Assessment of cardiac sympathetic regulation by respiratory‐related arterial pressure variability in the rat

Open Access
Publisher Website
Google Scholar
Abstract
1 Mechanical ventilation evokes a corresponding arterial pressure variability (APV) which is decreased by β-adrenoceptor antagonism. Therefore, in this study we set out to determine whether the respiratory-related APV can be used to assess cardiac sympathetic tone. 2 Computer-generated broad-band mechanical ventilation (0–3 Hz) was applied to Sprague-Dawley rats that had been anaesthetized with ketamine and paralysed with pancuronium. APV and its relationship to lung volume variability (LVV–APV) was systematically quantified with auto- or cross-spectral frequency domain analysis. 3 APV and LVV–APV transfer magnitudes between 0.5 and 1.5 Hz showed dose-dependent suppression by propranolol from 0.01 to 1 mg kg−1, while the static value of arterial pressure remained unchanged. Stroke volume variability, assessed by the use of a pulse contour method, exhibited a similar pattern of suppression by propranolol. In contrast, heart rate variability was not lowered with propranolol. 4 The effect of propranolol on respiratory-related APV persisted even in the presence of combined α-adrenoceptor and muscarinic receptor blockade by phentolamine and atropine. 5 The frequency range of 0.5–1.0 Hz was optimal for LVV–APV transfer magnitude to correlate with cardiac sympathetic tone. 6 We conclude that respiratory-related APV may provide a valid assessment of cardiac sympathetic regulation which is independent of parasympathetic and vascular sympathetic influences in ketamine-anaesthetized and positive pressure-ventilated rats.