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166-419: The primary purpose of a pacemaker is to maintain an even heart rate , either because the heart's natural cardiac pacemaker provides an inadequate or irregular heartbeat, or because there is a block in the heart's electrical conduction system. Modern pacemakers are externally programmable and allow a cardiologist to select the optimal pacing modes for individual patients. Most pacemakers are on demand, in which

332-521: A binary system meant that Zuse's machines were easier to build and potentially more reliable, given the technologies available at that time. The Z3 was not itself a universal computer but could be extended to be Turing complete . Zuse's next computer, the Z4 , became the world's first commercial computer; after initial delay due to the Second World War, it was completed in 1950 and delivered to

498-632: A central processing unit (CPU) in the form of a microprocessor , together with some type of computer memory , typically semiconductor memory chips. The processing element carries out arithmetic and logical operations, and a sequencing and control unit can change the order of operations in response to stored information . Peripheral devices include input devices ( keyboards , mice , joysticks , etc.), output devices ( monitors , printers , etc.), and input/output devices that perform both functions (e.g. touchscreens ). Peripheral devices allow information to be retrieved from an external source, and they enable

664-419: A keyboard , and computed and printed the results, demonstrating the feasibility of an electromechanical analytical engine. During the first half of the 20th century, many scientific computing needs were met by increasingly sophisticated analog computers, which used a direct mechanical or electrical model of the problem as a basis for computation . However, these were not programmable and generally lacked

830-524: A mass-production basis, which limited them to a number of specialized applications. At the University of Manchester , a team under the leadership of Tom Kilburn designed and built a machine using the newly developed transistors instead of valves. Their first transistorized computer and the first in the world, was operational by 1953 , and a second version was completed there in April 1955. However,

996-429: A monolithic integrated circuit (IC) chip. Kilby's IC had external wire connections, which made it difficult to mass-produce. Noyce also came up with his own idea of an integrated circuit half a year later than Kilby. Noyce's invention was the first true monolithic IC chip. His chip solved many practical problems that Kilby's had not. Produced at Fairchild Semiconductor, it was made of silicon , whereas Kilby's chip

1162-461: A vagal maneuver takes longer and only lowers the rate to a much smaller extent. Heart rate is not a stable value and it increases or decreases in response to the body's need in a way to maintain an equilibrium ( basal metabolic rate ) between requirement and delivery of oxygen and nutrients. The normal SA node firing rate is affected by autonomic nervous system activity: sympathetic stimulation increases and parasympathetic stimulation decreases

1328-652: A 1998 retrospective, it was the first working machine to contain all of the elements essential to a modern electronic computer. As soon as the Baby had demonstrated the feasibility of its design, a project began at the university to develop it into a practically useful computer, the Manchester Mark 1 . The Mark 1 in turn quickly became the prototype for the Ferranti Mark 1 , the world's first commercially available general-purpose computer. Built by Ferranti , it

1494-409: A 2013 study found that "The overall risk of clinically significant adverse events related to EMI (electromagnetic interference) in recipients of CIEDs (cardiovascular implantable electronic devices) is very low. Therefore, no special precautions are needed when household appliances are used. Environmental and industrial sources of EMI are relatively safe when the exposure time is limited and distance from

1660-512: A Chip (SoCs) are complete computers on a microchip (or chip) the size of a coin. They may or may not have integrated RAM and flash memory . If not integrated, the RAM is usually placed directly above (known as Package on package ) or below (on the opposite side of the circuit board ) the SoC, and the flash memory is usually placed right next to the SoC. This is done to improve data transfer speeds, as

1826-414: A beat by beat basis and is called "demand pacing". In the case of a dual-chamber device, when the upper chambers have a spontaneous or stimulated activation, the device starts a countdown to ensure that in an acceptable – and programmable – interval, there is an activation of the ventricle, otherwise again an impulse will be delivered. The more complex forms include the ability to sense and/or stimulate both

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1992-468: A capsule and are small enough to allow the generator to be placed within the heart, therefore avoiding the need for pacing leads. As pacemaker leads can fail over time, a pacing system that avoids these components offers theoretical advantages. Leadless pacemakers can be implanted into the heart using a steerable catheter fed into the femoral vein via an incision in the groin. Modern pacemakers usually have multiple functions. The most basic form monitors

2158-440: A combination of autorhythmicity and innervation, the cardiovascular center is able to provide relatively precise control over the heart rate, but other factors can impact on this. These include hormones, notably epinephrine, norepinephrine, and thyroid hormones; levels of various ions including calcium, potassium, and sodium; body temperature; hypoxia; and pH balance. The catecholamines , epinephrine and norepinephrine, secreted by

2324-488: A given age, the standard deviation of HR max from the age-specific population mean is about 12bpm, and a 95% interval for the prediction error is about 24bpm. For example, Dr. Fritz Hagerman observed that the maximum heart rates of men in their 20s on Olympic rowing teams vary from 160 to 220. Such a variation would equate to an age range of -16 to 68 using the Wingate formula. The formulas are quite accurate at predicting

2490-517: A low pH value. Alkalosis is a condition in which there are too few hydrogen ions, and the patient's blood has an elevated pH. Normal blood pH falls in the range of 7.35–7.45, so a number lower than this range represents acidosis and a higher number represents alkalosis. Enzymes, being the regulators or catalysts of virtually all biochemical reactions – are sensitive to pH and will change shape slightly with values outside their normal range. These variations in pH and accompanying slight physical changes to

2656-403: A medieval European counting house , a checkered cloth would be placed on a table, and markers moved around on it according to certain rules, as an aid to calculating sums of money. The Antikythera mechanism is believed to be the earliest known mechanical analog computer , according to Derek J. de Solla Price . It was designed to calculate astronomical positions. It was discovered in 1901 in

2822-525: A much more general design, an analytical engine , was possible. The input of programs and data was to be provided to the machine via punched cards , a method being used at the time to direct mechanical looms such as the Jacquard loom . For output, the machine would have a printer, a curve plotter and a bell. The machine would also be able to punch numbers onto cards to be read in later. The engine would incorporate an arithmetic logic unit , control flow in

2988-529: A number of successes at breaking encrypted German military communications. The German encryption machine, Enigma , was first attacked with the help of the electro-mechanical bombes which were often run by women. To crack the more sophisticated German Lorenz SZ 40/42 machine, used for high-level Army communications, Max Newman and his colleagues commissioned Flowers to build the Colossus . He spent eleven months from early February 1943 designing and building

3154-533: A person increases their cardiovascular fitness, their HR rest will drop, and the heart rate reserve will increase. Percentage of HR reserve is statistically indistinguishable from percentage of VO 2 reserve. This is often used to gauge exercise intensity (first used in 1957 by Karvonen). Karvonen's study findings have been questioned, due to the following: For healthy people, the Target Heart Rate (THR) or Training Heart Rate Range (THRR)

3320-446: A prototype firewall device, called MedMon, which is designed to protect wireless medical devices such as pacemakers and insulin pumps from attackers. Complications from having surgery to implant a pacemaker are uncommon (each 1-3% approximately), but could include: infection where the pacemaker is implanted or in the bloodstream; allergic reaction to the dye or anesthesia used during the procedure; swelling, bruising or bleeding at

3486-577: A rate-responsive pacemaker using parameters such as the QT interval , pO 2 – pCO 2 (dissolved oxygen or carbon dioxide levels) in the arterial-venous system, physical activity as determined by an accelerometer , body temperature , ATP levels, adrenaline , etc. Instead of producing a static, predetermined heart rate, or intermittent control, such a pacemaker, a 'Dynamic Pacemaker', could compensate for both actual respiratory loading and potentially anticipated respiratory loading. The first dynamic pacemaker

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3652-540: A reduced startle response has been associated with a passive defense, and the diminished initial heart rate response has been predicted to have a greater tendency to dissociation. Current evidence suggests that heart rate variability can be used as an accurate measure of psychological stress and may be used for an objective measurement of psychological stress. The heart rate can be slowed by altered sodium and potassium levels, hypoxia , acidosis , alkalosis , and hypothermia . The relationship between electrolytes and HR

