释义 |
blood pressure
blood pressuren. Abbr. BP The pressure exerted by the blood against the walls of the blood vessels, especially the arteries. It varies with the strength of the heartbeat, the elasticity of the arterial walls, the volume and viscosity of the blood, and a person's health, age, and physical condition.blood pressure n (Physiology) the pressure exerted by the blood on the inner walls of the arteries, being relative to the elasticity and diameter of the vessels and the force of the heartbeat blood′ pres`sure n. the pressure of the blood against the inner walls of the blood vessels, esp. of the arteries during different phases of contraction of the heart. Compare diastole, systole. [1870–75] blood pressure The pressure of the blood in the vessels, especially the arteries, as it circulates through the body. Blood pressure varies with the strength of the heartbeat, the amount of blood being pumped, and the health of the blood vessels. See more at high blood pressure.blood pressureThe pressure of blood against blood-vessel walls, especially the walls of arteries.ThesaurusNoun | 1. | blood pressure - the pressure of the circulating blood against the walls of the blood vessels; results from the systole of the left ventricle of the heart; sometimes measured for a quick evaluation of a person's health; "adult blood pressure is considered normal at 120/80 where the first number is the systolic pressure and the second is the diastolic pressure"systolic pressure - the blood pressure (as measured by a sphygmomanometer) during the contraction of the left ventricle of the heartdiastolic pressure - the blood pressure (as measured by a sphygmomanometer) after the contraction of the heart while the chambers of the heart refill with bloodarterial pressure - the pressure of the circulating blood on the arteries; "arterial pressure is the product of cardiac output and vascular resistance"venous pressure - the pressure exerted on the walls of the veins by the circulating bloodcirculation - movement through a circuit; especially the movement of blood through the heart and blood vesselsforce per unit area, pressure, pressure level - the force applied to a unit area of surface; measured in pascals (SI unit) or in dynes (cgs unit); "the compressed gas exerts an increased pressure"vital sign - sign of life; usually an indicator of a person's general physical condition; "he was still alive but his vital signs were weak" | Translationsblood (blad) noun1. the red fluid pumped through the body by the heart. Blood poured from the wound in his side. 血液 血液2. descent or ancestors. He is of royal blood. 血統 血统ˈbloodless adjective1. without the shedding of blood. a bloodless victory. 未流血的 未流血的2. anaemic. She is definitely bloodless. 貧血的 贫血的ˈbloody adjective1. stained with blood. a bloody shirt; His clothes were torn and bloody. 血污的 血污的2. bleeding. a bloody nose. 流血的 流血的3. murderous and cruel. a bloody battle. 血腥的 血腥的4. used in slang vulgarly for emphasis. That bloody car ran over my foot! (用以發洩不滿的粗俗俚語)該死的,討厭的 (用以加强语气,很多人认为含冒犯意)非常,很 ˈbloodcurdling adjective terrifying and horrible. a blood-curdling scream. 令人毛骨悚然的 恐怖的,令人毛骨悚然的 blood donor a person who gives blood for use by another person in transfusion etc. 供血者 供血者blood group/type any one of the types into which human blood is classified. Her blood group is O. 血型 血型ˈblood-poisoning noun an infection of the blood. He is suffering from blood-poisoning. 血中毒 血中毒blood pressure the (amount of) pressure of the blood on the walls of the blood-vessels. The excitement will raise his blood pressure. 血壓 血压ˈbloodshed noun deaths or shedding of blood. There was much bloodshed in the battle. 流血,傷亡 流血ˈbloodshot adjective (of eyes) full of red lines and inflamed with blood. 充血的 充血的ˈbloodstained adjective stained with blood. a bloodstained bandage. 染血的 沾染着血的ˈbloodstream noun the blood flowing through the body. The poison entered her bloodstream. 血流 血流ˈblood test noun an analysis of a patient's blood to find out if he/she has any diseases. etc. 驗血 验血ˈbloodthirsty adjective1. eager to kill people. a bloodthirsty warrior. 嗜血的,嗜殺成性的 嗜血的,残忍的 2. (of a film etc) full of scenes in which there is much killing. 充滿殺戮的 充满凶杀的ˈbloodthirstiness noun 嗜殺成性 残忍好杀ˈblood transfusion noun the process of giving blood to someone through the veins during an operation etc. 輸血 输血,输血法 ˈblood-vessel noun any of the tubes in the body through which the blood flows. He has burst a blood-vessel. 血管 血管in cold blood while free from excitement or passion. He killed his son in cold blood. 冷血地 残忍地See blood pressure
blood pressure
blood pressure, force exerted by the blood upon the walls of the arteries. The pressure in the arteries originates in the pumping action of the heart, and pressure waves can be felt at the wrist and at other points where arteries lie near the surface of the body (see pulsepulse, alternate expansion and contraction of artery walls as heart action varies blood volume within the arteries. Artery walls are elastic. Hence they become distended by increased blood volume during systole, or contraction of the heart. ..... Click the link for more information. ). Since the heart can pump blood into the large arteries more quickly than it can be absorbed and released by the tiny arterioles and capillaries, considerable inner pressure always exists in the arteries. The contraction of the heart (systole) causes the blood pressure to rise to its highest point, and relaxation of the heart (diastole) brings the pressure down to its lowest point. Blood pressure is strongest in the aorta, where the blood leaves the heart. It diminishes progressively in the smaller blood vessels and reaches its lowest point in the veins (see circulatory systemcirculatory system, group of organs that transport blood and the substances it carries to and from all parts of the body. The circulatory system can be considered as composed of two parts: the systemic circulation, which serves the body as a whole except for the lungs, and the ..... Click the link for more information. ). Blood pressure manifests itself dramatically when an artery is severed or pierced and the blood (under pressure) ejects in spurts. Since blood pressure varies in different arteries, the pressure in the brachial artery of the forearm serves as a standard. A sphygmomanometer measures blood pressure in millimeters of mercury; blood pressure gauges that do not use mercury also produce readings that are expressed in terms of millimeters of mercury. Normal blood pressure readings for healthy young people should be below 120 mm for systolic pressure and 80 mm for diastolic pressure, commonly written as 120/80 and read as "one-twenty over eighty." With age, and the constriction of the small arteries and then the larger ones, blood pressure increases, so that at 50 years, a person may typically have a systolic pressure between 140 and 150, and a diastolic pressure of about 90. Factors other than heart action and the condition of the arteries also influence blood pressure. Temporary high blood pressure usually occurs during or following physical activity, nervous strain, and periods of rage or fear. Therapy for persistent high blood pressure, sometimes called hypertensionhypertension or high blood pressure, elevated blood pressure resulting from an increase in the amount of blood pumped by the heart or from increased resistance to the flow of blood through the small arterial blood vessels (arterioles). ..... Click the link for more information. , consists of sufficient rest, a diet low in salt and alcohol, reduction