stethoscope

stethoscope The stethoscope is an instrument for listening to sounds originating within the body. It was invented in 1816 by the French physician, Rene Laennec. The older diagnostic method of direct auscultation — applying the ear to the chest wall — was known to the ancient Greeks, but had fallen out of general use. It was, however, experimented with by Jean-Nicolas Corvisart, at the end of the eighteenth century. Laennec, who had been Corvisart's student, took a special interest in chest disorders. One day, he was consulted by a young woman with the symptoms of heart disease. Still a young man, Laennec felt too embarrassed to press his head against his patient's bosom. Remembering a children's game, he picked up a sheet of paper, rolled it into a tube, and placed one end upon the woman's chest. He was able to hear the sounds of her heart and her breathing quite distinctly. The stethoscope had been invented.

Leannec experimented with various materials and shapes for his new instrument, finalizing upon a simple hollow wooden cylinder, about 25 cm long. With this tool, Laennec undertook a comprehensive investigation of the sounds emanating from the heart and lungs, correlating his findings with post-mortem results. His treatise on the subject is the basis of our modern understanding of the pathology of the lung.

While there was some early opposition, Laennec's innovation came into general use quite quickly. The development of clinical teaching in the hospitals provided students with the necessary supply of patients upon whom to practice. By the 1850s, the stethoscope had become virtually the indispensable badge of office of the medical practitioner. Its widespread adoption encouraged the development of other methods of physical diagnosis.

However, despite Laennec's claims, the stethoscope possessed only a few technical advantages over direct auscultation. In most circumstances, the instrument did not enable one to hear the thoracic sounds any more clearly than one could with the unaided ear. What it did do was enable the physician to examine the patient's chest more conveniently, more hygienically, and less intrusively. In 1828, N. P. Comins, in Edinburgh, designed a stethoscope with a hinge in the middle of its barrel, to facilitate bedside application. Comins also suggested that a binaural stethoscope might be clinically useful, and in 1851 Arthur Leared designed an instrument with two flexible rubber tubes. This was the basis of the modern stethoscope, equipped with either an open bell or a diaphragm at the chestpiece, but it did not come into common use until the 1890s. Throughout the nineteenth century, many other modifications were suggested to improve the acoustics or the ease of use of the instrument, and methods for amplifying the heart and lung sounds were investigated.

While now superseded, to a large extent, in the diagnosis of lung disorders by the X-ray machine and other imaging techniques, and of heart disorders by investigative techniques ranging from the electrocardiogram to the ultrasonic scanner, the stethoscope remains indispensible in the initial detection of abnormalities in both hospital and general practice. Numerous applications have been found outside the thoracic region, such as in the monitoring of bowel function and of pregnancy, and in the measurement of blood pressure.

Malcolm Nicolson

See also sounds of the body.