Abstract

Estimation of ventilatory capacity is valuable for the early diagnosis of obstructive lung disease, for assessing its severity and response to treatment and for investigating breathlessness. Its importance was stressed in a recent ‘Medicine Today’ programme on BBC 2.¹ Ventilatory capacity depends mainly on the vital capacity² and the maximum speed of expiration, which in turn depends on airways resistance. For routine practice methods of measuring these should be simple, sensitive and give repeatable results with robust apparatus. A selection of apparatus is given at the end of this article.