Artificial valves

Physical trauma to RBC (artificial valves) Excessive sequestration in the spleen Intracorpuscular factors Heredity... 

Dipyridamoie Inhibits phosphodiesterase, increasing cAMP levels to potentiate PGI 2 (platelet aggregation inhibitor). T levels of adenosine (a coronary artery vasodilator) Has few clinical effects alone. With warfarin, prevents emboli from artificial valves. With aspirin, enhances lifespan of platelets in patients with thrombotic disease. Also used in prophylaxis of angina and migraine headaches. May worsen angina, dizziness, headache, syncope, Gl disturbances, rash. ... 

One difficulty with the implantation of mechanical hearts, artificial valves, or blood vessels is that there may be regions of blood stagnation inside these artificial organs. Thrombi can form there, and have been known to cause life-threatening incidents in organ replacement patients. The difficulty is... 

Nonlimb Prosthetic Devices. Other prosthetic devices include artificial eyes, breasts, heart valves, and pacemakers. The body s natural heart valve may need to be surgically replaced if it no longer functions properly because of disease, aging, or a birth defect. This vital prosthetic heart component is made from plastic, metal, or pig tissue. Calcification of the prosthetic heart valves is the major cause of product problems, and efforts have been aimed at constructing artificial valves with surfaces that resist calcification. Technological advancements in the durability of the tissue heart valves are also an area of research and could be more applicable to younger patients. 

In addition to drug delivery, collagen has been used in applications in the medical-pharmaceutical interface, including tissue engineering (i.e., composites of collagen with hydroxyapatite and tricalcium phosphate in bone grafts or as artificial valve and vessel substitutes) [417] and surgical sutures [418]. 

Biocompatible and lubricous coatings Crosslinked or grafted coatings have been used on contact lenses to enhance wetting, on silicone rubber indwelling catheters to prevent occlusion, and on prosthetic devices, such as artificial valves, intraocular lenses, vascular grafts, and pacemakers to improve device biocompatibility. [66-71 ]... 

Although the artificial valves certainly have room for further improvement, the superior prognosis for the patient with a replacement heart valve is dramatic and convincing. 

Heart, artificial Heartguard 30 Heart-lung machine Heart pacers Heart valves... 

Biomedical Applications. In the area of biomedical polymers and materials, two types of appHcations have been envisioned and explored. The first is the use of polyphosphazenes as bioinert materials for implantation in the body either as housing for medical devices or as stmctural materials for heart valves, artificial blood vessels, and catheters. A number of fluoroalkoxy-, aryloxy-, and arylamino-substituted polyphosphazenes have been tested by actual implantation ia rats and found to generate Httle tissue response (18). 

One successful total artificial heart is ABIOMED s electric TAH. This artificial heart consists of two seamless blood pumps which assume the roles of the natural heart s two ventricles (Fig. 7). The pumps and valves are fabricated from a polyurethane, Angioflex. Small enough to fit the majority of the adult population, the heart s principal components are implanted in the cavity left by the removal of the diseased natural heart. A modest sized battery pack carried by the patient suppHes power to the drive system. Miniaturized electronics control the artificial heart which mns as smoothly and quietly as the natural heart. Once implanted, the total artificial heart performs the critical function of pumping blood to the entire body (6). 

Since (c) is larger than (a) in the previous step, too thick a cake will be formed and it will not wash or dry adequately unless the effective submergence is artificially restricted to yield the design cake thickness. This may be accomplished by proper bridge-block adjustment or by vacuum regulation within the form zone of the filter valve. 

Wear of medical devices and biomaterials can affect quality of life. Wear of tooth fillings, artificial joints and heart valves can be inconvenient, costly (more frequent replacement) or even life-threateiiiiig (premature breakdowns). Wear of components can also cause accidents. Worn brakes and tires can cause automobile accidents, worn electrical cords can result in electrocution and fires and worn out seals can lead to radiation leaks at nuclear power plants. 

Figure 6-31 illustrates control schemes for the single stage unit which allow greater stability in performance. As the load changes for a fixed suction pressure, the process fluid is replaced by an artificial load (usually air Figure 6-31, item 1) to maintain constant ejector operation. An artificial pressure drop can be imposed by valve (2), although this is not a preferred scheme. Wlten the addi-... 

Carbon is inactive in blood and is not rejected from the human body. It is therefore increasingly used in artificial limbs, tendons and heart valves. 

Condensers are sized so that they can reject the system heat load under maximum conditions of air or water temperature. In colder weather, the condensing temperature will fall with that of the cooling medium and this may cause difficulties in correct operation of the plant. In particular, the pressure across the expansion valve (see also Chapter 8) may be too low to circulate the required mass flow of the refrigerant. Under such circumstances, artificial means must be used to keep the head pressure up, always remembering that the condensing pressure should be kept as low as practical for power economy. 

Polymers are a fundamental part of the modem world, showing up in everything from coffee cups to cars to clothing. In medicine, too, their importance is growing for purposes as diverse as cardiac pacemakers, artificial heart valves, and biodegradable sutures. 

The cardiac pump theory states that the active compression of the heart between the sternum and vertebrae creates an artificial systole in which intraventricular pressure increases, the atrioventricular valves... 

The produced oil or gas is connected to surface flowlines from the wellhead pumping unit or surface regulating valve assembly typically referred to as a Christmas tree but to its arrangement. The flowlines collect the oil or gas to local tank batteries or central production facilities for primary oil, water, and gas separation. The reliability of electrical submersible pumps (ESPs) has increased to the point where the submersible electrical pump is commonly used for the production of liquid hydrocarbons where artificial lift is required for production. 

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