AUSCULTATION (Latin auscultare to listen, listen) — the listening of the sound phenomena connected with activity of internals, applied to assessment of this activity and diagnosis of its disturbances.
The act of breath, reduction of heart, the movement of a stomach and guts cause elastic vibrations which part reaches a body surface in fabric structures.
These fluctuations are usually not heard at distance, but can be listened if to put an ear to a body of the patient (a straight line And.) or via the device for And. (indirect And.).
And. it is offered by R.T.H. Laennec in 1816, described and entered by it into medical practice in 1819. He invented a stethoscope. R.T.H. Laennec proved clinical value And., checking results it according to section data, described and gave the name to almost all auskultativny phenomena (vesicular and bronchial breath, dry and wet rattles, crepitation, noise). And. also hearts became an important diagnostic method of pulmonary diseases and soon it began to be applied in Russia where in 1824 there were works devoted to this method.
Development And. it is connected with improvement of a stethoscope [Pyorri (R. A. Piorry), F. G. Yanovsky, etc.], the invention of a binaural stethoscope (Η. F. Filatov, etc.), phonendoscope and studying of physical bases And. [Skoda (J. Skoda), R. Geigel, A. A. Ostroumov, V.P. Obraztsov, etc.].
The Auskultativny signs accompanying activity of different bodies represent noise of various duration.
The measurements of frequency ranges of these noise performed by means of the modern acoustic measuring equipment taking into account features of the acoustic analyzer of the person, showed that auskultativny signs occupy quite wide strip of frequencies (the general frequency range), in a cut the doctor manages to distinguish them. Besides, existence for each of auskultativny signs of narrower frequency range within which the sign keeps «melody» without distortions (characteristic frequency range) was revealed. Frequency ranges of the main auskultativny signs of cordial activity and breath are specified in tables 1 and 2. As appears from these tables, the general frequency range of the main auskultativny signs is located within 20 — 5600 Hz, and characteristic range — within 20 — 1400 Hz.
From the point of view of both acoustics, and clinic it is possible to distinguish auskultativny signs low - average and high-frequency with characteristic frequency range respectively — from 20 to 180 Hz, from 180 to 710 Hz and from 710 to 1400 Hz. The melody of difficult sounds, including and auskultativny signs, is defined not only the frequency range, but as well distribution of amplitudes in this frequency range and duration of a signal. The frequency range of an auskultativny sign is higher, the it has smaller sound energy. So, the frequency range of cardiac sounds is lower than the frequency range of noise (tab. 1), and energy of tones is much higher than noise energy of heart.
At And. features of the acoustic analyzer of the person shall be considered. The ear of the person perceives sound vibrations with a frequency from 20 to 20 Ltd companies of Hz, but is the most sensitive to frequencies in the range apprx. 1000 Hz. Therefore at equal sound energy sounds with the frequencies close to 1000 Hz, sounds of lower or high ranges seem louder, than. The person more difficult perceives a weak sound after strong: the loud cardiac sound as if masks silent diastolic noise.
Age decrease in hearing belongs to area of high frequencies and therefore does not cause loss of ability of recognition of auskultativny signs since their characteristic frequency does not exceed 1500 Hz. For recognition of additional tone at a cantering rhythm V.P. Obraztsov offered a way of direct auscultation of heart, the cut is a necessary condition dense pressing of an ear to a body of the patient with formation of the closed air-vessel; at the same time low-frequency additional tone (see tab. 1) gives feeling more tactile, than acoustical. Straight line And. keeps the value for clinic (especially in pediatrics) thanks to the fact that in such a way many sounds (e.g., cardiac sounds, silent bronchial breath) are perceived much better, without distortions and from a bigger body surface. But it is not applicable for And. over - subclavial, axillary poles and other similar body parts.
