Preference and auscultatory skill

This was determined by comparing the observers’ response with the true classification based on interpretation of the waveforms obtained by computer-based analysis taken as gold-standard (figure 1).¹¹ A rating was considered correct if a recommended term or an accepted synonym was used to describe it (term use ascribed to preference). The use of any incorrect term was ascribed to lack of auscultatory skill.

The left column shows typical values for the frequency (Hz) and duration (ms) of the five lung sounds. The middle column lists the site of sound recording. The two rightward columns show, respectively, the amplitude-time plots in unexpanded and time-expanded modes (amplitude is measured in arbitrary units, and time in seconds). The unexpanded plots contain screenshots of 3 respiratory cycles, starting always by inspiration. The red, horizontal line below each sound shows the place where the time-expanded sections were obtained. The unexpanded waveform of the normal breath sound (sample #1) shows a strong inspiratory component relative to the expiratory component. The time-expanded waveform shows random fluctuations is similar to those of a white noise. The unexpanded waveform of the wheeze (sample #2) has a strong expiratory component, which appears as sinusoidal oscillations characteristic of musical sounds in the time-expanded waveform. In unexpanded waveform, the fine crackles (sample #3) appear as spikes that correspond with rapidly damped wave deflections seen in the time-expanded waveform. The unexpanded waveform of the stridor (sample #4) shows a strong inspiratory component that appears as sinusoidal oscillations in the time-expanded waveform. The pleural friction rub (sample #5) has an unexpanded waveform characterised by a series of vertical spikes in a pattern that is indistinguishable from that produced by crackles. The greater amplitude and longer duration of the pleural friction rub can be seen in the time-expanded plot.