Copyright © 1997 by the European Society of Cardiology.
© 1997 The European Society of Cardiology
Catecholamines contribute to exertional dyspnoea and to the ventilatory response to exercise in normal humans
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*Department of Physiology, University of Glasgow Glasgow, U.K.
Department of Cardiology, Western Infirmary, University of Glasgow Glasgow, U.K.
Department of Statistics, University of Glasgow Glasgow, U.K.
Received 19 May 1997; accepted 30 May 1997.
Correspondence: Dr A. L. Clark, Department of Cardiology, Western Infirmary, Dumbarton Road, Glasgow G11 6NT, U.K.
Abstract
BACKGROUND: Exogenous catecholamine administration in humans stimulates ventilation. The present study was designed to investigate whether increased endogenous catecholamine release influences objective measures of ventilation and subjective measures of breathlessness in normal subjects.
METHODS: Yohimbine, a pre-synaptic a2 adrenoceptor antagonist, or placebo was administered to 10 normal male subjects in a double-blind cross-over fashion. Ventilation and metabolic gas exchange were measured during steady state exercise at 60% of previously determined maximal oxygen consumption. Venous lactate and noradrenaline were measured during exercise. Subjects' sensation of breathlessness and fatigue were recorded using visual analogue scales.
RESULTS: Plasma noradrenaline was higher following yohimbine administration (at 6 min exercise; 4·58±0·56 nmol.l–1 vs 8·74±1·53; P<0·05). Oxygen consumption was unchanged, but ventilation was greater throughout exercise following yohimbine. The sensation of exertion was greater following yohimbine, and at any given level of ventilation, the sensation of exertion was greater.
CONCLUSIONS: Yohimbine administration causes increased noradrenaline release. This is associated with an increased ventilatory response and an increase in the sensation of exertion during steady state exercise. An increase in circulating noradrenaline might be a mechanism for both increased ventilation and pathological conditions of breathlessness such as chronic heart failure.
Key Words: Yohimbine • ventilation • exertional dyspnoea
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