Assessment of Baroreceptor Reflex Function During Mental Stress and Relaxation

Abstract

This paper describes a method of measuring baroreceptor cardiac reflex sensitivity noninvasively from spontaneous patterns of blood pressure and interbeat interval, and the application of this technique in psychophysiology. Baroreflex function was assessed in 24 female volunteers during relaxation and performance of the cold pressor test and a non-verbal mental arithmetic task. Blood pressure and interbeat interval were monitored continuously from the finger using the vascular unloading technique. Sequences of three or more cardiac cycles were identified over which systolic blood pressure increased progressively in conjunction with lengthening interbeat interval, or systolic blood pressure decreased as interbeat interval was reduced. The regression between systolic blood pressure and interbeat interval was computed as an index of baroreflex sensitivity. Relaxation was associated with a small prolongation of interbeat interval, whereas baroreflex sensitivity increased from 17.1 to 19.8 ms/mmHg. Baroreflex sensitivity was reduced significantly during mental arithmetic (mean 14.2 ms/mmHg) but not during the cold pressor test (mean 17.4 ms/mmHg). The difference between mental arithmetic and the cold pressor test may be related to the relative intensity of cardiac and vascular responses in the two situations. The implications of these results for the understanding of behavioural influences on haemodynamic function are discussed and the advantages of noninvasive methods are considered.

A program to assess baroreceptor cardiac reflex function

“…As can be seen, both baroreceptor reflex sensitivity and power are reduced during the mental load task compared with the baseline period, all of these differences being significant at the .01 level. The decrease in the baroreceptor reflex sensitivity during the mental load task is supported by the findings of Steptoe and Sawada (1989), who used a mental arithmetic task. In addition to that study, in the present experiment, greater baroreceptor sensitivity was obtained in the "up" sequences than in the "down" sequences (these differences being significant in the baseline period), confirming research in cats by Bertinieri et al (1985) and findings by other authors (Mancia et al, 1983).…”

“…Also related to the signal-stationarity assumption of the spectral analysis is the need to use relatively long sampling periods (more than 4 min) in order to obtain reliable results. Free of the statistical requirements of spectral methods, the time domain technique has the potential advantage of permitting baroreflex analysis over phasic tasks and short time periods (Steptoe & Sawada, 1989). …”

“…Some data also suggest that this mechanism could play some role in human essential hypertension (McCubbin, Green, & Page, 1956;Steptoe & Sawada, 1989), since the reflex is supressed in hypertensive subjects (Bertinieri et al, 1987;Gribbin, Pickering, Sleight, & Peto, 1971). It is known that the baroreceptor cardiac reflex function is sensitive to psychological manipulations, reducing its sensitivity (expressed as the change in interbeat interval per unit change in systolic blood pressure) during mental stress (Robbe et al, 1987;Steptoe & Sawada, 1989).…”

“…Some data also suggest that this mechanism could play some role in human essential hypertension (McCubbin, Green, & Page, 1956;Steptoe & Sawada, 1989), since the reflex is supressed in hypertensive subjects (Bertinieri et al, 1987;Gribbin, Pickering, Sleight, & Peto, 1971). It is known that the baroreceptor cardiac reflex function is sensitive to psychological manipulations, reducing its sensitivity (expressed as the change in interbeat interval per unit change in systolic blood pressure) during mental stress (Robbe et al, 1987;Steptoe & Sawada, 1989).Until recently the sensitivity of the baroreceptor reflex was evaluated by means of two methods that produced experimental alterations of the cardiovascular function. The oldest method is a pharmacological technique in which interbeat interval and systolic blood pressure responses caused by intravenous injection of a pressor agent, normally phenylephrine, are measured (Smyth, Sleight, & Pickering, 1969).…”

Love Styles and Cardiovascular Responder Types

“…Using the ECG and the impedance cardiograph signals, pre-ejection period (PEP), an inverse index of β adrenalin mediated sympathetic activity, was determined with a 60-s ensemble-averaging technique . Baroreflex sensitivity (BRS), an index of parasympathetic activity, was calculated using the sequence method (Steptoe & Sawada, 1989).Beat-by-beat SBP, DBP, and HR were averaged over the 60-s periods, and then PEP and BRS were calculated for the same periods. These values were furthermore averaged to produce baseline and task values, respectively.…”