Mediate and immediate auscultation. Methods, quiet, normal chest sounds, tubal, bronchial, vesicular, respiratory, cardiac. Juvenile respiratory murmur. Horse, left side, right. Ox, left side, right. Accidental sounds, rumbling, gurgling, crepitation, friction. Sheep, special features. Goat, force. Pig, Dog, Birds, morbid chest sounds. Increase, general, partial. Decrease, general, partial. Absence. Bronchial sound in excess, in improper place. Cavernous, amphoric, mucous sounds. Râles, sonorous, sibilant, mucous, submucous, crepitant, subcrepitant. Creaking, metallic, tinkling, gurgling, splashing, friction. Timbre of Cough. Palpitation. Mensuration.
This is a term used in medicine to denote the mode of exploring an organ by applying the ear over the region in which it is situated and deducing the healthy or diseased condition by the sounds heard. First employed by Lænnec in human medicine it was quickly availed of for the lower animals by Delafond and Leblanc.
Auscultation is mediate or immediate. Immediate Auscultation is practised by applying the ear directly upon the skin, either bare or covered with a handkerchief. In Mediate Auscultation an instrument called a stethoscope is employed to convey the sound from the surface of the body to the ear of examiner. The common stethoscope is formed of soft wood (cedar or ebony) or of gutta percha, is from five to seven inches long and a quarter of an inch in the bore. The end applied on the skin is widened into a funnel three-fourths of an inch across at the mouth; the opposite end is flattened out to apply to the ear, is about two inches in diameter and has a hole in the centre to convey the sound. A flexible stethoscope is also used either with one or two ear pieces and though less convenient in general than the common variety possesses this advantage when the heart is being examined that it conveys the sound without the impulse of that organ.
In mediate auscultation the ear should be closely applied to the surface, the right ear being used for the left side and the left ear for the right, but a preference should always be exercised in favor of that in which the sense of hearing is most acute. If a handkerchief is used a single fold only must be applied, otherwise the two layers may rub on each other and produce distracting sounds. In mediate auscultation the instrument should be held perpendicularly to the surface, accurately applied alike to the skin and the ear, and pressed firmly on the surface to condense the soft structures beneath the skin and render them more conducting. If held by the hand care must be taken to avoid the slightest movement of the fingers on the stethoscope, and long hairs should be prevented from entering the tube as being likely to produce additional sounds.
Among other points the following must be attended to in auscultation. Avoid a position in which the animal can strike you with its hind limbs. If necessary in irritable or ticklish subjects have one fore leg held up. Select a quiet time and place, early morning or night is usually best. Endeavor to protect the patient from the irritation of insects or the examinations may be fruitless. Never auscultate over a contracting muscle; the sound of muscular contraction will prevent a correct result. If the natural sounds are indistinct increase them by exercise. The smaller animals are examined with the greatest facility standing upon a table or held in the upright posture with the body resting on the thighs or on the hind feet only. Birds can be held by the wings which may be raised and drawn inward towards the median line to expose the back and sides of the chest.
In all healthy animals two distinct sounds are heard over the chest:—the tubal or bronchial sound, and the vesicular or respiratory murmur. The bronchial sound caused by the air sucking through the larger bronchi is best heard by applying the ear to the breast over the lower end of the windpipe or to the upper third of the chest immediately behind the shoulder. The respiratory murmur is clear and full in the middle third of the chest immediately behind the shoulder. It is louder and more prolonged in inspiration than in expiration and in the right lung than the left especially in cattle and sheep in which the former is more capacious. It is louder in young animals than in old, hence the name of juvenile respiration applied by Leblanc. In thin animals it is better heard than in fat ones, the chest walls being thinner, firmer, and more conducting. In animals of a nervous temperament like the English racer it is more distinct than in the Norman, Clydesdale and other heavier breeds. Deep, broad capacious chests emit a stronger sound than such as are shallow, narrow and short. Exercise, fear or any excitement accelerating the respiratory act increases the sound. A full stomach, certain narcotics and other depressing influences lessen it. Other things being equal the sound is lower in cattle and sheep than in other domestic animals.
