the world, Russia included. The first papers devoted to auscultation methods were published in Russia in 1824.
The development of auscultation technique is connected with improvement of the stethoscope (Piorri, Yanovsky, and others), invention of the binaural stethoscope (Filatov and others), invention of the phonendoscope, and the study of the physical principles of auscultation (Skoda, Ostroumov, Obraztsov, and others). The modern stethoscope was invented by the American physician George Philip Cammann.
Elaboration of methods for recording sounds (phonography) that arise in various organs has become a further development of auscultation. The graphic record of heart sounds was first made in 1894 by Einthoven. Improved phonographic technique made it possible to solve many important auscultation problems and showed the importance of this diagnostic method
Respiratory act, cardiac contractions, movements in the stomach and the intestine produce vibrations in the surrounding tissues. Some of these vibrations reach the surface of the body and can thus be heard directly by the physician's ear or by using a phonendoscope. Both direct and indirect auscultation is used in practical medicine. Immediate or direct auscultation is more effective (heart sounds and slight bronchial respiration are better heard by direct auscultation) because the sounds are not distorted and are taken from over a larger surface (the area covered by the physician's ear is larger than that of the stethoscope chest piece, or bell). Immediate auscultation is unpractical for auscultation of the supraclavicular fossa and armpits and sometimes for hygienic considerations. Mediate (instrumental) auscultation ensures better localization and differentiation of the sounds of various etiology on a small area (e.g. in auscultation of the heart), although the sounds themselves are slightly distorted by resonance. Sounds are usually more distinct with mediate auscultation.
During mediate auscultation with a solid stethoscope, vibrations are transmitted not only by the air inside the instrument but also through the solid part of the stethoscope and the temporal bone of the examiner (bone conduction). A simple stethoscope manufactured from wood, metal or plastics consists of a tube with a bell which is pressed against the chest wall, the other end of the stethoscope bearing a concave plate for the examiner's ear. Binaural stethoscopes are now widely used. These consist of two rubber or plastic tubes ending with self-retaining ear pieces connected to a single chest piece. The binaural stethoscope is more convenient, especially for auscultation of children and seriously ill patients. Phonendoscopes differ from simple stethoscopes in that they have a membrane covering the bell. Stethoscopes with electrical sound amplification were designed. They, however, were declined by most physicians because of difficulties in differentiation and interpretation of sounds which can be achieved by
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experience. Amplifiers that are now available do not ensure uniform amplification of all frequencies and this distorts the sounds.
A stethoscope is a closed acoustic system where air serves as a transmitting medium for sounds. Therefore, if the tube is clogged, or communicates with ambient air, auscultation becomes impossible. The skin against which the bell of the stethoscope is pressed acts as a membrane whose acoustic properties change under pressure: if the pressure on the skin increases higher frequencies are better transmitted, and vice versa. Excess pressure on the bell damps vibration of the underlying tissues. A large bell better transmits lower frequencies.
The human ear perceives vibrations in the range from 16-20 to 20000 per second, i.e. from 16 to 20000 Hz; variations in frequency are differentiated better than in the sound intensity. The highest sensitivity of the ear is to sounds of 2000 Hz. The sensitivity decreases sharply with decreasing frequency. For example, it decreases to 50 per cent at 1000 Hz and to 0.9 per cent at 100 Hz. It should also be remembered that a weak sound is perceived with difficulty after a loud sound.
Auscultation techniques
Special rules should be followed during auscultation paying particular attention to conditions in which it is carried out. The first requirement is silence in the room and the absence of any extraneous sounds that might mask the sounds heard by the physician. The ambient temperature should provide comfort for the undressed patient. During auscultation the patient is either sits or stands upright. If the patient is in grave condition he may remain lying in bed. During auscultation of the lungs of a lying patient, his chest is first auscultated on one side and then the patient is turned to the other side and auscultation is continued.
