Popular Science Monthly/Volume 25/June 1884/Stethoscopy
By SAMUEL HART, M. D.
ONE fifth of the adult population of Christendom is suffering from chest or thoracic diseases of a degree varying from the insignificant to the most grave; while another fifth is living in constant fear of being or becoming their victims.
In fact, diseases of the lungs and heart far exceed those of any-other class in prevalence and fatality—consumption, so called, causing one fourth of the mortality between the ages of seventeen and thirty-five years—while diseases of the heart are of well-known formidable character, and raise the proportion of thoracic or pectoral diseases to a surprising ratio.
The study of this subject, as regards the causes and preventives, the symptoms and cure, has received the diligent attention of scientists and sanitarians as well as of physicians.
Leaving to the physician his subject in its multiple and exhaustless forms, I propose in this paper to give some account of the practical diagnosis, or methods of determining the nature, exact locality, and extent of thoracic disease, by means of stethoscopy, or the physical exploration of the chest.
The thorax incloses the essentially vital organs—the lungs with their pleurae, or delicate membranous coverings, and the heart with its pericardium and great blood-vessels. These, actuated through their system of nerve-filaments, give the rhythmic heavings of respiration and the throb and pulses of the blood-circulation.
Although so admirably guarded against harm by the strong and elastic chest-walls, and against all inimical approach by that ever-vigilant sentinel, the epiglottis, they are, from the very nature of their functions, preeminently subject to danger from without as well as from within. The delicate mechanism of living lung-tissue can not be subjected to direct observation; the minute cells for containing air would be crushed by air admitted from without, and the heart arrested for a moment for inspection would never beat again; yet the vital operations of these organs are well understood and their morbid conditions can be read almost as if exposed to view.
On firmly applying the ear to the walls of the chest of a person in health, certain sounds can be heard, varying in loudness and clearness with the quarter of the chest at which the ear is applied, and with the age or individual peculiarity of the person examined, or his state of action or repose. The double sound of the heart, embracing what are known as the first and second sounds, is heard distinctly: the former caused by the strong muscular contractions of the ventricles, mainly the left, whose function it is to distribute the blood to the system. This contraction causes the pulse, with its many qualities of quick or slow, soft or hard, regular or intermittent, and others which furnish to the tactus eruditus valuable indications of the physical condition not only of the heart itself, but also of the system at large.
The sounds of respiration are also heard: the inflation of healthy air-cells, producing the vesicular murmur, is audible even to the unaided ear.
This direct application of the ear to the chest (called immediate auscultation) is preferred by some as having advantages over the mediate or instrumental method. The former is, however, open to some objections which are readily apparent, both as regards the subject and the examiner; while the stethoscopic method possesses numerous advantages, without the objections.
The following is a brief description of the appliances ordinarily in use in exploring the thoracic contents:
First in importance among these is the stethoscope (Fig. 1). This instrument, in its primitive form, was exceedingly simple: at first a cylinder of paper, rolled tightly and of convenient length. A ready substitute was found in wood; and this was carved or turned to give lightness and to improve appearance. Cedar and ebony have been preferred, as being of fine quality and easily polished. Vulcanite and
various metals are also used, made in similar form—i. e., a tube of suitable length, expanded at one end into a hollow cone for application to the chest, and suited at the other end to the rim or opening of the ear. In these as in all other forms the object is to insure, when in use, a confined column of air extending from the bare walls of the chest of the person examined to the ear of the listener; and upon the completeness of the adjustment and consequent inclosure of the air depends the efficiency of the instrument, since the confined air—not the instrument—is the medium of conduction of the sounds.
The flexible tube was used later as a step in stethoscopic evolution, which gives the advantage of allowing comfortable respiration without disturbing the inclosed air of the tube by the movements of breathing, which tend to press the instrument alternately against the ear of the listener (Fig. 2).
