The Relationship Between Airflow and Lung Sound Amplitude in Normal Subjects

Few investigators have examined the relationship between airflow and lung sound amplitude; the available data are contradictory. I measured airflow at the mouth and compared the peak flow ( V˙max) to mean and peak lung sound amplitude (mean AMP and peak AMP) at four sites on the chest wall (right and left anterior apices and posterior bases) in four healthy young adults. At each site, the sounds produced by 20 breaths at V˙max ranging between 1.5 and 4 L/s ( V˙var) were measured by an automated technique. Ten breaths during nearly constant V˙max breathing ( V˙con) also were measured at each site. The lung sound amplitudes at the four sites in each subject were grouped and compared to V˙max by linear regression analysis. The same sounds were also submitted to an automated V˙-correction procedure to evaluate its adequacy in automatically adjusting for the effect of variations in V˙max on lung sound amplitude. The data showed that lung sound amplitude (mean or peak) was linearly related to V˙ in all subjects (r for mean AMP vs V˙max:0.77, 0.85, 0.69,0.89; r for peak AMP vs V˙max:0.80, 0.83, 0.79, 0.88), p