New Anesthesia Machine to Include Ventilator for Surgical Teams
By Karen Fleming-Michael
Special to American Forces Press Service
FORT DETRICK, Md., July 28, 2004 When Army Maj. Brad West spent two and a half months in Iraq recently, he made a little bit of anesthesia history: The nurse anesthetist introduced the "ventilatory assist device" to his unit, the 250th Forward Surgical Team (Airborne).
Mark Arnold points out features of the ventilatory assist
device for forward surgical teams. Photo by Karen Fleming-Michael
(Click photo for screen-resolution image);high-resolution image available.
He offered the device as a replacement to a 1980s-era anesthesia vaporizer that works for the surgical teams but has limitations, the most striking of which is that it's no longer being made.
A team of engineers, anesthesia providers and combat developers has been looking at a Kansas-based company's off-the-shelf device for two years, ever since they learned the currently fielded one would be unavailable. The Army bought five of the Food and Drug Administration-approved devices and tested them in 10 Army medical centers, including Walter Reed and Brooke Army Medical Centers.
"In reality, (the ventilatory assist device) is a middle ground," said West, now serving as the chief anesthetist for the Army's Trauma Training Center in Miami. "It's somewhere between what we exactly want and what we have. It's a step in the right direction and is going to continue to get better."
The first feature the ventilatory assist device offers is in its name: a ventilator, built right in. The older machine -- called the draw-over anesthesia machine -- forced the anesthesia provider to manually squeeze a bag to breathe for the unconscious patient.
"If you're giving anesthesia, you'd like to be able to set up a ventilator and have the ventilator automatically ventilate the patient for you," said Col. Dean Calcagni, an Army anesthesiologist assigned to the Telemedicine and Advanced Technology Research Center here. "You need your hands free during the surgery to administer drugs, give (intravenous) fluids, give blood and maintain an anesthesia record. You can (manually bag) patients as long as it's necessary. But if you end up having to do it, you end up compromising some of those other things."
Calcagni said anesthesia providers keep faithful anesthesia records to see trends in how the patient is responding by monitoring their blood pressure or pulse or gas levels. In fact, the seal for the American Society of Anesthesiologists has a lighthouse with the word "vigilance" under it.
"Every patient is different, and some of them haven't read the textbooks so they don't know to respond the way they're supposed to so that vigilance is at the heart of what we do," Calcagni said. "You have to be focused in on that individual patient's response (through the anesthesia record)."
Having to manually bag a patient in a forward surgical team operating room is an unneeded distraction for the team that treats extremely critical patients. Often, West said, the person administering the anesthesia with a draw-over device in a forward surgical team typically grabs a medic, who otherwise could be helping other patients, to help with bagging.
"The (ventilatory assist device) gives you the freedom 'not to set it and forget it' but to set it and monitor your patient," he said. "You're not so tied to (the machine) that you can't assist your partner (the team's second anesthesia provider) with whatever is going on."
Training on the new device will be much easier because it's closer to what's used in hospitals, said Mark Arnold, project manager for the ventilatory assist device from the U.S. Army Medical Materiel Development Activity here.
"It doesn't have as much sophistication as machines do in a hospital, but it's sophisticated enough," he said. "That's a fine line that we always walk: It has to be sophisticated enough, but every level of sophistication that you add, it adds to complexity of spare parts, training and maintenance."
Engineers tested the machine rigorously to make sure it's deployable. Cringing, they dropped the device from heights of four feet, put it in an environmental chamber for high temperature and high humidity tests and put it through the "talcum powder test" to simulate how dust affects the machine.
"We always imagined those tests were a lot harsher than they needed to be until we saw the stuff coming back from Iraq which has been a poster child for military durability standards," Arnold said.
"Equipment there takes a beating just because it's a tough place. Military standards, though they seem to be extreme at first blush, are pretty realistic."
Maintaining the ventilatory assist device is a relatively easy chore because of the device's simplicity, West said.
"I can take it apart with my own tools, completely disassemble and reassemble it, and fix it myself," he said.
The trauma training center where West hangs his stethoscope brings in forward surgical teams as groups before they deploy. The teams work together on real trauma cases. Ryder Trauma Center, where the Army's center is collocated, sees 3,600 cases a year. And the center's staff shows the Army's trauma teams the equipment they will be using in the field. West has teams take the ventilatory assist device apart and reassemble it so they're comfortable with it and has them run through scenarios using it on mannequins.
