René Laënnec Revolutionizes the Diagnosis of Chest Diseases with His Invention of the Stethoscope
René Laënnec Revolutionizes the Diagnosis of Chest Diseases with His Invention of the Stethoscope
In 1816 French physician René Laënnec began using a device of his own invention to listen to the sounds of the living heart and lungs. This simple advance revolutionized the diagnosis of chest diseases and later contributed to understanding their pathology and therapeutics—that is, what they are and how to treat them.
Some of the best observers in the history of medicine lived in the early nineteenth century. The state of medical science then was such that physicians could cure almost nothing but could recognize and describe a great deal that would escape physicians today. Using only their five senses, their skill in observation and description was generally more acute than that of today's doctors, who have at their service arsenals of diagnostic instruments and therefore do not have to depend so much upon direct physical examination.
Even the best physical examination, however, can provide only a superficial, incomplete account of the health of the patient. Doctors have always sought better methods to examine patients and diagnose disease. Sometimes these better methods involve new instruments, sometimes new techniques, sometimes both.
In the 1750s Viennese physician Leopold Auenbrugger (1722-1809) discovered that the healthy chest and the diseased chest sound different when struck. The healthy chest, dry and full of air, sounds like a cloth-covered drum. The diseased chest, which may contain various thick fluids, sounds more muffled. Auenbrugger developed a technique of striking the patient's chest gently but firmly with his fingers, and he learned to recognize the many meanings of the different sounds in different parts of the chest. He called this technique "percussion" and published his results in Latin in 1761.
The medical community did not think highly of percussion until Napoleon Bonaparte's personal physician, Baron Jean Nicolas Corvisart des Marets (1755-1821), published his French translation of Auenbrugger's treatise in 1808. After that percussion was universally accepted, almost overnight. One of Corvisart's students was René-Théophile-Hyacinthe Laënnec (1781-1826).
As diagnosticians, both Corvisart and Laënnec understood the importance of listening carefully to the patient's chest. They also realized that percussion alone was not sufficient. They practiced a technique called "auscultation," or listening directly to chest sounds, which in those days meant that the physician had to put his ear on the patient's body.
Auscultation has been known since antiquity. The founder of the Western medical tradition, Hippocrates (460-375 b.c.), advocated it. The problem with auscultation was not to convince doctors of its value. Rather, the problem was mechanical: how to get the ear close enough. Hearing the chest clearly and accurately was difficult with fat patients. A patient might have lice or skin conditions that would spread to the doctor if he got too close. A woman might feel offended with the doctor's ear on or near her breasts. In those days the social demands of modesty and delicacy dissuaded male physicians from close physical contact with their female patients.
One day in 1816 Laënnec was frustrated trying to examine an unusually fat woman with symptoms of heart disease. Her gender, her obesity, and the size of her breasts prevented him from listening to her heart. Almost instinctively he rolled up a few sheets of paper into a tight tube, put one end of this cylinder to his ear and the other on her chest. What he heard amazed him. The chest sounds were louder and clearer than he had ever heard them before, and the background noise was mostly eliminated when he blocked his other ear. This was the first stethoscope.
Laënnec named the instrument from two Greek words, stêthos ("chest") and skopos ("one who watches"), because he and Corvisart thought that it almost enabled them to "see" inside the chest. Laënnec called the technique of using the stethoscope "mediate auscultation" and distinguished it from "immediate auscultation," or putting the ear directly on the patient.
Laënnec instantly recognized the great advance he had created in diagnostic and clinical medicine, but he did not publish his results right away. Instead, he spent the next few years gathering data on the many different chest sounds and what they meant. He studied the chest sounds of dying patients and then verified his conjectures at autopsy. Thus, he could correlate sounds heard through the stethoscope with the conditions of diseased tissue in cadavers.
When he was ready, he introduced his discovery in 1819 in a massive two-volume work: De l'auscultation médiate, ou traité du diagnostic des maladies des poumons et du coeur ("On Mediate Auscultation, or: A Treatise on the Diagnostics of the Diseases of the Lungs and Heart"). This was soon translated into English by Sir John Forbes as A Treatise on the Diseases of the Chest, in Which They Are Described According to Their Anatomical Characters, and their Diagnosis, Established on a New Principle by Means of Acoustick Instruments. The second edition of Laënnec's book (1826) was even more thorough in depicting pathological, anatomical, and therapeutic findings and quickly became a classic in the English-speaking world when Forbes published his translation in 1827.