Horse. The ear pressed strongly upon the breast where the windpipe enters detects a strong blowing sound referable to the lower end of the trachea and the bronchi. In young foals a respiratory murmur is heard when the stethoscope is applied in front of the shoulder, the limb being meanwhile drawn backward. A similar murmur may be heard, but less distinctly over the shoulder blade at this age.
Left Side. Behind the shoulder in the upper third of the chest the sound is loud and somewhat harsh, the respiratory murmur being here supplemented by the noise of the air rushing through the larger bronchia. From the 13th rib the respiratory sound is alone heard and becomes weaker to the second last (17th).
In the middle third the respiratory murmur is moderately clear from the 4th to the 6th rib, it becomes louder and clearer to the 9th from which its force gradually diminishes and is lost over the 16th. In the lower third over the 4th, 5th, and 6th ribs the respiratory sound is replaced by the sounds of the heart, each beat being distinctly divided into two sounds, the first dull and prolonged, the second short and quick. The respiratory murmur is heard over the 7th and 8th ribs, is weaker on the 9th and lost over the 10th. In the middle and lower thirds but especially towards the posterior part of the chest, abdominal sounds are often heard. They consist chiefly in gurgling or in a noise like that caused by the air rushing into a bottle which has been turned upon its side when full of water. Such sounds are easily distinguishable from those occurring in a diseased chest as they bear no relation to the rhythmical action of breathing.
Right Side. In the upper and middle thirds the sounds do not differ from those of the left side. In the lower third the respiratory sound is clear from the 4th to the 7th ribs; from this it decreases and is lost at the 10th.
Ox. In very lean cattle the respiratory murmur heard in front of the shoulder and over the scapula is more distinct than in the same region of the horse.
Left Side. In the upper third a clear respiratory murmur is heard over the 8th, 9th and 10th ribs but is lost about the 11th. In the middle third the vesicular sound is feeble at the lower margin of the region and immediately behind the shoulder because of the proximity of the base of the heart. Towards the upper margin it is loud and harsh being complicated by the tubal sound. It is full and clear over the 7th rib whence it decreases in force to be lost at the 11th above and the 10th below. In the lower third the double heart beat is alone heard over the lower part of the 4th rib, the respiratory murmur reappears over the 5th and 6th whence it becomes weaker and is lost at the lower and upper margin of the region respectively over the 8th and 9th ribs.
Right Side. The sounds of the upper third simply repeat those of the left side. In the middle third the chief difference is the greater clearness and strength of the respiratory and tubal sounds immediately behind the shoulder. In the lower third a moderately strong respiratory murmur is rendered harsh by a tubal sound due to the proximity of the large bronchus going to the anterior lobe of the right lung. The respiratory murmur continues with diminishing force to be lost over the 8th and 9th ribs.
Accidental but healthy Sounds. These are more loud and frequent in the ox than in the horse. There is the same irregular rumbling and gurgling especially on the posterior parts of the chest. Gurgling as from a full bottle inverted is often clearly heard over the last six ribs on the left side, and appears due to the passage of liquids between the paunch and honey comb bag. An occasional sound as of water falling into an empty barrel is heard in the same region in cases of slight tympany and after saliva has been swallowed. Rumbling sounds are chiefly heard over the last ribs on the right side where the large and small intestines are situated. The superadded sounds in the ox are those of crepitation and friction. The crepitation or fine crackling due to a dryness of the areolar tissue under the skin is frequently present in oxen in average health. A fine crepitation is also heard on the left side from the bursting of myriads of minute bubbles of air generated among the contents of the paunch during the process of digestion. This is especially marked after the animal has fed on green food or potatoes. A loud friction or rubbing sound, which may be imitated by placing the back of one hand upon the ear and rubbing the palm of the opposite hand upon it, is likewise heard over the left side after eating. It is produced by the movements of the paunch during contraction and not being synchronous with the respiratory acts cannot be confounded with the friction sounds of pleurisy to be hereafter noticed.
