Company News
Moving Forward
Reprinted with permission from Comprint Military Publications, FORT DETRICK STANDARD. Written by Karen Fleming-Michael
Sterilizing medical instruments in the field can be tricky — so tricky that it's not done by far-forward surgical teams, the first stops for wounded service members who need surgery fast.
Photo by Lt. Col. Thomas Winthrop The "Big Bertha" steam sterilizer, shown at Walter Reed Army Medical Center, is currently fielded to combat support hospitals. A new plasma sterilizer in development may one day supplement Bertha. |
Because those teams are meant to be mobile, they travel light and can't accommodate the weight, size or power requirements of current field sterilizers.
"FSTs (forward surgical teams) should have sterilization capability. They're a little bit too light," said Lt. Col. Thomas Winthrop, who for the last three years has been the chief of central material service, which does all the sterilization work for the Walter Reed Army Medical Center. "Sterilization is a critical factor in the FSTs because they can't do it, and they can't keep going long. I would think if they were going to add anything they would add a sterilizer."
A new plasma sterilizer in advanced development at the Army Medical Materiel Development Activity, however, may be able to meet those forward surgical teams' needs in coming years.
"The company has prototypes running right now that are killing things. The basic science is done,"said Mark Arnold, USAMMDA's product manager for the machine being developed by a Minnesota-based company called Phygen. "A lot of the scientists developing this were physicists who were doing military-directed physics in Russia and have moved on to more peaceful programs in the United States."
Plasma, which engineers and physicists call the "fourth state of matter," is a highly ionized gas state, Arnold said, like the gas inside a fluorescent light tube. The new sterilizer uses plasma to energize a hydrogen peroxide vapor and kill microorganisms.
"It has multiple killing techniques," Arnold said. "It ionizes (both) the oxygen found in normal air and hydrogen peroxide to kill bugs."
Killing bugs — lots of them — makes the difference between clean and sterile. To make something sterile, Arnold said, there has to be a "six-log kill" of the microorganisms to meet FDA requirements.
"In other words, you have to move a decimal point six places to the left," he said. "So if you had a million bacteria you'd have one left, (for it to be) considered sterile. When you wash your hands and the soap says it kills 99.9 percent of the bacteria, you've barely scratched the surface in terms of killing bacteria." Ultimately, Phygen expects its sterilizer to have a 12-log kill.
Winthrop's crew at Walter Reed are expert germ killers. They keep five steam and three older plasma sterilizers working around the clock, sterilizing about 300 instrument sets and 100 clinic items a day. (Those older plasma sterilizers, incidentally, take a different approach than the one Phygen is working on, Arnold said. They use plasma just to get rid of hydrogen peroxide vapors and don't use plasma to energize the oxygen and hydrogen peroxide.)
"It's the sterilization that makes you a hospital. We do the most sterilizing in the whole Department of Defense at Walter Reed," he said. "There's nobody in the Navy or the Air Force that come close to us."
Winthrop, because of his experience both as a sterilization guru and nurse specializing in robotic surgery, computed tomography and vascular surgery, is skeptical when new sterilizers come along.
"There's no sterilization that has covered everything yet, and if there was something out there, everybody would be jumping on it," he said. "There are so many pitfalls in new technology in this field that you've got to be careful. What I want is something that will work and not leave us in a lurch when we really need it."
Of steam, gas, chemicals and plasma, steam is Winthrop's favorite course of sterilization. Having deployed for a year and a half with "Big Bertha" steam sterilizers at the 212th Mobile Army Surgical Hospital, or MASH, he saw their value. Bertha's been around since the latter part of the Vietnam War and is very low tech, so much so that you can get almost all the parts to keep it going at a hardware store.
"I always kept a steam sterilizer up for emergency cases. If you treat them nice, (Big Berthas) will run forever," he said. "There's no one answer for sterilizing most things but for the field, steam is really the only answer. Steam penetrates, the other stuff doesn't."
Arnold agreed that steam sterilizers have earned their bragging rights, and said the new technology will supplement steam, not replace it.
"There are some things that you cannot use (the plasma sterilizer) to sterilize," he said. "You can't sterilize water used for wound irrigation in a plasma sterilizer." The manufacturer's testing, however, has shown the device can sterilize gauze, drapes, gowns, masks and other fabrics.
Arnold would, however, like to see the new plasma sterilizer replace the chemical glutaraldehyde that's used in FSTs. The chemical sticks to instruments and dulls them over repeated "cleanings."
"The interesting thing about (glutaraldehyde) is microbiologists use the exact material to glue cells on to slides — and that's why instruments get grungy when you clean with glutaraldehyde, because you're gluing protein onto the instruments," he said. "They get sterilized; they don't get clean. They're icky."
The new sterilizer has other benefits that make it useful for forward surgical teams as well as bricks-and-mortar medical facilities. It takes from 20 to 58 minutes to sterilize whatever is in its chamber, and because it operates at low temperature, users don't have to wait for instruments to cool before they can be used. As for environmental concerns, Arnold said the new sterilizer won't present any. The hydrogen peroxide vapor breaks down into water vapor and oxygen, and when the electricity is turned off, the plasma turns back into air.
Weight, volume and power are the "holy trinity for field medical equipment --as a matter of fact, for Army equipment in general," Arnold, an engineer said. "This does really well on all of those."
The sterilizer's weight will depend on how large it is, but it will be "substantially lighter" than conventional ones, he said, because it won't need high-pressure boilers and pressure chambers. The technology is also scalable, so it can have a very small or very large diameter.
"We have some 24-inch diameter sterilizers in the field right now, and that would probably be the one size sterilizer that we'd build," Arnold said.
Power-wise, the new sterilizer uses one-sixth of the wattage that steam sterilizers currently use. These savings may be the reason a forward surgical team may one day be able to have sterilization capability.
"The (steam) sterilizers right now use 9,000 watts of electricity each, and these will be down to 1,500 watts apiece. That's a big savings," Arnold said. "You maybe don't have to bring along as many generators. You don't burn as much fuel."
The new one won't be as low tech, though, as a steam sterilizer. It will need electrical equipment to create the high voltages that are used to create the plasma and will have a vacuum pump. It will also have some sort of basic computer, like a kitchen timer, to maintain the same level of reliability as the current sterilizer.
"Anything on a computer is going to be a problem in the field, no matter what," Winthrop said. Most modern equipment has some computers in it, Arnold said, so getting around them isn't likely. "Your cell phone has a very powerful computer in it, and the average car has about 10 computers in it," he said.
Phygen was aided by a 2005 Congressional appropriation of $1.4 million and expects to have a preproduction sample of the new sterilizer within the next two years. Arnold said the Army will help the company work through some of the military-unique requirements. "Most manufacturers have no idea how bad the environment is out there," he said, adding that he'd like to see the sterilizer be made rugged at its onset rather than trying to ruggedized it later.
Equipment testing will be done at Fort Detrick once a mature prototype is available, and user testing will also occur at a location to be settled on in the future.
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