a. Mercury-in-glass thermometer
Mercury Thermometer Digital Thermometer
Digital Pacifier Thermometer
Digital Tympanic Thermometer
Thermometer
Thermometers measure temperature, by using materials that change in some way when they are heated or cooled. In a mercury or alcohol thermometer the liquid expands as it is heated and contracts when it is cooled, so the length of the liquid column is longer or shorter depending on the temperature. Modern thermometers are calibrated in standard temperature units such as Fahrenheit or Celsius.
A mercury-in-glass thermometer, invented by German physicist Daniel Gabriel Fahrenheit, is a thermometer consisting of mercury in a glass tube. Calibrated marks on the tube allow the temperature to be read by the length of the mercury within the tube, which varies according to the temperature. To increase the sensitivity, there is usually a bulb of mercury at the end of the thermometer which contains most of the mercury; expansion and contraction of this volume of mercury is then amplified in the much narrower bore of the tube. The space above the mercury may be filled with nitrogen or it may be a vacuum.
Maximum thermometer
A special kind of mercury thermometer, called a maximum thermometer, works by having a constriction in the neck close to the bulb. As the temperature rises the mercury is pushed up through the constriction by the force of expansion. When the temperature falls the column of mercury breaks at the constriction and cannot return to the bulb thus remaining stationary in the tube. The observer can then read the maximum temperature over a set period of time. To reset the thermometer it must be swung sharply, or the constriction may be pulled down with a magnet. This is similar to the design of a medical thermometer.
Physical properties
Mercury will solidify (freeze) at -38.83 °C (-37.89 °F) and so may only be used at higher temperatures. Mercury, unlike water, does not expand upon solidification and will not break the glass tube, making it difficult to notice when frozen. If the thermometer contains nitrogen the gas may flow down into the column and be trapped there when the temperature rises. If this happens the thermometer will be unusable until returned to the factory for reconditioning. To avoid this some weather services require that all mercury thermometers be brought indoors when the temperature falls to -37 °C (-34.6 °F). In areas where the maximum temperature is not expected to rise above -38.83 °C (-37.89 °F) a thermometer containing a mercury-thallium alloy may be used. This has a solidification (freezing) point of -61.1 °C (-78 °F).
Early History The first thermometers were called thermoscopes and while several inventors invented a version of the thermoscope at the same time, Italian inventor Santorio Santorio was the first inventor to put a numerical scale on the instrument. Galileo Galilei invented a rudimentary water thermometer in 1593 which, for the first time, allowed temperature variations to be measured. In 1714, Gabriel Fahrenheit invented the first mercury thermometer, the modern thermometer.
b. Vaccination The two public health interventions that have had the greatest impact on the world’s health is clean water and vaccines. Thanks to such pioneers as Jenner and Pasteur, a handful of vaccines prevent illness or death for millions of individuals every year. But there is still a long way to go. Immunization, the most cost-effective public health intervention, continues to be under-used. It is profoundly tragic that almost two million children still die each year from diseases for which vaccines are available at low cost. And over 90,000 fall victim to paralytic polio, which could also have been prevented by immunization. Indeed many years elapsed between the invention of current vaccines and their widespread use in immunization programs. The reasons for these delays are many and complex. If history is to serve any useful purpose, it should help us to find ways to such delays in future.
The closing years of the 19th century and the early years of the 20th century were marked by the achievements of great vaccine scientists such as Pasteur. Since the introduction of vaccinia by Jenner 200 years ago (“vaccination” in its true sense), nine major diseases of man have been controlled to a greater or lesser extent through the use of vaccines (Table 1). Several other vaccines have been used in individuals at risk from disease of such as rabies and plague, but have not been systemetically applied on a global scale. While BCG has been widely administered to newborns, thus successfully preventing complications such as meningitis and miliary tuberculosis, administration of the vaccine has not resulted in control of the disease.Table: The date of introduction of first generation of vaccines for use in humans.
