| Study of an acoustic technique to detect cavitation produced by a tilting disc valve. | |
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MedLine Citation:
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PMID: 8834731 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
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BACKGROUND AND AIM OF THE STUDY: Transient cavitation has been directly observed near operating mechanical heart valves in vitro and inferred in vivo via the observation of pitting on explanted clinically used valves. Visual detection of cavitation bubbles, however, cannot be accomplished in vivo or when any opaque fluid, e.g. blood, is used. METHODS: This study examines a passive acoustic technique for detecting cavitation caused by a 27 mm tilting disc valve. We captured, valve closing sounds in vitro and attempted to detect a shift of energy into higher frequencies due to emission of broad-band noise caused by collapsing bubbles. The valve tester consists of a piston pump which directly drives the valve, a 16 cm diameter cylindrical lucite atrium and an air chamber in parallel to provide compliance. Water was used as a blood analog fluid. The cycle rate was altered to vary valve loading and produce cavitation. Acoustic signals were detected by a miniature hydrophone and a large area transducer and the waveforms were spectrum analyzed to 200 kHz and 500 kHz respectively. Cavitation onset was determined rising a high speed video camera. RESULTS: It was found that even under non-cavitating conditions, significant energy was produced at frequencies greater than 100 kHz, and this energy increased with increased load. The proportion of energy in high frequency bands, however, remained fairly constant when cavitation was not present and began to rise only after the cavitation threshold was reached. To isolate cavitation as an independent variable, data were taken with all system parameters constant, but using water under two different conditions. Degassed 17 degrees C water produced no visualizable bubbles, while aerated tap water at 43 degrees C showed a high degree of cavitation. CONCLUSIONS: The results indicate that cavitation, while causing a shift of energy to higher frequencies, is not the only mechanism responsible for the shift of energy into higher frequencies. |
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Authors:
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B A Herman; J M Porter; R F Carey |
Publication Detail:
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Type: Journal Article |
Journal Detail:
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Title: The Journal of heart valve disease Volume: 5 ISSN: 0966-8519 ISO Abbreviation: J. Heart Valve Dis. Publication Date: 1996 Jan |
Date Detail:
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Created Date: 1996-12-04 Completed Date: 1996-12-04 Revised Date: 2007-11-15 |
Medline Journal Info:
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Nlm Unique ID: 9312096 Medline TA: J Heart Valve Dis Country: ENGLAND |
Other Details:
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Languages: eng Pagination: 90-6 Citation Subset: IM |
Affiliation:
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Center for Devices and Radiological Health, Food and Drug Administration, Rockville, Maryland, USA. |
Export Citation:
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| MeSH Terms | |
Descriptor/Qualifier:
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Acoustics
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instrumentation* Biomechanics Blood Pressure / physiology Fourier Analysis Heart Auscultation / instrumentation Heart Valve Prosthesis* Hemodynamics / physiology* Humans Models, Cardiovascular* Prosthesis Design Prosthesis Failure Signal Processing, Computer-Assisted / instrumentation Sound Spectrography / instrumentation |
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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