3818-562: A sequence of sets of values. The whole machine was to be controlled by a read-only program, which was complete with provisions for conditional branching . He also introduced the idea of floating-point arithmetic . In 1920, to celebrate the 100th anniversary of the invention of the arithmometer , Torres presented in Paris the Electromechanical Arithmometer, which allowed a user to input arithmetic problems through

3984-759: A series of visceral receptors with impulses traveling through visceral sensory fibers within the vagus and sympathetic nerves via the cardiac plexus. Among these receptors are various proprioreceptors , baroreceptors , and chemoreceptors , plus stimuli from the limbic system which normally enable the precise regulation of heart function, via cardiac reflexes. Increased physical activity results in increased rates of firing by various proprioreceptors located in muscles, joint capsules, and tendons. The cardiovascular centres monitor these increased rates of firing, suppressing parasympathetic stimulation or increasing sympathetic stimulation as needed in order to increase blood flow. Similarly, baroreceptors are stretch receptors located in

4150-539: A significant fraction of the population, current equations used to estimate HR max are not accurate enough. Froelicher and Myers describe maximum heart formulas as "largely useless". Measurement via a maximal test is preferable whenever possible, which can be as accurate as ±2bpm. Heart rate reserve (HR reserve ) is the difference between a person's measured or predicted maximum heart rate and resting heart rate. Some methods of measurement of exercise intensity measure percentage of heart rate reserve. Additionally, as

4316-475: A study conducted on 8 female and male student actors ages 18 to 25, their reaction to an unforeseen occurrence (the cause of stress) during a performance was observed in terms of heart rate. In the data collected, there was a noticeable trend between the location of actors (onstage and offstage) and their elevation in heart rate in response to stress; the actors present offstage reacted to the stressor immediately, demonstrated by their immediate elevation in heart rate

4482-460: A successful demonstration of its use in computing tables in 1906. In his work Essays on Automatics published in 1914, Leonardo Torres Quevedo wrote a brief history of Babbage's efforts at constructing a mechanical Difference Engine and Analytical Engine. The paper contains a design of a machine capable to calculate formulas like a x ( y − z ) 2 {\displaystyle a^{x}(y-z)^{2}} , for

4648-433: A suite of chemoreceptors innervated by the glossopharyngeal and vagus nerves. These chemoreceptors provide feedback to the cardiovascular centers about the need for increased or decreased blood flow, based on the relative levels of these substances. The limbic system can also significantly impact HR related to emotional state. During periods of stress, it is not unusual to identify higher than normal HRs, often accompanied by

4814-447: A surge in the stress hormone cortisol. Individuals experiencing extreme anxiety may manifest panic attacks with symptoms that resemble those of heart attacks. These events are typically transient and treatable. Meditation techniques have been developed to ease anxiety and have been shown to lower HR effectively. Doing simple deep and slow breathing exercises with one's eyes closed can also significantly reduce this anxiety and HR. Using

4980-402: A universal Turing machine. Early computing machines had fixed programs. Changing its function required the re-wiring and re-structuring of the machine. With the proposal of the stored-program computer this changed. A stored-program computer includes by design an instruction set and can store in memory a set of instructions (a program ) that details the computation . The theoretical basis for

5146-577: A wide range of tasks. The term computer system may refer to a nominally complete computer that includes the hardware , operating system , software , and peripheral equipment needed and used for full operation; or to a group of computers that are linked and function together, such as a computer network or computer cluster . A broad range of industrial and consumer products use computers as control systems , including simple special-purpose devices like microwave ovens and remote controls , and factory devices like industrial robots . Computers are at

Artificial cardiac pacemaker - Misplaced Pages Continue

5312-447: Is a conducted tachyarrhythmia with ventricular rate of 600 beats per minute, which is comparable to the heart rate of a mouse. For general purposes, a number of formulas are used to estimate HR max . However, these predictive formulas have been criticized as inaccurate because they only produce generalized population-averages and may deviate significantly from the actual value. ( See § Limitations .) Notwithstanding later research,

5478-434: Is a desired range of heart rate reached during aerobic exercise which enables one's heart and lungs to receive the most benefit from a workout. This theoretical range varies based mostly on age; however, a person's physical condition, sex, and previous training also are used in the calculation. The THR can be calculated as a range of 65–85% intensity, with intensity defined simply as percentage of HR max . However, it

5644-410: Is an alternative to transcutaneous pacing. A pacemaker wire is placed into a vein, under sterile conditions, and then passed into either the right atrium or right ventricle. The pacing wire is then connected to an external pacemaker outside the body. Transvenous pacing is often used as a bridge to permanent pacemaker placement. It can be kept in place until a permanent pacemaker is implanted or until there

5810-473: Is an emergency procedure that acts as a bridge until transvenous pacing or other therapies can be applied. Temporary epicardial pacing is used during open heart surgery should the surgical procedure create atrio-ventricular block. The electrodes are placed in contact with the outer wall of the ventricle (epicardium) to maintain satisfactory cardiac output until a temporary transvenous electrode has been inserted. Transvenous pacing, when used for temporary pacing,

5976-564: Is complex, but maintaining electrolyte balance is critical to the normal wave of depolarization. Of the two ions, potassium has the greater clinical significance. Initially, both hyponatremia (low sodium levels) and hypernatremia (high sodium levels) may lead to tachycardia. Severely high hypernatremia may lead to fibrillation , which may cause cardiac output to cease. Severe hyponatremia leads to both bradycardia and other arrhythmias. Hypokalemia (low potassium levels) also leads to arrhythmias, whereas hyperkalemia (high potassium levels) causes

6142-652: Is crucial to derive an accurate HR max to ensure these calculations are meaningful. Example for someone with a HR max of 180 (age 40, estimating HR max As 220 − age): The Karvonen method factors in resting heart rate (HR rest ) to calculate target heart rate (THR), using a range of 50–85% intensity: Equivalently, Computer A computer is a machine that can be programmed to automatically carry out sequences of arithmetic or logical operations ( computation ). Modern digital electronic computers can perform generic sets of operations known as programs . These programs enable computers to perform

6308-415: Is defined as a resting heart rate below 60 bpm. However, heart rates from 50 to 60 bpm are common among healthy people and do not necessarily require special attention. Tachycardia is defined as a resting heart rate above 100 bpm, though persistent rest rates between 80 and 100 bpm, mainly if they are present during sleep, may be signs of hyperthyroidism or anemia (see below). There are many ways in which

6474-584: Is important to consider leads as a potential nidus for thromboembolic events. The leads are small-diameter wires from the pacemaker to the implantation site in the heart muscle, and are usually placed intravenously through the subclavian vein in order to access the right atrium. Placing a foreign object within the venous system in such a manner may disrupt blood-flow and allow for thrombus formation. Therefore, patients with pacemakers may need to be placed on anti-coagulation therapy to avoid potential life-threatening thrombosis or embolus. These leads may also damage

6640-404: Is no longer a need for a pacemaker and then it is removed. Permanent pacing with an implantable pacemaker involves transvenous placement of one or more pacing electrodes within a chamber, or chambers, of the heart, while the pacemaker is implanted under the skin below the clavicle. The procedure is performed by incision of a suitable vein into which the electrode lead is inserted and passed along

6806-454: Is reached more quickly and the period of repolarization is shortened. However, massive releases of these hormones coupled with sympathetic stimulation may actually lead to arrhythmias. There is no parasympathetic stimulation to the adrenal medulla. In general, increased levels of the thyroid hormones ( thyroxine (T4) and triiodothyronine (T3)), increase the heart rate; excessive levels can trigger tachycardia . The impact of thyroid hormones

