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Finding Hidden Damage in the Brain
Editor's Note: The following article originally appeared in Duke Nursing magazine.
Durham, NC - Former Pittsburgh Steelers player Mike Webster suffered from dementia and depression for years. The National Football League ultimately ruled that multiple concussions he received during games caused degenerative brain disease that permanently disabled him.
Soldiers coming home from Iraq after receiving multiple concussions during roadside blasts have been found to be more prone to suicidal thoughts than those who never had a concussion or who had only one.
In an article in the Journal of Neuroscience Nursing, a nurse writes about the depression, memory loss and slowed thinking she experienced for a year after she received a mild concussion in a car accident.
A concussion was once considered no big deal. But now health care workers know better. "Add the evidence from emergency room patients together with the evidence from the NFL and the military, and it's a pretty serious problem," says Charles Vacchiano, professor of nursing. "But how do you unmask potential cognitive dysfunction after a concussion?"
Many people with concussions have normal brain scans and may perform normally on cognitive tests, even though they have localized damage. Maybe practitioners could intervene sooner if there were a way to reveal hidden deficits.
Vacchiano is testing a simple way to do just that. During a 26-year career in the U.S. Navy as a nurse anesthetist and director of the Biomedical Sciences Division at the Naval Aerospace Medical Research Laboratory, Vacchiano learned a lot about how the brain behaves when exposed to certain stressors. To try to uncover concussion damage, he's harnessing a condition he's very familiar with -- hypoxia, or lack of oxygen.
Hypoxia can hijack cognitive function and behavior in a few short minutes, causing people to become disoriented and process things more slowly, almost as if they were drunk.
An example? "This goes way back, but have you ever seen a movie called An Officer and a Gentleman?" Vacchiano says. If you're a Richard Gere fan, you'll remember the scenes of flight training in which the Gere character's friend has a meltdown after a few minutes in a low-oxygen environment.
"Remember how the guy went ballistic?" Vacchiano says. "The idea is, you are exposed to a hypoxic environment, and if you can't realize what's happening, recognize the symptoms, and put your mask back on and turn on your oxygen, then you fail. You're not going to become a pilot. That's what happened to that character. He was washed out of flight training."
Parts of that movie were filmed at the altitude chamber in Pensacola, Fla., where Vacchiano has conducted studies, and where he went through altitude training himself. The chamber simulates what naval pilots flying at high altitude would go through if the airplane's systems suddenly failed. "At 40,000 or 50,000 feet, if cabin pressurization or the oxygen supply fail, you only have maybe 30 seconds of consciousness to take some sort of action, or you're going to crash," Vacchiano says. "So that's why the military trains pilots to learn to recognize hypoxia."
Traditionally, during this training, some of the air in the altitude chamber is sucked out, which reduces oxygen pressure in the environment and the amount of oxygen that gets into the blood. In the early 2000s, the navy expressed interest in figuring out some other way to conduct altitude training, because the reduced air pressure carries a health risk, including ruptured eardrums or the bends, which is what happens to divers who go from high-pressure to low-pressure environments too quickly.
Vacchiano's naval research lab was tasked with solving this problem. As an anesthetist, he was familiar with patients who became hypoxic in the operating room. "I thought, can't we just build a machine that dilutes the amount of oxygen that you breathe in while you're sitting right here in this room, rather than taking you to altitude? Doesn't that make sense? Just use a gas-mixing device," Vacchiano says.
Working with an engineer, Vacchiano developed and patented such a machine, called the reduced-oxygen breathing device (ROBD). It delivers a custom mixture of oxygen and nitrogen through a mask, simulating any type of reduced-oxygen environment desired. Wired magazine called the silver and black rectangular machine "hypoxia in a box," and that describes it pretty accurately. It's much less expensive and safer than an altitude chamber, and the navy still uses it for refresher altitude trainings.
Fast forward 10 years. Retired from the Navy and conducting research and teaching in Duke's nurse anesthesia program, Vacchiano began reading in the nursing literature about the need to better manage people with concussions. He decided to make use of his invention again. A brain that harbors damage from a concussion may function normally in the short term because it has some cognitive reserve; the undamaged parts compensate. Vacchiano has launched a study using his "hypoxia in a box" to temporarily disrupt that compensation mechanism.
In a small exam room in Duke Clinic, Vacchiano hands a visitor a pulse oximeter, which uses the amount of different wavelengths of light absorbed by hemoglobin pulsing under the skin to measure the amount of oxygen molecules in the blood.
"Clip this on your ear and let's see if you have any oxygen in your system," says Vacchiano, upbeat even at 8 a.m. He and clinical research coordinator Patricia Patterson are preparing for the arrival of a study participant, someone who's had a concussion in the last six months. She will don a mask connected to Vacchiano's gas-mixing device, then take a computer-based cognitive test.
On one visit, the participant will take the test while breathing room air, then, on a different day, take it again while breathing air that's slightly oxygen deprived -- 13 percent oxygen. The pulse oximeter confirms that the machine is achieving the intended reduction in blood oxygen saturation.
Most people don't notice the difference between the different oxygen concentrations, Vacchiano says, noting that the air you normally breathe is about 21 percent oxygen, and when you're on a commercial airplane, it's reduced to about 15 to 16 percent oxygen. But Vacchiano suspects that mild hypoxia may cause people who have small areas of concussion damage to do slightly worse on the cognitive test than those without a concussion.
"If the hypoxia does what it should, which is eliminate that cognitive reserve, people with a concussion will have to use that part of the brain that's been damaged, revealing hidden deficits so we can take steps to treat them," Vacchiano says.
Throughout his naval career, Vacchiano's novel ideas solved problems. He's hoping he can help solve this one. "These computerized tests are available anywhere, and the setup to deliver the mild hypoxia is not particularly difficult either," he says. "If we can develop a simple test to identify those people with concussions who need treatment and get them into it early, we can prevent some long-lasting deficits."
The research is funded by the Tri Service Nursing Research Program, part of the Department of Defense.
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