Effects of lung volume and airflow on the frequency spectrum of vesicular lung sounds

The purpose of this study was to determine whether the vesicular lung sound frequency spectrum is affected by changes in lung volume and airflow. Nine healthy young nonsmokers were studied. The dependent variables were the points that divide the power spectrum of the vesicular lung sound into quarters (1st, 2nd and 3rd quartiles (Q1, Q2 and Q3]. Recording sites were the right upper anterior (RUL) and lower posterior (RLL) chest wall. Lung sounds were high-pass filtered at 100 Hz. To evaluate the effect of volume, lung sounds were recorded during an inspiratory vital capacity (VC) maneuver at near constant airflow rates. The spectral parameters were determined at each sixth of the VC. To assess the effects of airflow, 5 of the subjects breathed from resting lung volume at peak inspiratory airflows of between 1 and 3.0 L/sec for a total of 16 breaths each and the frequency parameters of the lung sounds occurring during peak inspiratory airflows were determined.

Volume effects: only at the RUL was there a small but significant decrease in all three parameters with increasing lung volume. Airflow effects: all parameters were independent of airflow except for a weakly positive relationship (r = 0.285, P less than 0.05) for Q3 at the RUL location. Individually, there were weakly significant trends in three of the five subjects. These data suggest that the frequency composition of the vesicular lung sound in groups of healthy adults is not systematically affected by changes in lung volume or airflow.