in weight where there is obesity, and increased exercise. Drug therapy may include diureticsdiuretic , drug used to increase urine formation and output. Diuretics are prescribed for the treatment of edema (the accumulation of excess fluids in the tissues of the body), which is often the result of underlying disease of the kidneys, liver, lungs, or heart (e.g. ..... Click the link for more information. , beta-blockersbeta-blocker or beta-adrenergic blocking agent , drug that reduces the symptoms connected with hypertension, cardiac arrhythmias, angina pectoris, migraine headaches, and other disorders related to the sympathetic nervous system. ..... Click the link for more information. , calcium-channel blockerscalcium-channel blocker, any of a class of drugs used in treating hypertension, angina pectoris, and certain arrhythmias. They prevent the calcium ions needed for muscle contraction from entering the cells of smooth and cardiac muscle. ..... Click the link for more information. , or ACE inhibitorsACE inhibitor or angiotensin-converting enzyme inhibitor , drug used to reduce elevated blood pressure (see hypertension), to treat congestive heart failure, and to alleviate strain on hearts damaged as a result of a heart attack (see infarction). ..... Click the link for more information. . Low blood pressure (hypotension) has not been studied as extensively as high blood pressure. If not caused by disease or injury, it is generally considered to be a benign or even advantageous condition; however, studies have linked hypotension with feelings of tiredness or faintness and minor psychiatric conditions in some people. Bibliography See N. H. Naqvi and M. D. Blaufox, Blood Pressure Measurement: An Illustrated History (1998). Blood Pressure the hydrodynamic pressure of blood in the blood vessels; it arises as a result of the work of the heart, which pumps the blood into the vascular system, and the resistance of the vessels. The level of the blood pressure in the arteries, veins, and capillaries varies and is a measure of the body’s functional condition. Arterial pressure undergoes rhythmic variations, increasing during contraction of the heart (systole) and decreasing during the period of its relaxation (diastole). Each new portion of blood discharged by the heart distends the elastic walls of the aorta and central arteries. During the cardiac pause the distended walls of the arteries collapse and push the blood through the arterioles, capillaries, and veins. In man and in many other mammals, the maximum (systolic) pressure is about 120 millimeters of mercury (mm Hg), and the minimum (diastolic) pressure is about 70 mm Hg. The difference between these two values (the amplitude- of pressure change with each heart contraction) is called the pulse pressure. Under physical or emotional stress a short-term increase in arterial pressure occurs, which represents a physiological adaptive reaction. Arterial pressure may be measured by the direct method—that is, insertion into the vessel of a cannula that is connected by a tube with a manometer (the Englishman S. Hales first measured arterial pressure in this way in 1733)—or by an indirect method—that is, by a sphygmomanometer. In man, the arterial blood pressure is usually measured on the arm above the elbow; the value thus determined corresponds to the blood pressure only in that artery and not the entire body. However, the figures obtained make it possible to form an opinion about the blood pressure of the person being examined. Figure 1. Blood pressure in various parts of the circulatory system. The broken line denotes the mean of the systolic and diastolic pressures. Venous pressure near the heart drops below zero (below atmospheric pressure). When the blood passes through the capillaries, the blood pressure drops from approximately 40 mm Hg at the arteriole endings to 10 mm Hg at the place where the capillaries shade into the venules. This decrease in blood pressure is caused by the friction of the blood against the walls of the small vessels; it maintains the flow of blood in them. The level of capillary pressure depends on the tonus of the arterioles and on venous pressure and to a considerable degree determines the conditions of the exchange of substances between the blood and the tissues. In the veins a further drop in blood pressure occurs; at the ostia venae cavae blood pressure drops below atmospheric pressure, which is due to the suction of the negative pressure in the thorax (see Figure 1). Venous pressure is measured by the direct method —insertion into the vein of a needle connected to a manometer. The level and variations in blood pressure act on the baroreceptors of the vascular system; thus, neural and humoral reactions occur, which are directed toward maintaining the blood pressure at the level characteristic for the given organism and toward self-regulation of blood circulation. G. I. KOSITSKII In man, the average arterial blood pressure is 115–125 mm Hg in systole (maximum) and 70–80 mm Hg in diastole (minimum). The average levels change with age. Table 1. Arterial pressure (mm Hg) |
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Age (in years) | Systolic pressure | Diastolic pressure |
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16-20. . . . . . . . . . | 100-120 | 70-80 | 20-40. . . . . . . . . . | 120-130 | 70-80 | 40-60. . . . . . . . . . | up to 140 | up to 90 | over 60. . . . . . . . . . | up to 150 | up to 90 |
Blood pressure that is persistently higher than the indicated figures, hypertension, may be a symptom of a number of diseases (hypertensive disease, nephritis). Low blood pressure, hypotension, may be physiological, may accompany a number of pathological states, or may be a separate disease. REFERENCESVal’dman, V. A. Venoznoe davlenie i venoznyi tonus, 2nd ed. Leningrad, 1947. Kositskii, G. I. Zvukovoi metod issledovaniia arterial’nogo davleniia. Moscow, 1959. Savitskii, N. N. Biofizicheskie osnovy krovoobrashcheniia i klinicheskie metody izucheniia gemodinamiki, 2nd ed. Leningrad, 1963.blood pressure[′bləd ‚presh·ər] (physiology) Pressure exerted by blood on the walls of the blood vessels. blood pressure the pressure exerted by the blood on the inner walls of the arteries, being relative to the elasticity and diameter of the vessels and the force of the heartbeat blood pressure
blood [blud] the fluid that circulates through the heart, arteries, capillaries, and veins and is the chief means of transport within the body. It transports oxygen from the lungs to the body tissues, and carbon dioxide from the tissues to the lungs. It transports nutritive substances and metabolites to the tissues and removes waste products to the kidneys and other organs of excretion. It has an essential role in the maintenance of fluid balance. In an emergency, blood cells and antibodies carried in the blood are brought to a point of infection, or blood-clotting substances are carried to a break in a blood vessel. The blood distributes hormones from the endocrine glands to the organs they influence. It also helps regulate body temperature by carrying excess heat from the interior of the body to the surface layers of the skin, where the heat is dissipated to the surrounding air. Blood varies in color from a bright red in the arteries to a duller red in the veins. The total quantity of blood within an individual depends upon body weight; a person weighing 70 kg (154 lb) has about 4.5 liters of blood in the body. Blood is composed of two parts: the fluid portion is called