Evaluation of Ultrasonic Bubble Detectors in vitro Using Calibrated Microbubbles at Selected Velocities.

摘要

Two standard Doppler ultrasonic devices, currently used for detecting bubbles in vivo, have been evaluated and compared in vitro using carefully calibrated uniform microbubbles rising at terminal velocity through a static aqueous medium. Two unexpected findings were observed: (a) the focal length of the transducer apparently decreases for smaller bubble sizes, and (b) a significant horizontal convection current was produced by one of the instruments. When the medium was in motion, it was found that the sensitivity varied markedly with bubble velocity. These findings are discussed with regard to the limitations of the Doppler technique for monitoring gas emboli in vivo and as an early warning for decompression sickness in divers.