But there has long been concern about unnecessary loss of blood and the need for transfusions and blood replacements," as well as nerve and tissue damage in the limbs.
It was exactly such limb damage that caused Dr. McEwen to turn his mind to the development of a more sophisticated tourniquet in the late 1970s.
He had just completed a PhD in engineering at the University of British Columbia on means of determining the level of consciousness of surgical patients during anesthesia. To that end, he'd conducted research in operating rooms at Vancouver General Hospital and had subsequently been invited by the hospital to establish a biomedical-engineering program.
"One day, I was asked to investigate some incidents where patients suffered nerve-related injuries as a result of older tourniquets being used," Dr. McEwen says. But a survey of the clinical literature turned up little in the way of an alternative.
"At first I looked for a device that might have some kind of alarms that warned people if the pressure went up. Then I looked for devices that had better pressure regulators. At the Mayo Clinic, for example, they were using what amounted to old pressure cookers, which used to have a weight, so when the steam built up in the pressure cooker, the weight lifted and blew off the steam."
"I figured if that was the state of the art, I could probably do a better job," Dr. McEwen says.
Noting that several other medical devices were then being modified through the addition of a microprocessor, he turned his mind to somehow connecting a computer to a modified blood-pressure cuff.
"I guess that's what triggered some of the creative processes, [that is,]what could be done if you used a computer with it," Dr. McEwen says.
It's just that capacity to look at problems in a different way and find novel applications for existing technology that truly defines Dr. McEwen's creativity, says colleague Michael Jameson, a biomedical technologist who has since worked with Dr. McEwen on the development of several new generations of tourniquets.
"I'm very much practically oriented. I will dismiss 20 things out of hand because I think they won't work, whereas Jim will find those 20 things and another 20, and think about them and not dismiss as readily," Mr. Jameson adds.
Convinced that a computer could be used to control pressure, and aided by a small grant from a B.C. research foundation in 1978, Dr. McEwen ultimately built a prototype and began testing it in the wards of Vancouver General Hospital.
The tests showed the microprocessor was an excellent means of regulating pressure and producing audio-visual alarms in the event of deviations such as over- or underpressurization. Because the pressure could be precisely regulated, "it made it much safer because you could use lower pressures. And it was much more accurate and reliable."
Dr. McEwen quickly patented the device, seven varieties of which are now sold commercially around the world under licence to Zimmer, the medical-devices subsidiary of pharmaceutical giant Bristol-Myers Squibb. Several more specialized models, including two pediatric varieties, are made and marketed in Canada by a spinoff firm that Dr. McEwen created, called Delfi Medical.
Whatever the model, the computer-controlled tourniquets have the capacity to tailor the required pressure to the individual patient. "The idea of the instrument is to figure out what the ideal pressure is for that patient to maintain the pressure in the cuff and, therefore, on the limb, at the lowest level that will stop blood flow. It's called the minimum effective pressure," Dr. McEwen says.
Achieving that mimimum pressure is particularly vital because the higher the pressure and the longer the time a tourniquet of any form is used, the greater the likelihood of muscle and nerve injuries, Dr. McEwen explains.
Now used in the surgical treatment of sports-related injuries such as arthroscopies, cartilage and ligament repairs, knee replacements, hand surgery and a wide variety of other procedures, there's no question that the invention has prevented an untold number of nerve injuries, says Vancouver orthopedic surgeon Brian Day.
"It's been one of the major advances ever in the field of operating on limbs," adds Dr. Day, who is an assistant professor of orthopedics at the University of British Columbia. "Previously, because the tourniquets were quite dangerous, there was a fairly high incidence of nerve injuries, vascular injuries and they've been as close as you can get to being eliminated. Where you use one of these, it's almost impossible, unless you purposefully override its safety features."
The average price: $10,000. But while some 20,000 of the tourniquets have been sold worldwide, Dr. McEwen says he isn't rolling in untold wealth. "But this is a business [in which]you can do well while doing good."
Well enough, certainly, that Dr. McEwen, 51, can indulge in week-long golf retreats and hire a personal trainer to help him keep in shape. The adjunct professor of orthopedics and engineering at UBC, and spouse Eileen, are the parents of three children: Jennifer, Julie Ann and Jeff.
Dr. McEwen also takes great pride in knowing he invented something that solved a real medical problem. "It was triggered by an accident, not by a desire to do something with technology. It was triggered by a real injury to several patients and a desire to see a long-term solution developed."
Many medical discoveries are often such responses to hazards, he notes.
"In biomedical areas and medical technology, you're confronted with all kinds of problems and a good engineer, a person trained in technology of one kind or another, can often see several different ways of doing things better, so that's often how it starts in these areas."
The value of collaboration has led Dr. McEwen to continue involvement with Vancouver General in the form of joint projects, although he's since left the hospital to head Delfi and another firm called Western Clinical Engineering.
Holder of more than 100 patents, Dr. McEwen has turned his mind to computer-controlled anesthesia devices, ophthalmological devices and various forms of medical robotics.
But he's equally determined to continue fiddling with tourniquets. "It still isn't perfected yet."
Mr. Jameson, who's now vice-president at Western Clinical Engineering, says there's no doubt Dr. McEwen will eventually perfect the system. "He can focus himself very well. And once he sets goals for himself, he strives to meet them."
Wayne Kondro is an Ottawa-based science writer. He can be reached regarding suggestions for the Globe's inventors series at 613-789-6458 or by e-mail at: wkondro@sympatico.ca