plasma" >plasma, and the solid portion or formed elements (suspended in the fluid) consists of the blood cells (erythrocytes and leukocytes) and the platelets. Plasma accounts for about 55 per cent of the volume and the formed elements account for about 45 per cent. ( and table.) Chemical analyses of various substances in the blood are invaluable aids in (1) the prevention of disease by alerting the patient and health care provider to potentially dangerous levels of blood constituents that could lead to more serious conditions, (2) diagnosis of pathologic conditions already present, (3) assessment of the patient's progress when a disturbance in blood chemistry exists, and (4) assessment of the patient's status by establishing baseline or “normal” levels for each individual patient. In recent years, with the increasing attention to preventive health care and rapid progress in technology and automation, the use of a battery of screening tests performed by automated instruments has become quite common. These instruments are capable of performing simultaneously a variety of blood chemistry tests. Some of the more common screening tests performed on samples of blood include evaluation of electrolyte, albumin, and bilirubin levels, blood urea nitrogen" >blood urea nitrogen (BUN), cholesterol, total protein, and such enzymes as lactate dehydrogenase and aspartate transaminase. Other tests include electrophoresis for serum proteins, blood gas analysis, glucose tolerance tests, and measurement of iron levels.Composition of the blood, which constitutes 8% of total body weight. From Applegate, 2000.blood bank 1. a place of storage for blood.2. an organization that collects, processes, stores, and transfuses blood. In most health agencies the blood bank is located in the pathology laboratory. It is operated by medical technologists under the direction of a pathologist.blood bank technologist a clinical laboratory scientist/medical technologist who has postgraduate education in blood banking and is certified by the Board of Registry of the American Society of Clinical Pathologists; designated as MT(ASCP)SBB. Specialists in blood bank technology perform both routine and specialized tests in blood bank immunohematology and perform transfusion services. The address of the American Association of Blood Banks is 8101 Glenbrook Road, Bethesda, MD 20814 (telephone 301-907-6582). The address of the Board of Registry of the American Society of Clinical Pathologists is P.O. Box 12270, Chicago, IL 60612. Their telephone number is 312-738-1336 and their web site is http://www.aabb.org.blood-brain barrier BBB; the barrier separating the blood from the brain parenchyma everywhere except in the hypothalamus. It is permeable to water, oxygen, carbon dioxide, and nonionic solutes, such as glucose, alcohol, and general anesthetics, and is only slightly permeable to electrolytes and other ionic substances. Some small molecules, e.g., amino acids, are taken up across the barrier by specific transport mechanisms.citrated blood blood treated with sodium citrate or citric acid to prevent its coagulation.cord blood the blood contained in the umbilical vessels at the time of delivery of the infant. It is rich in stem cells that could be used in place of bone marrow for a transplant; thus, it is sometimes collected and stored for future use.blood count determination of the number of blood cells in a given sample of blood, usually expressed as the number in a cubic millimeter; it may be either a count" >complete blood count or a count of just one of the elements such as an count" >erythrocyte count, count" >leukocyte count or a count" >platelet count. Methods include manual counts using a hemacytometer" >hemacytometer and automated counts using a flow cytometer, a Coulter counter, or other means. The blood count is useful in the diagnosis of various blood dyscrasias, infections, or other abnormal conditions and is one of the most common tests done on the blood. Called also blood cell count. (See accompanying table.)defibrinated blood whole blood from which fibrin has been separated during the clotting process.blood gas analysis laboratory studies of arterial and venous blood for the purpose of measuring oxygen and carbon dioxide levels and pressure or tension, and hydrogen ion concentration (pH). (See accompanying table.) Analyses of blood gases provide the following information: PaO2—partial pressure (P) of oxygen (O2) in the arterial blood (a) SaO2—percentage of available hemoglobin that is saturated (Sa) with oxygen (O2) PaCO2—partial pressure (P) of carbon dioxide (CO2) in the arterial blood (a) pH—an expression of the extent to which the blood is alkaline or acidic HCO3−—the level of plasma bicarbonate; an indicator of the metabolic acid-base status These parameters are important tools for assessment of a patient's acid-base balance. They reflect the ability of the lungs to exchange oxygen and carbon dioxide, the ability of the kidneys to control the retention or elimination of bicarbonate, and the effectiveness of the heart as a pump. Because the lungs and kidneys act as important regulators of the respiratory and metabolic acid-base balance, assessment of the status of a patient with any disorder of respiration and metabolism includes periodic blood gas measurements. The partial pressure of a particular gas in a mixture of gases, as of oxygen in air, is the pressure exerted by that gas alone. It is proportional to the relative number of molecules of the gas, for example, the fraction of all the molecules in the air that are oxygen molecules. The partial pressure of a gas in a liquid is the partial pressure of a real or imaginary gas that is in equilibrium with the liquid. PaO2 measures the oxygen content of the arterial blood, most of which is bound to hemoglobin, forming oxyhemoglobin. The SaO2 measures the oxygen in oxyhemoglobin as a percentage of the total hemoglobin oxygen-carrying capacity. A PaO2 of 60 mm Hg represents an SaO2 of 90 per cent, which is sufficient to meet the needs of the body's cells. However, as the PaO2 falls, the SaO2 decreases rapidly. A PaO2 below 55 indicates a state of hypoxemia that requires correction. Normal PaO2 values at sea level are 80 mm Hg for elderly adults and 100 mm Hg for young adults. However, some patients with chronic obstructive pulmonary disease can tolerate a PaO2 as low as 70 mm Hg without becoming hypoxic. In caring for patients with this condition, it is important to know that attempts to elevate the PaO2 level to the normal level can be dangerous and even fatal. It is best to establish a baseline for each individual patient before supplementary oxygen is given, and then to assess his condition and the effectiveness of his therapy according to this baseline. The PaCO2 gives information about the cellular production of carbon dioxide through metabolic processes, and the removal of it from the body via the lungs. The normal range is 32 to 45 mm Hg. Values outside this range indicate a primary respiratory problem associated with pulmonary function, or a metabolic problem for which there is respiratory compensation. In the newborn the normal PaO2 is 50 to 80 mm Hg. At 40 to 50 mm Hg cyanosis may become apparent. Respiratory distress in an infant who is unable to ventilate the lungs adequately will produce a drop in PaO2 level. However, there is no marked increase in PaCO2 level in some infants as in adults with respiratory distress because many infants can still eliminate carbon dioxide from the lungs even though weakness prevents