The binaural stethoscope (Fig. 3) of Dr. Camman, of New York city, is unquestionably the best instrument known. Its name signifies its peculiar advantages. Two tubes (one for each ear), suitably curved,
and each furnished with a rounded bulb for accurate fitting to the opening of the ear, are connected at the other ends with a hollow cone for application to the chest of the person examined. The cones or chest-pieces are of various sizes, and are adjusted and used interchangeably according to the required extent of field which has its limits between one and two inches in diameter. They are made from ebonized wood, vulcanite, or soft rubber, the latter being required to
prevent painful pressure on uneven surfaces of the chest. In a part of their course the tubes are elastic, the remainder being metallic. They are so constructed as to be easily and perfectly adjustable to the ears by softly elastic springs. By this arrangement both ears are not only equally engaged with the same sounds, but other sounds are practically excluded. This feature is fairly represented in the binocular microscope and in the stereoscope, which possess the full advantages derived from the use of both eyes. Thus the stethoscope heightens and places in relief our auditory perception of the movements and conditions of deep-seated vital organs, giving prominence to the lines and shades of a picture otherwise flat and indistinct. It will, of course, conduct all sounds communicated to it from without, thus making it necessary to avoid all frictional contact with the instrument, even of the lightest clothing; and the listener will steady it deftly by thumb and finger to escape confusion from a multiplicity of sounds. By the practiced ear, however, most of the numerous adventitious sounds can readily be eliminated and the attention successfully fixed on the one sought.
The means next in importance in questioning the condition within the thoracic cavity is percussion. It consists in striking upon the chest with carefully-suited force with the tips of one or more of the fingers slightly bent; or with a light elastic hammer called the percussor (Fig. 4). The finger of the other hand or a solid, flattened disk, the pleximeter, must be held firmly against the chest to receive the stroke and to educe the proper resonance. The percussion-sound, though apparently unmusical, must have its intensity, be high or low, and have its peculiar timbre—all requiring acuteness of hearing and judgment in interpretation.
The spirometer is of use for measuring in cubic inches the maximum
Fig. 4.—Flint's Percussor and Pleximeter.
amount of respirable air, of which each individual has his normal quantity, but which is subject to changes from organic affections of the lungs.
The cyrtometer is used for delineating the external contour of the chest and for exact comparison of one side with the other.
Numerous other instruments are of real utility, only one of which, however, will be mentioned.
The sphygmograph is an instrument of somewhat complicated mechanism. It is used to "feel the pulse" and to record its impressions. It will give its frequency and rhythm, its varying tension and strength, the condition of the heart and certain valves, with a delicacy and exactitude which, compared with the results obtainable by the most sensitive finger, are like the perfect work of photography compared with the attempts of the juvenile charcoal artist. With its touch upon the heart or its vessels, and its pen apparently in sympathy and vital connection with them it will record in delicate but infallible tracery the diagnosis, and mayhap the prognosis, of the subject under examination, which may be read with trembling expectation.
In this instrument the impulse of the blood-movements is communicated to the pen by water contained in flexible tubes. The oblong receptacle, also containing water, is connected with one of these tubes. It has on one side an elastic projection which is to be securely fixed upon the pulse to be examined. All vibrations received by it are transmitted by the water through the tube to the chamber. On the upper surface of the chamber is a delicate membrane which receives the vibrations with every requisite as to quality and exactitude. The movement of its wave is, however, microscopic, and, in order to render it visible and legible, an exceedingly light and sensitive lever terminating in a pen is so placed in contact with the membrane as to amplify manifold in tracings the movement it receives. The inscription is received on a slip of smoked glass, which is made to move before the pen with precision by a mechanism which also acts as the chronograph, indicating the time at the lower edge of the glass in seconds and
Fig. 5.—Keyt's Compound Sphygmograph.
fifths. A second pen with similar connection is made to trace on the same slide the movement of another pulse at a distant part of the system.
Space will not permit of reference to the numerous and important accessory contrivances of the complete instrument, nor to the numerous indicatory marks on the following cuts. To the specialist they are significant and essential. Simultaneous tracings of the heart and a large blood-vessel of the neck are shown below (Fig. 6). It should be explained that the upward stroke in the tracing answers to the heart-beat; the downward stroke and succeeding wavelets indicate the recoil of the blood and the tension of the vessels; while the whole cycle with its chronometric line below furnishes a wonderful map.