Artificial cardiac pacemaker - Misplaced Pages Continue

6972-548: Is referred to as CRT-P (for pacing). For selected patients at risk of arrhythmias, CRT can be combined with an implantable cardioverter-defibrillator (ICD): such devices, known as CRT-D (for defibrillation), also provide effective protection against life-threatening arrhythmias. Conventional placement of ventricular leads in or around the tip or apex of the right ventricle, or RV apical pacing, can have negative effects on heart function. It has been associated with increased risk of atrial fibrillation , heart failure , weakening of

7138-431: Is referred to as an arrhythmia . Abnormalities of heart rate sometimes indicate disease . While heart rhythm is regulated entirely by the sinoatrial node under normal conditions, heart rate is regulated by sympathetic and parasympathetic input to the sinoatrial node. The accelerans nerve provides sympathetic input to the heart by releasing norepinephrine onto the cells of the sinoatrial node (SA node), and

7304-490: Is rhythmically generated by the sinoatrial node . It is also influenced by central factors through sympathetic and parasympathetic nerves. Nervous influence over the heart rate is centralized within the two paired cardiovascular centres of the medulla oblongata . The cardioaccelerator regions stimulate activity via sympathetic stimulation of the cardioaccelerator nerves, and the cardioinhibitory centers decrease heart activity via parasympathetic stimulation as one component of

7470-442: Is similar to an individual driving a car with one foot on the brake pedal. To speed up, one need merely remove one's foot from the brake and let the engine increase speed. In the case of the heart, decreasing parasympathetic stimulation decreases the release of ACh, which allows HR to increase up to approximately 100 bpm. Any increases beyond this rate would require sympathetic stimulation. The cardiovascular centre receive input from

7636-463: Is the stored program , where all the instructions for computing are stored in memory. Von Neumann acknowledged that the central concept of the modern computer was due to this paper. Turing machines are to this day a central object of study in theory of computation . Except for the limitations imposed by their finite memory stores, modern computers are said to be Turing-complete , which is to say, they have algorithm execution capability equivalent to

7802-461: Is the most recent, had the largest data set, and performed best on a fresh data set when compared with other formulas, although it had only a small amount of data for ages 60 and older so those estimates should be viewed with caution. In addition, most formulas are developed for adults and are not applicable to children and adolescents. Maximum heart rates vary significantly between individuals. Age explains only about half of HR max variance. For

7968-657: Is typically of a much longer duration than that of the catecholamines. The physiologically active form of triiodothyronine, has been shown to directly enter cardiomyocytes and alter activity at the level of the genome. It also impacts the beta-adrenergic response similar to epinephrine and norepinephrine. Calcium ion levels have a great impact on heart rate and myocardial contractility : increased calcium levels cause an increase in both. High levels of calcium ions result in hypercalcemia and excessive levels can induce cardiac arrest . Drugs known as calcium channel blockers slow HR by binding to these channels and blocking or slowing

8134-498: The American Heart Association , some home devices have the potential to occasionally inhibit a single beat. Cellphones do not seem to damage pulse generators or affect how the pacemaker works. It is recommended that objects containing magnets, or generating a significant magnetic field, should not be in close proximity to a pacemaker. Induction cooktops, in particular, can pose a risk. Before medical procedures,

8300-619: The Antikythera wreck off the Greek island of Antikythera , between Kythera and Crete , and has been dated to approximately c.  100 BCE . Devices of comparable complexity to the Antikythera mechanism would not reappear until the fourteenth century. Many mechanical aids to calculation and measurement were constructed for astronomical and navigation use. The planisphere was a star chart invented by Abū Rayhān al-Bīrūnī in

8466-507: The E6B circular slide rule used for time and distance calculations on light aircraft. In the 1770s, Pierre Jaquet-Droz , a Swiss watchmaker , built a mechanical doll ( automaton ) that could write holding a quill pen. By switching the number and order of its internal wheels different letters, and hence different messages, could be produced. In effect, it could be mechanically "programmed" to read instructions. Along with two other complex machines,

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8632-641: The ETH Zurich . The computer was manufactured by Zuse's own company, Zuse KG , which was founded in 1941 as the first company with the sole purpose of developing computers in Berlin. The Z4 served as the inspiration for the construction of the ERMETH , the first Swiss computer and one of the first in Europe. Purely electronic circuit elements soon replaced their mechanical and electromechanical equivalents, at

8798-412: The adrenal medulla form one component of the extended fight-or-flight mechanism. The other component is sympathetic stimulation. Epinephrine and norepinephrine have similar effects: binding to the beta-1 adrenergic receptors , and opening sodium and calcium ion chemical- or ligand-gated channels. The rate of depolarization is increased by this additional influx of positively charged ions, so the threshold

8964-497: The microcomputer revolution in the 1970s. The speed, power, and versatility of computers have been increasing dramatically ever since then, with transistor counts increasing at a rapid pace ( Moore's law noted that counts doubled every two years), leading to the Digital Revolution during the late 20th and early 21st centuries. Conventionally, a modern computer consists of at least one processing element , typically

9130-411: The tricuspid valve leaflets , either during placement or through wear and tear over time. This can lead to tricuspid regurgitation and right-sided heart failure , which may require tricuspid valve replacement . Sometimes leads will need to be removed. The most common reason for lead removal is infection; however, over time, leads can degrade due to a number of reasons such as lead flexing. Changes to

9296-451: The vagus nerve provides parasympathetic input to the heart by releasing acetylcholine onto sinoatrial node cells. Therefore, stimulation of the accelerans nerve increases heart rate, while stimulation of the vagus nerve decreases it. As water and blood are incompressible fluids, one of the physiological ways to deliver more blood to an organ is to increase heart rate. Normal resting heart rates range from 60 to 100 bpm. Bradycardia

9462-447: The vagus nerve . During rest, both centers provide slight stimulation to the heart, contributing to autonomic tone. This is a similar concept to tone in skeletal muscles. Normally, vagal stimulation predominates as, left unregulated, the SA node would initiate a sinus rhythm of approximately 100 bpm. Both sympathetic and parasympathetic stimuli flow through the paired cardiac plexus near

9628-413: The vena cava and the right atrium into the right ventricle to stimulate the septum , and another passing through the vena cava and the right atrium and inserted through the coronary sinus to pace the epicardial wall of the left ventricle. Often, for patients in normal sinus rhythm, there is also a lead in the right atrium to facilitate synchrony with the atrial contraction. Thus, the timing between

9794-504: The "second generation" of computers. Compared to vacuum tubes, transistors have many advantages: they are smaller, and require less power than vacuum tubes, so give off less heat. Junction transistors were much more reliable than vacuum tubes and had longer, indefinite, service life. Transistorized computers could contain tens of thousands of binary logic circuits in a relatively compact space. However, early junction transistors were relatively bulky devices that were difficult to manufacture on

9960-525: The 1920s, Vannevar Bush and others developed mechanical differential analyzers. In the 1890s, the Spanish engineer Leonardo Torres Quevedo began to develop a series of advanced analog machines that could solve real and complex roots of polynomials , which were published in 1901 by the Paris Academy of Sciences . Charles Babbage , an English mechanical engineer and polymath , originated

10126-814: The 1999–2008 period, 71 bpm was the average for men, and 73 bpm was the average for women. Resting heart rate is often correlated with mortality. In the Copenhagen City Heart Study a heart rate of 65 bpm rather than 80 bpm was associated with 4.6 years longer life expectancy in men and 3.6 years in women. Other studies have shown all-cause mortality is increased by 1.22 (hazard ratio) when heart rate exceeds 90 beats per minute. ECG of 46,129 individuals with low risk for cardiovascular disease revealed that 96% had resting heart rates ranging from 48 to 98 beats per minute. The mortality rate of patients with myocardial infarction increased from 15% to 41% if their admission heart rate

