Diagnosis and Classification of Hypertension / Measurement of Blood Pressure

Hypertension is one of the most common medical conditions encountered by nurses during their professional lives and measurement of blood pressure is one of the most frequently utilized nursing practice skills that are taught to nursing students in nursing schools. Nursing board examinations will always contain questions related to diagnosis and management of hypertension (in relation to evidence based practice). Moreover, in health care facilities, clinical assessment of almost every patient should include measurement of blood pressure to establish or rule out the diagnosis of hypertension. Therefore, it is a good idea to learn a great deal about hypertension to ensure the delivery of optimum care to hypertensive patients. Blood pressure is defined as the pressure exerted by a column of blood on the walls of blood vessels. Blood pressure differs in different blood vessels (arteries, capillaries and veins); therefore, it should be understood that the term blood pressure refers to the arterial blood pressure which fluctuates during systole and diastole.​ ​ Systolic Blood Pressure is the highest level of blood pressure produced during a cardiac cycle and it is dependent upon cardiac output. Diastolic Pressure on the other hand is dependent upon peripheral resistance and it refers to the minimum pressure that remains in the blood vessels during a cardiac cycle. The difference between systolic and diastolic blood pressures is termed Pulse Pressure, which is considered to be the driving force behind the pulsatile nature of blood flow in blood vessels. The force that assists in moving the blood in forward direction is known as Mean Arterial Pressure; this is the average pressure that ensues during a cardiac cycle. Calculation of Mean Arterial Pressure is done using the following formula: 1/3 * Pulse Pressure + Diastolic Blood Pressure = Mean Arterial Pressure Some Physiological facts about Blood Pressure - Blood pressure demonstrates an increasing trend with age: Children (Systolic 90-120 mmHg; Diastolic 50-80 mmHg) Adults (Systolic 100-140 mmHg; Diastolic 60-90 mmHg) Elderly (Systolic up to 160 mmHg; Diastolic below 90 mmHg) - Females have comparatively lower blood pressures due to the action of progesterone that relaxes vascular smooth muscles. - Pregnancy increases systolic pressure (increased cardiac output due to increased blood volume) but tends to lower the diastolic pressure (decreased peripheral resistance due to progesterone). - Blood pressure tends to decrease in warm environment and vice versa. - Blood pressure is lower during sleep as compared to the alert state. - Excitement or sympathetic stimulation may elevate blood pressure. The same is true about exercise. - Posture can affect the blood pressure. - Blood pressure rises after food intake. Defining Hypertension Hypertension is a medical condition in which the blood pressure of an individual remains persistently above the normal level. The following information/terminology is essential in this regard; - Blood pressure = cardiac output * vascular resistance - Primary or Essential Hypertension – consistently high blood pressure due to an unknown cause/disease. - Secondary Hypertension – high blood pressure that is due to an ongoing disease condition. - Isolated Systolic Hypertension – Common among elderly individuals (systolic pressure ≥ 140 mmHg but diastolic pressure below 90 mmHg). - Hypertensive Emergency = Diastolic pressure >130 mmHg & Systolic pressure >200 mmHg. - White Coat Hypertension – white coat is a hallmark of medical environment. People who tend to demonstrate high blood pressures in such environments are said to have white coat hypertension. Measurement of Blood Pressure & Diagnosis of Hypertension Before attempting to record blood pressure, the following conditions should be met; - The subject should be allowed to sit comfortably for a few minutes. This will ensure that the subject becomes mentally and physically relaxed. - Clothing from the upper arm should be removed to prevent constriction of blood vessels. - The ‘cuff’, ‘zero of the sphygmomanometer’ and the ‘heart’ should all be at the same level. - Smoking during the preceding 30 minutes may affect the reading. So, make sure the subject has not smoked during this interval. - Caffeine intake may affect the reading; therefore make sure an hour has passed if the subject reports taking caffeine. - The subject should be told to avoid talking during the process. The cuff should then be wrapped around middle of the arm, to make sure the cuff lies over the brachial artery. Radial artery can be palpated to check for pulse. Inflation of the cuff will compress the brachial artery; hence radial pulse will vanish when the pressure in the cuff exceeds the pressure in the brachial artery. The cuff should be inflated about 30 mmHg further; before it is allowed to deflate slowly. The rate of fall of mercury column should not exceed 2 mmHg / heart-beat. The diaphragm of stethoscope should be placed over the brachial artery to hear its pulsation. The first audible sound corresponds to systolic pressure and the last sound to diastolic pressure, respectively. Additional readings should be taken to estimate the average diastolic and systolic pressures if arrhythmia is present. However, a gap of at least 1 minute should be present between two consecutive readings. The following table may be used for classification of hypertension. Category Systolic (mmHg) Diastolic (mmHg) Optimal <120 <80 Normal 120-129 80-84 High Normal 130-139 85-89 Grade 1 Hypertension (Mild) 140-159 90-99 Grade 2 Hypertension (Moderate) 160-179 100-109 Grade 3 Hypertension (Severe) ≥ 180 ≥ 110 Isolated Systolic Hypertension >140 <90 [ European Society of Hypertension (ESH) & European Society of Cardiology (ESC) Guidelines – (2003-2007) ]


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