The functional significance of clinical signs in diffuse airway obstruction

Abstract

THE CLINICAL signs of chronic bronchitis, asthma and emphysema were known long before their functional basis had been elucidated. Even today, when the dynamics of diffuse airway obstruction are better understood, these signs are often interpreted in purely clinical terms. It may be thought that a detailed knowledge of the source of wheezing in chronic bronchitis is not essential; for practical purposes it is sufficient that a disease and a clinical sign occur together. Such an empirical approach has certain disadvantages. Differences in the finer details of clinical signs are likely to be overlooked if their functional significance is not appreciated. The translation of a sign like wheezing into nosological terms does not advance understanding, while lung sounds treated as signals of physiological events provide valuable clues to abnormal pulmonary function. Besides, it is satisfying to know how one observation is related to another. The dynamics of airway obstruction in chronic bronchitis, emphysema and asthma are described in the preceding pages by Pride. The following review of the clinical signs is intended as a companion piece, in which a knowledge of the physiological concepts of diffuse airway obstruction is taken for granted. A fuller account of these clinical signs and their meaning in terms of pulmonary function will be found in papers by Forgacs (I 967, I 969)) Campbell (I 969) and Godfrey et al. (1970).