* 1798 Smallpox
* 1855 Rabies
* 1897 Plague
* 1923 Diptheria
* 1926 Pertussis
* 1927 Tuberculosis (BCG)
* 1927 Tetanus
* 1935 Yellow FeverAfter World War II
* 1955 Injectible Polio Vaccine (IPV)
* 1962 Oral Polio Vaccine (OPV)
* 1964 Measles
* 1967 Mumps
* 1970 Rubella
* 1981 Hepatitis B
Although the first vaccines were, in some respects, crude, they have proved to be robust and efficient, and continue to be the workhorses of global immunization programs. They have dramatically reduced the burden of death and disease from these nine infections, and have given credibility to the entire preventive health movement. During the 1920s, diphtheria and tetanus toxiods, whole cell pertussis vaccine and BCG were introduced. Thanks to the development of the chorioallantoic membrane for culturing viruses, a yellow fever vaccine was available by 1935. After the Second World War, there followed an explosion of technology, resulting in the emergence of other vaccines still in use today. These included the killed and oral polio vaccines, and the measles, mumps and rubella vaccines.Early National Immunization Programmes 1900-1973. During this period, the use of available vaccines was largely confined to industrialized countries. For instance, smallpox vaccine was offered to all age groups, but only those at risk – health care workers and travellers – were specially targeted. As a result, coverage was patchy and outbreaks continued to occur throughout the world. When this happened, massive vaccination efforts were mounted by health authorities, often very successfully, to contain the infection through vaccination and isolation or quarantine of infected individuals or suspected cases.
Other vaccines such as BCG were gradually introduced in the West, (Table 2) as they became available. Better off-families who could afford vaccination benefited most – the poor benefited the least. Because of low, irregular coverage, communities continued to be devastated intermittently by outbreaks of these vaccines – preventable diseases throughout the 1930s and 1940s.
An injectable form of killed polio vaccine (IPV) became available in 1955, resulting in widespread administration in schools and clinics in industrialized countries across a broad age range resulting in a marked drop in cases in these countries. In 1962, the oral polio vaccine (OPV) replaced IPV and continues to be the vaccine of choice for eradication of the virus. Despite initial low coverage, the vaccine showed itself capable of dramatically reducing the number of polio cases when administered to a wide age range over a short period of time.Table: Vaccines used in national immunization programs upto 1974.
* Small pox
* BCG
* Diphtheria toxiod
* Tetanus toxiod
* Pertussis
* IPV & OPV
* Measles
In terms of strategy, the early programs offered routine immunization through regular maternal and child health services. While efforts were made to encourage acceptance, no major effort was made to achieve total coverage. The implied target was to raise coverage, but there was no disease reduction target specified. The early years of 19th century saw widespread but haphazard use of Jenner’s vaccine. However, application of smallpox vaccine was systematic in Mexico and
Guatemala around 1805 (ref 2). The first attempt to use it on a global scale began in 1956 when the World Health Organization and others selected smallpox for eradication from the globe.
It was not the first time disease eradication had been mooted. Already the scientific community had considered the possibility of eradicating bovine contagious pleuropneumonia (a highly fatal disease of cattle), hookworm, yellow fever, malaria and yaws. Now with a clear strategy and a highly effective, affordable vaccine, it wa possible to unite all countries in a mighty effort to rid themselves of this disease and the tremendous annual cost it incurred. To meet this special circumstance, very high population coverage with the smallpox vaccine was used. Finally in the late 1960s, an additional strategy was developed whereby cases were identified through intensive surveillance and confined (“attainment”), and possible contacts within a given radius were vaccinated. Details of this effort are chronicled elsewhere (ref 3).
The next notable attempt at large-scale control was undertaken in
Gambia in 1967-1970 when Foege and his team administered measles vaccine in a mass country-wide campaign. As a result, indigenous measles was entirely absent from
Gambia until 1972. However, due to inability to sustain immunization coverage, the situation soon reverted to pre-campaign levels (ref 4).
The Expanded Program On Immunization (EPI) Following the impressive success of the smallpox eradication programme, the World Health Organization looked for otheractivities that could build on what had already been achieved. In 1974 the Expanded Programme On Immunization was created. “Expanded” because most programmes until then had only used smallpox, BCG and diptheria, tetanus and pertussis (DTP) vaccines. EPI would include two new diseases. The six diseases chosen were tuberculosis, diptheria, neonatal tetanus, whooping cough, poliomyelitis and measles. Selection was made on the basis of a high burden of disease and the availability of a well-tried vaccines at an affordable price. “Expanded” also meant increased coverage – incredibly, less than 5% of children in developing countries were being reached at that time by immunization services.
Gradually, global coverage for the six vaccines rose, although success was not uniform. Regions and countries with the greatest resources, infrastructure and political will were able to raise coverage faster and higher. Many organizations such as UNICEF and Rotary International became partners in the program. Between 1974 and 1980, the program developed training materials and disseminated them widely. In those busy years, almost every country in the world adopted the principle of a national immunization program. (Many used and continue to use the name “EPI” which has become a trade mark). Hundreds of training courses in dozens of languages were conducted resulting in a huge mobilization of human resources. Personnel were trained in the management of the program so that every community was reached (at least in theory) by some form of immunization service. The number of doses administered and the number of target diseases occurring were recorded and reported.