Sheep. The diaphragm being attached to the last rib as in the horse the respiratory murmur may be heard to the second last. The shoulders being more movable than in the ox the anterior part of the chest can be more satisfactorily examined. The vesicular murmur is heard along the whole lower third on the left side though the heart sounds are superadded over the 4th, 5th and 6th ribs. Crepitation from the subcutaneous areolar tissue is rarely heard. Otherwise the sounds of the chest and abdomen correspond to those of the ox.
Goat. This animal differs from the sheep mainly in the greater force and clearness of the respiratory murmur.
Pig. It seems ridiculous to speak of auscultating the pig, yet he is sometimes thin enough and quiet enough to permit of one obtaining satisfactory results. Gentle treatment and scratching the back and abdomen will often persuade him to be temporarily quiet and docile. The vesicular murmur is very clear in the middle third of the chest on either side, but diminishes gradually on the last six ribs, and disappears on the second last. It is much less intense in the upper and lower thirds. In the posterior part of the chest rumbling and gurgling abdominal sounds are frequent.
Dog. The respiratory murmur is very clear over the whole chest. It is most intense along the middle third and becomes less clear on the 4 or 5 last intercostal spaces. The mobility of the shoulder permits an examination of nearly the entire chest. The respiratory murmur may be heard over the entire length of the lower third on the left side though the heart’s sounds are equally heard over the 4th, 5th and 6th ribs. Rumbling and gurgling abdominal sounds are much less frequent than in herbivora and omnivora.
Birds. The respiratory murmur is loud, clear and almost harsh on the sides of the thorax, beneath the wings, and considerably softer as heard on the back.
The close study of the healthy chest sounds upon the living animal is an essential prerequisite to the appreciation of the morbid. The abnormal noises are so varied, merge into each other by such imperceptible degrees, and so coexist and complicate each other that they often prove extremely puzzling to the unpractised ear. It is no more necessary that the musician should educate his ear to appreciate the most delicate gradations of musical notes, than that the auscultator should educate his in the sounds of the healthy and diseased chest. Written instructions are of about equal value in the two cases, they prove auxiliaries in the acquisition of knowledge but they can never supersede the practical study of the chest. A mere theoretical knowledge is too often useless in the presence of the patient.
The abnormal chest sounds are either modifications of those existing in health, or superadded sounds which have no counterpart in the healthy chest.
Modifications of healthy sounds. The vesicular or respiratory murmur may be increased or diminished in force or it may be entirely absent.
Increase of the respiratory murmur, is merely an increase in force without any modification in character and resembles juvenile respiration. If increased equally over the entire chest it is general, if only in a part it is partial. General increase of the vesicular murmur is heard after an animal has been submitted to moderate exertion for ten or fifteen minutes. In animals at rest it is heard in active fevers and in the symptomatic fever which attends acute inflammations.
Partial increase as for example in one lung only, or in circumscribed parts of both lungs, and especially along their superior borders, is indicative of disease of the lungs or the pleuræ. It testifies to the impermeability to air of some other portion of lung, from congestion, splenisation, hepatisation, plugging of a bronchial tube with tenacious mucous, tubercular deposits, tumors, emphysema, or hydrothorax. (See under these names.) The healthy portion of lung in such cases takes on the function of the whole, and the loud breathing is called supplementary.
Diminution of the respiratory murmur, like its increase, may be partial or general. General diminution is seen in anæmia, in low fevers, in all very prostrate conditions from the mere want of power to dilate the chest; in general emphysema (broken wind, heaves), in general miliary tubercular deposit in the lungs, or in that form in cattle in which the tubercle has been replaced by cretaceous deposits, from the animal’s inability to fully dilate the air cells; in enteritis, peritonitis and metritis the chest is more fully dilated because of the pain attendant on that act, and the breathing being short and quick the murmur is correspondingly low. In certain brain diseases with sluggish respiration the sound is equally feeble.
