Fourier analysis of blood pressure profiles.

This short review deals with the use of the Fourier technique to analyze diurnal blood pressure (BP) profiles obtained by noninvasive ambulatory monitoring. A Fourier series with four harmonics strikes an acceptable balance between the accuracy and complexity required to model the diurnal profile accurately in most subjects. A weighting procedure makes it possible to allow for the varying time intervals between consecutive pressure readings. Studies based on a single recording are insufficient to characterize an individual with respect to the statistical parameters describing the diurnal BP profile, regardless of whether they are obtained by Fourier analysis or by other methods. The Fourier approach provides the means to translate 24 h BP profiles into interpretable statistical parameters, such as the amplitude and acrophase of the overall model and the harmonics. These parameters can subsequently be used in further statistical analyses. In conclusion, the Fourier approach makes the description of complex, asymmetrical, and multiphasic BP profiles possible. By using the procedures of linear multiple regression, commonly provided by software packages, the calculations can be readily implemented on microcomputers without requiring advanced skills in mathematics or programming techniques.