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Blood Pressure Tips

Blood Pressure Tips

Blood pressure is the pressure exerted by the blood on the wallsof the Blood Pressurebloodvessels. Unless indicated otherwise, blood pressure is understood tomean arterial blood pressure, i.e. the pressure in the large arteries,such as the brachial artery (in the arm). The pressure of the bloodin other vessels is lower than the arterial pressure.

The peak pressure in the arteries during the cardiac cycle is the systolicpressure, and the lowest pressure (at the resting phase of the cardiaccycle) is the diastolic pressure. Typical values for the arterial bloodpressure of a resting, healthy adult are approximately 120 mmHg systolicand 80 mmHg diastolic (written as 120/80 mmHg), with large individualvariations.

Last Updated - 24th November 2005

Blood pressure is not static, but undergoes natural variations fromone heartbeat to another or in a circadian rhythm; it also changes inresponse to stress, nutritional factors, drugs, or disease.

Measurement

Blood pressure is most accurately measured invasively by placing acannula into a blood vessel and connecting it to a electronic pressuretransducer. This invasive technique is regularly employed in intensivecare medicine, anesthesiology, and for research purposes, but it isassociated with complications such as thrombosis, infection, and bleeding.Therefore, the less accurate techniques of manual or oscillometric measurementpredominate in routine examinations.

Most often, arterial blood pressure is measured manually using a sphygmomanometer.This is an inflatable cuff placed around the upper arm, at roughly thesame vertical height as the heart in a sitting person, attached to amanometer. The cuff is inflated until the artery is completely occluded.Listening with a stethoscope to the brachial artery at the elbow, theexaminer slowly releases the pressure in the cuff. When blood flow barelybegins again in the artery, a "whooshing" or pounding sound(first Korotkoff sound) is heard. The pressure is noted at which thissound began. This is the systolic blood pressure. The cuff pressureis further released until no sound can be heard (fifth Korotkoff sound).This is the diastolic blood pressure.

Oscillometric methods are used in long-term measurement as well asin clinical practice. Oscillometric measurement (also termed NIPB =Non-Invasive Blood Pressure) is incorporated in many bedside patientmonitors. It relies on a cuff similar to that of a sphygmomanometer,which is connected to an electric pump and a pressure transducer. Thecuff is placed on the upper arm and is automatically inflated. Whenpressure is gradually released, the small oscillations in cuff pressurethat are caused by the cyclic expansion of the brachial artery are recordedand used to calculate systolic and diastolic pressures.

Values are usually given in millimetres of mercury (mmHg). Normal rangesfor blood pressure in adult humans are:

Systolic between 90 and 135 mmHg (12 to 18 kPa)
Diastolic between 50 and 90 mmHg (7 to 12 kPa)

In children the observed normal ranges are lower; in the elderly, theyare more often higher. Clinical trials demonstrate that people who maintainblood pressures in low end of these pressure ranges have much betterlong term cardiovascular health and are considered optimal. The principalmedical debate is the aggressiveness and relative value of methods usedto lower pressures into this range for those who don't maintain suchpressure on their own. Elevations, more commonly seen in older people,though often considered normal, are associated with increased morbidityand mortality. The clear trend from double blind clinical trials (forthe better strategies and agents) has increasingly been that lower endsup being demonstrated to result in less disease/better outcomes longterm.

Physiology

The mean blood pressure in the arteries supplying the body is a resultof the heart pumping blood from the veins back into the arteries.

The mean blood pressure value is determined by the volume of bloodthe heart is pumping per minute, termed cardiac output, versus the resistanceof the 20,000 to 30,000 arterioles, termed total peripheral resistance,through which the blood must flow to reach the capillaries and thenveins.

The up and down fluctuation of the arterial blood pressure resultsfrom the pulsatile nature of the cardiac output. The pulse pressureis determined by the interaction of the stroke volume versus the volumeand elasticity of the major arteries.

The larger arteries, including all large enough to see without magnification,are low resistance (assuming no advanced atherosclerotic changes) andconduit vessels with high flow rates but producing very little pressuredrop. For instance, about 5 mmHg mean pressure decrease in the bloodflow traveling from the heart all the way to the toes is typical, assumingthe individual is supine (horizontal with respect to gravity).

Pathophysiology

If the blood pressure exceeds these normal values, one speaks of arterialhypertension. Blood pressure that is too low is known as hypotension.The former is rarely an acute problem, while the latter may be a signof severe disease and requires more urgent medical attention.

Any level of blood pressure puts mechanical stress on the arterialwalls. The higher the pressure, the more stress that is present andthe more atheroma tend to progress. Veins, when used as surgical bypasses,typically develop atheroma much more rapidly than arteries in the sameindividual.

When blood pressure and blood flow is very low, the perfusion of thebrain may be critically decreased (i.e. the blood supply is not sufficient),causing lightheadedness, weakness and fainting. Sometimes the bloodpressure drops significantly when a patient stands up from sitting.This is known as orthostatic hypotension. Other causes of low bloodpressure include:

If there is a significant difference in the pressure from one arm tothe other, that may indicate a narrowing (e.g. due to aortic coarctation,aortic dissection, thrombosis or embolism) of an artery.

