The stethoscope

Abstract

In spite of the development diagnostic methods, the stethoscope has been an important medical tool. Nepertheless, this literature revision (1941 - 1994) has the purpose of presenting to medical students and health professionals historical and technical aspects concerning auscultation. The authors have done a bibliographic revision form 1941 to 1994 on this subject. Since XIV Century, when stethoscope was discovered, several researches bad been done in an attempt to find a more sensitive one. So far, an ideal stethoscope ought to have the following characteristics: ear pieces must be well adjusted to ear with their axles parallel to the external auditive canal in order to avoid air escape and noise from outside; hasted must be parallel to the bigger axles of the auditive canal. The dimensions of the tube must be 25-30 cm long and diameter of 3 mm to avoid the distortion of sounds; receiver chamber (Bell+Diaphragma): the use the bell is more appropriate for auscultation of low frequency sounds and the diaphragma for high frequency ones. The conclusion is that there is no stethoscope which fulfills all the characteristics considered to be ideal for auscultation. However, there have been several ongoing researches to improve accoustic performance of the stethoscopes.