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HISTORY OF TECHNOLOGY, TECHNOLOGY, OBJECTS AROUND US
Artificial human organs. History of invention and production
Directory / The history of technology, technology, objects around us Modern medical technology allows you to replace completely or partially diseased human organs. An electronic heart pacemaker, a sound amplifier for people suffering from deafness, a lens made of special plastic - these are just some examples of the use of technology in medicine. Bioprostheses driven by miniature power supplies that respond to biocurrents in the human body are also becoming more widespread.
During the most complex operations performed on the heart, lungs or kidneys, invaluable assistance to physicians is provided by the "Artificial Circulatory Apparatus", "Artificial Lung", "Artificial Heart", "Artificial Kidney", which assume the functions of the operated organs, allow for a while to suspend their work. "Artificial lung" is a pulsating pump that delivers air in portions at a frequency of 40-50 times per minute. An ordinary piston is not suitable for this: particles of the material of its rubbing parts or a seal can get into the air flow. Here and in other similar devices, corrugated metal or plastic bellows are used - bellows. Purified and brought to the required temperature, the air is supplied directly to the bronchi. The "heart-lung machine" is similar. Its hoses are surgically connected to the blood vessels. The first attempt to replace the function of the heart with a mechanical analogue was made as early as 1812. However, until now, among the many manufactured devices, there are no completely satisfying doctors. Domestic scientists and designers have developed a number of models under the general name "Search". This is a four-chamber sac-type ventricular prosthesis designed for implantation in an orthotopic position. The model distinguishes between the left and right halves, each of which consists of an artificial ventricle and an artificial atrium. The constituent elements of the artificial ventricle are: body, working chamber, inlet and outlet valves. The ventricle housing is made of silicone rubber by layering. The matrix is immersed in a liquid polymer, removed and dried - and so on over and over again, until a multi-layer heart flesh is created on the surface of the matrix. The working chamber is similar in shape to the body. It was made from latex rubber, and then from silicone. The design feature of the working chamber is a different wall thickness, in which active and passive sections are distinguished. The design is designed in such a way that even with full tension of the active sections, the opposite walls of the working surface of the chamber do not touch each other, which eliminates the injury of blood cells. Russian designer Alexander Drobyshev, despite all the difficulties, continues to create new modern Poisk designs that will be much cheaper than foreign models. One of the best foreign systems for today "Artificial heart" "Novakor" costs 400 thousand dollars. With her, you can wait at home for an operation for a whole year. There are two plastic ventricles in the "Novakor" suitcase. On a separate trolley there is an external service: a control computer, a control monitor, which remains in the clinic in front of the doctors. At home with the patient - a power supply, rechargeable batteries that are replaced and recharged from the mains. The task of the patient is to follow the green indicator of the lamps showing the charge of the batteries. Devices "Artificial kidney" have been working for quite a long time and are successfully used by physicians. Back in 1837, while studying the processes of movement of solutions through semipermeable membranes, T. Grechen was the first to use and put into use the term "dialysis" (from the Greek dialisis - separation). But only in 1912, on the basis of this method, an apparatus was constructed in the United States, with the help of which its authors carried out the removal of salicylates from the blood of animals in an experiment. In the device, which they called "artificial kidney", collodion tubes were used as a semi-permeable membrane, through which the animal's blood flowed, and outside they were washed with an isotonic sodium chloride solution. However, the collodion used by J. Abel turned out to be a rather fragile material, and later other authors tried other materials for dialysis, such as the intestines of birds, the swim bladder of fish, the peritoneum of calves, reed, and paper. To prevent blood clotting, hirudin, a polypeptide contained in the secretion of the salivary glands of a medical leech, was used. These two discoveries were the prototype for all subsequent developments in the field of extrarenal cleansing. Whatever the improvements in this area, the principle remains the same. In any case, the "artificial kidney" includes the following elements: a semi-permeable membrane, on one side of which blood flows, and on the other side - a saline solution. To prevent blood clotting, anticoagulants are used - medicinal substances that reduce blood clotting. In this case, the concentrations of low-molecular compounds of ions, urea, creatinine, glucose, and other substances with a small molecular weight are equalized. With an increase in the porosity of the membrane, the movement of substances with a higher molecular weight occurs. If we add to this process an excess hydrostatic pressure from the side of the blood or a negative pressure from the side of the washing solution, then the transfer process will be accompanied by the movement of water - convection mass transfer. Osmotic pressure can also be used to transfer water by adding osmotically active substances to the dialysate. Most often, glucose was used for this purpose, less often fructose and other sugars, and even more rarely products of other chemical origin. At the same time, by introducing glucose in large quantities, one can get a really pronounced dehydration effect, however, increasing the concentration of glucose in the dialysate above certain values is not recommended due to the possibility of complications. Finally, it is possible to completely abandon the membrane-flushing solution (dialysate) and obtain an exit through the membrane of the liquid part of the blood: water and substances with a molecular weight of a wide range. In 1925, J. Haas performed the first human dialysis, and in 1928 he also used heparin, since long-term use of hirudin was associated with toxic effects, and its very effect on blood coagulation was unstable. For the first time, heparin was used for dialysis in 1926 in an experiment by H. Nehels and R. Lim. Since the materials listed above turned out to be of little use as a basis for creating semipermeable membranes, the search for other materials continued, and in 1938 cellophane was used for the first time for hemodialysis, which in subsequent years remained the main raw material for the production of semipermeable membranes for a long time. The very first "artificial kidney" device suitable for wide clinical use was created in 1943 by W. Kolff and H. Burke. Then these devices were improved. At the same time, the development of technical thought in this area at first concerned, to a greater extent, the modification of dialyzers, and only in recent years began to affect the devices themselves to a large extent. As a result, two main types of dialyzer appeared, the so-called coil dialyzer, where cellophane tubes were used, and plane-parallel, in which