The purpose of use of devices for And. simplification of recognition of auskultativny signs by weakening of one and strengthening of other sounds is. Already the first stethoscope provided the best otgranicheniye of the sounds of a different origin perceived from the small site (e.g., at And. heart); besides, changing intensity of pressing a stethoscope, the doctor has an opportunity to weaken low sounds and by that as if to emphasize high (at increase in pressure of a funnel of a stethoscope at skin carrying out low sounds worsens, and high improves). The wide funnel reproduces low sounds better.
And. there are by an irreplaceable diagnostic method for a research of lungs, heart and vessels, and also for determination of arterial pressure (on Korotkov's way), recognitions of arteriovenous aneurisms, intracranial aneurisms, etc.
And. matters at a research of digestive organs (intestinal noise, a friction murmur of a peritoneum, noise of narrowing of guts), and also at a research of joints (a friction murmur of intra joint surfaces of an epiphysis).
By means of the combined use And. and percussions (a method of auskultatorny percussion) define border between adjacent bodies (especially between hollow and dense) in an abdominal cavity. The head (bell) of a phonendoscope is placed in the point which is obviously located over the studied body, and a finger make very easy percussion (or a poskablivaniye) on skin radially from the periphery in the direction to a phonendoscope; the timbre and intensity of the heard sound sharply change over required border. In such a way specify position of bottom edge of a liver, border of a tympanites over a stomach, the top level of ascites, etc.
The «patient — a stethoscope (or stetofonendoskop) — an ear of the doctor» system shall be at And. tight; if it is reported with fresh air, And. in most cases becomes impossible.
Difficulties And. consist not so much in the weak audibility how many in differentiation and the correct interpretation of difficult sounds at And., what is reached only on the basis of experience.
Devices for And. on medical appointment are divided into devices of general purpose (for the adults inspected), pediatric and obstetric; there are also veterinary devices.
By the principle of action devices for And. share on acoustic (without transformation of energy) and electronic (with double transformation of energy). Use of acoustic devices — a stethoscope and a stetofonendoskop is widespread in customary medical practice.
Stethoscope — monaural acoustic, with a rigid sound wire the device for And.; in operation it is not always convenient — forces to bend to the patient that complicates And. the lying person.
Stetofonendoskop — the binaural acoustic device with a flexible sound wire — is the simple, convenient device in operation. Stetofonendoskop has, as a rule, two bells (head): stethoscopic and fonendoskopichesky (with a membrane). The stethoscopic bell serves for listening low - and mid-frequency, and fonendoskopichesky average and high-frequency auskultativny signs. Use only does not improve one of bells, and complicates recognition of auskultativny signs.
The main requirements to devices for And. their acoustic properties, i.e. ability to perceive fluctuations of «a skin membrane» for the purpose of simplification of recognition by doctors of auskultativny signs and to transfer sound vibrations to an ear of the doctor are. Acoustic properties of devices for And. can subjectively be estimated in the course of listening: at good acoustic properties of the device with its help all found auskultativny signs are surely distinguished, at bad properties — only a part of signs; besides, these properties are reflected objective acoustic characteristics of the device, however to a crust, there is no time the standard way of their measurement yet.
B. E. Votchal with soavt, offered a method of measurement of acoustic characteristics of stetofonendoskop in conditions, the closest to real auscultation. G. I. Arvin with soavt, developed the stand for measurement of the relative amplitude-frequency characteristics (RAFC) of stetofonendoskop. Measurement of OAChH of a stetofonendoskop at the stand is carried out by means of as if indirect and direct And.: at first on the acoustic equivalent of a thorax of the person («an artificial breast») excited by the generator of mechanical oscillations it is put investigated stetofonendoskop, connected at the exit to an acoustic equivalent of ears of the person («artificial ears»), and the level of sound pressure in «an artificial ear» with various frequencies of the generator registers. Then on «an artificial breast» «the artificial ear» is imposed directly and the level of sound pressure is measured in it at the same frequencies. The difference of sound pressure (in decibels) depending on frequency gives OAChH of a stetofonendoskop.