This graphic method includes cardiography, in which a tracing is obtained of the pulsations of the heart, and pneumography, in which are recorded the movements of respiration. It includes also the multiple simultaneous method, in which two or more vital movements—for instance, of the heart, pulse, and respiration—are recorded at the same time, showing their exact relations to each other. The sphygmograph, in the compound form of Dr. Keyt (Fig. 5), with a chronographic
attachment, is a modern mechanical help in stethoscopy of great value, and has given important light on questions of physiology and pathology. It is an instrument of precision, of scientific interest and importance, and in difficult physical explorations the graphic method is found almost indispensable.
A few cases will now be given illustrative of practice in stethoscopy. A patient has the following symptoms: "Shortness of breath, smotherings, cough with little expectoration, pain of the side, varying from the sharp stitch to the dull and aching pain." The illness and distress are evident, and though the question of present relief is uppermost in the patient's mind, he has sufficient intelligence to demand and to comprehend the cause. From the symptoms given it may with about equally reasonable grounds be supposed that the trouble depends upon organic changes of the heart, its valves, or its pericardium; of the lungs or their pleuræ; or upon disturbances not directly connected with these organs at all, but arising from impressions transmitted through the reflex system of nerves; or it may be owing to a combination of two or more of these causes.
No amount of experience or tact will enable the physician to do more than to guess the diagnosis from these symptoms. He is unable to prescribe intelligently the needed means of relief and of the expected cure except by means of physical exploration of the chest. On inspection, increased frequency of breathing is observed: this is a suggestion only.
On applying the stethoscope the heart is found somewhat displaced, but perfectly healthy as regards its size, its valves, its membranous coverings—an important step by way of exclusion of certain possible conditions.
The whole of the left lung is found performing its functions healthfully. Nor is any disease found in the upper portion of the right lung; but, on searching the lower two thirds of this side, there is found an entire absence of all sounds of respiration; and, under percussion, no normal resonance due to the presence of spongy lung-tissue is heard—the sound is non-resonant, A partial resonance would be dullness; in this case it is "flat."
These data prove the absence of all healthy lung-tissue in the lower two thirds of the right side of the chest. What, then, occupies this region? The lung solidified by morbid changes may be there; or it may be displaced by a tumor, or by fluids; and each of these morbid conditions has nearly the indications mentioned. On carefully examining the upper limit of flatness of sound, while the patient is sitting or standing, it is found to extend exactly horizontally around the chest. Next, requiring the patient to recline backward, the physician finds the boundary-line of flatness to have changed to two or three inches lower on the front, while upon the back of the chest it will be higher than before; yet the line is still strictly horizontal.
The significance of this test is that, though the chest has changed its position, its movable contents, obeying their physical law, tend to preserve a horizontal surface.
Certain complications may prevent the availability of this "hydrostatic test"; but when found it is infallible, and in this case excludes all of the supposed conditions.
The diagnosis now is, that the right lung has been compressed into a narrow compass in the upper part of the chest by the gradual accumulation of from thirty to forty ounces of fluid; and this fluid has also so encroached upon the heart as to cause some displacement and to embarrass its action as well as that of the left lung. These conditions account fully for the symptoms mentioned, and for the distress of the patient.
Negatives, exclusions, and probabilities alone are inadmissible; a diagnosis is required. The examiner may not guess from the symptoms; his tests must be objective, and as positive as the laws of physics. They must not fail, for the life of his patient is at stake; and the treatment to follow will prove his skill, or, may be, his fatal error. If a small hollow needle be pressed through the chest-walls into the suspected region, the outpouring fluid will bring the needed relief and will verify the predictions of the ear by actual sight, weight, and measurement. This case is one of no uncommon occurrence, the treatment almost painless, and very satisfactory as to present relief and the prospect of permanent cure; the lung may expand to its normal size, and resume its functions healthfully. And the case is one requiring only the ordinary and easier means of diagnosis.
