Vesicular lung sound amplitude mapping by automated flow-gated phonopneumography

A recently developed automated apparatus capable of determining vesicular lung sound amplitude rapidly and accurately was used to construct detailed inspiratory vesicular sound amplitude maps in eight healthy male subjects to determine the normal amplitude patterns on the chest wall. The sounds were recorded in 2-cm steps along the following lines bilaterally: A, vertically, clavicle to abdomen, 6 cm from the sternal border; B, vertically, from the level of T1 to the lung bases, 6 cm from the spine; and C, horizontally, from the sternal border to the spine at the level of the nipple. Sound amplitude was measured at an airflow rate of 1.3 l/s. The resulting amplitude maps revealed considerable intra- and intersubject variation with frequent amplitude heterophony. Th patterns for the subjects as a group were as follows: series A, amplitude decreasing with distance from the clavicle; series B, amplitude increasing with distance from T1 with a peak at the bases; and series C, approximately equal amplitude at all positions. The findings in series B and C are, in general, consistent with an explanation of ventilation following hydrostatic gradients. The series A pattern and the intersubject variability in amplitude are inconsistent with this explanation and suggest that the inspiratory vesicular sound amplitude is not simply a result of ventilation distribution but involves other as yet undefined factors.