Respiratory influences on muscle sympathetic nerve activity and limb vascular conductance in the steady‐state

Abstract

BackgroundIn patients with hypertension, volitional slowing of the respiratory rate has been purported to reduce arterial pressure via withdrawal of sympathetic tone.MethodsWe examined the effects of paced breathing at 7, 14, and 21 breaths per minute with reciprocal changes in tidal volume, on blood pressure, muscle sympathetic nerve activity, forearm blood flow, and forearm vascular conductance in 21 adults (8 F/13 M, 36±14 years).ResultsAlterations in breathing frequency and tidal volume did not affect steady‐state levels of blood pressure, sympathetic activity, blood flow, or vascular conductance (all p>;0.05) despite a frequency‐dependent alteration in within‐breath modulation of sympathetic outflow (i.e. increased modulation during low frequency/high volume breathing) (p=0.000). These findings were consistent across wide ranges of: 1) resting blood pressure, 2) baseline sympathetic activity, 3) cardiovascular disease risk factors.ConclusionResults from the current study challenge the notion that slow, deep breathing lowers arterial pressure by suppressing average sympathetic outflow and calls into question the concept that changes in sympathetic activity via volitional slowing of the respiratory rate is potentially beneficial in the treatment of hypertension. Support: AHA 10PRE3870000(JKL), NIH R01HL105820(WGS), NIH R01HL15469(JAD)