The effects of ICI 118,587 and atenolol on the responses to exercise and on breathlessness in healthy subjects.

The effects of ICI 118,587 and atenolol on the responses to submaximal exercise and on breathlessness were studied in six healthy subjects. Atenolol reduced heart rate at rest and during exercise whereas ICI 118,587 increased resting heart rate but caused a small reduction in the highest heart rate achieved during exercise. Neither ICI 118,587 nor atenolol significantly changed minute ventilation or oxygen uptake either at rest or during exercise. There were no effects on bronchomotor tone. The assessment of breathlessness was validated for the subjects participating in the study. Atenolol increased the intensity of breathlessness in relation either to ventilation or to oxygen uptake. This effect was not secondary to a change in bronchomotor tone but was possibly related to changes in pulmonary haemodynamics. On the other hand, the relationships of breathlessness to ventilation or to oxygen uptake were unchanged by ICI 118,587. The effects of ICI 118,587 on exercise tolerance and dyspnoea in patients with impaired cardiac function should now be determined.