Cuff blood pressure measurements by doctors and self blood pressure measurements by patients reflect imprecisely 24-hour or daytime mean blood pressure values. This limits the physician's ability to diagnose the absence or presence of hypertension. It also limits his ability to evaluate the response to non-pharmacologic interventions or antihypertensive drugs. This is a major disadvantage because the prognosis of hypertensive persons depends to a large extent on the blood pressure attained during treatment. Ambulatory blood pressure monitoring is a valid method for assessing the effectiveness of antihypertensive treatment because it allows the physician: (1) to determine whether the initially elevated blood pressure is reduced under the various circumstances of the patient's lifetime; and (2) to exclude that this reduction is associated with hypotensive events that might interfere with organ nutrition and function during the day and night. However, this approach has a cost that makes its use impractical in clinical practice, except in cases in which there are reasons to suspect very low or excessively high blood pressures in conditions that are out of the reach of sphygmomanometry. Furthermore, the prognostic value of on-treatment ambulatory blood pressures is still unknown. On the other hand, studies on new antihypertensive agents derive great benefits from the use of ambulatory blood pressure monitoring. This is emphasized by the fact that the ambulatory blood pressure values are more reproducible than isolated cuff blood pressure values, allowing the number of patients necessary to establish an antihypertensive effect to be reduced. Furthermore, these values are little affected by placebo influences thus permitting simplification of the study design. Finally, sequential analysis of the data obtained provides accurate information on the duration of the antihypertensive effect, and thus on the optimal posology to be adopted. However, ambulatory blood pressure monitoring does have technical problems. In the case of noninvasive monitoring, the ability to measure blood pressure phasic events and variability is limited. Another problem, which is of greater importance, is that non-invasive blood pressure monitoring devices generate a number of artifactual and imprecise readings. These problems cannot be entirely eliminated by editing the blood pressure tracing.
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