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10292-925: The CIEDs is maximized. The risk of EMI-induced events is highest within the hospital environment." The study lists and tabulates many sources of interference, and many different potential effects: damage to circuitry, asynchronous pacing, etc. Some sources of hazard in older devices have been eliminated in newer ones. Activities involving strong magnetic fields should be avoided. This includes activities such as arc welding with certain types of equipment, and maintaining heavy equipment that may generate strong magnetic fields. Some medical procedures, particularly magnetic resonance imaging (MRI), involve very strong magnetic fields or other conditions that may damage pacemakers. However, many modern pacemakers are specified to be MR conditional or MRI conditional , safe to use during MRI subject to certain conditions. The first to be so specified

10458-619: The Cambridge EDSAC of 1949, became operational in April 1951 and ran the world's first routine office computer job . The concept of a field-effect transistor was proposed by Julius Edgar Lilienfeld in 1925. John Bardeen and Walter Brattain , while working under William Shockley at Bell Labs , built the first working transistor , the point-contact transistor , in 1947, which was followed by Shockley's bipolar junction transistor in 1948. From 1955 onwards, transistors replaced vacuum tubes in computer designs, giving rise to

10624-591: The EDVAC in 1945. The Manchester Baby was the world's first stored-program computer . It was built at the University of Manchester in England by Frederic C. Williams , Tom Kilburn and Geoff Tootill , and ran its first program on 21 June 1948. It was designed as a testbed for the Williams tube , the first random-access digital storage device. Although the computer was described as "small and primitive" by

10790-455: The ENIAC were six women, often known collectively as the "ENIAC girls". It combined the high speed of electronics with the ability to be programmed for many complex problems. It could add or subtract 5000 times a second, a thousand times faster than any other machine. It also had modules to multiply, divide, and square root. High speed memory was limited to 20 words (about 80 bytes). Built under

10956-531: The MOS transistor, was invented at Bell Labs between 1955 and 1960 and was the first truly compact transistor that could be miniaturized and mass-produced for a wide range of uses. With its high scalability , and much lower power consumption and higher density than bipolar junction transistors, the MOSFET made it possible to build high-density integrated circuits . In addition to data processing, it also enabled

11122-455: The Scottish scientist Sir William Thomson in 1872 was of great utility to navigation in shallow waters. It used a system of pulleys and wires to automatically calculate predicted tide levels for a set period at a particular location. The differential analyser , a mechanical analog computer designed to solve differential equations by integration , used wheel-and-disc mechanisms to perform

11288-493: The U.S. Although the ENIAC was similar to the Colossus, it was much faster, more flexible, and it was Turing-complete. Like the Colossus, a "program" on the ENIAC was defined by the states of its patch cables and switches, a far cry from the stored program electronic machines that came later. Once a program was written, it had to be mechanically set into the machine with manual resetting of plugs and switches. The programmers of

11454-574: The US but widely used in Latin America and Europe. The DDDR mode is most commonly used as it covers all the options though the pacemakers require separate atrial and ventricular leads and are more complex, requiring careful programming of their functions for optimal results. Automatic pacemakers are designed to be over-ridden by the heart's natural rate at any moment that it gets back to a non-pathologic normal sinus rhythm and can reinitiate influencing

11620-452: The US market) made FDA-approved MR-conditional pacemakers. The use of MRI may be ruled out by the patient having an older, non-MRI Conditional pacemaker, or by having old pacing wires inside the heart, no longer connected to a pacemaker. A 2008 US study found that the magnetic field created by some headphones used with portable music players or cellphones may cause interference if placed very close to some pacemakers. In addition, according to

11786-538: The US, John Vincent Atanasoff and Clifford E. Berry of Iowa State University developed and tested the Atanasoff–Berry Computer (ABC) in 1942, the first "automatic electronic digital computer". This design was also all-electronic and used about 300 vacuum tubes, with capacitors fixed in a mechanically rotating drum for memory. During World War II, the British code-breakers at Bletchley Park achieved

11952-498: The active site on the enzyme decrease the rate of formation of the enzyme-substrate complex, subsequently decreasing the rate of many enzymatic reactions, which can have complex effects on HR. Severe changes in pH will lead to denaturation of the enzyme. The last variable is body temperature. Elevated body temperature is called hyperthermia , and suppressed body temperature is called hypothermia . Slight hyperthermia results in increasing HR and strength of contraction. Hypothermia slows

12118-898: The advent of the integrated circuit (IC). The idea of the integrated circuit was first conceived by a radar scientist working for the Royal Radar Establishment of the Ministry of Defence , Geoffrey W.A. Dummer . Dummer presented the first public description of an integrated circuit at the Symposium on Progress in Quality Electronic Components in Washington, D.C. , on 7 May 1952. The first working ICs were invented by Jack Kilby at Texas Instruments and Robert Noyce at Fairchild Semiconductor . Kilby recorded his initial ideas concerning

12284-434: The aortic sinus, carotid bodies, the venae cavae, and other locations, including pulmonary vessels and the right side of the heart itself. Rates of firing from the baroreceptors represent blood pressure, level of physical activity, and the relative distribution of blood. The cardiac centers monitor baroreceptor firing to maintain cardiac homeostasis, a mechanism called the baroreceptor reflex. With increased pressure and stretch,

12450-451: The atria to precede that of the ventricles improves the pumping efficiency of the heart and can be useful in congestive heart failure. Rate responsive pacing allows the device to sense the physical activity of the patient and respond appropriately by increasing or decreasing the base pacing rate via rate response algorithms. The DAVID trials have shown that unnecessary pacing of the right ventricle can exacerbate heart failure and increases

12616-558: The atria. Increased venous return stretches the walls of the atria where specialized baroreceptors are located. However, as the atrial baroreceptors increase their rate of firing and as they stretch due to the increased blood pressure, the cardiac center responds by increasing sympathetic stimulation and inhibiting parasympathetic stimulation to increase HR. The opposite is also true. Increased metabolic byproducts associated with increased activity, such as carbon dioxide, hydrogen ions, and lactic acid, plus falling oxygen levels, are detected by

12782-411: The atrial and ventricular chambers. From this the basic ventricular "on demand" pacing mode is VVI or with automatic rate adjustment for exercise VVIR – this mode is suitable when no synchronization with the atrial beat is required, as in atrial fibrillation. The equivalent atrial pacing mode is AAI or AAIR which is the mode of choice when atrioventricular conduction is intact but the sinoatrial node of

12948-411: The atrial and ventricular contractions, as well as between the septal and lateral walls of the left ventricle can be adjusted to achieve optimal cardiac function. CRT devices have been shown to reduce mortality and improve quality of life in patients with heart failure symptoms; a LV ejection fraction less than or equal to 35% and QRS duration on EKG of 120 ms or greater. Biventricular pacing alone

13114-950: The average HR max at age 76 was about 10bpm higher than the Haskell and Fox equation. Consequently, the formula cannot be recommended for use in exercise physiology and related fields. HR max is strongly correlated to age, and most formulas are solely based on this. Studies have been mixed on the effect of gender, with some finding that gender is statistically significant, although small when considering overall equation error, while others finding negligible effect. The inclusion of physical activity status, maximal oxygen uptake, smoking, body mass index, body weight, or resting heart rate did not significantly improve accuracy. Nonlinear models are slightly more accurate predictors of average age-specific HR max , particularly above 60 years of age, but are harder to apply, and provide statistically negligible improvement over linear models. The Wingate formula

13280-451: The average heart rate of a group of similarly-aged individuals, but relatively poor for a given individual. Robergs and Landwehr opine that for VO2 max , prediction errors in HR max need to be less than ±3 bpm. No current formula meets this accuracy. For prescribing exercise training heart rate ranges, the errors in the more accurate formulas may be acceptable, but again it is likely that, for

13446-412: The base of the heart. The cardioaccelerator center also sends additional fibers, forming the cardiac nerves via sympathetic ganglia (the cervical ganglia plus superior thoracic ganglia T1–T4) to both the SA and AV nodes, plus additional fibers to the atria and ventricles. The ventricles are more richly innervated by sympathetic fibers than parasympathetic fibers. Sympathetic stimulation causes the release of

