The stethoscope is perhaps the most familiar symbol of the medical profession. It serves an important practical function as well: it’s designed to enable doctors to listen to a patient’s body as it functions, so they can hear anything that might be off.
The first stethoscope was developed in 1816 by a French pediatrician named René Laënnec, a tapered wooden tube resembling a contemporary hearing aid. The first flexible stethoscope appears to have been created less than 15 years later. The next improvement, in 1851, was the addition of a second earpiece by the Irish physician Arthur Leared.
The stethoscope has not significantly changed its design since that time. George Cammann, who made some refinements facilitating the commercial production of the instrument, also wrote about its diagnostic use. The only real change was the division of the listening part on two sides, for the heart and the lungs.
There are two major types of stethoscope:
- Acoustic stethoscopes use a hollow tube filled with air to transmit sound. The sensitive listening end vibrates with the patient’s heartbeat or respiration, which vibrates the air in the tube. The earpiece is connected to the other end of the air column, and so the wearer is able to hear the patient’s breathing and heart that way. Although they can be very quiet, an amplification system was developed around the close of the 20th century.
- Electronic stethoscopes use a microphone to pick up the sounds and convert them into electrical signals. These signals can be heard by medical personnel, transmitted wirelessly to a receiver, recorded, or even loaded onto a computer and analyzed. These analytic tools make diagnosis easier and surer, but the equipment is more complicated.
The “ear trumpet” variety of stethoscope is still in use. It is how fetal heartbeat can be heard. It’s also called a pinard, having been introduced to obstetrics by a French doctor named Adolphe Pinard.
Listening as a diagnostic method takes some practice, but it is the fastest, lowest-tech method of finding heart murmurs, irregular heartbeat, and respiratory difficulties.