[Monitoring of the permeability of the inferior esophageal sphincter using sound signals]

An original method is described for graphic display of sounds arising from the cardia during the swallowing of saliva or water. Two dynamic microphones were placed on the skin of epigastric xyphoid area and simultaneously on the latero-cervical position. The following conditions must be filled: position of the subject (upright or lying), correct application of microphone with pressure (2 kPa), specially for the xyphoid situation. For graphic restitutions from magnetic signal, a time-recording paper was used, on line or off line, with an analogical device including Butterworth band active filter (optimal frequency range 0.8-1.2 kHz), amplifier and integrator (tau = 2 s). Occurrence of typical cardia sounds were 86-97 % for saliva and 95-100 % for water in two normal subjects for the evaluation of reproducibility (one man and one woman 35 and 47 years old respectively, n = 234 sequences, interval 20 s). Using the distance between the upper and lower microphones, the esophageal time transit can be measured. The signal was more unconstantly recorded for saliva 40 +/- 44 % in adults (n = 10) and 76 +/- 17 % in children (n = 7), than for 80 et 87 % for water respectively. The optimal interval between two swallows appeared to be 15-25 s. In patients with presumption of achalasia (n = 8), the two phonic signals were recorded during esophageal pressure measurement. The presence of esophageal sounds seems to be the sign of absence of achalasia.