Table: Vaccines used by the Expanded Program on Immunization from 1974 onwards* BCG
* Polio
* DTP
* Measles
Added Later
* Yellow Fever * Hepatitis B
c. Stethoscope
Modern acoustic stethoscope The stethoscope (Greek words, stéthos – chest and skopé – examination) is an acoustic medical device for auscultation, i.e. listening to internal sounds in the human body. It is most often used to listen to heart sounds and breathing (breath sounds), though it is also used to listen to intestines and blood flow in arteries and veins.
History
The stethoscope was invented in France in 1816 by René-Théophile-Hyacinthe Laennec. It consisted of a wooden tube and was monaural. In 1851 Arthur Leared invented a binaural stethoscope, and in 1852 George Cammann perfected the design of the instrument for commercial production, which has become the standard ever since. Cammann also authored a major treatise on diagnosis by auscultation, which the refined binaural stethoscope made possible. By 1873, there were descriptions of a differential stethoscope that could connect to slightly different locations to create a slight stereo effect, though this did not become a standard tool in clinical practise. Rappaport and Sprague designed a new stethoscope in the 1940′s which became the standard by which other stethoscopes are measured. The Rappaport-Sprague was later made by Hewlett-Packard, and today there are still cardiologists who consider it to be the finest acoustic stethoscope. Several other minor refinements were made to stethoscopes until in the early 1960′s Dr. Littmann, a Harvard Medical School professor, created a new stethoscope that was lighter than previous models. Littmann followed a long tradition — stethoscopes designed by physicians.
The Monaural Stethoscope
The stethoscope was invented in 1816 when a young French physician named Rene Theophile Hyacinthe Laennec was examining a young female patient. Laennec was embarrassed to place his ear to her chest ( Immediate Auscultation ), which was the method of auscultation used by physicians at that time. He remembered a trick he learned as a child that sound travels through solids and thus he rolled up 24 sheets of paper, placed one end to his ear and the other end to the woman’s chest. He was delighted to discover that the sounds were not only conveyed through the paper, but they were also louder and clearer.
The first recorded manuscript documenting auscultation using the stethoscope ( Mediate Auscultation) was in March 8, 1817, when Laennec noted examining a Marie-Melanie Basset, who was 40 years old.
Interestingly, Laennec preferred to have his instrument simply called “Le Cylindre,” as he thought naming such a fundamental instrument was unnecessary. He became remorse at the names it was being given by his colleagues and decided that if it should be called anything, it should be “Stethoscope,” which is derived from the Greek words for ‘I see’ and ‘the chest.’
Laennec then took his idea further. He set up a small shop in his home, with a wood-turning lathe
and many different materials. He created a stethoscope from a turned piece of wood, hollow in the center. It was made of two pieces. One end had a hole to place against the ear, and the other was hollowed out into a cone. There was a third piece that fit into this cone which had a hollow brass cylinder placed inside it. This piece was placed in the stethoscope to listen to the heart, and
removed to examine the lungs. Laennec published his classic treatise on mediate auscultation in 1819.
The Binaural Stethoscope
In 1852, Dr. George Cammann of
New York produced the first recognized usable binaural stethoscope. He was working as a physician at the Northern Dispensary in
New York City and had seen Marsh’s model. He also had a model of a soft metal, multiple-tubed stethoscope made by H. Landouzy in 1841, which was designed for two people to listen at the same time. And Charles J. B. Williams claims to have made a binaural stethoscope with lead tubes in 1843. Cammann did not claim to have the original idea for a binaural stethoscope, only to have developed a practical instrument that could be used in clinical practice.
Cammann had some help in designing his stethoscope and, interestingly, never patented the stethoscope believing it should be freely available to physicians. The stethoscope was named Cammann’s Stethoscope by the manufacturer of the original instrument, George Tiemann.