inhaling an adequate oxygen supply. All infants being ventilated and receiving oxygen therapy require frequent blood gas analyses and also pH, base excess, and oxygen saturation levels to avoid oxygen toxicity and acid-base imbalance. Blood pH gives information about the patient's metabolic state. A pH of 7.4 is considered normal; a value lower than 7.4 indicates acidemia and one higher than 7.4 alkalemia. Because the amount of CO2 in the blood affects its pH, abnormal PaCO2 values are interpreted in relation to the pH. If the PaCO2 value is elevated, and the pH is below normal, respiratory acidosis from either acute or chronic hyperventilation is suspected. Conversely, a PaCO2 below normal and a pH above normal indicates respiratory alkalosis. When both the PaCO2 and the pH are elevated, there is respiratory retention of CO2 to compensate for metabolic acidosis. If both values are below normal, there is respiratory elimination of CO2 (hyperventilation) to compensate for metabolic acidosis. Abnormal levels of bicarbonate (HCO3−) in the plasma are also interpreted in relation to the pH in the diagnosis of disturbances in the metabolic component of the acid-base balance. The normal range for HCO3− is 22 to 26 mEq per liter. Abnormally low levels of both HCO3− and pH indicate acidosis of metabolic origin. Conversely, elevations of both of these values indicate metabolic alkalosis. The kidneys maintain bicarbonate levels by filtering bicarbonate and returning it to the blood; they also produce new bicarbonate to replace that which is used in buffering. Therefore, a decreased HCO3− and an increased pH level indicate either retention of hydrogen ions by the kidneys or the elimination of HCO3− in an effort to compensate for respiratory alkalosis. Conversely, if the HCO3− level is increased and the pH is decreased, the kidneys have compensated for respiratory acidosis by retaining HCO3− or by eliminating hydrogen ions.blood gas analysis, mixed venous blood gas analysis performed on a blood sample obtained from the pulmonary artery.blood gas analysis, transcutaneous the determination of PO2 and PCO2 by placement of a heated electrode over the skin to get an inference of PaO2 and PaCO2.blood group the phenotype of erythrocytes defined by one or more cellular antigenic structural groupings under the control of allelic genes. In clinical practice there are four main blood groups or blood types: A, B, O, and AB (see table). In addition to this major grouping there is an Rh-hR system that is important in the prevention of erythroblastosis fetalis resulting from incompatibility of blood groups in mother and fetus. The ABO blood group system was first introduced in 1900 by Karl Landsteiner; in 1920 group AB was discovered by van Descatello and Sturli. Identification of these four major blood groups represented a major step toward resolving the problem of blood transfusion reactions resulting from donor-recipient incompatibility. In 1938 Landsteiner and Weiner discovered another blood factor related to maternal-fetal incompatibility. The factor was named Rh because the researchers were using rhesus monkeys in their studies. Further research has uncovered additional factors in the Rh group. Although more than 90 factors have been identified, many of these are not highly antigenic and are not, therefore, a cause for concern in the typing of blood for clinical purposes. The term factor, in reference to blood groups, is synonymous with antigen, and the reaction occurring between incompatible blood types is an antigen-antibody reaction. In cases of incompatibility, the antigen, located on the red blood cells, is an agglutinogen and the specific antibody, located in the serum, is an agglutinin. These are so named because whenever red blood cells with a certain factor come in contact with the agglutinin specific for it, there is agglutination or clumping of the erythrocytes. In determining blood group, a sample of blood is taken and mixed with specially prepared sera. One serum, anti-A agglutinin, causes blood of group A to agglutinate; another serum, anti-B agglutinin, causes blood of group B to agglutinate. Thus, if anti-A serum alone causes clumping, the blood is group A; if anti-B serum alone causes clumping, it is group B. If both cause clumping, the blood group is AB, and if it is not clumped by either, it is identified as group O.occult blood that present in such small amounts as to be detectable only by chemical tests or by spectroscopic or microscopic examination.peripheral blood that obtained from acral areas, or from the circulation remote from the heart; the blood in the systemic circulation.blood poisoning popular term for septicemia" >septicemia.blood pressure 1. the pressure of the blood against the walls of any blood vessel.2. the term usually refers to the pressure of the blood within the arteries, or pressure" >arterial blood pressure. This pressure is determined by several interrelated factors, including the pumping action of the heart, the resistance to the flow of blood in the arterioles, the elasticity of the walls of the main arteries, the blood volume and extracellular fluid volume, and the blood's viscosity, or thickness. The pumping action of the heart refers to how hard the heart pumps the blood (force of heartbeat), how much blood it pumps (the cardiac output), and how efficiently it does the job. Contraction of the heart, which forces blood through the arteries, is the phase known as systole. Relaxation of the heart between contractions is called diastole. The main arteries leading from the heart have walls with strong elastic fibers capable of expanding and absorbing the pulsations generated by the heart. At each pulsation the arteries expand and absorb the momentary increase in blood pressure. As the heart relaxes in preparation for another beat, the aortic valves close to prevent blood from flowing back to the heart chambers, and the artery walls spring back, forcing the blood through the body between contractions. In this way the arteries act as dampers on the pulsations and thus provide a steady flow of blood through the blood vessels. Because of this, there are actually two blood pressures within the blood vessels during one complete beat of the heart: a higher blood pressure during systole (the contraction phase) and a lower blood pressure during diastole (the relaxation phase). These two blood pressures are known as the systolic pressure and the diastolic pressure, respectively. It is generally agreed that a reading of 120 mm Hg systolic and 80 mm Hg diastolic are the norms for a blood pressure reading; that is, it represents the average blood pressure obtained from a large sampling of healthy adults. In general, a blood pressure of 95 mm Hg systolic and 60 mm Hg diastolic indicates hypotension. However, a reading equal to or below this level must be interpreted in the light of each patient's “normal” reading as determined by baseline data. On the basis of validated research on the long-term effects of an elevated blood pressure, it is generally agreed that some degree of risk for major cardiovascular disease exists when the systolic pressure is greater than or equal to 140 mm Hg, and the diastolic pressure is greater than or equal to 90 mm Hg. Life expectancy is reduced at all ages and in both males and females when the diastolic pressure is above 90 mm Hg. (See accompanying table.)Measurement of the Blood Pressure. The blood pressure is usually measured in the artery of the upper arm, with a sphygmomanometer. Measurement of