Contribution of Vascular and Neural Segments to Baroreflex Sensitivity in Response to Postural Stress

Abstract

Background/Aims: The baroreflex pathway has a vascular and a neural segment, both being modulated by variations in peripheral blood pressure (BP). Besides overall baroreceptor sensitivity (BRS), defined as the spectral relationship between changes in peripheral BP and R-R interval within the frequency band of 0.05–0.15 Hz, vascular and neural segment contributions to the overall BRS can be distinguished. We test the hypothesis that changes in overall BRS following a postural maneuver mainly originate from the vascular (peripheral pressure to carotid artery diameter) rather than the neural segment (carotid artery diameter to R-R interval). Methods: Peripheral pressure (Finapress), carotid artery diameter (ultrasound in B-/M-mode) and electrocardiogram values of 20 young subjects in supine and upright-seated postures were recorded simultaneously. Transfer gains were computed for the segmental and overall responses. Results:Postural change significantly increases peripheral BP and carotid artery diameter. The vascular segment has a uniform spectral distribution. Statistical analyses revealed that postural change decreased overall (p < 0.004) and vascular (p < 0.0001) transfer gains, but did not modify neural gain. Conclusions:Unlike the neural segment, the vascular segment is frequency non-specific. The decrease in overall BRS due to a postural change is mainly explained by the reduced transfer gain of the vascular segment.

Trigonometric Regressive Spectral Analysis Reliably Maps Dynamic Changes in Baroreflex Sensitivity and Autonomic Tone: The Effect of Gender and Age

“…Our findings match that of previous studies demonstrating an increased BRS during controlled breathing at 0.1 Hz [35], [36], [37], and a decreased BRS after postural change from lying to standing [23], [27], [38]. The improvement of BRS during deep slow breathing at 0.1 Hz has been, at least partially, ascribed to an increase in vagal tone and a concomitant decrease in sympathetic activity [35], [39].…”

“…It has been suggested that the increased sympathetic tone may lead to changes of mechanical vessel wall properties such as increased stiffness. Saeed et al (2009)[38] demonstrated a smaller distention of the carotid vascular wall during standing after a comparable blood pressure change resembling a smaller stimulus for baroreceptor activation. We and others [6], [42] also revealed a positive association between changes in BRS and in parasympathetic activity (high frequency power of RRI) during postural change.…”

The Role of Ultrasonography in the Assessment of Arterial Baroreflex Function

“…These studies suggest that the propensity to orthostatic intolerance may be greater in those with structural vascular disease that affect the mechanical transduction properties of the integrated baroreflex arc. 41 …”

From Radio Frequency Data to Vascular Diagnosis

“…ATL Mark 9, HDI, Advanced Technology Laboratories, Bothell, Washington, USA) allowing continuous assessment of D d and Dd (the increase in diameter per cardiac cycle). 88,89 By including RF data describing carotid diameter in the BRS calculation, estimates of the functionality of the baroreflex have significantly improved, particularly for investigating the influence of atherosclerotic factors, such as age and hypertension. However, BRS should not be evaluated without acknowledging the effects of other parameters such as arterial morphology.…”