OSCILLOGRAPHY

From Big Medical Encyclopedia

OSCILLOGRAPHY (Latin oscillum swing, fluctuation + grech, grapho to write, represent) — in biology and medicine graphic registration of oscillatory processes (electric, electromagnetic, mechanical or transformed in electric) in living tissues by means of the self-recording measuring device. The fluctuations of electric potentials arising at excitement in elements of nervous and muscular tissue vary over a wide range: on amplitude (from units of microvolts to tens of millivolts); durations (from ten-thousand fractions of a second before the whole seconds); to frequency (from shares of hertz to thousands of hertz). For the most exact and undistorted registration of fluctuations in each separate case the method of a research and type of the measuring device — an oscillograph shall be correctly chosen. E.g., for registration of the mechanical motions of a body of the person caused by cordial reductions and the movement of blood on large vessels the method is used ballistokardiografiya (see); for registration of rather slow fluctuations of potentials of a brain — electroencephalography (see); fluctuations of potentials of heart — electrocardiography (see), vektorkardiografiya (see), allowing to judge also the direction of action of the electromotive forces of heart; for registration of time histories of a magnetic component of the electromotive force of heart, contactless (with a body of the person) a method magnetocardiography (see), etc. An oscillography call also graphic record of pulse fluctuations (oscillations) of blood pressure reproduced by the aneroid capsule and transferred to the writing-down device.

Oscillographs — devices for measurement and registration of dependences between two or several quickly changing sizes of oscillatory processes. Oscillographs have no sufficient sensitivity for direct registration of low-voltage potentials biol, objects. Therefore electric potentials move on the recorder only after preliminary strengthening by means of amplifiers. Oscillographs find broad application in a wedge, practice as devices for funkts, diagnoses and at pilot studies.

By the principle of action oscillographs are divided on inertial (for record of rather slow oscillatory processes) and inertialess (for a research of fluctuations of high frequency), and by the principle of operation of the chart recorder — electric and not electric.

Electric oscillographs can be divided on magnetic and electric, electromagnetic, electron beam, magnetic, and but to a way of registration — into devices with directly visible record (ink, thermal, electrostatic on samoproyavlya-yushchuyusya photographic paper), with record on a magnetic tape and with photorecord.

The magnetic and electric oscillograph — the device, in Krom interaction of the magnetic field formed during the passing of electric current on the conductor (a loop, the coil frame) with magnetic field of a permanent magnet causes removal of the conductor in proportion to the size of the proceeding current that is registered on paper or by means of optical system (a loop oscillograph), or by means of a stream of ink (a jet oscillograph). In a loop oscillograph on a loop or the coil frame the pocket mirror reflecting a ray of light on photographic paper becomes stronger, edges moves progressively. At a magnitnoelektrichesky oscillograph with jet record instead of a pocket mirror the thinnest is strengthened (3000 — 8000 nanometers) a glass capillary, through to-ry under pressure of 10 — 20 atm special ink moves. Such galvanometers it is possible to register fluctuations with a frequency up to 800 Hz.

The electromagnetic oscillograph is based on the principle of the movement of a permanent magnet in the electromagnetic field. Electromagnetic vibrators found broad application in modern electrocardiographs, electroencephalographs, elektromiograf (see. Electromyography ), polyphysiocolumns. They allow to carry out visible ink, thermal or electrostatic record.

The magnetic oscillograph allows to record processes on a magnetic film or on the magnetized wire at the bearing frequency, edges is modulated by bioelectric signals.

Fig. 1. Device and scheme of inclusion of an oscillographic electron-beam tube: To — the cathode; H — filament of the cathode; M — the modulating electrode (manages intensity of an electron beam); At — the first anode (focuses an electron beam); A2 — the second anode (in addition accelerates the movement of electrons); A3 — the main anode (accelerates the movement of electrons); OP — the vertical and horizontal rejecting plates (provide development of an electron beam on a vertical and a horizontal): E — the screen of a tube covered with a phosphor; UAi — tension on the first anode; UA2 — tension on the second anode.

Electron beam, or electronic, the oscillograph has high sensitivity and allows to register processes with the broad range of frequencies. The principle of operation of the device is based on use of properties of an electron-beam tube (fig. 1). As the screen of a tube serves the inner surface of a glass flask covered with a layer of a phosphor to-ry begins to shine under the influence of the electron beam falling on it. The luminescence of the screen can proceed also later a nek-swarm time after the termination of a cathode rays. Time of afterglow can be short (less than 10 microseconds), an average (10 — 100 microseconds) and long (more than 100 microseconds).

Fig. 2. Flowchart of the elementary oscillograph.

In medicine most often apply electronic oscillographs with long afterglow. Changing potential on a managing electrode it is possible to change quantity of the electrons moving to the screen i.e. to regulate brightness of a spot on the screen, and creating tension between the vertical and horizontal rejecting plates — to manage an electron beam. The flowchart of the elementary oscillograph is shown in fig. 2.

Electronic oscillographs happen one - two - and multichannel, to the electronic memory allowing «to stop» a signal on the screen of a tube with alphanumeric indication on the screen of a tube, etc.

In medical practice all-technical oscillographs, napr, the electronic oscillographs of S1-48B, S1-68, S1-65 and also which are specially designed for the medical purposes an electronic oscillograph with memory of OSP2-01, a 8-channel oscillograph of IM-789, a 24-channel figurative oscillograph Neva-MT intended for registration fiziol, parameters in a range of frequencies from 0 to 2500 Hz at medical control, etc. are used.

Not electric oscillographs — devices for a research of oscillations (fluctuations) of a vascular wall. Originally allowed to make only sightings. They received the name of ostsillometr, and the method of a research was called an ostsillometriya. The first ostsillometr (Marey's capsule) was designed in 1880 by E. Marey. In 1904 L. I. Uskov offered a design of the first arterial oscillograph. In 1905. Frank (O. of Frank) invented the segmented (mirror) capsule, edges allowed to replace the mechanical recorder with a beam of light thanks to what the shortcomings connected with an inertance of record were a little reduced.

Until recently the arterial oscillograph was eurysynusic. He allowed to receive oscillograms of various arteries (record of a dynamic curve of the ABP), and also sizes and forms of pulse fluctuations of a vascular wall at various extents of its squeezing. However because of high inertness and small accuracy not electric arterial oscillographs are gradually replaced. Instead of them portable arterial oscillographs with photorecord appeared. They are applied to measurement and registration of the ABP parameters of vessels of extremities by a takhoostsillografichesky method.



Bibliography: Turichin A. M., etc. Electric measurements of not electric. sizes, L., 1975.


Yu. T. Gunner, G. A. Putan, G. I. Heymets.

Яндекс.Метрика