Carotid haemodynamics during sympathetic nervous system stimulation via handgrip and cold pressor testing in young healthy subjects: A feasibility study

Introduction: Assessing arterial and haemodynamic properties in response to a physiological perturbation might provide additional information on an individual's "vascular health". The aim of this study was to assess the feasibility of measuring changes in carotid stiffness and haemodynamics in response to sympathetic nervous system stressors, such as the Hand Grip Test (HGT) and the Cold Pressor Test (CPT). Methods: A non-invasive protocol, consisting of two HGT's at 30% and 40% of maximal voluntary contraction and a CPT, was performed in 12 young healthy volunteers (6 males/6 females). Measurements included continuous finger blood pressure recordings (NexFin; non-dominant hand) and ultrasound measurement of common carotid diameter distension and flow velocity at discrete moments in time during the protocol (GE Vivid 7 system). Carotid distension (δD/D), local wave speed using the waterhammer equation (PWV_WH) and reflection magnitude (RM; ratio of backward to forward diameter wave) were derived from the data. Results: Consistent with the overall increase in blood pressure, carotid diameter increased while δD/D decreased. PWV_WH and RM showed high variability during both HGT's and CPT. Conclusion: It is feasible to monitor the carotid haemodynamic response to selected sympathetic nervous system stimulus. Moreover, the analysis showed supporting evidence of specific physiological response to regulate adequately each stress stimulus.