"You need to know how to use your equipment before you need it, whether it's an M-16 or 9 mm (weapon) or it's medical equipment," said West, who's served on forward surgical teams for three years.
Having a device that's similar to what's used in a bricks-and-mortar hospital is the right way to provide care, Calcagni said.
"The Army says 'fight as you train and train as you fight.' For us in the medical field, that training occurs in our delivery of peacetime medical care," he said. "Whenever possible, you want to introduce equipment and have them use and get comfortable with it when they're in a medical center."
The new device also plays well with field oxygen-generation systems being developed, Arnold said, because it takes low-pressure oxygen, which is what oxygen concentrators all make.
"The pieces are fitting together there," he said.
The ventilatory assist device also has a canister that scrubs carbon dioxide out of the patient's exhaled air and reuses leftover oxygen, so it cuts down on the amount of oxygen logisticians need to supply in cylinders.
"The patient is breathing in a loop, and the device recycles any oxygen that is exhaled," Arnold said. "This way we only have to feed the patient about a liter of oxygen a minute. Even if you don't have an oxygen generator and you're using cylinders, the oxygen supply will last a lot, lot longer because it doesn't go to waste."
Any new medical device encounters the rub of the capability it affords users against the logisticians' nemeses of weight and size. The ventilatory assist device, in its first iteration, offers the anesthesia provider more freedom on the job but it is bigger, heavier and more costly than what it's replacing.
"It's a little like comparing apples to oranges," Arnold said, "because the machine does more. As a tradeoff, it might mean the difference between taking an extra anesthesia provider or an extra person to do the bagging."
The draw-over device, which resembles a shiny cappuccino maker, weighs in at about 20 pounds, container and all, which is why it was selected for use by forward surgical teams that have to travel light. The ventilatory assist device, on the other hand, tops the scale at 80 pounds in its box. The older machine's box is 10 by 14 by 14 inches, and the ventilatory assist device is twice that. Finally, where the draw-over vaporizer cost about $2,000 apiece, the ventilatory assist device runs about $20,000.
"The first iteration of the VAD is larger than the Army wants it to be," West said. "It's the beginning of the evolution of the far-forward capability so we can have a ventilator along with the capability of delivering anesthesia. What we would really like to have is something that's 12 by 12 by 12 (inches) that has a handle on top of it. This is the first step in the process of developing that new technology far forward."
Calcagni, who provides anesthesia once a week in a local military hospital, said the Army is looking at three more approaches for military anesthesia. The first is bringing a computer-driven infusion pump that would deliver a precise dose of a needed intravenous anesthetic. A lot of anesthesia providers who have gone to the field have ended up forgoing an anesthesia machine -- because they're so big and bulky and require maintenance -- for total intravenous anesthesia, or TIVA," Calcagni said.
"There's an art to doing total intravenous anesthetic because for pharmacokinetics -- the distribution of the drug in the body and how long it takes to build up in the bloodstream -- you have to do a loading dose before you can reach a constant state. That's kind of done by the seat of the pants," he said.
By having a computer control the infusion pump, it takes the seat-of-the-pants guesswork out of providing the correct doses. Calcagni said there have been millions of anesthetics delivered by this method in Europe but not the United States because it's not an FDA-approved technique. In recent months, the Telemedicine and Advanced Technology Research Center entered into a cooperative research and development agreement with a company in Europe to work on gaining FDA approval for the technique.
Secondly, military anesthetists are also exploring using catheters to deliver regional anesthesia -- or nerve blocks -- for extremity wounds to let soldiers stay lucid while receiving care instead of being "gorked" throughout their treatment, Calcagni said. Finally, the telemedicine folks are developing simulators like pilots use to help train anesthesia providers.
"Some say that flying is 99 percent boredom punctuated by 1 percent sheer terror if you're a pilot, and it's probably similar to that in anesthesia," Calcagni said. "There are rare events that can be catastrophic events that you have to recognize and respond to early. If you experience them, you'll want to have seen them before and gone through the drill of how to respond to them."
(Karen Fleming-Michael is a staff writer based at Fort Detrick, Md.)