The stethoscope is the traditional tool of the doctor. But its value is limited to examining only certain parts of the body. Because it is used to amplify sounds, most often of the chest or abdomen, it is a vital instrument for the heart or chest specialist. In the case of the chest, it allows the doctor to hear two sets of sounds: those produced by the heart, and those from the lung and air passages. The ‘lub-dup’ heart sounds are produced by closure of the valves that direct blood through the chambers of the heart. The first sound, or’lub corresponds to closure of the tricuspid and mitral valves, which separate the chambers of the heart, whereas the second sound, or ‘dup’, is caused by closure of the pulmonary and aortic valves, which are situated at the outlets of the heart. If the valves are diseased the character or timing of the sounds may change. The doctor may also detect additional sounds, or ‘murmurs’, arising from turbulent blood flow across the abnormal valves. If the heart is failing in its pumping action, third and fourth (’added’) sounds may become audible. In partial arterial obstruction, murmurs can sometimes be heard. If arteriosclerosis is suspected, the course of some arteries may be traced and auscultated in order to reveal possible problems.
The breathing sounds heard through the stethoscope result from air passing in and out of the trachea (windpipe) and smaller airways in the lungs. In the presence of infection or another disorder, such as spasm of the air passages (during a asthma attack), these sounds alter in character. Within the abdomen, bowel sounds can be heard with the stethoscope. These squeaks and gurgles arise from the normal action of the intestines. Certain characteristic, high-pitched noises may occur in early bowel obstruction, whereas advanced obstruction is characterized by an ominous silence. Special stethoscopes are used for examining pregnant women. A doctor uses a short, trumpet-shaped stethoscope on the woman’s abdomen to listen to the foetal heartbeat. An electronic stethoscope may also be used.