Cammann’s model was made with ivory earpieces connected to metal tubes. These were held together by a simple hinge joint, and tension was applied by way of an elastic band. Attached to these were two tubes covered by wound silk. These converged into a hollow ball designed to amplify the sound, and attached to the ball was a conical shaped, bell chest piece.
| Original version of the Laennec stethoscope made of a turned dense, finely grained, light colored wood, circa 1819. This cylindical stethoscope is made with three parts fitting together by wood screw thread and brass tube fitting with an overall length of 12.6 inches and a diameter of 1.5 inches. Both ends are slightly concave. This first version is illustrated in Laennec’s first edition text on auscultation which described the stethoscope as having an overall length of 12 inches and a diameter of 1.5 inches. Laennec turned the first stethoscopes himself and these were somewhat longer than described in his text. The stethoscope shown above has the same features as a surviving stethoscope that is tracable to Laennec himself which is shown in the photos and description to the right. On the left the stethoscope is assembled with the chest plug protruding from the funnel shaped, chest end of the stethoscope. On the right the stethoscope is taken apart revealing the wood screw thread that attaches the two parts of the body of the stethoscope and the chest plug with brass tube fitting that holds the chest plug in place in the funnel shaped chest end. |
Current practice
The stethoscope is used in aid of diagnosing certain diseases and conditions. The stethoscope is able to transmit certain sounds and exclude others. Before the stethoscope was invented, doctors placed their ear next to the patient’s body in hopes of hearing something. Stethoscopes are often considered as a symbol of the doctor’s profession, as doctors are often seen or depicted with a stethoscope hanging around their neck. Stethoscopes are also used by mechanics to isolate sounds of a particular moving engine part for diagnosis.
Types of stethoscopes
Acoustic
Acoustic stethoscopes are familiar to most people, and operate on the transmission of sound from the chestpiece, via air-filled hollow tubes, to the listener’s ears. The chestpiece usually consists of two sides that can be placed against the patient for sensing sound — a diaphragm (plastic disc) or bell (hollow cup). If the diaphragm is placed on the patient, body sounds vibrate the diaphragm, creating acoustic pressure waves which travel up the tubing to the listener’s ears. If the bell is placed on the patient, the vibrations of the skin directly produce acoustic pressure waves traveling up to the listener’s ears. The bell transmits low frequency sounds, while the diaphragm transmits higher frequency sounds. This 2-sided stethoscope was invented by Rappaport and Sprague in the early part of the 20th century. The problem with acoustic stethoscope is that the sound level is extremely low, making diagnosis difficult.
Electronic
Electronic stethoscopes overcome the low sound levels by amplifiying body sounds. Currently, a number of companies offer electronic stethoscopes, and it can be expected that within a few years, the electronic stethoscope will have eclipsed acoustic devices. Electronic stethoscopes require conversion of acoustic sound waves to electrical signals which can then be amplified and processed for optimal listening. Unlike acoustic stethoscopes, which are all based on the same physics, transducers in electronic stethoscopes vary widely. The simplest and least effective method of sound detection is achieved by placing a microphone in the chestpiece. This method suffers from ambient noise interference and has fallen out of favor. Another method, used in Welch-Allyn’s Meditron stethoscope, comprises placement of a piezoelectric crystal at the head of a metal shaft, the bottom of the shaft making contact with a diaphragm. 3M also uses a piezo-electric crystal placed within foam behind a thick rubber-like diaphragm. Thinklabs uses a stethoscope diaphragm with an electrically conductive inner surface to form a capacitive sensor. This diaphragm responds to sound waves identically to a conventional acoustic stethoscope, with changes in an electric field replacing changes in air pressure. This preserves the sound of an acoustic stethoscope with the benefits of amplification. More recently, ambient noise filtering has become available in electronic stethoscopes, with 3M’s Littmann 3000 and Thinklabs ds32a offering methods for eliminating ambient noise.
Prior to 1855 George Tiemann marked his medical instruments as Tiemann, after 1855 used the mark G. Tiemann & Co. and later used the mark Tiemann & Co. The markings on the above models help date these stethoscopes and are consistent with the introduction of the Cammann stethoscope in 1852.
d. Antiseptic
Antiseptic is an agent that kills or inhibits the growth of microorganisms on the external surfaces of the body. Antiseptics should generally be distinguished from drugs such as antibiotics that destroy microorganisms internally, and from disinfectants, which destroy microorganisms found on nonliving objects. Germicides include only those antiseptics that kill microorganisms. Some common antiseptics are alcohol, iodine, hydrogen peroxide, and boric acid. There is great variation in the ability of antiseptics to destroy microorganisms and in their effect on living tissue. For example, mercuric chloride is a powerful antiseptic, but it irritates delicate tissue. In contrast, silver nitrate kills fewer germs but can be used on the delicate tissues of the eyes and throat. There is also a great difference in the time required for different antiseptics to work. Iodine, one of the fastest-working antiseptics, kills bacteria within 30 sec. Other antiseptics have slower, more residual action. Since so much variability exists, systems have been devised for measuring the action of an antiseptic against certain standards. The bacteriostatic action of an antiseptic compared to that of phenol (under the same conditions and against the same microorganism) is known as its phenol coefficient. Joseph Lister was the first to employ the antiseptic phenol, or carbolic acid, in surgery, following the discovery by Louis Pasteur that microorganisms are the cause of infections. Modern surgical techniques for avoiding infection are founded on asepsis, the absence of pathogenic organisms. Sterilization is the chief means of achieving asepsis.