The acutest ear and the most practiced discernment are required in meeting the difficulties arising from complications of diseases, and the absence of those sounds and changes which are sufficiently distinct and characteristic—a condition to be expected in all earlier stages of pectoral troubles.
A life-insurance agent brings to his company's medical examiner an individual whom he considers an exceptionally "good risk." He has the facial appearance, the physique, and record of perfect health. The examiner, in making up the rigid descriptive list for his company, must assure them, as "parties of the first part," that in this case the sounds of the heart are perfectly natural; that its movements are entirely correct as regards their rhythm, strength, and frequency; that the pulse does not intermit, etc.; and that there is no disease or morbid condition, or tendency thereto. Tested by the spirometer, the applicant is found to breathe easily the amount of air known to be the average for persons of his size (more strictly, height). By the usual tests of auscultation nothing is found wrong. On a more scrutinizing review of the case, as becomes the faithful officer who is to be the impartial judge on the trial, a small area is found near the upper portion of one lung where, by percussion, the normal resonance has given place to a degree of dullness—a sound which signifies the half-way limit between the resonance of perfect health and the "flatness" of advanced change.
This quality of sound would pass unobserved, except for easy comparison with the adjacent portion of the same lung, and with the corresponding part of the opposite one. The dullness is found to be better shown by light percussion than by more forcible strokes—an indication of the superficial situation of the changed tissue.
On again applying the stethoscope over the region, the natural vesicular quality of the inspiratory murmur is found to be changed to the broncho-vesicular murmur—indicating partial solidification of lung, which, if more complete, would give the bronchial or tubular sound. The pitch of its tone is raised, and it is "rough" or "harsh." A sound of expiration is also heard distinctly, while normally it is barely audible.
There are now three facts which tend to becloud the otherwise good record of the case.
A further test may be made by auscultation of the applicant's voice. On applying the stethoscope upon the place mentioned, the subject is required to speak or count in his ordinary tone of voice. There will be heard sounds apparently near the ear, approaching in distinctness to words—not articulate, as would be heard in complete solidification, but easily distinguished from the distant jarring sound of a healthy lung, called vocal fremitus.
The applicant has now through his own honest voice given adverse testimony. Try next whether he shall whisper a confirmation of the same unfavorable story. The whispering voice heard through solidified lung-tissue is increased in intensity and raised in pitch. which, discouraging symptoms being found in this case, may suffice although further tests are available.
There are now five witnesses, each of whose testimony is more than "circumstantial"; collectively they agree perfectly and are invariably truthful.
The following decision must be rendered: The applicant is in possession of health so good, and a record so favorable, that he has probably made his application for life-insurance in all fairness, but, subjected to the company's exact tests, he is debarred. He must be rejected on the ground of organic pulmonary lesion. A portion of one of his lungs is by some morbid process changed from its delicate, spongy structure to one which is more solid; the air-vesicles have been encroached upon by material which not only has interfered with their functions (though inappreciably to himself), but which may prove a progressive and fatal invasion.
This case is one of a numerous and highly important class—an individual in fair health, without symptoms of any disease, is, by the stethoscopic ordeal, accounted a "bad risk," or is denied the advantages of assurance, and informed that some hygienic or curative course is essential for his safety.
On the other hand it may be stated that, without multiplying illustrations, there are very numerous instances in which the subjective indications (symptoms) of organic disease are so prominent and the distress so urgent as to appear conclusive proof of imminent danger. A test of a few moments' time will make the correct diagnosis and furnish a comforting stethoscopic negative.
Disorders of the heart, although of less frequent occurrence than those of the lungs, are of equal importance and require the best skill of the examiner.