The skin to which the bell of the phonendoscope is pressed should be hairless because hair produces additional friction which interferes with differentiation and interpretation of the sounds. When using a stethoscope its bell should be pressed firmly and uniformly to the patient's skin but the pressure should be moderate since excess pressure damps vibration of the skin to diminish the intensity of the sounds. The bell of the stethoscope should be held by the thumb and the forefinger. The posture of the patient should be varied in order to ensure better conditions for auscultation of each particular organ. The respiration of the patient should be regulated by the physician and in some cases the patient is asked to cough (e.g. rales in the lungs may disappear or change their properties after expectoration).
Many various stethoscopes and phonendoscopes are now produced by the medical industry but they differ mostly in design. It is important that the physician should use an instrument to which he got accustomed. An experienced physician will always feel it difficult to differentiate and interpret sounds if a new stethoscope is used for some reasons. This explains
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the necessity of sufficient theoretical knowledge on the part of the physician so that he might correctly interpret the heard sounds. Hence it is the necessity of constant training in auscultation. Only the permanent use of this diagnostic technique will make it a useful tool of diagnosis.
Auscultation of the lungs
Auscultation of the lungs should be performed according to a plan. Stethoscope or phonendoscope should be placed in strictly symmetrical points of the right and left sides of the chest. Auscultation begins with the anterior wall of the chest, from its upper part, in the supraand subclavicular regions, and then the stethoscope should be moved downward and laterally. The lungs are then auscultated in the same order from the posterior wall of the chest and in the axillary regions. In order to increase the area of auscultation between the scapulae, the patient should be asked to cross his arms on the chest and in this way to displace his shoulder-blades laterally from the spine, while for convenience of auscultation of the axillary regions he should place his hands on the back of the head.
The posture does not matter, but the patient should better sit up on a stool with his hands on the laps. The patient may stand, but the physician should remember that deep breathing (hyperventilation of the lungs) may cause vertigo and the patient may faint. Bearing this in mind, and also to ensure a tight contact between the stethoscope and the skin (especially if a one-piece stethoscope is used) the physician should always use his free hand to support the patient on the side opposite to the point of application of the stethoscope bell.
Respiratory murmurs (breath sounds) during various phases of respiration are first compared during auscultation of the lungs as well as their character, length, and intensity (loudness). Then these sounds are compared with the respiratory murmurs at the symmetrical points of the other half of the chest (comparative auscultation). Attention should be paid to the main respiratory sounds, such as vesicular (alveolar) breathing which is heard over the pulmonary tissues, and bronchial (laryngotracheal) breathing which is heard over the larynx, trachea, and large bronchi.
In the presence of pathology in the airways, in the alveolar tissue or in the pleura, adventitious sounds such as rales, crepitation, and pleural friction are heard in addition to the main breath sounds during inspiration and expiration. These adventitious sounds should be examined only after the character of the main sounds has been established. Normal breathing sounds should be better auscultated with the nasal breathing (with the patient's mouth closed) while adventitious sounds are better heard with deep respiration through the open mouth.
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Vesicular breathing (vesicular/ alveolar respiration)
Respiratory sounds known as vesicular respiration arise due to vibration of the elastic elements of the alveolar walls during their filling with air in inspiration. The alveoli are filled with air in sequence. Therefore, the summation of the great number of sounds produced during vibration of the alveolar walls gives a long soft (blowing) noise that can be heard during the entire inspiration phase, its intensity gradually increasing. This sound can be simulated by pronouncing the sound “T” during inspiration, or by drawing tea from a saucer. Alveolar walls still vibrate at the initial expiration phase to give a shorter second phase of the vesicular breathing, which is heard only during the first third of the expiration phase, because vibrations of elastic alveolar walls are quickly dampened by the decreasing tension of the alveolar walls.
