The place of exercise testing in the investigation of patients with respiratory disorders.

Exercise testing may yield important information in the clinical assessment of patients with a wide variety of conditions. An objective measure of exercise capacity is obtained; limiting factors are identified; the adaptive capacity of the heart and lungs is measured; diagnoses are confirmed or excluded. This paper argues the case for a series of exercise testing procedures which vary from simple ("stages I and II") to complex ("stages III and IV"), which allows exercise testing to be widely applied to clinical investigation and which reserves complex and invasive procedures for the clinical situations in which the information is necessary. Examples are presented to illustrate the relative value of the procedures and the information obtained from each.