Evaluation of reproducibility of spontaneous baroreflex sensitivity at rest and during laboratory tests.

OBJECTIVE: The aim of the present study was to examine the reproducibility of arterial baroreflex sensitivity (BRS) provided by the spontaneous baroreflex method at rest and during laboratory tests.
METHODS: Twenty healthy volunteers were studied 24 h apart, in the same laboratory and under the same environmental conditions, at rest, during active standing, while performing mental arithmetics and during static hand-gripping. Systolic blood pressure, mean arterial pressure and pulse interval were continuously and non-invasively measured by using a Finapres device. BRS was evaluated by analysing the slopes of spontaneously occurring sequences of three or more consecutive beats in which systolic blood pressure and pulse interval of the following beat both increased or decreased, in the same direction, in a linear fashion. Individual BRS were obtained by averaging all slopes computed within a given test.
RESULTS: Under each test condition BRS did not differ significantly between the two consecutive days, showing strikingly similar values. The mean group coefficients of variation (CVAR), obtained by averaging individual CVAR, between the two experimental days were 15.0, 13.9 and 19.7% for resting, standing, static hand-gripping and mental arithmetic, respectively. No relationships were found between individual CVAR and individual mean arterial pressure, pulse interval and number of baroreflex sequences under any tested condition, on both experimental days.
CONCLUSIONS: These results show that the spontaneous baroreflex method provides good BRS reproducibility under various stimuli that affect the neural control of circulation differently. They also suggest that BRS variability is dependent neither on haemodynamic modifications nor on the degree of baroreflex engagement, but it seems to reflect an inherent feature of the way in which arterial baroreflex modulate the heart period.