Normal vesicular breathing is better heard over the anterior surface of the chest, below the 2nd rib, laterally of the parasternal line, and also in the axillary regions and below the scapular angle, i.e. at points where the largest masses of the pulmonary tissue are located. Vesicular breathing is heard worse at the apices of the lungs and their lowermost parts, where the masses of the pulmonary tissue are less abundant. While carrying out comparative auscultation, it should be remembered that the expiration sounds are louder and longer in the right lung due to a better conduction of the laryngeal sounds by the right main bronchus, which is shorter and wider. The respiratory sound sometimes becomes bronchovesicular over the right apex; or it may be mixed due to more superficial and horizontal position of the right apical bronchus.
Alterations in vesicular respiration
Vesicular breathing can vary, i.e. it may be louder or softer for both physiological and pathological reasons.
Physiological weakening of vesicular respiration occurs in patients with thicker chest wall due to excessively developed muscles or subcutaneous fat. Physiological intensification of vesicular respiration may be observed in patients with underdeveloped muscles or subcutaneous fat. Intensified vesicular breathing is characteristic of children with a thin chest wall, good elasticity of the alveoli and the interalveolar septa. This respiration is called “puerile respiration” (L puer child). Vesicular respiration is intensified during exercise; respiratory movements become deeper and more frequent. Physiological changes in vesicular respiration always involve both parts of the chest, and respiratory sounds are equally intensified or weakened at the symmetrical points of the chest.
In pathology, alterations in vesicular breathing may be both uniand bilateral, or else only over one lobe of the lung. Respiratory sounds become weaker or inaudible at all; or they may be intensified. Alterations in vesicular respiration in such cases depend on the amount of intact alveoli and the properties of their walls, the amount of air contained in them, on the length
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and strength of the expiration and inspiration phases, and finally on the conditions of sound conduction from the vibrating elastic elements of the pulmonary tissue to the surface of the chest.
Pathologically decreased vesicular respiration can be due to a significantly diminished number of the alveoli because of atrophy and gradual degradation of the interalveolar septa and formation of larger vesicles incapable of collapsing during expiration. This pathological condition is observed in pulmonary emphysema, at which the remaining alveoli are no longer elastic; their walls become incapable of quick distention and do not give sufficiently strong vibrations.
Decreased vesicular breathing can be due to inflammation and swelling of the walls in a part of the lung and decreased amplitude of their vibration during inspiration, which is characteristic of early acute lobar pneumonia. During the second stage of this disease, the alveoli of the affected part of the lung become filled with effusion and vesicular breathing becomes inaudible over this region. Vesicular breathing can be decreased also in insufficient delivery of air to the alveoli through the air ways because of their mechanical obstruction (e.g. by a tumour). Air admission to the alveoli can be decreased in patients with a markedly weakened inspiration phase (as a result of inflammation of the respiratory muscles, intercostal nerves, rib fracture, extreme asthenia of the patient and adynamia).
Vesicular respiration decreases also due to obstructed conduction of sound waves from the source of vibration (alveolar walls) to the chest surface, as, for example, in thickening of the pleural membranes or accumulation of air or fluid in the pleural cavity. If the amount of fluid or air in the pleural cavity is great, respiratory sounds are not heard. Conduction of sound to the surface of the chest may be absent in atelectasis of the lung due to complete obstruction of the lumen in the large bronchus.
Abnormally increased vesicular respiration can be heard during expiration or during both respiratory phases. Increased expiration depends on obstruction to the air passage through small bronchi or their contracted lumen (inflammatory edema of the mucosa, bronchospasm). Expiration becomes louder and longer.
Deeper vesicular respiration during which the inspiration and expiration phases are intensified, is called harsh (or coarse, rough) respiration. It occurs in marked and non-uniform narrowing of the lumen in small bronchi and bronchioles due to inflammatory edema of their mucosa (bronchitis).
Another type of pathological respiration is interrupted or cogwheel respiration. This vesicular respiration is characterized by short jerky inspiration efforts interrupted by short pauses between them; the expiration is usually normal. Interrupted breathing also occurs in non-uniform contraction of the respiratory muscles, e.g. when a patient is auscultated in a cold room,
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