Partial diminution of murmur is more surely indicative of lung disease. It may arise from partial congestion when a supplementary murmur will be observable over other parts of the lungs, and a crepitant râle soon appears in the congested part; from local emphysema in which there is increased resonance in percussing the part; from tubercular or cretaceous deposit, when there will be exaggerated murmur elsewhere, or from bronchitis with blocking up of one or more small bronchial tubes and with louder respiratory sound in other parts.
Absence of respiratory murmur may be due to various causes, all of a diseased nature. Hepatisation of lung may be recognized when this condition is found associated with a crepitating râle around the margin of the silent part, and when percussion shows its solidity and want of resonance. Splenisation is associated with absence of respiratory sound and dullness on percussion, but no surrounding crepitation. Absence of sound in water in the chest is confined to the lower part of the chest, keeps the same level and ratio of increase in front and behind, and in the horse on the two sides, and has been preceded by the characteristic catching breathing and the friction sounds of pleurisy. Large tumors and extensive and circumscribed tubercular deposit will give rise to absence of sound over a limited area and plugging up of one or more bronchial tubes will lead to a similar result. Hepatisation of lung and water in the chest are, however, the common causes of loss of respiratory murmur.
The bronchial or tubal sound may be increased in pitch and in harshness in two conditions. 1st. In the early stages of bronchitis when the lining mucous membrane of the air passages is dry, thickened and inelastic. 2d. When that portion of lung intervening between one of the larger tubes and the surface of the chest is solid (hepatised) and thus proves a better conductor of sound than in the normal condition.
Superadded abnormal sounds. The bronchial sounds may be altered in their character so as to become cavernous, amphoric or mucous (rattling). The cavernous sound is usually caused by the presence in the lung of the cavity left after the discharge of an abscess or softened tubercle into a bronchial tube. It is thus preceded by cough and white, creamy discharge from the nose. If the discharge is fetid and grumous there has probably been circumscribed gangrene of the lung. An approximation to the sound may be produced by blowing into a widemouthed glass or porcelain vessel. The sound of amphoric respiration on the contrary is like that made by blowing into a narrow necked bottle. It is due to a similar cavity with a small orifice or to the existence of pneumothorax communicating by a narrow canal with a bronchial tube. It is rare in the lower animals, but Delafond mentions one case in the horse and two in dogs.
Râles. The remaining morbid sounds are known as râles, or rattles. They may either be referable to the bronchial tubes or the lung tissue. They are called dry or humid, according as they convey the idea of air drawn through a dry tube or one containing liquid.
The dry râles are due to narrowing of the bronchial tubes from the pressure of adjacent tumors, the thickening of the mucous membrane or the deposition on the surface of layers of tenacious mucus. The greater the narrowing the shriller the sound, and hence the distinction of bronchial râles into sonorous and sibilant (whistling).
The sonorous râle has been variously exemplified by the humming of a gnat, the cooing of a wood pigeon or the bass notes of a violin. It commonly bespeaks the onset of bronchitis and testifies to the thickened, dry and rigid character of the tubes, but may give place in as short a time as three hours to a mucous râle from the occurrence of a free secretion. It rarely extends over two or three days. Sometimes when caused by a piece of tenacious mucus obstructing a tube, it is very transient disappearing at once when the mucus is expelled by coughing. Sometimes it is modified by an occasional clicking sound from the flapping of a shred of semi-solid mucus attached to the walls of a bronchial tube. This disappears when breathing becomes more hurried.