blood pressure. From Applegate, 2000. This consists of a rubber cuff and a gauge or column of mercury for measuring pressure. The rubber cuff is wrapped about the patient's arm, and then air is pumped into the cuff by means of a rubber bulb. As the pressure inside the rubber cuff increases, the flow of blood through the artery is momentarily checked. A stethoscope is placed over the artery at the elbow and the air pressure within the cuff is slowly released. As soon as blood begins to flow through the artery again, Korotkoff sounds are heard. The first sounds heard are tapping sounds that gradually increase in intensity. The initial tapping sound that is heard for at least two consecutive beats is recorded as the systolic blood pressure. The first phase of the sounds may be followed by a momentary disappearance of sounds that can last from 30 to 40 mm Hg as the gauge needle (or mercury column) descends. It is important that this gap" >auscultatory gap not be missed; otherwise, either an erroneously low systolic pressure or high diastolic pressure will be obtained. During the second phase following the temporary absence of sound there are murmuring or swishing sounds. As deflation of the cuff continues, the sounds become sharper and louder. These sounds represent phase three. During phase four the sounds become muffled rather abruptly and then are followed by silence, which represents phase five. Although there is disagreement as to which of the latter phases should represent the diastolic pressure, it is usually recommended that phase five, the point at which sounds disappear, be used as the diastolic pressure for adults, and phase four be used for children. The reason for this is that children, having a high cardiac output, often will continue to produce sounds when the gauge is at a very low reading or even at zero. In some adult patients whose arterioles have lost their elasticity, the fifth phase is also extremely low or nonexistent. In these cases, it is recommended that three readings be recorded: phase one and phases four and five. For example, the blood pressure would be written as 140/96/0. On most occasions, however, the blood pressure is written as a fraction. The systolic pressure is written as the top number, a line is drawn, and the diastolic pressure is written as the bottom number. Errors in blood pressure measurement can result from failure of the cuff to reach and compress the artery. The cuff diameter should be 20 per cent greater than the diameter of the limb, the bladder of the cuff must be centered over the artery, and the cuff must be wrapped smoothly and snugly to ensure proper inflation. When a mercury gauge is used, the meniscus should be at eye level to avoid a false reading. Direct Measurement of Blood Pressure. Critically ill patients who require continuous monitoring of the blood pressure may have a catheter inserted into an artery and attached to a catheter-monitor-transducer system. The blood pressure is displayed on an oscilloscope at the bedside so that the patient's pressure can be determined at a glance. This intra-arterial technique of blood pressure monitoring provides accurate, objective, and continuous data on the patient's status.blood pressure, mean arterial MAP; the average pressure within an artery over a complete cycle of one heartbeat; in the brachial artery, calculated to be the diastolic pressure plus 1/3 of the difference between the systolic and diastolic pressures.blood stream bloodstream.blood urea nitrogen see urea nitrogen.blood volume 1. the total quantity of blood in the body; the volume" >plasma volume added to the volume." >red cell volume.2. a laboratory test performed to determine this. The indicators used to determine these measurements are 125I-labeled human serum albumin for plasma volume and 51Cr-labeled erythrocytes for red cell volume. The regulation of blood volume in the circulatory system is affected by the intrinsic mechanism for fluid exchange at the capillary membranes and by hormonal influences and nervous reflexes that affect the excretion of fluids by the kidneys. A rapid decrease in the blood volume, as in hemorrhage, greatly reduces the cardiac output and creates a condition called shock or circulatory shock. Conversely, an increase in blood volume, as when there is retention of water and salt in the body because of renal failure, results in an increase in cardiac output. The eventual outcome of this situation is increased arterial blood pressure. The blood volume in the pulmonary circulation is approximately 12 per cent of the total blood volume. Such conditions as left-sided heart failure and mitral stenosis can greatly increase the pulmonary blood volume while decreasing the systemic volume. As would be expected, right-sided heart failure has the opposite effect. The latter condition has less serious effects because the volume of the systemic circulation is about seven times that of the pulmonary circulation and it is therefore better able to accommodate a change in fluid volume. Tests. Clinical assessment of blood volume can be accomplished in a number of ways, for example, by measuring the patient's blood pressure while he is lying down, sitting, and standing. The quality and volume of peripheral pulses will give information about blood volume, as does determining the ease and speed with which a compressed vein will refill after pressure is released. Neck veins that are engorged indicate hypervolemia; the collapse of these veins indicates hypovolemia. A more accurate assessment can be done through the use of intravascular catheters such as the central venous pressure catheter, which measures pressure in the right atrium, and the swan-ganz catheter, which measures pressure on both sides of the heart. Measurement of blood volume is accomplished by using substances that combine with red blood cells, for example, iron, chromium, and phosphate, or substances that combine with plasma proteins. In either case the measurement of the blood volume is based on the “dilution” principle. That is, the volume of any fluid compartment can be measured if a given amount of a substance is dispersed evenly in the fluid within the compartment, and then the extent of dilution of the substance is measured. For example, a small amount of radioactive chromium (51Cr), which is widely used to determine blood volume, is mixed with a sample of blood drawn from the patient. After about 30 minutes the 51Cr will have entered the red blood cells. The sample with the tagged red blood cells is then returned by injection into the patient's bloodstream. About 10 minutes later a sample is removed from the patient's circulating blood and the radioactivity level of this sample is measured. The total blood volume is calculated according to this formula:When volume is used to arrive at the total blood volume, a dye (usually T-1824, also known as Evans blue) is injected into the circulating blood. The dye immediately combines with the blood proteins and within 10 minutes is dispersed throughout the circulatory system. A sample of blood is then drawn and the exact quantity of dye is measured. Using the information about plasma volume obtained by applying the above formula, the total blood volume can be calculated, provided the hematocrit is also known. The formula for this calculation is:whole blood that from which none of the elements has been removed, sometimes specifically that drawn from a selected donor under aseptic conditions, containing citrate ion or heparin, and used as a blood replenisher.