In searching for its disordered conditions it is necessary to keep in mind the anatomical features of the organ. As a piece of mechanism it is a pump, constructed of pliant, fleshy walls; it has four chambers with numerous valves, and its columnæ and chordæ. Protected from friction and abrasion by the constantly renewed fluid within its strong membranous incasement, it expends an incredible amount of force in its incessant and exclusive work of propelling the blood. But it must also be considered as a sensitive center with an apparently independent vitality, in direct communication, through its web-work of nerves of the sympathetic system, with every organ and tissue of the body, according to whose demands, as well as to the varying activities of the brain, it regulates its movements.
The manner of this response is frequently so energetic and tumultuous as to cause much mental disquietude, if not real physical distress, and to furnish the well-known question, whether there be "functional or organic disease."
Its vigorous impulsion, its notable sounds, and its location near the chest-walls, render a study of the condition of the heart entirely practicable by stethoscopic auscultation. By this method its size, its location, and the state of each of its valves can be learned with much precision.
The heart-sounds are sufficiently loud and distinct to be susceptible of much exactitude of description and characterization. The contraction of the ventricles, which mainly produces the "first sound," is the exertion of a force equal to the grasp of a strong hand; it is forcible and quick, but its time as represented by its sound is measurable. This sound is composed of two elements—one of propulsion, with a "booming" quality which is the characteristic, and one of valvular, or sudden clicking sound. Its rhythm, as observed in its succession, is trochaic.
The "second sound" is principally caused by the sudden arrest by the semi-lunar valves, of the column of blood in its tendency to return to the heart under the elastic recoil of the arteries after their forcible distention. It is quick and valvular; it is higher in pitch than the first sound and its rhythm is iambic.
Each of these sounds is more or less ringing and clear and has its appropriate timbre.
After an almost imperceptible interval, the "first sound" is followed by the "second," then by a rest; the whole cycle occupying about one second of time. Its divisions may be represented as follows: first sound, 10; second sound, 10; rest, 10. Each has its exact normal place of greatest intensity and perfection, relative to the external topography of the chest, and variations from this rule will be an index of change of structure within the heart itself, or of displacement from malformations or morbid conditions of the adjacent organs.
It is convenient to designate as heart-sounds those sounds which are normal, and as heart-murmurs those sounds which are adventitious and, as a rule, indicative of organic changes.
The murmurs are of peculiar character, of great variety, and usually of important significance. They originate either within the heart (endocardial) from defective valves or obstructed orifices, or else without it (exocardial) from friction against morbid accumulations within its membranous envelope; or, finally, though exceptionally, they are found to depend upon certain conditions of the blood.
The murmurs are very numerous and variable, and difficult of description according to any rules of rhythmics, melodies, or dynamics; as will be seen from the following names applied to them—and these only a fraction of the whole list: sawing, rasping, scratching, scraping, grinding, creaking, rubbing, churning, blowing, whistling, cooing, purring. And, as if from poverty of language, fashion or necessity has led to borrowing from abroad; as frémissement cataire, bruit de souffle, bruit de scie, etc. The terms in use should through some conventionality be revised. Many of them, however, are practicably indispensable and fairly expressive of sounds actually and distinctly heard, for which a verbal rendering is necessary.
The loudness and clearness of the murmurs are by no means proportionally indicative of their gravity; since one barely audible may from its location and character be a low premonition of mischief, while a more demonstrative one may have no important significance.
In a rare case, a musical murmur was heard exactly resembling the notes of the cuckoo; it was so loud as not to be the exclusive property of stethoscopists, for it could be heard at a distance of several feet. Moreover, it was shown by the "demonstrator," post longam vitam, that the heart whence the sound had proceeded was entirely free from all organic disease.
The mechanism concerned and the method of determining the kind and location of a murmur may be referred to very briefly.
As an example, organic disorder of the aortic semilunar valve will be presumed. Imperfections of this valve are among the more frequent diseases of circulation, and are of import more or less serious according to their extent; its total failure nullifies every anatomical perfection in all the other organs of circulation.
