Characteristics of the right cervical vagal activity during baseline and Valsalva-like manoeuvre

Vagal nerve activity has been shown to be impacted in the case of Heart Failure. A direct recording of vagal nerve activity could be useful to investigate its characteristics, especially in the case of the vagal nerve stimulation therapy, which has been shown to be useful in heart failure patients. The objective of this paper is to validate the measurement of vagal nerve activity in a heart failure sheep model and to examine its characteristics and relationships with other cardiovascular parameters. Three sheep were implanted with an electrode on the right cervical vagus nerve and nervous activity were recorded together with left ventricular pressure and intraventricular electrocardiogram. Baseline periods showed fluctuations of vagal activity at the respiratory rate, correlated with fluctuations of ventricular pressure. Those fluctuations disappeared after a distal section of the nerve. Valsalva-like manoeuvres were induced in the sheep, and nervous activity was raised during the continuous positive pressure and lowered during the apnea. Another experiment on a pig also showed that the modifications of vagal activity during a Valsalva were suppressed by the application of the local anaesthesia xylocaine.