pressure (P) [presh´ur] force per unit area.arterial pressure (arterial blood pressure) blood pressure (def. 2).atmospheric pressure the pressure exerted by the atmosphere, usually considered as the downward pressure of air onto a unit of area of the earth's surface; the unit of pressure at sea level is one atmosphere. Pressure decreases with increasing altitude.barometric pressure atmospheric p.blood pressure 1. see blood pressure.2. pressure of blood on walls of any blood vessel.capillary pressure the blood pressure in the capillaries.central venous pressure see central venous pressure.cerebral perfusion pressure the mean arterial pressure minus the intracranial pressure; a measure of the adequacy of cerebral blood flow.cerebrospinal pressure the pressure of the cerebrospinal fluid, normally 100 to 150 mm Hg.continuous positive airway pressure see continuous positive airway pressure.filling pressure see pressure" >mean circulatory filling pressure.high blood pressure hypertension.intracranial pressure see intracranial pressure.intraocular pressure the pressure exerted against the outer coats by the contents of the eyeball.intrapleural pressure (intrathoracic pressure) pleural pressure.intrinsic positive end-expiratory pressure elevated pressure" >positive end-expiratory pressure and dynamic pulmonary hyperinflation caused by insufficient expiratory time or a limitation on expiratory flow. It cannot be routinely measured by a ventilator's pressure monitoring system but is measurable only using an expiratory hold maneuver done by the clinician. Its presence increases the work needed to trigger the ventilator, causes errors in the calculation of pulmonary compliance, may cause hemodynamic compromise, and complicates interpretation of hemodynamic measurements. Called also auto-PEEP and intrinsic PEEP.maximal expiratory pressure maximum expiratory pressure.maximal inspiratory pressure the pressure during inhalation against a completely occluded airway; used to evaluate inspiratory respiratory muscle strength and readiness for weaning from mechanical ventilation. A maximum inspiratory pressure above −25 cm H2O is associated with successful weaning.maximum expiratory pressure (MEP) a measure of the strength of respiratory muscles, obtained by having the patient exhale as strongly as possible against a mouthpiece; the maximum value is near capacity" >total lung capacity.maximum inspiratory pressure (MIP) the inspiratory pressure generated against a completely occluded airway; used to evaluate inspiratory respiratory muscle strength and readiness for weaning from mechanical ventilation. A maximum inspiratory pressure above −25 cm H2O is associated with successful weaning.mean airway pressure the average pressure generated during the respiratory cycle.mean circulatory filling pressure a measure of the average (arterial and venous) pressure necessary to cause filling of the circulation with blood; it varies with blood volume and is directly proportional to the rate of venous return and thus to cardiac output.negative pressure pressure less than that of the atmosphere.oncotic pressure the osmotic pressure of a colloid in solution.osmotic pressure the pressure required to stop osmosis through a semipermeable membrane between a solution and pure solvent; it is proportional to the osmolality of the solution. Symbol π.partial pressure the pressure exerted by each of the constituents of a mixture of gases.peak pressure in mechanical ventilation, the highest pressure that occurs during inhalation.plateau pressure in mechanical ventilation, the pressure measured at the proximal airway during an end-inspiratory pause; a reflection of alveolar pressure.pleural pressure the pressure between the visceral pleura and the thoracic pleura in the pleural cavity. Called also intrapleural or intrathoracic pressure.positive pressure pressure greater than that of the atmosphere.positive end-expiratory pressure (PEEP) a method of control mode ventilation in which positive pressure is maintained during expiration to increase the volume of gas remaining in the lungs at the end of expiration, thus reducing the shunting of blood through the lungs and improving gas exchange. A PEEP higher than the critical closing pressure prevents alveolar collapse and can markedly improve the arterial Po2 in patients with a lowered functional residual capacity, as in acute respiratory failure.Effects of the application of positive end-expiratory pressure (PEEP) on the alveoli. A, Atelectatic alveoli before PEEP application. B, Optimal PEEP application has reinflated alveoli to normal volume. C, Excessive PEEP application overdistends the alveoli and compresses adjacent pulmonary capillaries, creating dead space with its attendant hypercapnia. From Pierce, 1995.pulmonary artery wedge pressure (PAWP) (pulmonary capillary wedge pressure (PCWP)) intravascular pressure, reflecting the left ventricular end diastolic pressure, measured by a swan-ganz catheter wedged into a small pulmonary artery to block the flow from behind.pulse pressure the difference between the systolic and diastolic pressures. If the systolic pressure is 120 mm Hg and the diastolic pressure is 80 mm Hg, the pulse pressure is 40 mm Hg; the normal pulse pressure is between 30 and 40 mm Hg.urethral pressure the pressure inwards exerted by the walls of the urethra, which must be counteracted in order for urine to flow through; see also profile" >urethral pressure profile.venous pressure the blood pressure in the veins; see also central venous pressure" >central venous pressure.water vapor pressure the tension exerted by water vapor molecules, 47 mm Hg at normal body temperature.wedge pressure blood pressure measured by a small catheter wedged into a vessel, occluding it; see also pulmonary capillary wedge pressure and wedged hepatic vein pressure.wedged hepatic vein pressure the venous pressure measured with a catheter wedged into the hepatic vein. The difference between wedged and free hepatic vein pressures is used to locate the site of obstruction in portal hypertension; it is elevated in that due to cirrhosis, but low in cardiac ascites or portal vein thrombosis.blood pres·sure (BP), the pressure or tension of the blood within the systemic arteries, maintained by the contraction of the left ventricle, the resistance of the arterioles and capillaries, the elasticity of the arterial walls, as well as the viscosity and volume of the blood; expressed as relative to the ambient atmospheric pressure. Synonym(s): piesisblood pressuren. Abbr. BP The pressure exerted by the blood against the walls of the blood vessels, especially the arteries. It varies with the strength of the heartbeat, the elasticity of the arterial walls, the volume and viscosity of the blood, and a person's health, age, and physical condition.blood pressure The force that blood in the circulation exerts on arterial walls, 2º to myocardial contraction, in response to various demands (e.g., exercise, stress, sleep), which is divided into systolic (due to heart contractions) and diastolic (relaxation phases). Blood pressure (BP) varies with age and sex. Standard level for normal systolic BP Adults—BP = 100 + age; Children—BP = 2 x age + 80. Standard level for normal diastolic BP ± 2/3 of above. Normal BP 120/80 mm Hg.blood pressure Cardiology The force that blood in the circulation