Use in surgery
The widespread introduction of antiseptic surgical methods followed the publishing of the paper Antiseptic Principle of the Practice of Surgery in 1867 by Joseph Lister, inspired by Louis Pasteur‘s germ theory of putrefaction. In this paper he advocated the use of carbolic acid (phenol) as a method of ensuring that any germs present were killed. Some of this work was preceded slightly by that of Dr. George H Tichenor and Ignaz Semmelweis. But every antiseptic, however good, is more or less toxic and irritating to a wounded surface. Hence it is that the antiseptic method has been replaced in the surgery of today by the aseptic method, which relies on keeping free from the invasion of bacteria rather than destroying them when present.
How it works
For the growth of bacteria there must be a certain food supply, moisture, in most cases oxygen, and a certain minimum temperature. These conditions have been specially studied and applied in connection with the preserving of food and in the ancient practice of embalming the dead, which is the earliest illustration of the systematic use of antiseptics. In early inquiries a great point was made of the prevention of putrefaction, and work was done in the way of finding how much of an agent must be added to a given solution, in order that the bacteria accidentally present might not develop. But for various reasons this was an inexact method, and to-day an antiseptic is judged by its effects on pure cultures of definite pathogenic microbes, and on their vegetative and spore forms. Their standardization has been effected in many instances, and a water solution of phenol of a certain fixed strength is now taken as the standard with which other antiseptics are compared.
Some common antiseptics
Alcohols
Most commonly used are ethanol (60-90%), 1-propanol (60-70%) and 2-propanol/isopropanol (70-80%) or mixtures of these alcohols. They are commonly referred to as “surgical alcohol”. Used to disinfect the skin before injections are given, often along with iodine (tincture of iodine) or some cationic surfactants (benzalkonium chloride 0.05 – 0.5%, chlorhexidine 0.2 – 4.0% or octenidine dihydrochloride 0.1 – 2.0%).
Quaternary ammonium compounds Also known as Quats or QAC’s, include the chemicals benzalkonium chloride (BAC), cetyl trimethylammonium bromide (CTMB), cetylpyridinium chloride (Cetrim), cetylpyridinium chloride (CPC) and benzethonium chloride (BZT). Benzalkonium chloride is used in some pre-operative skin disinfectants (conc. 0.05 – 0.5%) and antiseptic towels. The antimicrobial activity of Quats is inactivated by anionic surfactants, such as soaps. Related disinfectants include chlorhexidine and octenidine.
Boric acid Used in suppositories to treat yeast infections of the vagina, in eyewashes, and as an antiviral to shorten the duration of cold sore attacks. Put into creams for burns. Also common in trace amounts in eye contact solution. Though it is popularly known as an antiseptic, it is in reality only a soothing fluid, and bacteria will flourish comfortably in contact with it.
Chlorhexidine Gluconate A biguanidine derivative, used in concentrations of 0.5 – 4.0% alone or in lower concentrations in combination with other compounds, such as alcohols. Used as a skin antiseptic and to treat inflammation of the gums (gingivitis). The microbicidal action is somewhat slow, but remanent. It is a cationic surfactant, similar to Quats.
Hydrogen peroxide Used as a 6% (20Vols) solution to clean and deodorise wounds and ulcers. More common 1% or 2% solutions of hydrogen peroxide have been used in household first aid for scrapes, etc. However, even this less potent form is no longer recommended for typical wound care as the strong oxidization causes scar formation and increases healing time. Gentle washing with mild soap and water or rinsing a scrape with sterile saline is a better practice.
