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ABSTRACT

Human body is the most complex machine. It contains many parts which are complex in nature.

When these parts are no longer able to function properly due to physical ailments or disability or

sudden failure, immediate medical attention is necessary.

Since, human life is precious and needs to be saved at any cost, it gets difficult when whole

organ sometimes becomes useless. In such cases organ transplantation needs to be done, which hasrejection problems. Technology

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CONTENTS PAGE NO.

ABSTRACT. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0

LIST OF FIGURES. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

CHAPTER 1 : ARTIFICIAL HEART . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

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CHAPTER 2 : ARTIFICIAL KIDNEYS. . . . . . . . . . . . . . . . . . . . . . . . . . . 6

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CONCLUSION AND FUTURE WORK. . . . . . . . . . . . . . . . . . . . . . . . . 14

REFERENCES. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15

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CHAPTER 1:

ARTIFICIAL HEART

Given the arduous physical demands placed on the human heart, it should come as no surprise thatheart disease represents one of society's gravest health risks. Essentially, heart disease is presentwhen the pumping and circulatory functions congenital and congestive forms of heart disease take anenormous toll on society. As noted previously, the heart's pumping action supplies the body with theoxygen and nutrient-rich blood it needs in order to function properly.Persons plagued by early andmiddle stage heart disease suffer from a shortage of these life-sustaining elements. Thus, suchpersons often tend to feel weak, fatigued, and short of breath.

Artificial heart technology represents society's most promising attempt at filling the above void.This technology has two main branches. Partial devices supplement patients' natural heart function,assisting those patients whose organs, while somewhat viable, are incapable of functioningadequately on their own.

Total artificial hearts (TAH), on the other hand, are devices that actually replace patients'natural hearts. Such devices are designed for situations in which natural organs are so damaged thateven supplementation via a partial device isn't enough to produce sufficient circulatory function.Collectively, partial and total artificial heart devices are classified as mechanical circulatory supportsystems (MCSS). Surgeons employing these devices face the unenviable challenge of outwitting thehuman body. Although it is relatively easy to slip pumps inside the body, it is difficult to do so in amanner that prevents the body from discovering this intrusion and ultimately rejecting the devices

Ventricular assist device

A ventricular assist device (VAD)is a mechanical circulatory device that is used to partially or

completely replace the function of a failing heart. VADs are designed to assist either the right

(RVAD) or left (LVAD) ventricle, or both at once (BiVAD). The type that is used depends primarily on

the underlying heart disease and the pulmonary arterial resistance that determines the load on the

right ventricle.

The pumps used in VADs can be divided into two main categories a) pulsatile pumps, that mimic the

natural pulsing action of the heart, and b) continuous flow pumps.

a) Pulsatile VADs use positive displacement pumps. In some of these pumps, the volume

occupied by blood varies during the pumping cycle, and if the pump is contained inside the

body then a vent tube to the outside air is required.

b) Continuous flow VADs are smaller and have proven to be more durable than pulsatile VADs.They normally use either a centrifugal pump or an axial flow pump. Both types have a

central rotor containing permanent magnets. Controlled electric currents running through

coils contained in the pump housing apply forces to the magnets, which in turn cause the

rotors to spin. In the centrifugal pumps, the rotors are shaped to accelerate the blood

circumferentially and thereby cause it to move toward the outer rim of the pump, whereas

in the axial flow pumps the rotors are more or less cylindrical with blades that are helical,

causing the blood to be accelerated in the direction of the rotor's axis. An important issue

with continuous flow pumps is the method used to suspend the rotor. Early versions used

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solid bearings; however, newer pumps, some of which are approved for use in the EU, use

either electromagnetic suspension ("maglev") or hydrodynamic suspension. These pumps

contain only one moving part.

Fig. : 1.1 VAD concept of heart Fig. : 1.2 VAD sectional view

Fig.1.3 : Surgical installation of a VAD

Pressure-Volume Relationship

This relationship was first described in Figure . End-systolic volume for a given cardiac cycleis estimated by one of the imaging techniques,while end-systolic pressure for that cardiac

cycle is obtained from the arterial pressure record at the point of the closure of the aortic

valve (the incisura). Values for several different cardiac cycles are obtained during infusionof a vasoconstrictor (which increases after load), and the data are plotted. As shown in Figure

1.4, increases in myocardial contractility are associated with a leftward shift in this

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relationship. Decreases in contractility (as may be caused by heart disease) are associatedwith a downward shift of the line. This method of assessing cardiac function is particularly

important because it provides an estimate of contractility that is independent of the end-

diastolic volume (preload from the pressure-volume loop described by the dotted line in

Figure 1.4 that increases in preload cause increases in stroke volume without changing theend-systolic volume. Thus only alterations in contractility will cause shifts in the end-systolic

pressure-volume relationship..