13612-647: The basic concept which underlies all electronic digital computers. By 1938, the United States Navy had developed an electromechanical analog computer small enough to use aboard a submarine . This was the Torpedo Data Computer , which used trigonometry to solve the problem of firing a torpedo at a moving target. During World War II similar devices were developed in other countries as well. Early digital computers were electromechanical ; electric switches drove mechanical relays to perform

13778-530: The best Arithmetician that euer [ sic ] breathed, and he reduceth thy dayes into a short number." This usage of the term referred to a human computer , a person who carried out calculations or computations . The word continued to have the same meaning until the middle of the 20th century. During the latter part of this period, women were often hired as computers because they could be paid less than their male counterparts. By 1943, most human computers were women. The Online Etymology Dictionary gives

13944-417: The beta–1 receptor. High blood pressure medications are used to block these receptors and so reduce the heart rate. Parasympathetic stimulation originates from the cardioinhibitory region of the brain with impulses traveling via the vagus nerve (cranial nerve X). The vagus nerve sends branches to both the SA and AV nodes, and to portions of both the atria and ventricles. Parasympathetic stimulation releases

14110-474: The body's physical needs, including the need to absorb oxygen and excrete carbon dioxide . It is also modulated by numerous factors, including (but not limited to) genetics, physical fitness , stress or psychological status, diet, drugs, hormonal status, environment, and disease/illness, as well as the interaction between these factors. It is usually equal or close to the pulse rate measured at any peripheral point. The American Heart Association states

14276-585: The body's blood supply and gas exchange until the surgery is complete, and sinus rhythm can be restored. Excessive hyperthermia and hypothermia will both result in death, as enzymes drive the body systems to cease normal function, beginning with the central nervous system. A study shows that bottlenose dolphins can learn – apparently via instrumental conditioning – to rapidly and selectively slow down their heart rate during diving for conserving oxygen depending on external signals. In humans regulating heart rate by methods such as listening to music, meditation or

14442-570: The calculation. These devices had a low operating speed and were eventually superseded by much faster all-electric computers, originally using vacuum tubes . The Z2 , created by German engineer Konrad Zuse in 1939 in Berlin , was one of the earliest examples of an electromechanical relay computer. In 1941, Zuse followed his earlier machine up with the Z3 , the world's first working electromechanical programmable , fully automatic digital computer. The Z3

14608-565: The concept of a programmable computer. Considered the " father of the computer ", he conceptualized and invented the first mechanical computer in the early 19th century. After working on his difference engine he announced his invention in 1822, in a paper to the Royal Astronomical Society , titled "Note on the application of machinery to the computation of astronomical and mathematical tables". He also designed to aid in navigational calculations, in 1833 he realized that

14774-415: The control of the pacemaker once implanted. Many of these have been made possible by the transition to microprocessor controlled pacemakers. Pacemakers that control not only the ventricles but the atria as well have become common. Pacemakers that control both the atria and ventricles are called dual-chamber pacemakers. Although these dual-chamber models are usually more expensive, timing the contractions of

14940-704: The core of general-purpose devices such as personal computers and mobile devices such as smartphones . Computers power the Internet , which links billions of computers and users. Early computers were meant to be used only for calculations. Simple manual instruments like the abacus have aided people in doing calculations since ancient times. Early in the Industrial Revolution , some mechanical devices were built to automate long, tedious tasks, such as guiding patterns for looms . More sophisticated electrical machines did specialized analog calculations in

15106-499: The data signals do not have to travel long distances. Since ENIAC in 1945, computers have advanced enormously, with modern SoCs (such as the Snapdragon 865) being the size of a coin while also being hundreds of thousands of times more powerful than ENIAC, integrating billions of transistors, and consuming only a few watts of power. The first mobile computers were heavy and ran from mains power. The 50 lb (23 kg) IBM 5100

15272-515: The decision of the British Government to cease funding. Babbage's failure to complete the analytical engine can be chiefly attributed to political and financial difficulties as well as his desire to develop an increasingly sophisticated computer and to move ahead faster than anyone else could follow. Nevertheless, his son, Henry Babbage , completed a simplified version of the analytical engine's computing unit (the mill ) in 1888. He gave

15438-404: The device may be inserted beneath the muscle (submuscular). The lead or leads are fed into the heart through a large vein guided by X-ray imaging ( fluoroscopy ). The tips of the leads may be positioned within the right ventricle , the right atrium , or the coronary sinus, depending on the type of pacemaker required. Surgery is typically completed within 30 to 90 minutes. Following implantation,

15604-460: The direction of John Mauchly and J. Presper Eckert at the University of Pennsylvania, ENIAC's development and construction lasted from 1943 to full operation at the end of 1945. The machine was huge, weighing 30 tons, using 200 kilowatts of electric power and contained over 18,000 vacuum tubes, 1,500 relays, and hundreds of thousands of resistors, capacitors, and inductors. The principle of

15770-483: The doll is at the Musée d'Art et d'Histoire of Neuchâtel , Switzerland , and still operates. In 1831–1835, mathematician and engineer Giovanni Plana devised a Perpetual Calendar machine , which through a system of pulleys and cylinders could predict the perpetual calendar for every year from 0 CE (that is, 1 BCE) to 4000 CE, keeping track of leap years and varying day length. The tide-predicting machine invented by

15936-481: The early 11th century. The astrolabe was invented in the Hellenistic world in either the 1st or 2nd centuries BCE and is often attributed to Hipparchus . A combination of the planisphere and dioptra , the astrolabe was effectively an analog computer capable of working out several different kinds of problems in spherical astronomy . An astrolabe incorporating a mechanical calendar computer and gear -wheels

16102-399: The early 20th century. The first digital electronic calculating machines were developed during World War II , both electromechanical and using thermionic valves . The first semiconductor transistors in the late 1940s were followed by the silicon -based MOSFET (MOS transistor) and monolithic integrated circuit chip technologies in the late 1950s, leading to the microprocessor and

16268-490: The electric activity in the heart when the pathologic event happens again. A " ventricular -demand pacemaker" produces a narrow vertical spike on the ECG , just before a wide QRS . The spike of an " atrial -demand pacemaker" appears just before the P wave . Comparably, a Triggered Pacemaker is activated immediately after an electrical activity is commenced in the heart tissue by itself. A "ventricular triggered pacemaker" produces

16434-477: The exact definition of the term "microprocessor", it is largely undisputed that the first single-chip microprocessor was the Intel 4004 , designed and realized by Federico Faggin with his silicon-gate MOS IC technology, along with Ted Hoff , Masatoshi Shima and Stanley Mazor at Intel . In the early 1970s, MOS IC technology enabled the integration of more than 10,000 transistors on a single chip. System on

16600-567: The existing device, disconnecting the leads from the old device and reconnecting them to a new generator, reinserting the new device and closing the skin. Once the pacemaker is implanted, it is periodically checked to ensure the device is operational and performing appropriately; the device can be checked as often as is deemed necessary. Routine pacemaker checks are typically done in-office every six months, though will vary depending upon patient/device status and remote monitoring availability. Newer pacemaker models can also be interrogated remotely, with

16766-466: The faster pacemaker cells driving the self-generated rhythmic firing and responsible for the heart's autorhythmicity are located. In one study 98% of cardiologists suggested that as a desirable target range, 50 to 90 beats per minute is more appropriate than 60 to 100. The available evidence indicates that the normal range for resting heart rate is 50–90 beats per minute (bpm). In a study of over 35,000 American men and women over age 40 during

16932-417: The firing rate. Normal pulse rates at rest, in beats per minute (BPM): The basal or resting heart rate (HR rest ) is defined as the heart rate when a person is awake, in a neutrally temperate environment, and has not been subject to any recent exertion or stimulation, such as stress or surprise. The normal resting heart rate is based on the at-rest firing rate of the heart's sinoatrial node , where