With the stethoscope suitably placed, a distinctly audible murmur will be detected. On observing the rhythmic succession of "first" and "second" sounds the murmur will be found to occur exactly with or in place of the latter, whose sudden click will at least be notably weakened. The murmur is found over the position of the semi-lunar valve and extending downward in a line toward the middle of the chest; it is slightly prolonged after the "second sound." No other murmurs are discovered. These are sufficient data for a diagnosis.
The observer has seen, as it were, two ounces of blood destined for the wants of the system driven through the semilunar gateway into the great vessels; this movement was accompanied by the normal booming "first sound" and was attended by no murmur. There was, then, no obstruction or narrowing of the orifice, nor roughness of the valve, that by consequent vibrations could produce a murmur. But the observer has seen the measure of blood, under the elastic pressure of the vessels, returned upon the semilunar valve for momentary support, where, instead of being promptly arrested by the three-winged leaflets, a portion passed between their narrowed or irregular edges into the heart, and at this instant of regurgitation the murmur was heard. The blood could flow unobstructedly from the heart, but its unfavorable retroversion was made possible by the organic imperfection called insufficiency of the semilunar valve of the aorta.
The sphygmograph alone would have written the above diagnosis in this uncomplicated case with entire completeness, and its tracings would have shown also, as a part of the pathological history, that the valvular defect originated many months ago; that, through the natural curative processes the heart had gradually increased in strength until full compensation for the defect had been reached; and that, with the growth of strength there had been corresponding enlargement, which, instead of being a morbid condition, however, is in this instance really conservative and favorable.
While stethoscopy possesses an interest amounting to fascination, from its vital importance, from the numerous difficulties which can be overcome by reasonable diligence, and from the great degree of exactitude on the whole attainable, it still has its difficulties intrinsic and its difficulties of circumstance. In its practice observations must be made principally through the single sense of hearing; for, practically, the organs which are within the range of a whisper are to the other senses as distant as the antipodes.
There are difficulties from within the chest, from overpowering abnormal sounds, as in the asthmatic subject, where the noisy "râles" entirely predominate, rendering auscultation of the heart temporarily impracticable.
Obscurities and difficulties arise in a negative way from lack of expression; occasionally, all sounds are distant and confused, responses are slow and ambiguous, and the observer is made to feel the need of a perfected microphone which shall amplify, localize, measure, and, in fine, characterize all obscure indications.
Difficulties from circumstances arise from disturbing voices or footsteps, or the roar and rattle of busy streets, and innumerable other sounds which may in part preoccupy the ear with their clangor. There are difficulties from disinclination on the part of the individual examined to offer the requisite time and facilities. There is too often incompetence on the part of the examiner; his sense of hearing as an auscultator may be defective, though not appreciable by any other test. He may never have acquired the requisite degree of skill gained only by persevering practice, commencing with the normal conditions in healthy persons, thence through every class and grade of morbid states, until he has become the trustworthy adept, if not the technical expert.
Difficulties exist to prevent the full popular benefit from stethoscopy, arising from the want of a better general knowledge of its claims and capabilities. Formerly, when the circulation of the blood and the functions of respiration were unknown and the arteries were supposed to be air-vessels, the materia medica was a wonderful list with which the physician made his round of experiments. In those days, in case of a mysterious death, the verdict of the coroner's court would be, "Died by the hand of God," and was considered as duly explicit.
Sufficient advancement has now been made not only to demonstrate the physiology of the lungs, heart, and arteries, but to comprehend every shade of their diseased conditions and to show that the larger part of the remedies once in use were entirely inapplicable; and the coroner, with no irreverent intent, but under the fear of the charge of ignorance, must now demonstrate the physical means and the exact locality of the fatal impress—perhaps found as a heart-obstruction, or a minute embolus deep in the labyrinth of the brain, to which some physiological clew may have led.
Aside from the inherent obscurity and difficulty connected with the subject of medicine, there remains as a heritage of by-gone ages an unwonted mystery associated with it, which should be more rapidly dispelled; and while the profession is making good progress in elaborating and writing its more exact laws, it is the duty of the intelligent laity to free themselves from the vestiges of mysticism, and seize upon the more prominent and available facts and principles which are their appropriate possession.