Chapter 70

### Blood Pressure Classification

The classification of blood pressure, described in the Seventh Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure (JNC 7) published in 2003,1 places patients into one of four categories (Table 70–1). Most notable is the designation of prehypertension, which combines what had previously been classified as normal and high-normal blood pressure. The basis for this reclassification was the recognition of the strong correlation between adverse outcomes and blood pressure levels, including levels previously considered normal. In addition, those with prehypertension were known to be at high risk to progress to hypertension. This new classification was aimed to identify individuals early in the progression of disease, at a time when lifestyle modifications could slow the progression or prevent the development of hypertension entirely.

Table 70–1. JNC 7 Classification of Blood Pressure for Adults

Since the JNC 7 publication, other published guidelines have generally retained the categories of stage 3 hypertension (systolic ≥180 mm Hg or diastolic ≥110 mm Hg) and isolated systolic hypertension.2-7 Although the European Society of Hypertension and the European Society of Cardiology recognized the potential value of the prehypertensive category, they expressed concern that the lay public's perception of the term would limit the adoption of this classification.2 In addition, they recommended thresholds for hypertension based on individual cardiovascular risk.

### Blood Pressure Measurement

To apply the previously mentioned classifications in clinical practice, blood pressure must be recorded accurately. However, measurement of blood pressure, although one of the most important measurements in clinical medicine, is also one of the measurements with the greatest source of error. Blood pressure can be measured intra-arterially by insertion of a catheter into the lumen of an artery, but this method is impractical and is rarely used in clinical examination, except in intensive care units. The gold standard for clinical measurement of blood pressure is readings taken by a trained health care provider using a mercury sphygmomanometer. Aneroid and automated sphygmomanometers have increased in popularity over recent years. When used as a substitute for a mercury sphygmomanometer, a protocol for regular periodic calibration of the device should be in place.1,8 Regardless of the device used, it is important to appreciate that blood pressure is a variable hemodynamic phenomenon that is influenced by many factors. Therefore, the circumstances and procedures for ...

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