Noise Reduction Stethoscope for United States Navy Application
NAVAL SUBMARINE MEDICAL RESEARCH LAB GROTON CT
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Conventional stethoscopes cannot function effectively unless ambient noise is maintained at approximate clinical levels approximately 70 dB SPL. This serious limitation inhibits diagnosis and monitoring of patients in a variety of common military medical situations in field hospitals, in high ambient noise environments such as engine rooms, in vehicles such as ambulances, fixed and rotary wing aircraft, or in hyperbaric chamber treatment facilities. Trying to measure blood pressure, determining if a faint heartbeat is present in a casualty, or listening to respiratory events can be nearly impossible under field conditions. Technology is immediately available to dramatically reduce this shortfall. The objective of this research was to evaluate several compact noise-reducingcanceling stethoscopes for field, moderately-loud medical- transport, and shipboard use in noisy environments. Three commercial off the shelf COTS noise reducing stethoscopes, having electronic outputs, were evaluated quantitatively in a controlled laboratory study. Laboratory data on detection of vital sounds in operationally- relevant sound-fields showed the devices. ability to adequately present abnormal heart and breath sounds in 90 to 95 dB SPL. By their design these devices could tolerate higher levels of environmental noise that normally would interfere with such detection. This is a significant improvement in the tolerable ambient sound-field over an average 76 dB SPL upper limit for detecting abnormal breath sounds, and an average 81 dB SPL upper limit for detecting abnormal heart sounds, when using a conventional device. After laboratory and operational evaluation, we are able to recommend two available COTS devices for military use, and to suggest a prototypic device, a vastly miniaturized version of one of the two devices we recomfof the various software programs that allow acoustic records of patient pathology.
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