Spectral analysis of 24 h blood pressure recordings.

Spectral analysis of blood pressure and heart rate signals allows overall blood pressure and heart rate variabilities to be split into their different frequency components. When used to analyze 24 h discontinuous blood pressure recordings, the low sampling frequency that characterizes these devices allows only the slow fluctuations in day and night blood pressure to be adequately described by the spectral approach. Conversely, spectral analysis of continuous blood pressure recordings provides information both on fast and slow changes in blood pressure and heart rate. Because blood pressure and heart rate powers are characterized by a 1/f distribution over the 24 h, slow fluctuations in blood pressure and heart rate contribute most importantly to 24 h variance, while faster components provide only a minor contribution. However, spectral analysis of the latter has raised considerable interest due to the possible association of these components with cardiovascular regulatory mechanisms. It is now possible to perform 24 h dynamic spectral analysis of blood pressure and heart rate on continuous blood pressure recordings obtained noninvasively by a finger pressure device.