Figure 2.

Selection of maximal inspiratory frames for analysis. Examples of frame selection in various vibration response imaging (VRI) waveform patterns are shown. The dot on the VRI waveform represents the area from which the maximal energy frame was chosen for analysis. (a) When inspiratory and expiratory vibrations are clearly separated, the maximal energy frame during inspiration (first peak) is chosen. (b) When nspiratory and expiratory vibrations merge into one peak, the highest energy frame is chosen. (c) When inspiratory and expiratory vibrations form a plateau, first frame at zero slope is chosen. (d) When no clear separation exists between inspiratory and expiratory vibrations, and the frame nearest the inflection point of the shoulder is chosen.