Usually used in an alcoholic solution (called tincture of iodine) or as Lugol’s iodine solution as a pre- and post-operative antiseptic. No longer recommended to disinfect minor wounds because it induces scar tissue formation and increases healing time. Gentle washing with mild soap and water or rinsing a scrape with sterile saline is a better practice. Novel iodine antiseptics containing iodopovidone/PVP-I (an iodophor, complex of povidone, a water-soluble polymer, with triiodide anions I3-, containing about 10% of active iodine, with the commercial name Betadine) are far better tolerated, don’t affect wound healing negativelly and leave a depot of active iodine, creating the so-called “remanent,” or persistent, effect. The great advantage of iodine antiseptics is the widest scope of antimicrobial activity, killing all principial pathogenes and given enough time even spores, which are considered to be the most difficult form of microorganisms to be inactivated by disinfectants and antiseptics.
Mercurochrome Not recognized as safe and effective by the U.S. Food and Drug Administration (FDA) due to concerns about its mercury content. Another obsolete organomercury antiseptics include bis-(fenylmercury) monohydrogenborate (Famosept).
Octenidine dihydrochloride A cationic surfactant and bis-(dihydropyridinyl)-decane derivative, used in concentrations of 0.1 – 2.0%. It is similar in its action to the Quats, but is of somewhat broader spectrum of activity. Octenidine is currently increasingly used in continental
Europe as a QAC’s and chlorhexidine (with respect to its slow action and concerns about the carcinogenic impurity 4-chloroaniline) substitute in water- or alcohol-based skin, mucosa and wound antiseptic. In aqueous formulations, it is often potentiated with addition of 2-phenoxyethanol.
Phenol (carbolic acid) compounds Phenol is germicidal in strong solution, inhibitory in weaker ones. Used as a “scrub” for pre-operative hand cleansing. Used in the form of a powder as an antiseptic baby powder, where it is dusted onto the belly button as it heals. Also used in mouthwashes and throat lozenges, where it has a methadone-like painkilling effect as well as an antiseptic one. Example: TCP. Other phenolic antiseptics include historically important, but today rarely used (sometimes in dental surgery) thymol, today obsolete hexachlorophene, still used triclosan and sodium 3,5-dibromo-4-hydroxybenzenesulfonate (Dibromol).
Sodium chloride Used as a general cleanser. Also used as an antiseptic mouthwash. Only a weak antiseptic effect, due to hyperosmolality of the solution above 0.9%.
Sodium hypochlorite Used in the past, diluted, neutralised and combined with potassium permanganate in the Daquin’s solution. Nowadays used only as disinfectant.
e. X-Ray
Mrs. Röntgen’s hand, the first X-ray picture of the human body ever taken. X-rays are electromagnetic waves of short wavelength, capable of penetrating some thickness of matter. Medical x-rays are produced by letting a stream of fast electrons come to a sudden stop at a metal plate; it is believed that X-rays emitted by the Sun or stars also come from fast electrons. Both light and radio waves belong to the electromagnetic spectrum, the range containing all different electromagnetic waves. Over the years scientists and engineers have created EM waves of other frequencies–microwaves and various IR bands whose waves are longer than those of visible light (between radio and the visible), and UV, EUV, X-rays and g-rays (gamma rays) with shorter wavelengths. The electromagnetic nature of x-rays became evident when it was found that crystals bent their path in the same way as gratings bent visible light: the orderly rows of atoms in the crystal acted like the grooves of a grating.
On 8 Nov, 1895, Wilhelm Conrad Röntgen (accidentally) discovered an image cast from his cathode ray generator, projected far beyond the possible range of the cathode rays (now known as an electron beam). Further investigation showed that the rays were generated at the point of contact of the cathode ray beam on the interior of the vacuum tube, that they were not deflected by magnetic fields, and they penetrated many kinds of matter.
A week after his discovery, Rontgen took an X-ray photograph of his wife’s hand which clearly revealed her wedding ring and her bones. The photograph electrified the general public and aroused great scientific interest in the new form of radiation. Röntgen named the new form of radiation X-radiation (X standing for “Unknown”). Hence the term X-rays (also referred as Röntgen rays, though this term is unusual outside of
Germany).
The images produced by X-rays are due to the different absorption rates of different tissues. Calcium in bones absorbs X-rays the most, so bones look white on a film recording of the X-ray image , called a radiograph. Fat and other soft tissues absorb less, and look gray. Air absorbs the least, so lungs look black on a radiograph.
f. Electrocardiogram
An electrocardiogram (EKG, ECG) is a test that measures the electrical signals that control the rhythm of your heartbeat.
