[Variability of blood pressure. Clinical and therapeutic implications]

The high degree of the intra-individual variability of blood pressure (BP) is related both to biological and technological factors: the biological components of variability are either linked to sympathetic system and respiratory movements or induced by physical and psycho-sensorial stresses; the technological sources of variability are the apparatus and the doctor. The consequences of this high variability can be quantified: the risk for a between-visit change of 35 mmHg for systolic BP (and 17 mmHg for diastolic BP) to be due to the spontaneous BP variability, is as high as 95%. Moreover, according to the regression to the mean, in selected patients with a mean SBP as high as 160 mmHg, a mean spontaneous decrease of 9 mmHg is expected to occur, at the next visit. The physician has then to manage the lack of accuracy of clinic BP measurements. For this purpose, three strategies have to be used: thoroughly examining the patient (if associated with an organ damage, the high BP undoubtedly requires to be treated); rigorously taking into account the published recommendations of BP measurements (the sources of error are now well known and may be easily corrected); finally, using the most sophisticated methods of BP measurements (elf BP measurement), semi-ambulatory or ambulatory BP monitoring, exercise testing), which in some circumstances, may provide useful additional information.