The principle of the stethoscope, namely, that sound travels better through solids than through air was known long before Laënnec. But he was the first to use this principle effectively in the practice of medicine. His challenge from 1816 to 1819 was to demonstrate to other physicians that the sounds heard with a stethoscope could provide more accurate diagnosis than those heard with the unaided ear. In other words, he had to prove that mediate auscultation was better medically than immediate auscultation. His arguments soon won many prominent converts who refined his research.
Laënnec's countryman Victor Collin (dates unknown) wrote Des diverses méthodes d'exploration de la poitrine et de leur application au diagnostic de ses maladies ("On the Various Methods of Exploring the Chest and Their Application to the Diagnostics of Chest Diseases"), which was translated into English by W. N. Ryland as Manual for the Use of the Stethoscope: A Short Treatise on the Different Methods of Investigating the Diseases of the Chest. Pierre Adolphe Piorry (1794-1879) combined the techniques of percussion and mediate auscultation and reported his results in De la percussion médiate ("On Mediate Percussion"). Jean-Baptiste Bouillaud (1796-1881) used the stethoscope to gather data for his classic description of endocarditis in Traité clinique des maladies du coeur ("Clinical Treatise on Heart Diseases."
Among the first of Laënnec's followers outside France was Irish physician William Stokes (1804-1878), whose books include An Introduction to the Use of the Stethoscope (1825) and A Treatise on the Diagnosis and Treatment of Diseases of the Chest (1837). Bohemian diagnostician Josef Skoda (1805-1881) made further advances in the classification and interpretation of chest sounds. His 1839 work Abhandlung über Perkussion und Auskultation ("Treatise on Percussion and Auscultation") has been translated into many languages and is useful for clinicians even today. The intricate descriptions of bronchitis and several other ailments by Philadelphia physician William Wood Gerhard (1809-1872) in Lectures on the Diagnosis, Pathology, and Treatment of the Diseases of the Chest (1842) remain unsurpassed for their accuracy and detail. Henry Ingersoll Bowditch (1808-1892) established the stethoscope as a diagnostic tool in America with The Young Stethoscopist; or, The Student's Aid to Auscultation (1846).
The published work of Laënnec, Forbes, Collin, Piorry, Bouillaud, Stokes, Skoda, Gerhard, Bowditch, and others was widely available to the medical community and clearly demonstrated the great medical value of the stethoscope. But many physicians worldwide were still reluctant to accept its use in their own practices. This reluctance was because of the shape and inconvenience of the instrument.
Laënnec had promptly replaced his earliest paper stethoscopes with wooden ones, about the same size and shape as a modern flashlight. Some of his successors used hollow wooden tubes for lung sounds and solid wooden tubes for heart sounds. Some used wooden tubes with ivory or brass attachments. But these were all "monaural" or "one-ear" stethoscopes. The physician could listen with only one ear and could not look directly at the patient while using this kind of instrument.
To try to overcome the significant disadvantages of the monaural stethoscope, British physician Nicholas Comins (dates unknown) proposed his design for a "binaural" or "two-ear" stethoscope in 1829, but it did not transmit sound as well as the monaural wooden tube and was soon abandoned. Many other clumsy attempts at a binaural stethoscope appeared in the next two decades.
The modern stethoscope is binaural and has a chestpiece consisting of two sides: a hollow "bell" for isolating low-frequency sounds and a flat "diaphragm" for isolating high-frequency sounds. About 30-40 cm. of flexible tubing runs between the bell/diaphragm assembly and the two earpieces. This now familiar shape did not begin to emerge until the 1850s. Through the independent efforts of British physician Arthur Leared (1822-1879), New York physician George P. Cammann (1804-1863), and others, practical binaural stethoscopes became commonly available after about 1856.
After the dawn of the binaural stethoscope, Austin Flint (1812-1886) made so much progress using mediate auscultation as a diagnostic tool that he was praised as "the American Laënnec." Among his important books in this field are Physical Exploration and Diagnosis of Diseases Affecting the Respiratory Organs (1856); A Practical Treatise on the Diagnosis, Pathology, and Treatment of the Diseases of the Heart (1859); and A Manual of Auscultation and Percussion, Embracing the Physical Diagnosis of Diseases of the Lungs and Heart, and of Thoracic Aneurism (1876).
ERIC V.D. LUFT
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