ECG as done by Willem Einthoven In 1856 Kolliker and Muller discovered the electrical activity of the heart when a frog sciatic nerve/gastrocenemius preparation fell onto an isolated frog heart and both muscles contracted synchronously. Alexander Muirhead attached wires to a feverish patient’s wrist to obtain a record of the patient’s heartbeat while studying for his DSc (in electricity) in 1872 at St Bartholomew’s HospitalThis activity was directly recorded and visualized using a Lippmann capillary electrometer by the British physiologist John Burdon Sanderson.The first to systematically approach the heart from an electrical point-of-view was Augustus Waller, working in St Mary’s Hospital in Paddington, London.His electrocardiograph machine consisted of a Lippmann capillary electrometer fixed to a projector. The trace from the heartbeat was projected onto a photographic plate which was itself fixed to a toy train. This allowed a heartbeat to be recorded in real time. In 1911 he still saw little clinical application for his work. The breakthrough came when Willem Einthoven, working in Leiden, The Netherlands, used the string galvanometer invented by him in 1901, which was much more sensitive than the capillary electrometer that Waller used.[5] Einthoven assigned the letters P, Q, R, S and T to the various deflections, and described the electrocardiographic features of a number of cardiovascular disorders. In 1924, he was awarded the Nobel Prize in Medicine for his discovery.
An electrocardiogram may show: · Evidence of heart enlargement. · Signs of insufficient blood flow to the heart. · Signs of a new or previous injury to the heart (heart attack). · Heart rhythm problems (arrhythmias). · Changes in the electrical activity of the heart caused by an electrolyte imbalance in the body. · Signs of inflammation of the sac surrounding the heart (pericarditis). An electrocardiogram cannot predict whether you will have a heart attack.
Why It Is Done An electrocardiogram (EKG, ECG) is done to:· Evaluate unexplained chest pain, especially when a heart attack is a possibility. Other possible causes of chest pain or discomfort that can be identified by an EKG include irregular heartbeats (arrhythmias), a heart chamber with thickened walls (hypertrophy), inflammation of the sac surrounding the heart (pericarditis), and reduced blood flow to the heart muscle (ischemia). · Monitor the heart’s electrical activity. · Determine whether thickening of the walls (hypertrophy) of a ventricle is present. · Monitor the effectiveness and possible side effects of certain medications that may affect the heart. · Check the function of mechanical devices (pacemakers or defibrillators) implanted in the heart to maintain a regular heart rhythm. An electrocardiogram may be used to evaluate symptoms of heart disease (such as unexplained chest pain, shortness of breath, dizziness, faintness, or palpitations) or when risk factors for heart disease (such as high blood pressure, high cholesterol, cigarette smoking, diabetes, or a family history of early heart disease) are present.
g. Antibiotic
Antibiotic: A drug used to treat infections caused by bacteria and other microorganisms. Originally, an antibiotic was a substance produced by one microorganism that selectively inhibits the growth of another. Synthetic antibiotics, usually chemically related to natural antibiotics, have since been produced that accomplish comparable tasks.
In 1926, Alexander Fleming discovered penicillin, a substance produced by fungi that appeared able to inhibit bacterial growth. In 1939, Edward Chain and Howard Florey further studied penicillin and later carried out trials of penicillin on humans (with what were deemed fatal bacterial infections). Fleming, Florey and Chain shared the Nobel Prize in 1945 for their work which ushered in the era of antibiotics.
Another antibiotic, for example, is tetracycline (brand names: Achromycin and Sumycin), a broad-spectrum agent effective against a wide variety of bacteria including Hemophilus influenzae, Streptococcus pneumoniae, Mycoplasma pneumoniae, Chlamydia psittaci, Chlamydia trachomatis, Neisseria gonorrhoea, and many others. The first drug of the tetracycline family, chlortetracycline, was introduced in 1948.