17098-508: The first Colossus. After a functional test in December 1943, Colossus was shipped to Bletchley Park, where it was delivered on 18 January 1944 and attacked its first message on 5 February. Colossus was the world's first electronic digital programmable computer. It used a large number of valves (vacuum tubes). It had paper-tape input and was capable of being configured to perform a variety of boolean logical operations on its data, but it

17264-725: The first attested use of computer in the 1640s, meaning 'one who calculates'; this is an "agent noun from compute (v.)". The Online Etymology Dictionary states that the use of the term to mean " 'calculating machine' (of any type) is from 1897." The Online Etymology Dictionary indicates that the "modern use" of the term, to mean 'programmable digital electronic computer' dates from "1945 under this name; [in a] theoretical [sense] from 1937, as Turing machine ". The name has remained, although modern computers are capable of many higher-level functions. Devices have been used to aid computation for thousands of years, mostly using one-to-one correspondence with fingers . The earliest counting device

17430-409: The form of conditional branching and loops , and integrated memory , making it the first design for a general-purpose computer that could be described in modern terms as Turing-complete . The machine was about a century ahead of its time. All the parts for his machine had to be made by hand – this was a major problem for a device with thousands of parts. Eventually, the project was dissolved with

17596-469: The formula "was never supposed to be an absolute guide to rule people's training." While this formula is commonly used (and easy to remember and calculate), research has consistently found that it is subject to bias, particularly in older adults. Compared to the age-specific average HR max , the Haskell and Fox formula overestimates HR max in young adults, agrees with it at age 40, and underestimates HR max in older adults. For example, in one study,

17762-444: The front of the chest in the region of the left or right shoulder. The skin is prepared by clipping or shaving any hair over the implant site before cleaning the skin with a disinfectant such as chlorhexidine . An incision is made below the collar bone and a space or pocket is created under the skin to house the pacemaker generator. This pocket is usually created just above the pectoralis major muscle (prepectoral), but in some cases

17928-434: The generator site, or around the heart, especially if the patient is taking blood thinners , elderly, of thin frame or otherwise on chronic steroid use. A possible complication of dual-chamber artificial pacemakers is 'pacemaker-mediated tachycardia' (PMT), a form of reentrant tachycardia. In PMT, the artificial pacemaker forms the anterograde (atrium to ventricle) limb of the circuit and the atrioventricular (AV) node forms

18094-672: The heart muscle and potentially shorter life expectancy. His bundle pacing (HBP) leads to a more natural or perfectly natural ventricular activation and has generated strong research and clinical interest. By stimulating the His–Purkinje fiber network directly with a special lead and placement technique, HBP causes a synchronized and therefore more effective ventricular activation and avoids long-term heart muscle disease. HBP in some cases can also correct bundle branch block patterns. A major step forward in pacemaker function has been to attempt to mimic nature by utilizing various inputs to produce

18260-423: The heart rate speeds up or slows down. Most involve stimulant-like endorphins and hormones being released in the brain, some of which are those that are 'forced'/'enticed' out by the ingestion and processing of drugs such as cocaine or atropine . This section discusses target heart rates for healthy persons, which would be inappropriately high for most persons with coronary artery disease. The heart rate

18426-409: The heart to become weak and flaccid, and ultimately to fail. Heart muscle relies exclusively on aerobic metabolism for energy. Severe myocardial infarction (commonly called a heart attack) can lead to a decreasing heart rate , since metabolic reactions fueling heart contraction are restricted. Acidosis is a condition in which excess hydrogen ions are present, and the patient's blood expresses

18592-426: The heart's native electrical rhythm. When the pacemaker wire or "lead" does not detect heart electrical activity in the chamber – atrium or ventricle – within a normal beat-to-beat time period – most commonly one second – it will stimulate either the atrium or the ventricle with a short low voltage pulse. If it does sense electrical activity, it will hold off stimulating. This sensing and stimulating activity continues on

18758-481: The impulse just after a pulse is created in the ventricular tissue and it appears as a simultaneous spike with QRS. An "atrial triggered pacemaker" is the mode in which an impulse is produced immediately after an electrical event in the atrium. It appears as a discharge following the p wave but prior to the QRS which is commonly widened. Cardiac resynchronization therapy (CRT) is used for people with heart failure in whom

18924-445: The incidence of atrial fibrillation. The newer dual-chamber devices can keep the amount of right ventricle pacing to a minimum and thus prevent worsening of the heart disease. A pacemaker may be implanted whilst a person is awake using local anesthetic to numb the skin with or without sedation , or asleep using a general anesthetic . An antibiotic is usually given to reduce the risk of infection. Pacemakers are generally implanted in

19090-466: The integrated circuit in July 1958, successfully demonstrating the first working integrated example on 12 September 1958. In his patent application of 6 February 1959, Kilby described his new device as "a body of semiconductor material ... wherein all the components of the electronic circuit are completely integrated". However, Kilby's invention was a hybrid integrated circuit (hybrid IC), rather than

19256-411: The integration. In 1876, Sir William Thomson had already discussed the possible construction of such calculators, but he had been stymied by the limited output torque of the ball-and-disk integrators . In a differential analyzer, the output of one integrator drove the input of the next integrator, or a graphing output. The torque amplifier was the advance that allowed these machines to work. Starting in

19422-494: The inward movement of calcium ions. Caffeine and nicotine are both stimulants of the nervous system and of the cardiac centres causing an increased heart rate. Caffeine works by increasing the rates of depolarization at the SA node , whereas nicotine stimulates the activity of the sympathetic neurons that deliver impulses to the heart. Both surprise and stress induce physiological response: elevate heart rate substantially . In

19588-452: The left and right ventricles do not contract simultaneously ( ventricular dyssynchrony ), which occurs in approximately 25–50% of heart failure patients. To achieve CRT, a biventricular pacemaker (BVP) is used, which can pace both the septal and lateral walls of the left ventricle . By pacing both sides of the left ventricle, the pacemaker can resynchronize the ventricular contractions. CRT devices have at least two leads, one passing through

19754-572: The legal situation is similar to removing a feeding tube, though as of 2010 there was no legal precedent involving pacemakers in the United States. A patient in many jurisdictions (including the US) is deemed to have a right to refuse or discontinue treatment, including a pacemaker that keeps them alive. Physicians have a right to refuse to turn it off, but are advised by the HRS panel that they should refer

19920-590: The machine did make use of valves to generate its 125 kHz clock waveforms and in the circuitry to read and write on its magnetic drum memory , so it was not the first completely transistorized computer. That distinction goes to the Harwell CADET of 1955, built by the electronics division of the Atomic Energy Research Establishment at Harwell . The metal–oxide–silicon field-effect transistor (MOSFET), also known as

20086-429: The minute the unexpected event occurred, but the actors present onstage at the time of the stressor reacted in the following 5 minute period (demonstrated by their increasingly elevated heart rate). This trend regarding stress and heart rate is supported by previous studies; negative emotion /stimulus has a prolonged effect on heart rate in individuals who are directly impacted. In regard to the characters present onstage,

20252-452: The modern computer was proposed by Alan Turing in his seminal 1936 paper, On Computable Numbers . Turing proposed a simple device that he called "Universal Computing machine" and that is now known as a universal Turing machine . He proved that such a machine is capable of computing anything that is computable by executing instructions (program) stored on tape, allowing the machine to be programmable. The fundamental concept of Turing's design

20418-403: The more famous Sir William Thomson. The art of mechanical analog computing reached its zenith with the differential analyzer , built by H. L. Hazen and Vannevar Bush at MIT starting in 1927. This built on the mechanical integrators of James Thomson and the torque amplifiers invented by H. W. Nieman. A dozen of these devices were built before their obsolescence became obvious. By the 1950s,

20584-457: The most accurate way of measuring any single person's HR max is via a cardiac stress test . In this test, a person is subjected to controlled physiologic stress (generally by treadmill or bicycle ergometer) while being monitored by an electrocardiogram (ECG). The intensity of exercise is periodically increased until certain changes in heart function are detected on the ECG monitor, at which point

