Auscultation using ultrasound-Doppler techniques

Abstract

An earlier presentation described a hybrid instrument using electromechanical and ultrasound-Doppler techniques to permit auscultation in extremely noisy environments, such as Army medical evacuation vehicles [Houtsma et al., J. Acoust. Soc. Am. 120, 3361 (2006)]. That paper presented the theories behind the hybrid instrument and provided simulations of auscultation in noisy environments. An update on the progress since the first report is presented. In one study, recordings of cardiac and pulmonary sounds from healthy volunteers aboard an in-flight Black Hawk helicopter are presented. As anticipated, auscultation with the electro-mechanical (acoustic) mode was impossible inside the aircraft. Using the ultrasound-Doppler mode, all heart sounds and most lung sounds were clearly audible. The best-audible lung sounds came from the mid-axillary left and right locations. A second study was performed to determine if the hybrid instrument could be used to detect the difference in sound in a correctly versus incorrectly ventilated swine. After some experimentation with precise auscultation sites, the listener was able to detect both heart and lung sounds reliably in both electromechanical and ultrasound-Doppler modes. Recommendations to improve the performance of the instrument in the next iteration of the device are presented.