flat membranes were used. In 1960, F. Keel designed a very successful version of a plane-parallel dialyzer with polypropylene plates, and over the course of a number of years this type of dialyzer and its modifications spread throughout the world, taking a leading place among all other types of dialyzers. Then the process of creating more efficient hemodialyzers and simplifying the technique of hemodialysis developed in two main directions: the design of the dialyzer itself, with single-use dialyzers occupying a dominant position over time, and the use of new materials as a semipermeable membrane. The dialyzer is the heart of the "artificial kidney", and therefore the main efforts of chemists and engineers have always been aimed at improving this particular link in the complex system of the apparatus as a whole. However, technical thought did not disregard the apparatus as such. In the 1960s, the idea arose to use the so-called central systems, that is, "artificial kidney" devices, in which dialysate was prepared from a concentrate - a mixture of salts, the concentration of which was 30-34 times higher than their concentration in the patient's blood. A combination of "drain" dialysis and recirculation technique has been used in a number of "artificial kidney" machines, for example by the American firm Travenol. In this case, about 8 liters of dialysate circulated at high speed in a separate container in which the dialyzer was placed and into which 250 milliliters of fresh solution was added every minute and the same amount was thrown into the sewer. At first, simple tap water was used for hemodialysis, then, due to its contamination, in particular with microorganisms, they tried to use distilled water, but this turned out to be very expensive and inefficient. The issue was radically resolved after the creation of special systems for the preparation of tap water, which includes filters for its purification from mechanical impurities, iron and its oxides, silicon and other elements, ion-exchange resins for eliminating water hardness and installations of the so-called "reverse" osmosis. Much effort has been expended on improving the monitoring systems of "artificial kidney" devices. So, in addition to constantly monitoring the temperature of the dialysate, they began to constantly monitor with the help of special sensors the chemical composition of the dialysate, focusing on the overall electrical conductivity of the dialysate, which changes with a decrease in salt concentration and increases with an increase in it. After that, ion-selective flow sensors began to be used in "artificial kidney" devices, which would constantly monitor the ion concentration. The computer, on the other hand, made it possible to control the process by introducing the missing elements from additional containers, or to change their ratio using the feedback principle. The value of ultrafiltration during dialysis depends not only on the quality of the membrane, in all cases the transmembrane pressure is the decisive factor, therefore pressure sensors have become widely used in monitors: the degree of dilution in dialysate, the pressure value at the inlet and outlet of the dialyzer. Modern technology using computers makes it possible to program the ultrafiltration process. Leaving the dialyzer, the blood enters the patient's vein through an air trap, which makes it possible to judge by eye the approximate amount of blood flow, the tendency of blood to clot. To prevent air embolism, these traps are equipped with air ducts, with the help of which they regulate the level of blood in them. Currently, in many devices, ultrasonic or photoelectric detectors are put on air traps, which automatically block the venous line when the blood level in the trap falls below a predetermined level. Recently, scientists have created devices that help people who have lost their sight - completely or partially. Miracle goggles, for example, were developed by the research and development manufacturing company Rehabilitation on the basis of technologies that were previously used only in military affairs. Like a night sight, the device operates on the principle of infrared location. The black-matte lenses of the glasses are actually Plexiglas plates, between which a miniature location device is enclosed. The entire locator, together with the spectacle frame, weighs about 50 grams - about the same as ordinary glasses. And they are selected, like glasses for the sighted, strictly individually, so that it is both convenient and beautiful. "Lenses" not only perform their direct functions, but also cover eye defects. Of the two dozen options, everyone can choose the most suitable for themselves. Using glasses is not difficult at all: you need to put them on and turn on the power. The source of energy for them is a flat battery the size of a cigarette pack. Here, in the block, the generator is also placed. The signals emitted by it, having come across an obstacle, come back and are caught by the "receiving lenses". The received impulses are amplified, compared with the threshold signal, and if there is an obstacle, the buzzer immediately sounds - the louder the closer the person came to it. The range of the device can be adjusted using one of two ranges. Work on the creation of an electronic retina is being successfully carried out by American specialists from NASA and the Main Center at Johns Hopkins University. At first, they tried to help people who still had some remnants of vision. “Televisions have been created for them,” write S. Grigoriev and E. Rogov in the Young Technician magazine, “where miniature television screens are installed instead of lenses. However, for the visually impaired, the picture is also decoded using a built-in computer.Such a device does not create special miracles and does not make the blind sighted, experts say, but it will allow the maximum use of the visual abilities that a person still has, and facilitate orientation. For example, if a person has at least part of the retina left, the computer will "split" the image in such a way that a person can see the environment at least with the help of the remaining peripheral areas. According to the developers, such systems will help approximately 2,5 million people suffering from visual impairments. But what about those whose retina is almost completely lost? For them, scientists from the eye center at Duke University (North Carolina) are mastering the operation of implanting an electronic retina. Special electrodes are implanted under the skin, which, when connected to nerves, transmit an image to the brain. The blind sees a picture consisting of individual luminous dots, very similar to the display board that is installed in stadiums, train stations and airports. The image on the "scoreboard" is again created by miniature television cameras mounted on a spectacle frame. And, finally, the last word of science today is an attempt to create new sensitive centers on the damaged retina using the methods of modern microtechnology. Prof. Rost Propet and his colleagues are now engaged in such operations in North Carolina. Together with NASA specialists, they created the first samples of a subelectronic retina, which is directly implanted in the eye. “Our patients, of course, will never be able to admire Rembrandt’s paintings,” the professor comments. “However, they will still be able to distinguish where the door is and where the window is, road signs and signboards…” Author: Musskiy S.A.
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