exerts on arterial walls, 2º to myocardial contraction in response to various demands–eg, exercise, stress, sleep, which is divided into systolic–due to heart contractions and diastolic–relaxation phases; BP varies with age and sex Rule of thumb for normal systolic BP–Adults BP = 100 + age; Children BP = 2 x age + 80; Diastolic BP should be ±2/3 Normal BP 120/80 mm Hg. See Hypertension, Hypotension, Sphygmomanometer–blood pressure cuff. blood pres·sure (BP) (blŭd presh'ŭr) The pressure or tension of the blood within the systemic arteries, maintained by the contraction of the left ventricle, the resistance of the arterioles and capillaries, the elasticity of the arterial walls, as well as the viscosity and volume of the blood; expressed as relative to the ambient atmospheric pressure.blood pressure, BPBLOOD PRESSURE: Relationship of blood pressure to changes in cuff pressure and the first and fifth Korotkoff sounds (BP 120/80)The tension exerted on the walls of arteries by: the strength of the contraction of the heart; the resistance of arterioles and capillaries; the elasticity of blood vessels; the blood volume; and blood viscosity. Normal blood pressure is defined as a systolic BP between 100 and 120 mm Hg and a diastolic BP below 80 mm Hg (in adults over age 18). Prehypertension is present when measured blood pressures are between 120 and 140 mm Hg systolic or between 80 and 90 mm Hg diastolic. When either the systolic pressure exceeds 140 mm Hg or the diastolic exceeds 90 mm Hg, and these values are confirmed on two additional visits, stage I hypertension (high blood pressure) is present. See: illustration Low blood pressure is sometimes present in healthy individuals, but it indicates shock in patients with fever, active bleeding, allergic reactions, active heart disease, spinal cord injuries, or trauma. Blood pressure should be checked routinely whenever a patient sees a health care provider because controlling abnormally high blood pressure effectively prevents damage to the heart and circulatory system as well as the kidneys, retina, brain, and other organs. Patient careElevated blood pressures should first be addressed by giving advice to patients about lifestyle modifications, such as limiting the intake of alcohol, following a diet approved by the American Heart Association, and increasing the level of physical exercise. Weight loss in obese patients is also advisable. Medications are added to lifestyle instructions most of the time. Antihypertensive medications are used according to evidence-based guidelines and the side effects these drugs may cause in particular patients. Diuretics, for example, are esp. helpful in blacks and elderly patients (but may be inadvisable in patients with gout); beta blockers are the drugs of choice in patients with a history of myocardial infarction (but would be contraindicated in patients with advanced heart block); alpha blockers are well suited for men with prostatic hypertrophy; and angiotensin-converting enzyme inhibitors prevent kidney disease in patients with diabetes mellitus. Other antihypertensive drug classes include the angiotensin II receptor antagonists, centrally active alpha antagonists, and calcium channel blockers. Low blood pressure is not treated in healthy patients; in patients with acute illnesses, it is often corrected with hydration or pressor agents. augmented diastolic blood pressureAn increase in diastolic pressure, usually by an artificial device, such as an intra-aortic balloon pump. See: intra-aortic balloon counterpulsationcentral blood pressureBlood pressure in the heart chambers, in a great vein, or close to the heart. If determined in a vein, it is termed central venous pressure; if in the aorta or a similar large artery close to the heart, it is designated central arterial pressure. chronic low blood pressureA condition in which the systolic blood pressure is consistently less than 100 mm Hg. In the absence of associated disease, low blood pressure is often a predictor of longevity and continued health. See: hypotension; orthostatic hypotensiondiastolic blood pressureThe blood pressure when the ventricles of the heart are filling with blood. In health this equals about 60 to 80 mm Hg. direct measurement of blood pressureDetermination of the blood pressure within the lumen of an artery or within a chamber of the heart with a catheter introduced into the organ and attached to a pressure-monitoring transducer. It is done by placing a sterile needle or small catheter inside an artery and having the blood pressure transmitted through that system to a suitable recorder. As the blood pressure fluctuates, the changes are recorded graphically. high blood pressureHypertension.indirect measurement of blood pressureA simple external method for measuring blood pressure. Palpation method: The same arm, usually the right, should be used each time the pressure is measured. The arm should be raised to heart level if the patient is sitting, or kept parallel to the body if the patient is recumbent. The patient's arm should be relaxed and supported in a resting position. Exertion during the examination could result in a higher blood pressure reading. Either a mercury-gravity or aneroid-manometer type of blood pressure apparatus may be used. The blood compression cuff should be the width and length appropriate for the size of the subject's arm: narrow (2.5 to 6 cm) for infants and children and wide (13 cm) for adults. The inflatable bag encased in the cuff should be 20% wider than one third the circumference of the limb used. The deflated cuff is placed evenly and snugly around the upper arm so that its lower edge is about 1 in above the point of the brachial artery where the bell of the electronic sensor will be applied. While feeling the radial pulse, inflate the cuff until the pressure is about 30 mm above the point where the radial pulse was no longer felt. Deflate the cuff slowly and record as accurately as possible the pressure at which the pulse returns to the radial artery. Systolic blood pressure is determined by this method; diastolic blood pressure cannot be determined by this method. This method is used for both continuous and intermittent readings, and while it formerly was used primarily in ICUs, it now is used routinely by nursing assistants on units throughout health care agencies and in clinics and physicians' offices. Measuring blood pressure at the wrist is more comfortable than a conventional BP cuff because it derives readings without pumping a bladder full of air, and with accuracy rivaling direct measurement from an arterial catheter. The sensor is placed directly over the radial artery and connected to an electronic monitor. Pressure is monitored every 15 heartbeats and systolic, diastolic, mean arterial pressure, waveforms, and pulse rate are displayed. The first reading appears in 15 seconds, and the sensor measures pressures from 40 to 240 mm Hg, with preset alarms to alert the nurse to extreme highs and lows. Results are not affected by low cardiac output, arrhythmias, hypothermia, or obesity, and this method is being used increasingly on adults in hospital special care units where frequent serial readings are required. Auscultatory method: Begin as above. After inflating the cuff until the pressure is about 30 mm above the point where the radial pulse disappears, place the bell