h. Pacemaker
Other names Artificial pacemaker; Permanent pacemaker; Internal pacemaker; Cardiac resynchronization therapy; CRT; Biventricular pacemaker A pacemaker is a small, battery-operated device that helps the heart beat regularly and at an appropriate rate.A pacemaker generally has two parts:
- Generator – contains the battery and the information to control the heartbeat
- Leads – wires used to connect the heart to the generator and send the electrical impulses to the heart to tell it to beat
Today’s generators weigh a little less than an ounce (30 grams). The pacemaker’s battery can last about 7 to 8 years. It will be regularly checked by your doctor, and replaced when necessary. Traditional pacemakers help control the right side of the heart to control the heart beat. This is called AV synchronization. A special type of pacemaker, called a biventricular pacemaker, works on both sides of the heart,. It synchronizes the right and left chambers (ventricles) of the heart and keeps them pumping together. This is called cardiac resynchronization therapy. All of today’s biventricular pacemakers can also work as an implantable cardio-defibrillator (ICD).IMPLANT SURGERY A pacemaker must be implanted under the skin. This procedure usually takes about 1 hour. You will be given a sedative to help you relax, but you will be awake during the procedure. Pain medicine will be given during the procedure. A small cut is made, usually on the left side of the chest. The health care provider uses x-rays to place the wires (leads) in the heart. After the leads are in place, they are connected to the pacemaker. The pacemaker is placed into the chest area, and the skin around it is closed with stitches. Most patients go home within 1 day of the procedure.COMPLICATIONS Complications of pacemaker surgery include bleeding, infection, dropped lung (uncommon), abnormal heart rhythms, and puncture of heart leading to bleeding around the heart (rare). A pacemaker can usually sense if the heartbeat is above a certain level, at which point it will automatically turn off. Likewise, the pacemaker can sense when the heartbeat slows down too much, and will automatically turn back on in order to start pacing again.WHY IT IS USED A pacemaker is often the treatment of choice for people who have a heart condition that causes their heart to beat too slowly (bradycardia). Less commonly, pacemakers may also be used to stop an abnormally rapid heart rate (tachycardia). Biventricular pacemakers have been used to treat severe heart failure.INTERFERENCE There are only a few devices in the environment today that which can interfere with a pacemaker.
- Arc welding equipment and equipment with powerful magnets have the potential to interfere with the pace generator.
- Most home appliances, such as a microwave, do NOT interfere with a pacemaker.
- Cell phones in the
U.S. do NOT interfere with pacemakers, but you should still keep them away from the pacemaker area (for example, do not store your cell phone in your shirt pocket).
The textbook definition of ultrasound is energy generated by sound waves of 20,000 or more vibrations per second. Ultrasound is used in a large array of imaging tools. Often used for medical diagnostics, ultrasound uses sound waves that are far above the frequency heard by the human ear. A transducer gives off the sound waves and reflected back from organs and a tissue, allowing a picture of what is inside the body to be drawn on a screen. Ultrasound can be used to look for tumors, analyze bone structure, or examine the health of an unborn baby.
Two researchers are noted in the history of ultrasound and medical imaging. They are: Doctor Karl Theodore Dussik of Austria, who published the first paper on medical ultrasonics in 1942, based on his research on transmission ultrasound investigation of the brain; and Professor Ian Donald of
Scotland, who developed practical technology and applications for ultrasound in the 1950s.
j. Genetic engineering
Genetic engineering is the use of various methods to manipulate the deoxyribonucleic acid (DNA) of cells to produce biological products or to change hereditary traits. Techniques used include using needles to insert DNA into an ovum, hybridomas (hybrids of cancer cells and of cells that make a desired antibody), and recombinant DNA, in which the DNA of a desired gene is inserted into the DNA of a bacterium. The bacterium then reproduces itself, yielding more of the desired gene. Another type is the polymerase chain reaction (PCR) which refers to a lab process in which a particular DNA segment is quickly replicated to create a large, easily analyzable sample. The process makes perfect copies of DNA fragments and is used in DNA fingerprinting.
The Human Genome Project, an ambitious attempt to map each human gene, was completed in 2003. Armed with this information, scientists hope to treat and cure many types of chronic diseases such as cancer, diabetes, Huntington’s disease, and neurofibromatosis (Elephant Man’s disease.)
Many genetically engineered products are already on the market. These include bacteria designed to digest oil slicks and industrial waste products, growth hormones for both humans and cows, drugs such as interferon and insulin, and plants that are resistant to insects and disease.
Genetic engineering techniques have also been used in the alteration of livestock and laboratory animals. The most famous of these animals was Dolly, the first cloned sheep. Genetically engineered products require the approval of at least one
U.S. government agency, such as the Food and Drug Administration or the Environmental Protection Agency.
The first genetically engineered pet was marketed in 2003 when scientists inserted a jellyfish gene into the common zebrafish to make them glow yellow-green in the dark. “Frankenfish” was expected to be a big novelty item but sales were flat.
Many people question both the ethics and the safety of genetic engineering. Because the science is so new, there is no way of predicting potential consequences to human health and safety should a genetically engineered animal escape the lab or if genetically altered food should turn out to have unexpected consequences. Several cases of genetically altered wheat infecting normal wheat crops have been reported. The infected crops were destroyed.
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