Dyspnoea: assessment and pharmacological manipulation.

A recent meeting of the European Society for Clinical Respiratory Physiology, held in Antwerp, focused on the mechanisms and management of respiratory symptoms. Dyspnoea received particular attention and this review is based on a talk presented at that meeting. The clinical problem posed by dyspnoea, or breathlessness, is of considerable magnitude. Precise data on its prevalence are lacking but it is the most common symptom in patients with cardiorespiratory disease. Many chronic diseases are associated with dyspnoea, notably cardiac failure and chronic obstructive pulmonary disease. Extrapolation from the epidemiological survey of the Respiratory Diseas~ Study Group of the RCGP [I) would suggest that. m the UK alone, approximately 750,000 patients with chronic bronchitis experience dyspnoea induced by walking on level ground. A therapeutic agent which reduces the sensation of dyspnoea would be expected to improve the quality of life for the patient by delaying the restrictions on Hfestyle imposed by breathlessness and by mitigating a symptom which causes distress and induces anxiety. This would be no substitute for specific therapy directed at the underlying disease process, but could be of value when the patholot:,ry is not reversible. Close analogies exist with the use of analgesics to treat pain. Discovery of drugs to reduce dyspnoea is difficult because the pathophysiological mechanisms are still in dispute. In addition, animal models are limited in the study of sensations. In this laboratory known pharmacological agents were used in studies on man to discover the possible mechanisms of dyspnoea. No progress could be made until methods were available for assessing breathlessness. Precision was necessary in these assessments and there had to be knowledge of the reliability and limitations of the method in view of its subjective nature. Over about ten years, experience has been gained ~hich provi?es opportunities to optimize future experunentaJ des1gn and to appreciate when credibility has been over-