Different Kinds of Stethoscopes

A stethoscope is a medical device that is used to listen to the heart, lungs, pulse and abdomen in a way that is non-invasive. A stethoscope helps physicians and other health care professionals find out whether a person has congestion in the lungs or an irregular heartbeat. The device was invented by Dr. Rene Theophile Hyacinthe Laennec in 1816, who created a cylinder form out of paper that allowed him to listen to sounds within a patient's body, including her heartbeat.

Beginning

• The first stethoscope that was manufactured by Laennec and used by other physicians was made up of a hollow wooden tube. It was known as a "Monaural" stethoscope because it only had one earpiece. Before the distribution of this device, doctors had to put their ears to patients' chest to listen to heartbeats. This type of stethoscope is still used today to listen to babies' heartbeats.

Significance

• Between the 1820s and 1900s, a number of different types of stethoscopes emerged, but some did not meet with success even though they influenced future models. One that was not used commercially by physicians was the first Binaural stethoscope, which was invented in 1829. It was invented by Nicholas Comins, and it consisted of a "bent tube" with a number of hinges that made it more comfortable for physicians to examine patients. Although this was not a popular model, many doctors followed with similar binaural-type models that featured two earpieces.

Development

• In the 1850s, a number of scientists came up with stethoscopes that featured two earpieces. One of the first that was commercially available was produced by Nathan Marsh in Cincinnati in 1851. It was made of India rubber and contained a diaphragm chest piece, but it was so bulky that is was difficult for doctors to use. In 1952, Dr. George Cammann created the first useable binaural stethoscope, which had short tubes, a chest piece made of ebony wood that was conically shaped and ivory earpieces. It was held together only by a single hinge joint, and the tubes connected to a hollow ball that heightened sounds.

Innovation

• In the late 1800s, the stethoscope was further developed so that diaphragm models became available. These stethoscopes were important because they allowed doctors to tell the difference between sounds produced by the heart and lungs as well as listen to higher-pitched sounds produced in the chest. Earlier models, which were known as bell chest stethoscopes, were designed to detect low-pitched sounds. The bell piece was the part at the end, attached to the tubes, which amplified sounds. The first practical diaphragm stethoscope was patented by Dr. Robert Bowles in 1894 and consisted of a chest piece that was made of flat-iron, which were placed where bell pieces had on earlier stethoscopes. The stethoscope was further improved when the first combination stethoscope, with both bell and diaphragm chest pieces, was developed by Howard Sprague in 1926. It allowed doctors to hear both high- and low-pitched sounds in the chest.

Use

• One type of stethoscope that is used widely today is the acoustic stethoscope. It consists of hollow tubes that lead down to a two-sided chest piece. It is a combination stethoscope with a bell, plastic disk, diaphragm, hollow cup and chest pieces. Through the diaphragm portion, sounds from the chest vibrate the chest piece, creating acoustic sound waves that travel up to the physicians' ears. Using the bell end, vibrations from the skin are what are used to create the acoustic sound waves. One issue with acoustic stethoscopes has been that they have a low sound quality.

Potential

• Another type of stethoscope that is used today is the electronic model. Electronic stethoscopes amplify sound waves, which are converted from acoustic to electronic waves. These stethoscopes are similar in appearance to acoustic models except that they feature microphones attached either inside the bell or behind the diaphragm chest piece that convert sound waves. They were designed for cardiologists and doctors who need to hear specific sounds in the chest more clearly, such as those produced by the respiratory system. Some electronic stethoscopes, such as 3M's Littmann 3000 and Thinklabs' ds32a, have the ability to filter out ambient noise, allowing for better diagnoses.