Dynamics of arterial blood pressure responses to sinusoidal work load in man.

Abstract

AbstractSystolic, diastolic, mean and pulse pressures in the radial artery, and heart rate in 7 physically active young men were subjected to frequency analysis by using sinusoidal work load as a forcing function. Subjects exercised in the supine position on a cycle ergometer. With the pedalling rate constant, the work load was varied sinusoidally over a range of drive frequencies between the two fixed extremes of 250 and 1050 kpm/min. Predicted step responses obtained by applying the trans fer functions estimated for radial systolic and pulse pressures showed close similarity to observed step responses, indicating linear properties of the underlying systems. Using known characteristics of the peripheral distortion of the pressure pulse, the responses of both the radial and central systolic and pulse pressures to work load could be described by second‐order transfer functions. Resonance occurred for periods near 7 min, indicating overshoots for both variables in the time domain. This behaviour suggests baroreflex inhibition as an explanation of an overdamped response of the heart rate. The changes in radial diastolic pressure were small and not clearly related to the drive frequency. The response of the radial mean pressure could not be described accurately by either first‐or second‐order functions, but exhibited phase lead features, suggesting sensitivity to rate of change in work load.