The sibilant (whistling) râle often acknowledges the same causes as the sonorous, but indicates a narrower closure of the tubes. More frequently it is heard further back on the chest and results from pulmonary emphysema and dilatation of the smaller bronchial tubes (broken wind, heaves). It is then heard chiefly in expiration and coincidently with the second quick lifting of the flank. It is further associated with the double lifting of the flank in expiration with the short, weak, paroxysmal cough and the indigestion characteristic of broken wind. If the whistling noise is so loud as to be heard without applying the ear to the chest it is called wheezing.
A mucous râle is caused by air passing through any liquid contained in the bronchial tubes, such as mucus, pus, or blood. It may be imitated by blowing a large number of soap bubbles in a thick lather and noticing them burst simultaneously or successively. It is chiefly observed in bronchitis after the preliminary dry stage of the mucous membrane has passed off and an abundance of mucus has been secreted. The nature of the sound will vary according as it comes from the larger or the smaller tubes or in other words as to whether the bubbles are large or small. That from the smaller tubes is sometimes called a submucous râle. Either of these râles may be temporary or permanent as the mucus may be momentarily cleared away by coughing.
The crepitant râle is a sound of very fine crackling which has been variously compared to the crackling of salt when put on red hot coals, the noise of a sponge expanding in water and the rubbing of a small lock of hair between the finger and thumb close to the ear. The existence of the crepitant râle usually denotes the existence of the early stage of inflammation of the lungs, and the progress of hepatization in such cases may be traced by the advance of the line of crepitation which precedes it. So the progressive absorption of exuded matter in recover may be equally followed by a line of crepitation gradually decreasing in area until it meets in a point. The observations will be corroborated by the dull sound elicited on percussing the parts. The production of the sound has been attributed to the passage of air through the thick mucus in the smallest bronchial tubes or more plausibly to the separation of the walls of the air sacs and cells during inspiration, they having been previously adherent by reason of the secretions.
Crepitation is not heard in all pulmonary inflammations. In weak animals with a low type of inflammation tending to gangrene, and in those cases of broncho-pneumonia in which a viscid mucus blocks up the bronchial tubes passing to the affected lobes, it may be altogether absent.
Crepitation may further occur without inflammation. Thus in pulmonary œdema (dropsy of the lung) and capillary hemorrhage in which liquids are effused in the smaller bronchial tubes and air sacs a crepitation is sometimes heard.
A modified crepitation (dry crepitant râle of Delafond) is usually heard over an emphysematous lung. The noise in this case has been compared to that induced by handling a sheet of paper.
The subcrepitant râle is another modification holding a place intermediate between the crepitant and the mucous râles. It has been likened to the sound of a moderate effervescence in beer or other liquid. It is referable to the presence of mucus in the smaller bronchial tubes and indicates bronchitis or broncho-pneumonia.
Still other sounds are heard in diseased conditions of the pleuræ. These are friction sound, creaking, metallic tinkling, and gurgling or splashing.
A friction sound is heard in the early stages of pleurisy and is caused by the dryness of the pleural surfaces from the absence of the halitus or vapor which normally moistens them and the deposition of layers of lymph by which the surfaces are rendered rough and uneven. An approximate sound may be observed by placing the palm of the left hand on the right ear and drawing a finger of the right softly over its back. The sound is quick and jerking, one or a few jerks only being heard with each inspiration as the act is cut short on account of the pain attending the friction. It is rarely heard in expiration. It is chiefly heard at the lowest part of the chest where the lungs have the greatest freedom of movement. The thinness of the walls of the chest above the breast bone in cattle and dogs permits the friction sound to be heard more distinctly than in the horse. After the lapse of twelve, twenty-four or forty-eight hours the friction sound disappears, the surfaces of the pleuræ being separated by the liquid effusion, but it may reappear when the fluid is absorbed in the process of recovery. Sometimes the friction is further manifested by vibration of the walls of the chest perceptible to the touch.
The creaking sound, as from the bending of a piece of strong leather is caused by the movement of a thick and solid false membrane binding the lungs to the side of the chest. This is often confounded with crepitation.
