Time-qualified evaluation of blood pressure excess

The authors discuss the possibility of computing indices representative of both the timing and the extent of blood pressure (BP) excess in order to improve the diagnosis and treatment of high blood pressure. This discussion is based on a computer-aided chronobiological analysis of a dense temporal series of BP data obtained by automatic ambulatory BP monitoring in clinically healthy subjects. It defines time-qualified reference limits for this biologic variable, based on original measurements or on BP rhythm parameters. It is found that if frequent, time-qualified BP measurements are taken over a 24- or (preferably) 48-h period by automatic ambulatory monitoring, rhythmic BP variability can be appropriately summarized by the characteristics of an approximating function, consisting of a fundamental such as a cosine function with a 24-h period plus at least one additional harmonic component. This individual BP profile can then be compared with a rhythmic reference limit obtained from an apparently healthy population to derive indices able to quantify and localize in time BP excess. In addition, chronobiological indices of BP excess can be used as a reliable basis to time treatment (if needed) and to evaluate its effectiveness