20750-518: The most widely cited formula for HR max is still: Although attributed to various sources, it is widely thought to have been devised in 1970 by Dr. William Haskell and Dr. Samuel Fox. They did not develop this formula from original research, but rather by plotting data from approximately 11 references consisting of published research or unpublished scientific compilations. It gained widespread use through being used by Polar Electro in its heart rate monitors, which Dr. Haskell has "laughed about", as

20916-489: The natural pacemaker is unreliable – sinus node disease (SND) or sick sinus syndrome . Where the problem is atrioventricular block (AVB) the pacemaker is required to detect (sense) the atrial beat and after a normal delay (0.1–0.2 seconds) trigger a ventricular beat, unless it has already happened – this is VDD mode and can be achieved with a single pacing lead with electrodes in the right atrium (to sense) and ventricle (to sense and pace). These modes AAIR and VDD are unusual in

21082-405: The neurotransmitter norepinephrine (also known as noradrenaline ) at the neuromuscular junction of the cardiac nerves. This shortens the repolarization period, thus speeding the rate of depolarization and contraction, which results in an increased heartrate. It opens chemical or ligand-gated sodium and calcium ion channels, allowing an influx of positively charged ions. Norepinephrine binds to

21248-526: The neurotransmitter acetylcholine (ACh) at the neuromuscular junction. ACh slows HR by opening chemical- or ligand-gated potassium ion channels to slow the rate of spontaneous depolarization, which extends repolarization and increases the time before the next spontaneous depolarization occurs. Without any nervous stimulation, the SA node would establish a sinus rhythm of approximately 100 bpm. Since resting rates are considerably less than this, it becomes evident that parasympathetic stimulation normally slows HR. This

21414-422: The normal resting adult human heart rate is 60–100 bpm. An ultra-trained athlete would have a resting heart rate of 37–38 bpm. Tachycardia is a high heart rate, defined as above 100 bpm at rest. Bradycardia is a low heart rate, defined as below 60 bpm at rest. When a human sleeps, a heartbeat with rates around 40–50 bpm is common and considered normal. When the heart is not beating in a regular pattern, this

21580-400: The number of chambers involved and their basic operating mechanism: The pacemaker generator is a hermetically sealed device containing a power source, usually a lithium battery , a sensing amplifier which processes the electrical manifestation of naturally occurring heart beats as sensed by the heart electrodes, the computer logic for the pacemaker and the output circuitry which delivers

21746-431: The pacemaker, or reprogram the devices, as has been demonstrated by a team of researchers. The demonstration worked at short range; they did not attempt to develop a long range antenna. The proof of concept exploit helps demonstrate the need for better security and patient alerting measures in remotely accessible medical implants. In response to this threat, Purdue University and Princeton University researchers have developed

21912-451: The pacing impulse to the electrodes. Most commonly, the generator is placed below the subcutaneous fat of the chest wall, above the muscles and bones of the chest. However, the placement may vary on a case-by-case basis. The outer casing of pacemakers is so designed that it will rarely be rejected by the body's immune system . It is usually made of titanium , which is inert in the body. Leadless pacemakers are devices that are as small as

22078-632: The patient should inform all medical personnel that they have a pacemaker. Having a pacemaker does not imply that a patient requires the use of antibiotics to be administered before procedures such as dental work. A panel of the Heart Rhythm Society , a US specialist organization based in Washington, DC, deemed that it was legal and ethical to honor requests by patients, or by those with legal authority to make decisions for patients, to deactivate implanted cardiac devices. Lawyers say that

22244-426: The patient to a physician who will. Some patients consider that hopeless, debilitating conditions, such as severe strokes or late-stage dementia, can cause so much suffering that they would prefer not to prolong their lives with supportive measures. Security and privacy concerns have been raised with pacemakers that allow wireless communication. Unauthorized third parties may be able to read patient records contained in

22410-514: The patient transmitting their pacemaker data using a transmitter at home connected to a cellular telephone network. During in-office follow-up, diagnostic tests may include: A patient's lifestyle is usually not modified to any great degree after the insertion of a pacemaker. There are a few activities that are unwise, such as full-contact sports and exposure of the pacemaker to intense magnetic fields. The pacemaker patient may find that some types of everyday actions need to be modified. For instance,

22576-511: The patient's chest, either in the anterior/lateral position or the anterior/posterior position. The rescuer selects the pacing rate, and gradually increases the pacing current (measured in mA) until electrical capture (characterized by a wide QRS complex with a tall, broad T wave on the ECG ) is achieved, with a corresponding pulse. Pacing artifact on the ECG and severe muscle twitching may make this determination difficult. External pacing should not be relied upon for an extended period of time. It

22742-486: The practical use of MOS transistors as memory cell storage elements, leading to the development of MOS semiconductor memory , which replaced earlier magnetic-core memory in computers. The MOSFET led to the microcomputer revolution , and became the driving force behind the computer revolution . The MOSFET is the most widely used transistor in computers, and is the fundamental building block of digital electronics . The next great advance in computing power came with

22908-433: The programming of the pacemaker may overcome lead degradation to some extent. However, a patient who has several pacemaker replacements over a decade or two in which the leads were reused may require lead replacement surgery. Heart rate Heart rate is the frequency of the heartbeat measured by the number of contractions of the heart per minute ( beats per minute , or bpm). The heart rate varies according to

23074-399: The rate and strength of heart contractions. This distinct slowing of the heart is one component of the larger diving reflex that diverts blood to essential organs while submerged. If sufficiently chilled, the heart will stop beating, a technique that may be employed during open heart surgery. In this case, the patient's blood is normally diverted to an artificial heart-lung machine to maintain

23240-443: The rate of baroreceptor firing increases, and the cardiac centers decrease sympathetic stimulation and increase parasympathetic stimulation. As pressure and stretch decrease, the rate of baroreceptor firing decreases, and the cardiac centers increase sympathetic stimulation and decrease parasympathetic stimulation. There is a similar reflex, called the atrial reflex or Bainbridge reflex , associated with varying rates of blood flow to

23406-548: The results of operations to be saved and retrieved. It was not until the mid-20th century that the word acquired its modern definition; according to the Oxford English Dictionary , the first known use of the word computer was in a different sense, in a 1613 book called The Yong Mans Gleanings by the English writer Richard Brathwait : "I haue [ sic ] read the truest computer of Times, and

23572-505: The retrograde limb (ventricle to atrium) of the circuit. Treatment of PMT typically involves reprogramming the pacemaker. Another possible complication is "pacemaker-tracked tachycardia," where a supraventricular tachycardia such as atrial fibrillation or atrial flutter is tracked by the pacemaker and produces beats from a ventricular lead. This is becoming exceedingly rare as newer devices are often programmed to recognize supraventricular tachycardias and switch to non-tracking modes. It

23738-591: The same time that digital calculation replaced analog. The engineer Tommy Flowers , working at the Post Office Research Station in London in the 1930s, began to explore the possible use of electronics for the telephone exchange . Experimental equipment that he built in 1934 went into operation five years later, converting a portion of the telephone exchange network into an electronic data processing system, using thousands of vacuum tubes . In

23904-514: The shoulder harness of a vehicle seatbelt may be uncomfortable if it falls across the pacemaker insertion site. Women will not be able to wear bras for a while after the operation, and later might have to wear bras with wide shoulder straps. For some sports and physical activities, special pacemaker protection can be worn to prevent possible injuries, or damage to the pacemaker leads. Pacemakers may be affected by magnetic or electromagnetic fields , and ionising and acoustic radiation . However,

24070-404: The stimulation of the heart is based on the dynamic demand of the circulatory system . Others send out a fixed rate of impulses. A specific type of pacemaker, called an implantable cardioverter-defibrillator , combines pacemaker and defibrillator functions in a single implantable device . Others, called biventricular pacemakers , have multiple electrodes stimulating different positions within

