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Blood pressure is a fundamental vital sign that guides acute and long-term clinical decision-making. Given its central role in directing care, accurate, consistent measurement of blood pressure is essential. Two primary values are recorded during blood pressure assessment. Systolic blood pressure (SBP) reflects the peak arterial pressure during ventricular systole, while diastolic blood pressure (DBP) represents the lowest arterial pressure during ventricular diastole. A third parameter, mean arterial pressure (MAP), can be derived from SBP and DBP and approximates the average arterial pressure throughout the cardiac cycle. Blood pressure is calculated using the following formula: MAP = (SBP + 2 x DBP) / 3

The most common source of error in blood pressure measurement is failure to follow proper technique. Results from multiple studies have quantified the effects of common mistakes. Smoking within 30 minutes of measurement can increase systolic blood pressure by up to 20 mm Hg, whereas a distended bladder may raise systolic and diastolic blood pressure by 10 to 15 mm Hg. Sitting without back support or crossing the legs can increase systolic pressure by approximately 10 mm Hg. Placing the cuff over clothing may alter readings by up to 50 mm Hg. Talking or active listening during measurement can increase systolic and diastolic blood pressure by approximately 10 mm Hg. Improper cuff size and arm positioning also introduce significant error. A cuff that is too large may produce falsely low readings, whereas one that is too small may yield falsely elevated values. Positioning the arm below the level of the right atrium yields higher readings, whereas positioning it above heart level yields lower values. These wide variations underscore the importance of strict adherence to proper measurement technique.[10] In addition to modifiable sources of error, unavoidable factors may also affect blood pressure measurement. Study results have demonstrated differences between readings obtained in clinical settings and those recorded in ambulatory environments. Hypertension may be overdiagnosed in patients with white-coat hypertension, in which anxiety related to the clinical setting causes a transient elevation in blood pressure. These individuals are normotensive outside the healthcare environment. Conversely, hypertension may be missed in patients with masked hypertension, who exhibit normal readings in the clinic but elevated pressures at other times of the day. This phenomenon may result from temporary lifestyle changes made before medical appointments.[9]

All healthcare professionals who measure blood pressure must understand the clinical significance of the values obtained. Familiarity with current guidelines and appropriate treatment thresholds is essential for timely and effective management.[15][16] Blood pressure measurement is a fundamental skill expected of clinicians, nurses, chiropractors, and other allied health professionals.