Blood Pressure Measurement in Clinical Practice

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Blood Pressure Measurement in Clinical Practice

The aim of this assignment is to discuss ‘the knowledge that underpins an aspect of measurement of nursing care in nursing’, with particular reference to practice experience.  For this purpose, the subject of blood pressure measurement will be examined.  Blood pressure is a process vital to homeostasis, and the efficient operation of a number of fundamental functions within the body.  The two main purposes blood pressure serves, is the circulation of blood flow throughout the body and vital organs such as the brain and coronary arteries, and the perfusion of tissues with blood in order to supply nutrients and remove waste products (Hinchliff, Norman and Schober, 1998).  

Consequently, blood pressure measurement is an important observation that is commonly used in a clinical setting, to aid the diagnosis, treatment and prevention of a number of cardiovascular and related disorders.  Measuring the blood pressure helps to assess the efficiency of the circulatory system.  The importance of these measurements lies in the fact that recent figures show 14% of deaths from coronary heart disease in men, and 12% of such deaths in women are associated to raised blood pressure (National Heart Forum, 2002).  

To effectively monitor blood pressure, it is first necessary to understand the basic physiological principles that regulate such a function.  Blood pressure may be defined as the force applied by blood flow, on the resisting walls of blood vessels.  This pressure varies within different areas of the circulatory system, with pressure being highest in the aorta, and gradually decreasing as blood is pumped on through the large arteries, small arteries, arterioles, capillaries and eventually the veins (Walsh, 1999).

Blood pressure is expressed as two numbers, e.g. 140/80.  This is due to the fact that there are two phases within a single heart beat.  Systolic pressure is the highest arterial blood pressure of a cardiac cycle, and occurs during the period when the left ventricle of the heart contracts, and blood is pumped out of the heart.  Diastolic pressure occurs in the period between two contractions, when the chambers of the heart widen, and fill with blood.  The difference between these pressures is called the pulse pressure.

Historically, blood pressure has been measured in millimetres of mercury (mmHg), using a sphygmomanometer and stethoscope.  Although electronic devices are more widely available now, they are more expensive, and require frequent calibration.  Therefore, sphygmomanometers are still the most common apparatus used for blood pressure measurement in more general clinical settings.  The sphygmomanometer is an instrument used to measure arterial blood pressure.  The most common type is that pioneered by the Italian Scipione Riva-Rocci in 1896 (O’Brien and Fitzgerald, 1994).  

It consists of a rubber cuff fastened around the upper arm and attached to a manometer, which is a device used to measure the pressure of a gas or liquid.  The pressure is usually measured using a mercury gauge, which measures the pressure by way of liquid mercury within a column calibrated in millimetres (Lewis and Kuhn, 1994), although aneroid gauges are also sometimes used.

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The actual technique used in the measurement of blood pressure can often present several potential sources of error (Watson 1997).  For example, measurement using a sphygmomanometer is a subjective, and can in itself be subject to error.  The British Hypertension Society has established guidelines on the routine reading of blood pressure measurement, which will be summarized subsequently.  By following these guidelines, at least some of these sources can be excluded.  There are a number of additional factors that can also contribute to inaccurate measurements, and these will be discussed later.

In order to maintain accurate blood pressure measurements, ...

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