24236-490: The stored-program computer was laid out by Alan Turing in his 1936 paper. In 1945, Turing joined the National Physical Laboratory and began work on developing an electronic stored-program digital computer. His 1945 report "Proposed Electronic Calculator" was the first specification for such a device. John von Neumann at the University of Pennsylvania also circulated his First Draft of a Report on

24402-486: The subject is directed to stop. Typical duration of the test ranges ten to twenty minutes. Adults who are beginning a new exercise regimen are often advised to perform this test only in the presence of medical staff due to risks associated with high heart rates. The theoretical maximum heart rate of a human is 300 bpm; however, there have been multiple cases where this theoretical upper limit has been exceeded. The fastest human ventricular conduction rate recorded to this day

24568-443: The success of digital electronic computers had spelled the end for most analog computing machines, but analog computers remained in use during the 1950s in some specialized applications such as education ( slide rule ) and aircraft ( control systems ). Claude Shannon 's 1937 master's thesis laid the foundations of digital computing, with his insight of applying Boolean algebra to the analysis and synthesis of switching circuits being

24734-438: The surgical wound should be kept clean and dry until it has healed. Some movements of the shoulder within a few weeks of insertion carry a risk of dislodging the pacemaker leads. The batteries within a pacemaker generator typically last 5 to 10 years. When the batteries are nearing the end of life, the generator is replaced in a procedure that is usually simpler than a new implant. Replacement involves making an incision to remove

24900-410: The vein, through the valve of the heart, until positioned in the chamber. The procedure is facilitated by fluoroscopy which enables the physician to view the passage of the electrode lead. After satisfactory lodgement of the electrode is confirmed, the opposite end of the electrode lead is connected to the pacemaker generator. There are three basic types of permanent pacemakers, classified according to

25066-482: The ventricles (the lower heart chambers) to improve their synchronization. Percussive pacing, also known as transthoracic mechanical pacing, is the use of the closed fist, usually on the left lower edge of the sternum over the right ventricle in the vena cava , striking from a distance of 20 – 30 cm to induce a ventricular beat (the British Journal of Anaesthesia suggests this must be done to raise

25232-412: The ventricular pressure to 10–15 mmHg to induce electrical activity). This is an old procedure used only as a life-saving means until an electrical pacemaker is brought to the patient. Transcutaneous pacing (TCP), also called external pacing, is recommended for the initial stabilization of hemodynamically significant bradycardias of all types. The procedure is performed by placing two pacing pads on

25398-412: The versatility and accuracy of modern digital computers. The first modern analog computer was a tide-predicting machine , invented by Sir William Thomson (later to become Lord Kelvin) in 1872. The differential analyser , a mechanical analog computer designed to solve differential equations by integration using wheel-and-disc mechanisms, was conceptualized in 1876 by James Thomson , the elder brother of

25564-406: Was a 16-transistor chip built by Fred Heiman and Steven Hofstein at RCA in 1962. General Microelectronics later introduced the first commercial MOS IC in 1964, developed by Robert Norman. Following the development of the self-aligned gate (silicon-gate) MOS transistor by Robert Kerwin, Donald Klein and John Sarace at Bell Labs in 1967, the first silicon-gate MOS IC with self-aligned gates

25730-625: Was an early example. Later portables such as the Osborne 1 and Compaq Portable were considerably lighter but still needed to be plugged in. The first laptops, such as the Grid Compass , removed this requirement by incorporating batteries – and with the continued miniaturization of computing resources and advancements in portable battery life, portable computers grew in popularity in the 2000s. The same developments allowed manufacturers to integrate computing resources into cellular mobile phones by

25896-537: Was built with 2000 relays , implementing a 22 bit word length that operated at a clock frequency of about 5–10 Hz . Program code was supplied on punched film while data could be stored in 64 words of memory or supplied from the keyboard. It was quite similar to modern machines in some respects, pioneering numerous advances such as floating-point numbers . Rather than the harder-to-implement decimal system (used in Charles Babbage 's earlier design), using

26062-511: Was delivered to the University of Manchester in February 1951. At least seven of these later machines were delivered between 1953 and 1957, one of them to Shell labs in Amsterdam . In October 1947 the directors of British catering company J. Lyons & Company decided to take an active role in promoting the commercial development of computers. Lyons's LEO I computer, modelled closely on

26228-443: Was developed by Federico Faggin at Fairchild Semiconductor in 1968. The MOSFET has since become the most critical device component in modern ICs. The development of the MOS integrated circuit led to the invention of the microprocessor , and heralded an explosion in the commercial and personal use of computers. While the subject of exactly which device was the first microprocessor is contentious, partly due to lack of agreement on

26394-825: Was developed in the late 16th century and found application in gunnery, surveying and navigation. The planimeter was a manual instrument to calculate the area of a closed figure by tracing over it with a mechanical linkage. The slide rule was invented around 1620–1630, by the English clergyman William Oughtred , shortly after the publication of the concept of the logarithm . It is a hand-operated analog computer for doing multiplication and division. As slide rule development progressed, added scales provided reciprocals, squares and square roots, cubes and cube roots, as well as transcendental functions such as logarithms and exponentials, circular and hyperbolic trigonometry and other functions . Slide rules with special scales are still used for quick performance of routine calculations, such as

26560-481: Was greater than 90 beats per minute. For endurance athletes at the elite level, it is not unusual to have a resting heart rate between 33 and 50 bpm. The maximum heart rate (HR max ) is the age-related highest number of beats per minute of the heart when reaching a point of exhaustion without severe problems through exercise stress. In general it is loosely estimated as 220 minus one's age. It generally decreases with age. Since HR max varies by individual,

26726-449: Was invented by Abi Bakr of Isfahan , Persia in 1235. Abū Rayhān al-Bīrūnī invented the first mechanical geared lunisolar calendar astrolabe, an early fixed- wired knowledge processing machine with a gear train and gear-wheels, c.  1000 AD . The sector , a calculating instrument used for solving problems in proportion, trigonometry , multiplication and division, and for various functions, such as squares and cube roots,

26892-475: Was invented by Anthony Rickards of the National Heart Hospital , London, UK, in 1982. Dynamic pacemaking technology could also be applied to future artificial hearts . Advances in transitional tissue welding would support this and other artificial organ/joint/tissue replacement efforts. Stem cells may be of interest in transitional tissue welding. Many advancements have been made to improve

27058-477: Was made of germanium . Noyce's monolithic IC was fabricated using the planar process , developed by his colleague Jean Hoerni in early 1959. In turn, the planar process was based on Carl Frosch and Lincoln Derick work on semiconductor surface passivation by silicon dioxide. Modern monolithic ICs are predominantly MOS ( metal–oxide–semiconductor ) integrated circuits, built from MOSFETs (MOS transistors). The earliest experimental MOS IC to be fabricated

27224-643: Was most likely a form of tally stick . Later record keeping aids throughout the Fertile Crescent included calculi (clay spheres, cones, etc.) which represented counts of items, likely livestock or grains, sealed in hollow unbaked clay containers. The use of counting rods is one example. The abacus was initially used for arithmetic tasks. The Roman abacus was developed from devices used in Babylonia as early as 2400 BCE. Since then, many other forms of reckoning boards or tables have been invented. In

27390-434: Was not Turing-complete. Nine Mk II Colossi were built (The Mk I was converted to a Mk II making ten machines in total). Colossus Mark I contained 1,500 thermionic valves (tubes), but Mark II with 2,400 valves, was both five times faster and simpler to operate than Mark I, greatly speeding the decoding process. The ENIAC (Electronic Numerical Integrator and Computer) was the first electronic programmable computer built in

27556-598: Was the Medtronic Revo MRI SureScan, approved by the US FDA in February 2011, which was the first to be specified as MR conditional. There are several conditions to use of MR Conditional pacemakers, including certain patients' qualifications and scan settings. An MRI conditional device has to have MRI settings enabled before a scan, and disabled afterwards. As of 2014 the five most commonly used cardiac pacing device manufacturers (covering more than 99% of

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