Sound component duration of healthy human pharyngoesophageal swallowing: a gender comparison study

Cervical auscultation is a noninvasive technique for studying swallowing that was first used in the 1960s. The aim of our study was to use the numeric acoustic recording technique for analyzing swallowing sound signals in healthy subjects while they ingested a defined volume and consistency of a specific substance. Twenty males and ten females were included in the study and given 10 ml of a barium suspension to swallow. A microphone was placed on the skin overlying the lateral border of the trachea, directly under the inferior border of the cricoid, and connected to a computer. For each sound recording, the total duration of the sound (td), the number (n) of sound components (SC), the duration of each SC (c1, c2, c3,...), and the intervals (i1, i2,...) between the SCs were measured. For all the recordings, the mean durations of acoustic parameters (TDm, C1m, C2m, C3m, I1m, I2m) were calculated and compared by using Student's t test. In the 20 male subjects, the mean acoustic parameters were calculated (MTDm, MC1m, MC2m, MC3m, MI1m, MI2m) and compared with the mean acoustic parameters (FTDm, FC1m, FC2m, FC3m, FI1m, FI2m) in the ten females by using a Wilcoxon nonparametric statistical test. We were able to interpret 80% of the recordings. The TDm was 710 +/- 28 ms. Three main SCs were detected: C1m = 100 +/- 56, C2m = 150 +/- 90, C3m = 80 +/- 54 ms; I1m = 100 +/- 66, I2m = 190 +/- 120 ms. No significant difference in these parameters was observed with respect to gender. This study enabled us to decompose the swallowing sounds into three main SCs and to quantify their normal durations. These results should prove useful for the assessment of sound variations in pathologic conditions.