of the stethoscope over the brachial artery just below the blood pressure cuff. Then deflate the cuff slowly, about 2 to 3 mm Hg per heartbeat. The first sound heard from the artery is recorded as the systolic pressure. The point at which sounds are no longer heard is recorded as the diastolic pressure. For convenience the blood pressure is recorded as figures separated by a slash. The systolic value is recorded first. Sounds heard over the brachial artery change in quality at some point prior to the point the sounds disappear. Some physicians consider this the diastolic pressure. This value should be noted when recording the blood pressure by placing it between the systolic pressure and the pressure noted when the sound disappears. Thus, 120/90/80 indicates a systolic pressure of 120 with a first diastolic sound change at a pressure of 90 and a final diastolic pressure of 80. The latter pressure is the point of disappearance of all sounds from the artery. When the values are so recorded, the physician may use either of the last two figures as the diastolic pressure. When the change in sound and the disappearance of all sound coincide, the result should be written as follows: 120/80/80. mean blood pressureThe sum of twice the diastolic blood pressure plus the systolic blood pressure, all divided by 3.negative blood pressureBlood pressure that is less than atmospheric pressure, as in the great veins near the heart.normal blood pressureA blood pressure between 100 and 120 mm Hg systolic and < 80 mm Hg diastolic.systolic blood pressureBlood pressure during contraction of the ventricles. It is normally 100 to 120 mm Hg. Higher systolic blood pressures are found in prehypertension and hypertension. Synonym: systolic pressureblood pressure The pressure exerted on the artery walls and derived from the force of the contraction of the lower chambers of the heart (the VENTRICLES). Blood pressure changes constantly. Peak pressure is called the systolic pressure and the running pressure between beats is called the diastolic pressure. Blood pressure in measured in millimetres of mercury. A typical normal reading is 120/80. See also HYPERTENSION and KOROTKOFF SOUNDS.Fig. 74 Blood pressure . The variation of blood pressure in different vessels. blood pressure the force exerted by blood against the walls of the blood vessels, caused by heart contractions forcing a constant volume of blood round a closed system. Strong contraction of the left ventricle (SYSTOLE) ejects blood at high pressure into the AORTA, stretching the arterial walls. When the heart relaxes (DIASTOLE), force is no longer exerted on the arterial blood so pressure drops, although maintenance of pressure is helped by elastic recoil of the arterial walls. These oscillations of blood pressure are largest in the aorta, gradually diminishing as the blood flows along the arteries, becoming nonexistent in the CAPILLARIES. The level of blood pressure also decreases from heart to tissue and back to the heart, these differences in pressure enabling the flow of blood around the system. Blood in the veins is prevented from moving backwards by the presence of one-way valves. Venous circulation is also enhanced by activity of the skeletal muscles, hence leg and arm movements aid blood flow back to the heart. Note that, although the comments above refer to the systemic circulation, a similar situation also applies in the smaller pulmonary system of mammals (see BLOOD CIRCULATORY SYSTEM). Several factors control the exact level of blood pressure: - heart action (rate of heartbeat, force per beat, volume per beat);
- peripheral resistance to blood flow in the capillary beds, caused by friction;
- elasticity of arteries;
- total blood volume (the higher the volume the higher the pressure);
- viscosity of blood (an increase in viscosity causes an increase in blood pressure but a decrease in flow rate).
sphygmomanometer An instrument for measuring the arterial blood pressure. There are various types, the most common consisting of an inflatable cuff that is placed around the upper arm (usually the left) and air pressure within the cuff is balanced against the pressure of the blood in the brachial artery. The pressure is estimated by means of a mercury or an aneroid manometer. A stethoscope is normally used in conjunction with the instrument to listen to the blood pressure sounds (a stethoscope is not needed with an electronic sphygmomanometer). Normal systolic and diastolic blood pressures in a young adult are about 120/80, respectively. The difference between the two pressures is called the pulse pressure. Blood pressure varies with age, gender, altitude, disease, stress, fear, excitement, exercise, etc. A normal range for systolic pressure is usually considered to be 100-140 mmHg and for diastolic pressure below 90 mmHg. See arteriosclerosis; hypertension; hypertensive retinopathy.blood pres·sure(BP) (blŭd presh'ŭr) Pressure or tension of the blood within the systemic arteries, maintained by the contraction of the left ventricle, the resistance of the arterioles and capillaries, the elasticity of the arterial walls, as well as the viscosity and volume of the blood; expressed as relative to the ambient atmospheric pressure. Patient discussion about blood pressureQ. how can i reduce my blood pressure? A. The main steps in lowering high blood pressure is to take some very important changes in lifestyle- consuming much less salt in food, losing weight and exercising regulary. If this doesn't help (and usually it doesn't help mainly when people don't try hard enought and make an effort), medications can be added to control the blood pressure. Q. what do i need to do to bring down my blood pressure? what cause a high blood pressure? what are the risks? of high blood pressure ? how can i deal with it effectively ?A. here are two really good sites that show you specifics: http://www.lifeclinic.com/focus/blood/loweringit.asp http://www.ehow.com/how_12778_eat-lower-blood.html?ref=fuel&utm_source=yahoo&utm_medium=ssp&utm_campaign=yssp_art Hope this helps. Q. What Are the Complications of High Blood Pressure? My wife suffers from high blood pressure. What are the possible complications that are so dangerous? Why is it important to keep high blood pressure under balance?A. While elevated blood pressure alone is not an illness, it often requires treatment due to its short and long-term effects on many organs. The risk is increased for: Cerebrovascular accident (CVAs or strokes), myocardial infarction (heart attack), hypertensive cardiomyopathy (heart failure due to chronically high blood pressure),hypertensive retinopathy - damage to the retina, hypertensive nephropathy- chronic renal failure due to chronically high blood pressure and hypertensive encephalopathy- confusion, headache and convulsions due to edema in brain that can lead to death. Therefore, it is considered very important to reduce blood pressure to normal levels with strict medical supervision.
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Words related to blood pressurenoun the pressure of the circulating blood against the walls of the blood vesselsRelated Words- systolic pressure
- diastolic pressure
- arterial pressure
- venous pressure
- circulation
- force per unit area
- pressure
- pressure level
- vital sign
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