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EMS House of DeFrance http://www.emshouse.com EMS Education - Articles Courtesy the EMS House of DeFrance http://www.defrance.org We all know emergency vehicles race to accident scenes with sirens blaring. But even at an accident scene the noise can be so loud and chaotic it can make listening to heartbeats and lungs impossible to hear. Well that may soon change with a new high-tech device -- a life-saving instrument. Ambulances, fire trucks, even Medivac helicopters -- they're first at an accident scene, but they're also loud, making it difficult for paramedics and doctors to listen to a patient's vital signs with a stethoscope. Donald Lehman, flight paramedic: "You can't hear lung sounds. You can't hear heart sounds inside of a running helicopter." William Bernhard, MD, anesthesiologist & master flight surgeon: "Traditional stethoscopes do not work well because of all the outside noise that interferes with the sounds we're trying to listen to." The solution? A new ultrasound stethoscope that ignores outside noise and allow medics to hear life-saving sounds inside the body. Dr. William Bernhard: "It's extremely helpful because it's the only thing out there on the market that will work." Electrical engineers developed the device. It sends an ultrasound wave into the body. When it hits moving organs, like the heart or lungs, it bounces back at a different frequency, called the Doppler Effect. This change in frequency is converted into sound that medics can hear. In fact, the ultrasound stethoscope is nearly impervious to loud noise and can transmit accurate readings at noise levels up to 120 decibels, similar to the volume experienced in the front row at a rock concert. Adrian Houtsma, PhD, U.S. Army aeromedical electrical engineer: "The exciting thing now is that we have a simple, hand-held device that can be used in these very high noise environments and gives a very, very clean, audible signal." Loud war zones make a standard stethoscope useless. The new device is now being field-tested for the Army, with the promise of picking up life-saving signals. Researchers are in the process of obtaining FDA approval for the device and are working to make sure it doesn't generate signals that interfere with aircraft or other equipment. BACKGROUND: A new type of stethoscope relies on ultrasound to enable doctors to hear the sounds of the body in extremely loud situations, such as during the transportation of patients in MedEVAC helicopters or wounded soldiers in Blackhawk helicopters. HOW IT WORKS: These new ultrasound models transmit a sound signal into the patient's body. This sound is reflected back to the stethoscope at a slightly different frequency because it bounces off the internal organs, changing the sound wave pattern -- essentially, the Doppler effect. The difference in frequencies between the transmitted sound wave and the returning sound wave received by the instrument can be computed to determine the motion of the internal organs. This difference in frequency is then converted into audible sound. Ultrasound stethoscopes produce a markedly different sound than conventional ones. An acoustic stethoscope yields a "lub-dub" sound from a heartbeat with the first beat being the strongest. An ultrasound stethoscope yields a "ta-da-ta" pattern with the second beat being the strongest. THE PROBLEM: Traditional stethoscopes transmit and amplify sound within the range of human hearing: from 20 hertz to 20,000 hertz. Most body sound, such as that of the heart and lungs, fall into the 100 to 200 hertz range. Current acoustic stethoscopes detect and amplify vibrations that allow doctors to hear the heart and lungs better. However, they become difficult to use around 80 decibels -- a noise level comparable to an alarm clock or a busy street -- and are useless above 90 decibels. The ultrasound stethoscope is nearly impervious to loud noise and can make accurate readings at noise levels up to 120 decibels, similar to the volume experienced in the front row at a rock concert. The
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