ABSTRACT

The development and diffusion of noninvasive ambulatory BP monitoring (ABPM) techniques (4) in more recent times has allowed intermittent monitoring of BP over 24 h via automated arm cuff inflations in a continuously increasing number of subjects. BP readings are usually obtained through the oscillometric method, while the microphonic technique to record Korotkoff sounds is employed in a minority of devices only. Unfortunately, the time intervals usually scheduled between automated readings by conventional ABPM techniques (usually ranging between 15 and 30 min) do not allow short-lasting BP changes to be quantified. Moreover, overall 24 h BPV, as quantified by the standard deviation (SD) of 24 h average BP values, cannot be reliably assessed in case of between measurement intervals longer than 10-15 min(5) (Figure 8.2). In spite of these methodological difficulties, noninvasive ABPM is now widely used to estimate not only mean BP levels but also BPV in clinical practice (Figure 8.3). Being noninvasive and readily available on a large

scale, ABPM has allowed the definition of the circadian pattern characterizing a physiological 24 h BP profile in populations of subjects. It has also offered the possibility to quantify its alterations in patients at higher risk of cardiovascular events, strongly supporting the potential role of an enhanced BPV in determining hypertension-related TOD and an increased rate of cardiovascular events More recent progress in the field has led to the development of an innovative approach that is

able to overcome the relative inaccuracy of conventional ABPM in assessing BPV. This approach is based on a technique able to monitor BP noninvasively on a beat-by-beat basis at the finger level in ambulant subjects, during their daily activities. This technique, implemented in the Portapres® (Finapres Medical Systems, Arnheim, The Netherlands) device (6), makes use of a servo-adjusted finger cuff inflation system combined with an infrared photoplethysmograph and a hydrostatic height correction tool able to continuously monitor finger BP changes in a calibrated fashion in ambulatory conditions over 24 or 48 h. The quantification of 24 h BP profiles as well as the assessment of fast BP fluctuations provided noninvasively by this approach were found to be similar to those obtained by simultaneous intraarterial BP monitoring (6,7).