Metallic tinkling is only heard when liquid and gas both exist in the pleural sac and is due to the falling of a drop from the shreds of false membrane above into the fluid contents below. The sound is somewhat like the falling of drops in a closed cask half full of water, or it may be fairly exemplified by placing the palm of the left hand flat on the right ear and striking the back of the hand smartly with the middle finger of the right. The sound is chiefly heard after the patient has changed its position and especially after rising. The explanation of this is that in the recumbent position the liquid changes its place and bathes parts which in standing are surrounded by gaseous products only. Drops accordingly fall into the liquid for some time with diminishing rapidity until they cease altogether. Other explanations of the sound but which less frequently exist are: the ascent of a bubble through the liquid and its bursting on the surface; and the sudden recoil of air from one wall of the plueral cavity to the other as the result of movement or sound generated in the deeper seated solid structures.
A gurgling or splashing sound is equally indicative of the presence of fluid and gas in the pleural sac. It is almost never heard unless after a sudden movement on the part of the patient causing considerable commotion in the contained liquid. Gurgling sounds transmitted from the abdomen are too often mistaken for this. In small animals with hydro-pneumothorax a quick shaking of the patient will develop it.
Auscultation of the Cough is sometimes valuable, though more difficult and less satisfactory in the lower animals than in man, chiefly because of the extensive movement of the ribs in the former. As conveyed through a healthy lung to the ear applied on the side of the chest, the sound is short, dull and indistinct. When the lung is more solid from hepatisation, pleural exudation or other cause, or when the bronchi are dilated the sound is loud and strong. The extent over which it may be heard thus forcibly agrees with the area of lung in a state of consolidation. When a considerable cavity or canal communicates with a bronchial tube and extends to near the surface of the lung the sound is loud and ringing. The note is specially clear and metallic when such a cavity opens into the bronchus by a narrow orifice; an apt illustration of this noise may be obtained by coughing into a narrow necked vessel.
The results obtained by auscultation should be confirmed by percussion before arriving at any definite conclusion as to the state of the chest. Consolidated lung tissue is a much better conductor of sound than the healthy, and sounds conveyed through this may be heard at a considerable distance from their point of origin. Thus the heart sounds are frequently heard over any part of the right side of the chest, and crepitation and other sounds may be heard in the centre of a hepatized portion. On all such occasions the dull sound elicited on percussion will not fail to correct the fallacy.
This is chiefly useful in cases of pleurisy. As already noticed the vibration of the chest walls which accompanies the early friction sound is sometimes perceptible by the hand applied on the side of the chest. Pressing firmly in the intercostal spaces at the affected part invariably causes wincing and in cattle grunting. Pinching the back in inflammatory chest diseases in cattle but especially in pleurisy has a similar effect.
Measurement of the chest gives less reliable results in the lower animals than in man. A cord four feet long should have one end placed on a definite point on the withers and not removed until both sides have been examined. It should be first carried down to a point in the middle of the breast bone and the distance marked by a knot; a comparison may be made by carrying to the same point over the opposite side. It should next be carried successively to the lower end of the 8th rib on the two sides and the difference marked, and lastly from the lower end of the third rib to the lower end of the eighth. These measurements should be made at one stage of the respiratory act, say when the chest is fully dilated, and similar measurements when the chest is collapsed to ascertain any difference in the expansion of the two sides of the chest. In the smaller animals any difference in the expansion of the two sides may be observed by inspection only, the practitioner standing directly behind the animal and watching the movements of the two sides from this standpoint.
A permanent dilatation of one side may be seen in water in the chest confined to one side, and particularly if of some standing. Complete hepatisation of one lung gives a similar result. The intercostal spaces are observed to be wider than usual in such cases, and the movements of the opposite side of the chest are much more extensive than of the affected one.
A collapse with limited movement of one side is an accompaniment of chronic disease of the lung, with wasting of its substance as in cases of tubercular deposit.