Valentín Rodríguez, Francisco I.

Profile Picture

Filters

20121
Reset filters

Settings

Citations

Publication Search Results

Now showing 1 - 1 of 1
  • Thumbnail Image
    Publication
    An acoustic method for real time air bubble detection in simulated blood vessels
    (2012) Valentín Rodríguez, Francisco I.; Cancelos, Silvina; College of Engineering; Leonardi, Stefano; Gutierrez, Gustavo; Department of Mechanical Engineering; Calcagno, Barbara
    Exposure to significant changes in ambient pressure commonly occurs in divers during surfacing. These changes induce the formation of nitrogen bubbles in tissues and the presence of these bubbles can cause symptoms of decompression sickness (DCS) to appear. Existing methods to minimize the formation of bubbles include denitrogenation strategies and the use of decompression tables. Although these tables are calculated using large safety margins, they are not guaranteed and the occurrence of DCS has been reported even in those who followed suggested protocols. Therefore, the development of a system capable of monitoring bubble presence, number and size, in real time, would be a reliable method for DCS prevention. In this work, we demonstrate a novel technique for bubble detection using a piezoelectric ring (PZT) placed around the human upper thigh and set to resonate at a specific frequency. Our approach uses microphones to monitor distortions in the resonant condition that were induced by the presence of bubbles. A prototype of a simplified human upper thigh was built and bubbles of controlled size were injected into the artificial blood vessel. Using a digitalized data acquisition system, electrical signals on the PZT and microphone were acquired. The results suggested that the presence of a single bubble within the chamber disrupted the signal, displaying a peak in current and phase angles as the bubble crossed the actuation area of the PZT ring. For stationary bubbles, electrical admittance (measured as a function of frequency) demonstrated a higher Pearson correlation coefficient as the bubble was insonated near its resonance frequency than in the absence of bubbles. A summation of Fourier coefficients of voltage signals captured from the pill microphones in the presence of bubbles demonstrated a 94% accuracy in detecting single bubbles, when compared to signals taken in the absence of bubbles. It was concluded that the proposed system produced a measurable response to the presence of large bubbles.