Chronic airflow obstruction.

Chronic airflow obstruction (CAO) affects at least half a million people (Royal College of Physicians, 1981) in this country and will continue to be a major cause of morbidity and early death for many years to come. Even if cigarette smoking stopped today its legacy in CAO would continue beyond the end of the century. While acute respiratory infections, respiratory failure, cor pulmonale and death are the most dramatic manifestations, the major impact of the condition is in causing long-term disability through breathlessness. A man with severe CAO often has a grossly impaired quality of life for many years before he ever consults a doctor and eventually becomes virtually immobile and housebound. The breathlessness and immobility of CAO is the result of a complex interaction of many factors. Airflow limitation on exercise reduces the maximum ventilation that can be achieved and is central to the sensation of breathlessness. However, cardiovascular function, the performance of skeletal muscle, (respiratory and non-respiratory), mood, personality and motivation all modify the sensation and also contribute independently to disability. This article sets out to explore some of the factors involved in the breathlessness of CAO and how they may point the way to future treatments. The sensation of breathlessness itself and the mechanisms involved have been well reviewed in the past (Howell, 1966; Guz, 1977) and are beyond the scope of this article.