Cardiac auscultation: a new method for instruction

Abstract

Context and setting The acoustic stethoscope provides important clinical information about the cardiovascular system and will continue to do so in the foreseeable future. Based upon recent reports, however, deterioration in general skills in cardiac auscultation has reached serious levels; therefore, better teaching methods are urgently needed. Why the idea was necessary Instruction in cardiac auscultation could be improved by a clear visual display of sounds, the availability of simultaneous and repetitive listening by multiple individuals, and the possibility for data storage and retrieval. In general, Echo and Doppler techniques have replaced the graphic display of heart sounds (phonocardiography), and, as a result, this latter method of display – traditionally an excellent teaching tool – is no longer used for instruction in auscultation. What was done In order to overcome these deficiencies, we have developed a new system that is inexpensive and consists of an ordinary acoustic stethoscope that has been modified by the insertion of a small microphone into the distal tubing near the chest piece, which is easily accomplished without special training. This microphone enhances sound quality and intensity and also communicates wirelessly with a computer or other similar stethoscopes. The computer’s screen may be as small as that on a portable hand-held device such as a cellular telephone. A waveform display can be modified (filtered) to correspond to the auditory perception. Although the recorded sounds are stationary, a moving cursor sweeps repeatedly over the image during playback and allows the listener to detect each sound with no time delay, ensuring that no components will be missed. Recorded sounds can subsequently be listened to at full or half speed (without loss of pitch). Half speed is useful in separating sounds from murmurs, characterising murmur timing and contour, and especially useful in the presence of tachycardia and in paediatric evaluation. Timing intervals, such as second sound splitting, can be measured with the tools supplied within this program. This system not only provides for immediate visual analysis, but images and sounds can be stored for later use in teaching and review. An electrocardiographic lead can be included for simultaneous timing of the heart sounds. Instruction is accomplished by listening while watching the images displayed on a screen. Also included is a library of pre-recorded normal and abnormal sounds, which provides an additional means of improving individual skills in cardiac auscultation. For large groups, a projector can display sounds visually while the simultaneous sounds are sent wirelessly to headset devices provided to the audience. In addition, all sounds may be displayed in spectral format, which is a means of showing frequency patterns versus time and is useful in practical applications such as distinguishing innocent from pathologic murmurs and assessing the presence and severity of aortic stenosis. The recorded sounds can be transmitted wirelessly to distant sites, providing a means for telemedical applications, as well as for record storage and retrieval. Evaluation of results and impact During the past 6 years, we have employed this method for training groups of all sizes including undergraduate students at our local university medical school. It has provided rapid early instruction and continuously receives positive responses from all recipients.