The stand for measurement of OAChH of stetofonendoskop models only a part of system indirect And.: acoustic properties of muscular tissue of a breast and external ear of the person. Nevertheless value medical judgment of acoustic properties of stetofonendoskop and their objective assessment on OAChH in some cases correlate.
Developed with the assistance of B. E. Votchal stetofonendoskop (bifonendoskop) the BF-1 models (fig. 1, 1) has as showed clinical tests, good acoustic properties. OAChH of a big stethoscopic bell of a bifonendoskop (fig. 2), as one would expect, is higher than OAChH of a small bell (the big area of the first allows to apprehend big sound energy).
OAChH of a fonendoskopichesky bell have two features: at frequencies of 20 — 300 Hz of OAChH the curve forms considerable «blockage» — 20 — 10 dB, and at more high frequencies — 500 — 1500 Hz — noticeable (more than 10 dB) rise, i.e. the membrane of this bell carries selectively out high-frequency and muffles low-frequency components of auskultativny signs.
Stetofonendoskop of general purpose of model 044 having also good acoustic properties is represented in fig. 1,2, and its OAChH — in fig. 3. Comparison of schedules of stethoscopic heads of the BF-1 models and 044 shows that OAChH of a big stethoscopic head «BF-1» at low frequencies is located above OAChH of the same head of model 044; it means that by means of the first doctors will be able easier to distinguish such low-frequency auskultativny signs as the III tone, a cantering rhythm, deaf I tone, etc.
Comparison of OAChH of fonendoskopichesky heads of these stetofonendoskop demonstrates that both of them give notable strengthening at high frequencies and noticeable easing at low frequencies.
Stetofonendoskopa are usually supplied with two couples of olives made of hard plastics. For simplification of obturation of acoustical pass of a stetofonendoskopa it is necessary to supply with at least three couples of olives of various diameter and, besides, olives shall be made of the soft material resistant to influence of an earwax.
Pediatric stetofonendoskop has specific acoustic properties and it is supplied with a head of smaller diameter, than at a stetofonendoskop of general purpose. The obstetric stethoscope has a funnel of a large diameter that is necessary for listening of weak sound phenomena of heart of a fruit. The obstetric stethoscope usually from a tree and plastic is produced. The domestic industry releases also obstetric stetofonendoskopa.
Electronic stethoscope — the device for And., in Krom double transformation of energy is applied. Fluctuations of «a skin membrane» are perceived by the microphone transforming mechanical oscillations to electric.
The last pass the amplifier who is usually supplied with regulators of low and high frequencies and the regulator of loudness. From an exit of the amplifier electric fluctuations move on stetotelefona which will transform electrical energy in sound, and the last is brought to an ear of the doctor.
Electronic stethoscopes were not widely used in medical practice since do not give still basic advantages before stetofonendoskopa; besides, they are difficult in management.
Bibliography: Arvin G. I., etc. The stand for measurement of acoustic characteristics of stetofonendoskop, Is new. medical instrument making, century 2, page 94, 1973; In B. E., Vodolazsky L. A. otchat. V. A igolik. Acoustic characteristics of stetofonendoskop and their measurement, Medical tekhn., No. 2, page 16, 1972; Gubergrits A. Ya. Direct research of the patient, page 212, etc., M., 1972; Zamotayev I. P., etc. Spectral analysis of the major auskultativny signs, Klin, medical, t. 52, J4» 5, page 97, 1974, bibliogr.; V. P is model. Chosen works, Kiev, 1950; Edens E. Lehrbuch der Perkussion und Auskultation, B., 1920; Jaeger M. Cardio-vascular examination down through the years, Spectrum, v. 10, No. 6, p. 81, 1964; Laennec R. T. H. De l’auscultation mediate ou trait6 du diagnostic des maladies des poumons et du coeur, P., 1819; Turner R. W. D. Auscultation of the heart, Edinburgh-L., 1972.
B. X. Vasilenko, JI. A. Vodolazsky.