Fig. 1.4 : P-V diagram for

Total Artificial Heart

Artificial hearts can now completely, if temporarily, replace the ventricles and valves with a device

made of plastic or other man-made materials, which does the job of pumping blood around.

The type of artificial heart that was given to Green, made by Syncardia Systems, works by using a

pump carried externally in a backpackpreviously, patients would have to be connected to a large,

immobile pump and would not have the freedom to move around.

Energy transmission

In the artificial hearts produced by AbioMed, an electronics package is implanted in theabdomen of the recipient of the transplant to monitor and control the pumping of the heart.

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Power is supplied from an external source to components under the skin, without penetratingit, using inductive electromagnetic couplingthe same principle as used by transformers to

transfer electricity between different circuits, as in the national grid.

At their simplest, systems of transcutaneous energy transmission will use an external power

supply connected to an external coil of wire, generating a magnetic field in it. This, in turn,

produces an induced voltage in a second coil implanted under the skin, and a rectifier is usedto change this alternating current into direct current that can be used to power the electronics

of the heart and its controller.

Though simple in theory, in practice there are complications that arise from the need to keep

the two coils aligned correctly as the patient moves, in delivering the correct level of power

so that there is no excess dissipated as heat to potentially damage surrounding tissue in thepatients body, and in making the components small enough to be carried around without too

much discomfort.

Fig. 1.5 :Centrifugal blood pump Fig. 1.6 : Exploded view of pump

Monitoring blood flow

A replacement heart needs to be able to monitor the flow of blood to regulate its pumping

and ensure that the correct amount of blood is delivered around the body.

Quicker pumping is required when the transplant recipient is more active, whereas the

opposite is true while he or she is resting.

Blood-flow monitors make use of ultrasoundthey bounce high-frequency sound waves off

blood cells coming out of the heart, the volume and speed can be measured using similarbasic principles to those behindradar.

Ultrasound is used because it can monitor the flow of blood without having to be in contactwith it.

http://www.physics.org/explore/radarhttp://www.physics.org/explore/radarhttp://www.physics.org/explore/radarhttp://www.physics.org/explore/radarhttp://www.physics.org/explore/radar

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Appropriate materials

Artificial hearts need to be made of light but durable materialsthe Syncardia version is

plastic whereas that made by AbioMed is a combination of titanium and a specially

developed polyurethane, called Angioflex.

Although the Abiomed heart is designed to have as few moving parts as possible, those that itdoes have are made from Angioflex and are tested to ensure that they are safe for contact

with blood and capable of withstanding beating 100 000 times a day for years on end.

Materials scientists can develop substances with specific properties by manipulating the

constituent elements and the way in which they are processed. Materials are characterised

using various techniques from condensed-matter physics including electron microscopy, x-

ray diffraction and neutron diffraction.

Because they were still quite large, the first devices produced were limited to around half the

male populationthose with the largest chest cavities. A newer, smaller, model is intendedto extend their availability to smaller people.

An artificial heart being produced by the French medical company Carmat and expected to

be available by 2013 will use chemically treated animal tissue to help avoid rejection by the

hosts immune system. Aerospace engineers from Airbus were also involved in its

development.

Artificial hearts combine, and improve upon, many existing physics ideas to produce a piece

of technology that saves livesalthough they are currently only approved as a stopgap untila donor heart can be found.

Fig. 1.5 : Total artificial heart blood flow and installation

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Advantages

1. Artificial ventricles are safe and effective methods for the treatment of end stage heart

failure.

2. An artificial heart as a bridge to transplantation gives patients the opportunity to wait for

an acceptable donor at home and allows nearly unlimited mobility.

3. Ventricular assist device as a bridge to myocardial recovery for patients with acute

myocarditis or postoperative heart failure still have limited success.

4.The absence of mechanical failures of the pumping

mechanism is very encouraging in the prospect of long-termtherapy for patients with advanced heart failure.

Disadvantages

1. Continuous-flow rotary pumps significantly reduce but do not eliminate the normal pressure amplitude

associated with the native circulation that may influence long-term organ function.

2. Although the risk of pump thrombosis and thromboembolism (particularly stroke) is low, it has not been

eliminated with the new pump design.

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CHAPTER 2

ARTIFICIAL KIDNEYS

Treatment with an artificial kidney is the most widely applied therapy for kidney failure. Substantial

improvements have been made in artificial kidney technology during the past decades, such as with regard to

membrane technology, dialysate composition, and medicate onto address side effects. Despite these

improvements, the high rates of mortality of critically ill patients with acute renal failure (ARF), ranging

between 50% and 70%, did not change for several decades . Also, the rates of morbidity and mortality ofpatients with end-stage renal disease (ESRD) receiving treatment with an artificial kidney remain high and the

survival advantage associated with renal transplantation is evident. The problems associated with ESRD are

increasing as the number of patients increases in industrialized countries, whereas the number of kidneys

available for transplantation remains relatively low