Venous pressure

Venous pressure is the blood pressure in a vein. It is much less thanarterial blood pressure. e.g. typically about 5 mmHg in the right atrium,8 mmHg in the left atrium. Measurement of pressures in the venous systemand the pulmonary vessels plays an important role in intensive caremedicine but requires invasive techniques.

Arterial hypertension Or High Blood Pressure

Arterial hypertension, or high blood pressure is a medical conditionwhere the blood pressure is chronically elevated. Persistent hypertensionis one of the risk factors for strokes, heart attacks and heart failure,and is a leading cause of chronic renal failure.

In patients with diabetes mellitus or kidney disease studies have shownthat blood pressure over 130/80 mmHg should be considered a risk factorand may warrant treatment.

Etiology - Essential hypertension

In essential hypertension

Pathophysiology

The mechanisms behind the factors associated with inessential hypertensionare generally fully understood, and are outlined below. However, thoseassociated with essential hypertension are far less understood. Whatis known is that cardiac output is raised early in the disease course,with total peripheral resistance normal; over time cardiac output dropsto normal levels but TPR is increased. Three theories have been proposedto explain this:

Inessential hypertension

Signs and symptoms

Hypertension - Hypertension isusually found incidentally - "case finding" by healthcareprofessionals. It normally produces no symptoms.

Malignant hypertension (or accelerated hypertension) is distinct asa late phase in the condition, and may present with headaches, blurredvision and end-organ damage.

It is recognised that stressful situations can increase the blood pressure;if a normally normotensive patient has a high blood pressure only whenbeing reviewed by a health care professional, this is colloquially termedwhite coat effect. Since most of what we know of hypertension and itsoutcome with or without modification is based on large series of readingsin doctors' offices and clinics (eg Framingham) it is difficult to besure of the significance of white-coat hypertension. Ambulatory monitoringmay help determine whether traffic and ticket inspectors produce similarsustained rises.

Hypertension is often confused with mental tension, stress and anxiety.While chronic anxiety is associated with poor outcomes in people withhypertension, it alone does not cause it.

Hypertensive urgencies and emergencies - Hypertension is rarely severe enough to cause symptoms. These onlysurface with a systolic blood pressure over 240 mmHg and/or a diastolicblood pressure over 120 mmHg. These pressures without signs of end-organdamage (such as renal failure) are termed accelerated hypertension.When end-organ damage is present, but in absence of raised intracranialpressure, it is called hypertensive urgency. Hypertension under thiscircumstance needs to be controlled, but hospitalization is not required.When hypertension causes increased intracranial pressure, it is calledmalignant hypertension. Increased intracranial pressure causes papilledema,which is visible on ophthalmoscopic examination of the retina.

Complications - While elevatedblood pressure alone is not an illness, it often requires treatmentdue to its short- and long-term effects on many organs. The risk isincreased for:

Pregnancy - Although few womenof childbearing age have high blood pressure, up to 10% develop hypertensionof pregnancy. While generally benign, it may herald three complicationsof pregnancy: pre-eclampsia, HELLP syndrome and eclampsia. Follow-upand control with medication is therefore often necessary.

Diagnosis

The diagnosis of hypertension is by definition made by three separatemeasurements at least one week apart. Two caveats to this criteria isit must be in the presence mild elevations and in the absence of endorgan damage. If either are not met, the diagnosis may be made withoutrepeat measurements in some cases.

Obtaining reliable blood pressure measurements relies on followingseveral rules and being cognizant of the many factors that influenceblood pressure reading.

For instance, measurements should be at least 1 hour after caffeine,30 minutes after smoking and without any stress. Cuff size is also important.The bladder should encircle and cover two-thirds of the length of thearm. The patient should be sitting for a minimum of five minutes. Thepatient should not be on any adrenergic stimulants, such as those foundin many cold medications.

When taking manual measurements, the person taking the measurementshould be careful to inflate the cuff at least 30 mmHg greater thansystolic pressure. A stethoscope should be placed lightly over the brachialartery. The arm should be at the level of the heart and the cuff shouldbe deflated at a rate of 2-3 mmHg/sec. Systolic pressure is the pressurereading at the onset of sounds. Diastolic pressure is then defined asthe pressure at which the sounds disappear. Two measurements shouldbe made at least 5 minutes apart and if there is a discrepancy of morethan 5 mmHg, a third reading should be done. The readings should thenbe averaged. An initial measurement should include both arms. Also,in elderly patients, it is recommended to measure pressures in multiplepostures as they are at risk for orthostatic hypotension.

Once the diagnosis of hypertension has been made it is important toattempt to identify reversible (secondary) causes. In the adult populationover 90% of all hypertension has no known cause and is therefore called"essential/primary hypertension". Often, it is part of themetabolic "syndrome X" in patients with insulin resistance:it occurs in combination with diabetes mellitus (type 2), combined hyperlipidemiaand central obesity. However, in the pediatric population the oppositeis true, most cases have a secondary cause and these should be pursuedmore aggresively.

Important causes of secondary hypertensionare:

Blood tests commonly performed in a newly diagnosed hypertension patientare:

Risk Factors

Prevention

When To Call A Physician


Disclaimer: The Blood Pressure Tips / Informationpresented and opinions expressed herein are those of the authors anddo not necessarily represent the views of TipsAndTreats.com and/orits partners.

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