[Short-term variability in arterial pressure and heart rate in man]

Short-term fluctuations in blood pressure (BP) and heart rate (HR) were analysed in a group of seventeen males with essential hypertension (n = 8) or with normotension (n = 9). Indirect finger BP was measured by a Finapres device. Analog-to-digital conversion of the BP was used to determine systolic, diastolic, and mean arterial pressure and HR every s. The equidistant sampling allowed a direct spectral analysis using a fast Fourier transform algorithm. BP recordings combined low frequency plus high frequency oscillations. The presence of high frequency oscillations of SBP probably reflects fluctuations in cardiac output. HR exhibited a combination of low and high frequency oscillations, such as systolic pressure. The corresponding spectra illustrate these observations. The high frequency (respiratory) oscillation corresponded to one peak easily detected on the spectrum of SBP and/or HR. Slow waves were detected in a 4-129 mHz range and divided into a 4-66 mHz low frequency region and a 66-129 mHz mid frequency region (Mayer waves). The sum of the values of consecutive bands was calculated to represent an integrated spectrum of each series of treatment. Controlled respiration produced at rest a marked increase in the high frequency component. HR variability increased with the level of HR. This study illustrates the applicability of a spectral procedures combined to an indirect BP measurement to study short-term oscillations of BP and HR.