Assessment of overall blood pressure variability and its different components.

Blood pressure (BP) is characterized by continuous fluctuations, including fast changes lasting only a few seconds as well as slower and more prolonged variations, with a time constant of minutes or hours. Assessing the relative contribution of these different components to overall blood pressure variance is now possible through a number of mathematical approaches, either in the time or in the frequency domain (spectral analysis). Due to its complex nature, a precise and detailed assessment of blood pressure variability can be obtained only from the analysis of continuous, beat-by-beat, blood pressure recordings. Some information, however, can also be derived from analysis of discontinuous blood pressure tracings, such as those commonly performed in a clinical setting. This would require that attention is paid both to the quality of the recordings and to the selection of suitable analysis methods that should cope with the discontinuous nature of the measurements to be processed and to their intrinsic low sampling frequency.