Aside from quantifying sympathetic nerve firing, we also are interested in assessing how sympathetic nerve activity is transduced into a blood pressure response. For this, a signal-averaging approach to sympathetic transduction has been utilized extensively in our lab. Specifically, each “burst” of sympathetic outflow (depicted below) is tracked for 10-15 heart beats and associated with the corresponding blood pressure changes over that time period.
Example of signal averaging procedure from one subject. Dotted Lines represent changes in mean arterial pressure (MAP) related to individual bursts of sympathetic outflow across 10 cardiac cycles, and the solid line represents the average MAP response for all bursts.
In addition, this signal-averaging technique can be extended to local vascular measures (blood flow; see other techniques), to track how sympathetic outflow decreases blood flow and vascular conductance (index of vasoconstriction; blood flow/mean arterial blood pressure) over 15 heart beats. The activity is then further characterized to provide insight into how different burst patterns and sizes affect blood pressure and blood flow/vascular conductance. Depicted below is customized LabView software developed in the Fadel Laboratory, enabling the real-time capture and synchronization of blood flow (calculated based on Arterial Diameter and Blood Velocity), blood pressure, and sympathetic nerve activity.
